Trends and Complications
Thomas C. Mort, MD
Associate Director, Surgical ICU
Associate Professor of Anesthesiology and Surgery
University of Connecticut School of Medicine
Daniel Tighe, DO
Anesthesiology and Critical Care Medicine
University of Connecticut School of Medicine
Obesity is a major health caredilemma. All aspects of medical care, including anesthesia, are affected by it. All physiologic systems are altered by obesity, which imparts a higher risk for complications in the perioperative period. Hypertension, diabetes, hypermetabolic syndrome, obstructive sleep apnea (OSA), reactive airway disease, and related cardiopulmonary maladies are all associated with obesity.1
Obesity adversely affects respiratory mechanics. This is particularly true regarding its effect on oxygenation and ventilation. Spontaneously breathing obese patients have decreased chest wall compliance, leading to an increased use of muscles of respiration. Functional residual capacity (FRC) is decreased in this patient group, leading to higher rates of perioperative hypoxia and more rapid desaturation, particularly in the supine position. Increased oxygen consumption adds to these alterations.1-3
The FRC decreases proportionally with body mass index (BMI) following induction of anesthesia in the supine position. Increased intraabdominal pressure reduces FRC, as well as total lung capacity, inspiratory capacity, vital capacity, and expiratory reserve volume.2,3 These, in kind, contribute to reduced oxygen reserves. In addition, small airway closure further decreases arterial oxygen levels. Induction of anesthesia may increase the intrapulmonary shunt. Post-induction microatelectasis may occur within minutes in obese patients.1,3Moreover, using a high fraction of inspired oxygen during the preoxygenation phase may propagate atelectasis.
Conversely, the risk–benefit balance of preoxygenation with 100% oxygen outstrips any atelectasis that may take place. Attempts to counter these changes with larger mechanical tidal volumes appear to be less effective for improving oxygenation in obese patients, compared with their lean counterparts. The risk for alveolar overdistention leading to barotrauma is a concern, yet augmentation of positive end-expiratory pressure is imperative to combat many of the alterations confronting obese patients.1-3
Excessive upper airway tissue, a relatively large tongue, widened neck circumference, and narrowing of the airway lumen predispose these patients to airway collapse, OSA, and nocturnal hypoxia.
The impact that obesity has on airway management is controversial.4-6 Obesity per se does not correlate with difficult intubation (direct laryngoscopy [DL]). However, associated factors in the obese—for example, high Mallampati score, OSA, enlarged neck circumference, and elevated BMI—likely affect airway management.4-11 Thus, mask ventilation, laryngoscopy, and intubation in the obese appear to be more problematic than in the lean patient population. Lastly, due to increased abdominal pressure secondary to increased adipose tissue, obese patients may be more likely to have gastroesophageal reflux disease and thus are at higher risk for regurgitation and aspiration. Problematic mask ventilation and esophageal intubation may further exaggerate these risks.9-11
Optimal Positioning for Preoxygenation and Airway Management
The supine position is often poorly tolerated by obese patients due to a reduction in their respiratory parameters. Supine positioning will increase intraabdominal pressures with a resultant decreased FRC and lung volumes and an increased ventilation/perfusion ratio (V/Q) mismatch, which contributes to rapid oxygen desaturation. This is exacerbated in an emergent situation where the patient may already be hypoxic prior to airway instrumentation.1,2 Thus, proper positioning can have a significant effect on oxygenation.
Positioning efforts to decrease the high intraabdominal pressure can significantly improve respiratory mechanics and oxygenation. Maneuvers such as head elevation of 20 to 25 degrees impart clear advantages in care for obese patients.12,13 In an extreme positioning maneuver, preoxygenation in the upright (80-90 degrees) position may delay desaturation during supine anesthesia induction. The majority of “patient positioning” literature focuses on elective operating room (OR) cases. Two recent publications that studied emergency intubation outside the OR in mainly non-morbidly obese (MO) patients incorporated head-of-bed elevation of 20 to 25 degrees with neck extension compared with supine patients. One suggested that patients in the non-supine position had reduced odds of airway-related complications,14 whereas the other suggested the position does not improve oxygenation during intubation of critically ill adults compared with the sniffing position and may worsen glottic view and increase the number of laryngoscopy attempts required for successful intubation.15
“Ramping” is a well-described position for obese patients being readied for airway manipulation. It is essentially positioning to obtain a horizontal plane (or higher) between the external auditory meatus and sternal notch.12 The goal is to provide upper torso and head/neck elevation coupled with neck extension so the patient’s face is parallel to the ceiling. This improves access to the airway in a variety of ways (Table 1). Blankets, towels, preformed foam pillows, the RAMP (Rapid Airway Management Positioner, AirPal) with inflated baffles to adjust position, reverse Trendelenburg positioning, elevated “head of bed,” HELP (head-elevated laryngoscopy positioning), and other maneuvers can be used to customize this positioning option for varied body shapes and sizes.16
Improved line of sight, improved laryngoscopy view
Augmented respiratory effort, improved pulmonary mechanics
Downward gravitational displacement of torso/breasts
“Open” submental space between mandible/chin and sternum
Ease mouth opening (more space for mandibular hinging)
Ease cricoid-laryngeal cartilage manipulation
Provide improved access for invasive/surgical options
More room to manipulate conventional/advanced laryngoscopic devices
Improved mask ventilation
Reduces or eliminates “entrapped” feeling from patient’s standpoint (compared with supine)a
a Authors’ impression.
Standard elevation of the neck flexion and head extension (7-10 cm, in the sniffing position) works well with lean body status. Routine efforts to place obese or MO patients in the sniffing position may essentially be negated by posterior abdominal thoracic adipose tissue and their relatively “short” neck. This adipose padding literally elevates the torso on the mattress, leading to widening (ie, worsening) of the 3 airway axes. This can be worsened depending on the mattress material and the degree of support it provides to the patient.
To compensate, adequate elevation of the head and neck should be provided to realign the 3 airway axes (oral, pharyngeal, laryngeal). Collins et al compared the conventional sniffing positioning versus the “ramped” position.10 The rampedposition significantly improved laryngeal view based on Cormack-Lehane scores (conventional DL). The ramped position (HELP) allows for combined cervical spine flexion with exaggerated extension of the atlanto-occipital joint and assists in aligning all 3 airway-related axes (oral, pharyngeal, laryngeal).8-12 Essentially, this allows obese individuals to be in a compensated sniffing position coupled with elevation of the head and torso to improve respiratory mechanics.
Other similar positioning maneuvers may offer improved management conditions and respiratory physiology. The 25-degree head-up sniffing position versus the conventional sniffing position in a non-MO population in an elective OR setting were compared. The head-up position had decreased time to intubation and less airway manipulations to optimize the view—for example, external laryngeal manipulation.17
Obesity in itself has been suggested to be a risk factor for difficult mask ventilation. This airway management issue, in addition to intubation, highlights practitioners’ challenges when caring for obese patients. Optimizing preoxygenation efforts is intimately related to body positioning. Providing continuous positive airway pressure and supporting preoxygenation in MO patients for induction of anesthesia can be beneficial, particularly when preoxygenation efforts are combined with HELP, for example, the 25-degree head-up position.19,20
Ramping assists the practitioner with airway manipulation and is more comfortable for the patient when compared with supine positioning. Recently, De Jong’s group suggested that the obese ICU population undergoing emergency intubation (compared to the elective OR setting) was twice as likely to experience a difficult intubation and 20 times as likely to suffer severe life-threatening complications related to intubation.18 In an emergent situation where the patient may be in respiratory distress, use of a supraglottic airway device (SAD) may be a better initial step to improve oxygenation and ventilation. It may serve as a temporizing step prior to conventional or video-assisted laryngoscopy (VAL) and intubation or may serve as an intubation conduit.
Recently, interest in apneic oxygenation has exploded as a potential low-cost, easily applied adjunct to airway management in the OR, the ICU, and emergency services. Providing a longer time delay to the onset of desaturation coupled with a higher minimum level of the desaturation nadir is attractive. This has the potential to improve the margin of safety by allowing for longer periods of airway manipulation with less profound hypoxia. Baraka et al studied nasopharyngeal oxygen supplementation in MO patients electively intubated in the OR (general anesthesia with muscle relaxation). The time to attain blood oxygen saturation (SpO2)level less than 95% was significantly prolonged in the apneic oxygenation group treated with nasopharyngeal oxygenation (240 vs 145 seconds).21Ramachandran et al found similar results; the lowest SpO2 levelin the apneic oxygenation group was higher than the control group, and these efforts delayed the onset of desaturation.22
Although apneic oxygenation appears helpful in staving off or delaying rapid desaturation, the patients studied were elective surgical cases. Can this be duplicated under urgent or emergent circumstances?
• Is its effectiveness applicable to a patient suffering from acute cardiopulmonary deterioration, acute hypoxic respiratory failure, a significant V/Q mismatch or dead space ventilation, or severe alveolar compromise from edema fluid, blood, or secretions?
• Which oxygen source and at what delivery rate is best for the obese patient?
• More specifically, how easily can this practice be adapted for the emergent intubation in remote hospital locations?
• Are the conventional nasal cannulas adequate or must one use a specially designed transnasal catheter that delivers oxygen into the nasopharyngeal cavity directing oxygen flow toward the trachea?
• Can it be used in the patient with a partial or complete airway obstruction?
• Can the nasopharyngeal catheter be placed safely in a coagulopathic patient in extremis?
• What flow rate is optimal; 5, 15, or 45 L per minute?
• Should the high-flow oxygen be terminated if partial or complete airway obstruction is encountered?
Many of these questions have been entertained in experimental and electivepopulations under controlled conditions. The acute care setting, which has the most to gain from such oxygenation efforts, has not been battle tested. In the only ICU emergency intubation study to date, the randomly controlled FELLOW trial analyzed 150 ICU patients undergoing emergency intubation.23 It suggested there was no difference in the control group (standard therapy) versus the high-flow nasal oxygen delivery group. They evaluated the lowest arterial oxygen saturation between induction and 2 minutes after completion of intubation. Is this a viable, clinically relevant marker to study? Criticisms of this study are based on these criteria for comparison between the two therapies.
Use of apneic oxygenation in the emergency department and emergency medical services that perform rapid sequence intubation (RSI) is an area of interest, as would be the remote non-OR locations in a hospital setting. Such investigations have shown either no difference or a reduction in the incidence of mild (SpO2<90%) or severe (SpO2 <80%) hypoxemia during RSI.23-30 Additionally, those patients who undergo non-RSI tracheal intubation (awake, topical–light sedation, or deep sedation ± muscle relaxation) may benefit from the ongoing delivery of oxygen during airway manipulation. On the positive side, there were no reported impediments or complications related to the use of apneic oxygenation or its deployment. If this therapy has possible benefits versus a minimal downside, would this be acceptable criteria for its inclusion as a routine adjunct (if low cost, easily applied, and readily available)?
This oxygenation adjunct could be a welcome addition to acute airway care. Wong et al recently wrote an excellent review of the subject. They stated the prerequisites for effective apneic oxygenation include optimal preoxygenationefforts, a patent airway, and access to an ongoing oxygen source for its delivery.31 Each of these requirements may be marginal or unattainable in the acute care setting outside the OR. Patients in the urgent/emergent setting may need RSI and cricoid pressure. Would this limit the usefulness of apneic oxygenation? Also, emergent intubation in a patient with altered pulmonary physiology—significant V/Q mismatch secondary to shunt physiology—may limit the effectiveness of apneic oxygenation.
Currently, there are no clear data to confirm, support, or refute its use in the obese population under urgent circumstances. It is, however, simple to initiate, easy to administer, inexpensive (via high-flow nasal cannulas), potentially available at the bedside, and appears to have no downside evidence. Until additional evidence accumulates to support or refute its use in this population, the airway team could consider it as potentially useful with very little expended effort on their part. The emergency intubation setting is ripe for further evaluation.
Obesity: Difficult to Intubate?
Overall, it is still unclear if obesity makes intubation more difficult. Brodsky8 and others have concluded that neither obesity per se (alone) nor high BMI are predictive of intubation difficulties (in the ramped position).4-10 However, large neck circumference and high Mallampati score seem to be fairly reliable predictors of potential intubation problems. The subgroup of MO patients who have a high Mallampati class (III and IV), OSA, and large neck circumference are more difficult to intubate.
Others have found associations between obesity and difficult intubation. Dohrn et al recently reported in an observational study of gastric bypass patients that BMI had no association with difficult intubation.32 Conversely, Lavi et al found that increasing BMI was associated with a higher prevalence of difficult intubation. Difficult intubation also was associated with a high Mallampati score (III or IV).33 Riad et al showed that men with elevated BMI and increased neck circumference were associated with difficult intubation and difficult mask ventilation.34
It is imperative for the reader to know that standardized positioning for this patient population for research purposes has not been established. The findings of some investigations may be influenced by variables in their positioning protocol. As previously stated, but well worth repeating, the patient’s height, weight, adipose distribution, neck circumference, neck length (“no neck”), cervical range of motion, mouth opening, presence or absence of dentition, and Mallampati class may individually, but more importantly collectively, influence specific positional needs to optimize airway management. All patients with a BMI of 45 kg/m2 are not shaped the same. Some are apple or pear shaped, and this may have a significant effect on the potential for mask ventilation, laryngoscopy and/or intubation difficulty.
Although bariatric surgery is on the rise, nonbariatric surgical anesthesia care is inundated with an increasing number of obese patients presenting for elective and emergent care, within and outside the OR. The Hartford Hospital Emergency Intubation Database has experienced an impressive rise in the incidence of obesity. Of note, from 1990 to 2016, the overall incidence of obesity was 44.5% in nearly 18,000 non-OR emergency intubation (NOREI) encounters. Yet, in the pre-American Society of Anesthesiologists (ASA) guideline era (Period A: 1990-1996, when all non-OR locations did not meet ASA guideline equipment recommendations), the incidence was merely 30.4%. This rose to 45% in the post-ASA guideline compliance time frame (ie, Period B: 1996-2006). The incidence of obesity has climbed further (48.8%, Period C: late 2006-present) during an era in which our airway team has ready access to VAL equipment across the institution. Categorizing obesity by BMI in this database has revealed an interesting trend: a steady level of patients with obesity (BMI 30-35 kg/m2) during the 3 time periods. However, a significant shift from obesity to the higher BMI categories is evident (Figure 1).
Obesity may affect a patient’s safety due to disrupted ventilation and oxygenation, coupled with the airway team’s efforts to counter such alterations. Moreover, the practitioners’ ability to secure the airway with conventional and advanced airway adjuncts may be quite challenging, particularly in an urgent or emergent setting. Obesity itself encompasses a wide array of size categories and may affect management choices and their effectiveness, particularly in the excessively high BMI levels (ie, BMI 50-100 kg/m2). Care of the obese in the elective setting remains the focus of much debate and investigation. Currently, however, there is little evidence-based research regarding NOREI.
In addition to medical comorbidities, obese patients in the elective OR setting may present a plethora of management issues, ranging from positioning, IV access, and surgical access and management. The anesthesia and surgical teams must address a multitude of concerns that typically do not hamper the care of a lean individual. The elective setting allows a more complete, balanced, and informative airway and patient evaluation. These factors are severely restricted in the urgent setting and only add to the stress and difficult of NOREI.
Obesity and its associated airway management conditions—elevated Mallampati score, OSA, increased neck circumference, etc—may contribute to formidable challenges for airway managers in any setting if approached as they would a lean counterpart. The gathering of appropriate and experienced personnel and assuring ready access to conventional and advanced airway management adjuncts that encompass the primary approach and the secondary rescue plan (Plan B, Plan C, etc) may be relatively easy to assemble, even in a busy OR setting. Yet, compared with a remote location in the hospital with an acutely deteriorating or decompensated MO patient, for example, the radiology department or the floor, the elective setting may then seem tame.
Optimizing patient positioning is a key component that should remain a fundamental concern for obese patients. Optimizing the 3 airway axes (oral, pharyngeal, tracheal) is the goal of positioning for management of the airway. Positioning of an obese patient requires special considerations to counterbalance the adipose distribution in the torso, head, and neck regions. Proper positioning confers many potential advantages (Table 1). Aligning the 3 axes can be best appreciated by observing the angle between the auditory meatus (ear canal) and the sternum. The goal is to align the ear canal at or above the level of the sternum. Positioning may be achieved by a variety of methods (preformed foam pillows, blankets, inflatable supports, reverse Trendelenburg, head-of-bed elevation, “back up,” optimizing neck/head extension).
Moreover, a mixture or hybrid approach of the above methods may be needed to customize positioning efforts to each patient’s individual needs. Regardless of how it is achieved, efforts expended toward optimal positioning are best performed prior to the initial attempt at airway management. The caveat of making the first attempt the best attempt holds true in these clinical situations. Repositioning an obese patient from a supine to a ramped approach (foam pillow, blankets, etc) post-induction could be a formidable or impossible task. Incremental readjustment of the patient’s position post-induction via electronic bed controls may assist in optimizing the position.
Positioning for optimal airway management in any locale will be influenced by the patient’s inherent body shape, height, weight, adipose distribution and the relationship of the head, neck, and torso (“no neck,” short neck, “buffalo hump,” large breasts). Thus, the practitioner should consider several options for optimizing the patient’s position. A hybrid approach is often useful; for example, the preformed foam pillow, alone, may not adequately serve in body shapes (short height plus “no neck” plus “round apple shape” vs excessive weight/adiposity that becomes engulfed in the mattress).
The OR table with its more consistent mattress characteristics is typically a known entity to airway management personnel. Conversely, the hospital bed may vary widely by location, particularly with the plethora of specialty beds and mattresses that are available. At the time of publication, our institution has 12 bed models and 7 varying mattress types (gel, air, foam, hybrid) with many mixed and matched configurations, depending on the patients’ needs.
The varieties of mattress options are a boon for patient comfort and wound/skin protection. The comfort advantages offered by the air, foam, or gel components often allow the patient to literally sink into the mattress, often to the detriment of the desired support of the head, neck and torso needed for airway management. Typically, significant worsening of the ear canal–sternum relationship occurs. Hence, incorporating an angulated foam ramp (Troop Elevation Pillow, CR Enterprises) or building a ramp (using blankets) may require additional adjustments to compensate for any influence from the underlying mattress.
Raising the head/back and reverse Trendelenburg positioning (electronic) are advantageous and available on most hospital beds. Head and neck extension may be limited in the hospital bed, particularly if the patient is sinking into the mattress. Positioning the patient high enough on the bed so that his or her head and neck are not impeded by the mattress may be difficult.
A simple caveat: Time and effort to optimize the patient’s position is a worthy investment and is best done prior to any intervention, if feasible. This may be difficult to apply during performance of advanced cardiovascular life support/cardiopulmonary resuscitation (ACLS/CPR), with a belligerent/agitated patient and certain trauma situations—cervical, thoracic, or lumbar precautions.
Airway challenges and subsequent airway and hemodynamic complications are magnified in urgent and emergency settings outside the OR. Intuitively, these challenges and complications would be exaggerated in the obese population. There is a void in NOREI research regarding obese and MO patients. Simply stating that “obesity” will lead to difficult airway management is thought by most to be misleading and inaccurate. Certainly, airway management difficulties are probably rooted in obesity-related conditions rather than the generic term “obese.” Moreover, an elevated BMI will not automatically indicate or predict difficulties. Many top athletes have an elevated BMI based on their marked increase in weight related to muscle mass.
Further, a BMI of 42 kg/m2, for example, may describe a pear-shaped individual (more weight distributed to the lower abdomen and below the waist) compared with an apple-shaped individual (weight distributed more evenly, including the upper torso, head and neck). These two body types may offer very different levels of challenge. Likewise, being fully edentulous or completely missing upper dentition is advantageous for laryngoscopy and intubation but may jeopardize mask ventilation. Nonetheless, an increased neck circumference, a high Mallampati score (III, IV), reduced neck mobility due to its relative length and surrounding adiposity, male gender, OSA, and the extremes of BMI (50-100 kg/m2) contribute to management difficulties (Table 2). Each individual patient has physical characteristics coupled with medical/surgical conditions and comorbidities that are distinct and warrant a customized plan for each rather than a standard approach.
Obesity: Factors Contributing to Management Difficulties
Positioning constraints (more personnel required)
Potential for ↑ gastric volume, ↓ pH, ↓ emptying time
Obstructive sleep apnea
Increased neck circumference
Reduced neck mobility/relatively “short” or “no” neck
Relatively large tongue/small mouth opening
Elevated Mallampati class (III, IV)
Redundant oro-hypopharyngeal tissues
Reduced pulmonary reserve (accelerated desaturation)
Mattress features (focused on comfort/wound/skin care)
Bed frame features (manual vs electronic control)
Obesity presents particular problems for airway managers with regard to head and neck positioning, increased and redundant oropharyngeal and hypopharyngeal tissues, mask ventilation difficulties and an increased risk forregurgitation and aspiration. These patient care issues may be exaggerated in a remote location under nonelective conditions due to secretions, bleeding, vomitus, edema, and cardiopulmonary alterations. The specific advantages of incorporating the suggestions of the ASA guidelines have not been specifically addressed in the obese population under nonelective clinical conditions.
The Hartford Database
For this review of NOREI airway management of the MO patient, the Hartford Hospital Emergency Intubation Database (1990-2017) was analyzed. It was categorized into 3 time periods: Period A, 1990-1996; Period B, 1996-2006; and Period C, 2006-2017
Three Time Periods Based on Compliance with ASA Guidelines
Period A (Pre-ASA) Incomplete penetration of non-operating room (OR) locations meeting the ASA guidelines equipment recommendations; OR/PACU equipped with difficult airway carts (DAC), bronchoscopy equipment (FOB), EtCO2 monitoring in compliance with guidelines.
Period B (Post-ASA) ASA guidelines compliant in all major care areas. DAC/FOB in all ICU, emergency department, radiology, cardiac suite, GI suite, and high-traffic patient care areas. 75 locations equipped with locked airway equipment tackle boxes with restocking/exchange program. Airway team carried equipment bags with adjunct airway devices to bedside. EtCO2 monitoring in compliance at each location.
Period C (B+VAL) ASA guidelines compliance (Period B) + video-assisted laryngoscopic equipment at bedside across the institution.aASA Practice Guidelines for Management of the Difficult Airway.
During the Period A era (1990-1996), the OR/PACU was compliant with the ASA equipment suggestions (difficult airway carts [DACs], bronchoscopic equipment, capnography in 1994 following the 1993 publication), but there was incomplete penetration of these suggestions in non-OR locations. As noted in Figure 1, the incidence of obesity in the database during Period A was merely 30.4%. This rose to 45% in the post-ASA guideline compliance time frame (Period B). It has continued to climb during the era in which our airway team has ready access to VAL equipment across the institution (Period C: 48.8%).
These time periods define the “before” and “after” periods with regard to the publication of the ASA’s “Practice Guidelines for Management of the Difficult Airway” (1993). The OR and PACU were initially in compliance with the published equipment suggestions. By 1996, the widespread deployment across the institution was complete with DACs fitted with bronchoscopic equipment in all major care areas, including the emergency department, 5 ICU locations, radiology, the endoscopy suite, the cardiac catheterization suite, and major high-traffic patient care areas. Seventy-five hospital locations were equipped with airway equipment tackle boxes containing conventional intubation equipment and end-tidal carbon dioxide (EtCO2)detection/monitoring equipment.
These tackle boxes, as well as the DACs, were supported by a restocking/exchange program to maintain their contents following their utilization. The anesthesiology department deployed 5 portable airway bags that contained accessory airway devices, as suggested by the ASA guidelines, and customized to the skills and experience of our anesthesiology department (bougie airway catheter, variety of Laryngeal Mask Airway [LMA]/intubating LMA [Teleflex] devices, Combitube [Medtronic], retrograde wire kit, cricothyrotomy kit, and transtracheal jet apparatus; Table 4). In Period C, these travel bags had the Airtraq (Prodol Meditec) and portable GlideScope Ranger (Verathon) added. A pole-mounted GlideScope GVL (Verathon) was wheeled to the bedside for each NOREI.
Contents of Portable Airway Bag
Bougie airway catheters
LMA Classic (sizes 3,4,5)
ILMA (sizes 3,4,5)
LMA ProSeal and LMA Supreme (sizes 3,4)
Combitube (small adult, adult)
Cook Melker Cricothyrotomy kit
Transtracheal jet ventilation setup
Airtraq disposable videoscope (2006)
GlideScope Ranger (2006)
Cook Retrograde Wire Set (2009)
Demographic data were collected from intubation procedure records and cross-checked with the medical record and personnel involved in the patient’s care to ensure accuracy of procedural details and the medical/surgical conditions of the patient. Airway management factors reviewed included the use of accessory airway devices as a primary approach and rescue, the number of intubation attempts, and the rate of complications (hypoxemia, SpO2<90%; severe hypoxemia, SpO2<80%; esophageal intubation; regurgitation; aspiration; bradycardia [heart rate <40 beats per minute]; and cardiac arrest).
Over the 27-year time frame, 17,628 patients who underwent urgent or emergent tracheal intubation outside the OR (NOREI) had intubation procedure sheets completed, which were entered into the department’s emergency intubation database. Patients were categorized by BMI measurements (BMI <25 kg/m2, non-obese; BMI 30-35 kg/m2, obese; BMI >35-50 kg/m2, MO; BMI >50 kg/m2, super MO).
The position used for the intubation procedure was noted (supine or ramped [head of bed elevated 25-30 degrees], reverse Trendelenburg, ramped; or sitting upright [>60 degrees]). The objective of the review of the database was to compare:
1. the lean patient group versus MO group for overall comparison of emergency intubation;
2. the 3 time periods regarding management and complications to determine any effect from the ASA guidelines on the care of MO patients in the emergency setting;
3. MO–supine position versus MO-ramped;
4. topical anesthesia ± light sedation for intubation preparation in MO patients; and
5. BMI subgroups MO versus super MO versus BMI greater than 75 kg/m2 to decipher any trends of management and complications.
The analysis was by BMI category:
• less than 25 kg/m2: lean; n=4,700 (26.7%);
• 25-30 kg/m2: overweight; n=5,078 (28.8%);
• 30-35 kg/m2: obese; n=2,969 (16.9%); and
• greater than 35 kg/m2: MO; n=4,858 (27.6%).
The overall first-pass success rate for laryngoscopy was 68.3% (for 5,250 VAL cases, 78% vs. for 12,035 DL cases, 60%). The overall first-pass success rate for any primary method (DL, fiber-optic bronchoscopy [FOB], VAL, LMA) was equally unimpressive, at 6 of 10 encounters. Another one-fourth of patients required 2 attempts and 1 in 6 required 3 or more. The use of accessory devices (in a primary or secondary role) was considerable over the 27-year period (44.8%, ). This is particularly impressive, given that airway personnel had little to no access to accessory airway devices during Period A. Incorporating accessory airway devices when confronted with failure of conventional laryngoscopy occurred in 1 in 5 emergency encounters (20.8%). The incidence of complications of the emergency airway interventions was impressive, certainly compared with the relatively tame elective conditions in the OR. Hypoxemia, esophageal intubation, regurgitation, and other airway and hemodynamic complications besieged those encounters that required 2 or more attempts.
Significant Management Eventsa
First-attempt success (laryngoscopy) 68.3%
First-attempt success (all methods) 59.8%
Accessory airway device used 44.8%
Mallampati classes III and IV 40.2%
Adjunct rescue device deployed 20.8%
Any hypoxemia: SpO2 <90% 18.3%
3+ attempts 15.0%
Severe hypoxemia: SpO2 <80% 8.6%
Esophageal intubation 7.7%
New-onset dysrhythmia 6.4%
Cardiac arrest 2.4%
Surgical airway 0.7%
All NOREI cases documented in database
These findings support the ASA guideline’s recommendation to limit intubation attempts to 3 (or 2), and subsequently moving to Plan B with rapid deployment of an accessory rescue device. The complications and the intubation characteristics noted in Table 5 reflect all 3 time periods accumulated over 27 years. Despite implementing the guideline’s recommendations, NOREI remains a serious patient safety issue.
Reviewing the assortment of airway devices used over time during emergency airway management, conventional laryngoscopy reigns as the most utilized (Table 6). Advanced video laryngoscopic devices were used in a substantial number of encounters (Period C). This is particularly impressive given that the technology was only available in the most recent 11 years (late 2006-2017) of the 27-year data collection period. Adjunct use of the bougie airway catheter to supplement DL accounted for nearly 6% of all encounters, primarily in Period B.
Successful Airway Management Methods
Airway Device Credited With Successful Intubation N=17,628
Conventional direct laryngoscopy (DL) 55.7%
Video-assisted laryngoscopy 27.9%
DL + bougie 5.8%
Supraglottic airway devicea 5.6%
Fiber-optic bronchoscopy 4.2%
Surgical airway 0.8%
aLMA, laryngeal mask airway, intubating LMA model.
The SAD serves as a popular rescue device for both conventional and advanced laryngoscopic techniques (5.6%). Elective use of a SAD as the primary mode of airway control represented less than 1% of the overall 1,139 SAD uses over the 27-year collection. Conversely, two-thirds of the cases using FOB were in the role of primary intubation technique, with the remainder serving as a rescue device following other failed interventions. Attaining a surgical airway—typically a procedure of last resort following failure or difficulty with other primary and accessory airway rescue devices—was the ultimate outcome in 134 encounters (0.8%).
Nonetheless, analysis of the overall database suggests that the incidence of airway and hemodynamic alterations and complications are striking and disturbing. The question to be asked is whether the initiatives employed made any strides toward improving patient safety. Perhaps reviewing the database over time could shed light on whether we are positively affecting patient care.
Following the initiation of the department’s emergency airway database, analysis of the early years (1990-1993) revealed alarmingly high rates of complications. This was the time period that predated the widespread availability of EtCO2detection. The availability of bronchoscopy was relatively restricted. A bougie catheter, a SAD (LMA, Combitube, etc.) and other rescue devices (retrograde wire, a transtracheal jet apparatus, cricothyrotomy) presided in the OR stock room. Moreover, their utilization certainly had not penetrated our routine practice. Conventional laryngoscopy, complemented by multiple attempts, often by multiple individuals, stood as the standard of care. A rescue surgical airway was typically the next management option.
Publication of the 1993 guidelines prompted a more organized approach to equipping the OR and PACU; dedicated DACs reflecting the guideline’s recommendations, accessory airway adjuncts (eg, bougie catheter, LMA, intubating LMA) on each anesthesia cart, readily available FOB, the setup of a reporting system to label difficult airway patients and a laminated copy of the ASA Difficult Airway Algorithm hanging from a chain on each anesthesia cart for easy access and review. By 1996, these improvements were deployed to non-OR patient care areas hospital-wide, as outlined earlier.
Within the first year of Period B (1996-1997), it became apparent that our efforts to improve patient safety seemed to be paying off. This was evident in the relatively explosive transition from DL management (alone) to use of DL with an adjunct bougie. This period also saw the implementation of SAD rescue for ventilation and/or intubation difficulties or failure, and adoption of the rescue role for the Combitube as a primary SAD following DL failure or, more likely, as a secondary SAD to back up LMA/ILMA failures.
Use of FOB as the primary approach to a patient with known or suspected difficult airway increased markedly in Period B. Obviously, its promotion via the ASA guidelines was assisted by the institutional push to provide ready access to FOB equipment for NOREI. Overall, the use of a variety of rescue devices for DL difficulty or failure flourished in Period B. Several factors were responsible for this change in practice.
In summary, practice changed during this period due to a variety of influences, including the immediate availability of equipment at the bedside for airway team members to deploy; ongoing team crisis simulation training for residents to practice difficult airway management scenarios; frequent lectures on the topic and discussion with departmental personnel; and a yearly airway management presentation and morbidity and mortality conference emphasizing airway management complications, strategies, and corrective and preventive actions.
NOREI patient encounters involving higher BMI and Mallampati class were notably increased. Concurrently, a higher first-pass success for laryngoscopy and all methods employed as a primary approach (Plan A) accompanied this demographic change. Subsequently, the need for 3+ attempts has been reduced over the 3 time periods, which likely has contributed to the falling incidence of oxygen desaturation, esophageal intubation, regurgitation, aspiration, new-onset dysrhythmia, bradycardia, and cardiac arrest. The need for establishing a surgical airway dropped by nearly 50% with the addition of accessory devices at the bedside (via a travel bag) and deployment of DACs at key high-traffic patient care locations beyond the OR and PACU.
Significant Management Events by Time Period
Overall (N=17,628) Period A
(n=3,283) Period B
(n=4,880) Period C
First-attempt success (laryngoscopy) 68.3% 55.3% 60.5% 69.2%a
First-attempt success (all methods) 59.8% 53.9% 47.7% 68.1%a
Accessory airway device used 44.8% 6.5% 39.6% 60.6%
Mallampati classes III and IV 40.2% 21.6% 37.7% 47.9%
Adjunct rescue device deployed 20.8% 6.1% 33.7% 20.0%
Any hypoxemia: SpO2 <90% 18.3% 28.0% 18.6% 14.8%b
3+ attempts 15.0% 24.5% 15.4% 10.2%a
Severe hypoxemia: SpO2 <80% 8.6% 13.9% 7.4% 7.4%b
Esophageal intubation 7.7% 16.9% 11.2% 2.7%a
New-onset dysrhythmia 6.4% 10.8% 7.0% 4.6%a
Bradycardia 2.6% 4.4% 3.0% 1.1%a
Cardiac arrest 2.4% 3.7% 2.3% 2.1%b
Regurgitation 1.7% 4.4% 1.7% 0.7%a
Aspiration 0.7% 1.8% 0.7% 0.2%a
Surgical airway 0.7% 1.8% 1.0% 0.3%a
a P<0.002 for Period C compared with both Periods A and B; b and Period C compared with Period A.
Table 8. Successful Airway Management Methods by Time Period
Airway Device: Successful Intubation Overall (N=17,628) Period A (n=3,283) Period B (n=4,880) Period C (n=9,465)
Conventional direct laryngoscopy (DL) 55.7% 93.7% 59.8% 40.5%
Video-assisted laryngoscopy 27.9% — — 51.9%
DL + bougie 5.8% 1.3% 16.1% 2.1%
Supraglottic airway device 5.6% 0.9% 14.9% 2.5%
Fiber-optic bronchoscopy 4.2% 2.2% 8.1% 2.8%
Surgical airway 0.8% 1.8% 1.0% 0.3%
Further reduction in the need for a surgical airway in Period C likely reflects the immediate availability of VAL at the bedside; its use as a primary intubation strategy (Plan A) and its rapid deployment when conventional approaches proved difficult (Plan B). Table 8 demonstrates the pronounced uptick in use of accessory airway devices during Period B when personnel had ready access to them. They were aggressively deployed as “Plan B” rather than relying on repeated attempts with DL, which was the standard approach employed in Period A. An author (TCM) noted that the introduction of VAL in the OR was accompanied by a significant drop-off in use of other accessory devices within the OR. This trend was also evident outside the OR in Period C for NOREI.
Accessory device success by time period (N=17,628).
VAL became the “Plan B” for difficulty with DL, and in many practitioners’ hands supplanted DL as “Plan A.” Use of Plan B devices (bougie, SAD, FOB) plummeted (Table 8) with the deployment and ready bedside access of VAL technology (Period C). The reduction in airway- and hemodynamic-related complications with the implementation of rapid bedside access to accessory devices (Period B) appears to be further improved with the addition of advanced laryngoscopic devices (VAL).
Although DL remains entrenched in a significant portion of NOREI encounters and can stand alone without adjuncts in the majority of patient encounters, access to the assortment of airway management devices appears to be complementary to each other. In further support of providing an assortment of conventional and advanced equipment for each patient encounter, this database suggests VAL has a failure rate between 5% and 10% in experienced hands for NOREI.
The Hartford Hospital database documented 490 difficult/failure cases of nearly 5,250 VAL-managed cases (NOREI). Such difficulty or failure led to instituting Plan B, and in many cases Plans C and D. Table 9 presents the rescue device credited with securing the airway following a VAL intervention. VAL serves admirably as a rescue for DL, and the reverse is also true. The SAD remains the most commonly used nonlaryngoscopic accessory device in the role of Plans B, C, and D when difficulty/failure is encountered with VAL-assisted NOREI.
Plan B for Difficulty/Failure (n=490)
SAD (LMA, Intubating LMA, Combitube) 202
Bougie (via deployed ETT)a 106
FOB (combination VAL+FOB) 89
DL (DL+bougie) 87 (3)
Surgical airway 3
Multiple devices deployed 78
a Deployed ETT tip at or above glottis or tip impinged on anterior tracheal wall (cricoid ring) uncorrectable by ETT rotation.
Comparison of Lean Versus MO Patient Groups
Within the database, lean (BMI <25 kg/m2) versus MO (BMI >35 kg/m2) patient populations were analyzed to decipher whether there were any differences in the airway management schema, trends, or patterns in management and to review the airway- or hemodynamic-related complications during NOREI.
One immediate distinction between the two groups was the disparity in higherMallampati score (class III and IV), with a nearly 4-fold increase in the MO group. The first-pass success rate for any type of laryngoscopy (DL, VAL) and for any primary airway management method (DL, VAL, FOB, SAD) was demonstrably higher in the lean group. Reliance on multiple attempts (3+) was 50% more common in MO patients. Lean patients experienced less desaturation—any desaturation (SpO2 <90%) or severe hypoxemia (SpO2 <80%)—during the airway encounter. The elective use of accessory airway devices as the primary intubation approach was nearly twice as common in the MO group. Equally, MO patients was twice as likely to require an adjunct rescue airway device due to difficulties with DL.
Comparison of Lean vs Morbidly Obese Patients With Overall Database
Lean (n=4,700) Morbidly Obesea(n=4,858) Overall (N=17,628)
First-attempt success (laryngoscopy) 68.3% 57.2% (P<0.002) 64.2%
First-attempt success (all methods) 65.5% 51.2% (P<0.01) 59.8%
Accessory airway device used 34.4% 64.2% (P<0.002) 44.8%
Mallampati classes III and IV 21.2% 75.1% (P<0.001) 40.2%
Adjunct rescue device deployed 17.2% 32.9% (P<0.002) 20.8%
Any hypoxemia: SpO2<90% 16.6% 22.1% (P<0.002) 18.3%
3+ attempts 12.0% 18.0% (P<0.002) 15.0%
Severe hypoxemia: SpO2<80% 7.9% 10.4% (P<0.01) 8.6%
Esophageal intubation 6.6% 7.2% (NS) 7.7%
New-onset dysrhythmia 6.7% 6.9% (NS) 6.4%
Bradycardia 2.5% 3.2% (NS) 2.6%
Cardiac arrest 2.8% 2.6% (NS) 2.4%
Regurgitation 1.8% 1.5% (NS) 1.7%
Aspiration 0.6% 0.7% (NS) 0.7%
Surgical airway 0.5% 1.0% (P<0.001) 0.7%
a Compared with Lean patient group.
NS, not significant.
Surprisingly, esophageal intubation was similar between both groups. This probably reflects the markedly higher deployment of nonconventional laryngoscopic equipment for airway management in the MO group. The incidence of regurgitation and aspiration was similar between both groups, as was the rate of new-onset dysrhythmia (eg, supraventricular tachycardia, atrial flutter or atrial/ventricular fibrillation, bradycardia, asystole, etc) that arose during or within five minutes of the execution of the tracheal intubation. A bradycardic response during intubation was commonly associated with desaturation (SpO2<90%, 78%). Only 22% of 464 bradycardic episodes were without desaturation. Nearly two-thirds (62%) of the patients who experienced new-onset bradycardia during intubation had concurrent severe hypoxemia (SpO2 <80%). Despite the difference between both groups regarding desaturation, the incidence of bradycardia and cardiac arrest was insignificant. However, the pursuit of a surgical airway alternative following failure of conventional and advanced airway devices was 2-fold higher in the MO group.
Successful Airway Management Methods: Lean vs Morbidly Obese
Airway Device: Successful Intubation Overall (N=17,628) Lean (n=4,700) Morbidly Obese (n=4,858)
Conventional direct laryngoscopy (DL) 55.7% 65.5% 35.8%
Video-assisted laryngoscopy 27.9% 23.0% 40.5%
DL + bougie 5.8% 4.7% 8.0%
Supraglottic airway device 5.6% 2.7% 9.5%
Fiber-optic bronchoscopy 4.2% 3.6% 5.3%
Surgical airway 0.8% 0.5% 1.0%
A comparison of successful methods used to secure the airway between the overall database and the lean versus MO groups. Again, there was a marked increase in the deployment of accessory airway devices, either as the primary approach or used in a rescue role in the MO group. This aggressive utilization of accessory airway devices and advanced technology may help to explain the relatively small differences seen in most of the airway- and hemodynamic-related complications. The airway team, in response to the propensity of an elevated Mallampati class and other known or suspected difficult airway characteristics, seems to have geared their strategy toward instrumenting the airway with nonconventional equipment rather than DL. This strategy seems to have had an effect on MO complications, making them similar to the leaner group.
To this point we have shown that the retrospective review of a large tertiary care institution’s NOREI database provides ample evidence that such airway interventions are not simple and are certainly not without significant and, at times, grave risk that threatens a patient’s safety as well as their life. If given the ability to choose whether one would prefer to manage a lean or an MO patient under emergent/urgent circumstances in the OR, most would probably choose a lean patient. This argument would probably hold true for NOREI given our understanding and perceptions that the MO patient population is more likely to offer a management challenge.
DL vs VAL success: lean vs morbidly obese.
Accessory device use: lean vs morbidly obese.
The data, albeit uncontrolled and nonrandomized, suggested that several intubation management issues—such as a lower first-pass success rate, increased incidence of multiple attempts (3+), and the incidence of oxygen desaturation—afflict the MO group more commonly. However, many of the other listed complications differed little between the two BMI categories. Table 11 shows the trend of more aggressive use of accessory airway devices with less reliance on conventional laryngoscopy in the MO group. This shift of intubation strategy stems from the ASA guideline’s suggestion to reduce DL attempts and transition quickly from DL to an accessory device as a backup rescue (Plan B). More recent data (Period C) suggest airway management strategy has shifted toward bypassing DL and incorporating advanced technology/accessory devices as the primary intubation approach (Plan A).
The impact of aggressively altering the airway management strategy in the MO population may be reflected in the incidence of life-threatening airway- and hemodynamic-related complications. The incidence of such intubation consequences is nearly equal between both groups (lean vs MO; Table 10). Therefore, simply reviewing the incidence of complications between both patient groups would not suggest any significant difference between them, and one may draw incorrect conclusions.
Emergency Intubation in MO Patients By Time Period
The comparison of each of the 3 time periods reflects a marked improvement in patient safety. Do these welcome trends of fewer complications and improved first-pass success apply to the MO group? Analyzing the database confirms that the stepwise improvement in intubation schema and success from Periods A<2192>B<2192>C for the overall database (Table 7) applied to the MO group. Similarly, significant reductions in both airway- and hemodynamic-related complications over Periods A<2192>B<2192>C for the overall database (Table 7) are also reflected in the MO group. The patient airway care initiatives deployed in Period B were complemented in Period C by the welcome addition of VAL.
Improvements were noted in most types of airway- and hemodynamic-related complications. The MO group suffered any oxygen desaturation (SpO2 <90%) at an astounding rate of 42.7% (Period A), which fell to 20% for Periods B and C (Figure 5). Severe desaturation was also cut in half (19% in Period A to 9.5% in Periods B and C). One-fourth of Period A patients suffered esophageal intubation. This was halved to 11.9% in Period B, with a subsequent reduction to 3.1% in the current time period (Period C; Figure 5). Regurgitation and aspiration enjoyed significant reductions, as did the rate of new-onset bradycardia.
Complications by time period: morbidly obese.
Complications by time period: morbidly obese.
The success of the primary intubation method. The success rate in Period A is extremely high for DL. This reflects the relative lack of choices available to the airway team in this time period. Conventional laryngoscopy eventually proved to be successful, but the multiple attempts led to significant patient harm. The uptick in the success of the primary intubation method in Period C was influenced by the airway team choosing VAL and elective FOB as the primary method to secure the airway.
The deployment of adjunct airway devices (non-DL) rose in Period B, reflecting what was seen in the overall database with a further boost with widespread availability of VAL in Period C (Figure 7). The elective use of VAL in Period C led to a sharp decline in the need to incorporate a Plan B adjunct device in the MO group as well as the overall database. First-pass success rose in Period C, with a subsequent reduction in those MO patients requiring 3+ attempts (Figure 8). There was a precipitous fall in the rate of cardiac arrest from 6.4% (Period A) to 1.8% (Period B) and 2.4% (Period C).
Successful Management Methods: Morbidly Obese (N=4,858)
Airway Device: Successful Intubation Period A (n=454) Period B (n=1,385) Period C (n=3,019)
Conventional direct laryngoscopy (DL) 87.4 38.3% 26.8%
DL + bougie 3.3% 24.0% 1.4%
Supraglottic airway device 2.0% 25.6% 3.1%
Fiber-optic bronchoscopy 2.9% 10.9% 3.0%
Surgical airway 4.2% 1.1% 0.5%
Video-assisted laryngoscopy — — 65.9%
The major factor contributing to the etiology of cardiac arrest during NOREI in Period A was airway management difficulties (severe desaturation, esophageal intubation with or without regurgitation, and aspiration). The primary etiology of 80% of Period A cardiac arrests (airway-related issues) was reduced to 25% of cardiac arrests in Periods B and C. The deployment and utilization of accessory equipment likely accounted for the significant reduction (Figure 9). Further, the need for attaining surgical airway access was reduced 85% over the 3 time periods (4.1%, A<2192>1.1%, B<2192>0.5%, C;).
Cardiac arrest and surgical airway by time period: morbidly obese.
The database provides a trend suggesting that over the 3 time periods, airway safety improved greatly for the group overall as well as MO patients. Reviewing the successful airway management methods demonstrates a substantial uptick in accessory device utilization. Although initial intubation attempts were more often credited to DL (55.7%; Table 11) over the 27-year review, the MO group benefited greatly from bedside accessibility of advanced devices in Periods B and C, leading to DL accounting for about one-third of cases (Table 11). Conventional laryngoscopy’s overall success rate was less than spectacular in the MO group (53.6%). Following deployment of accessory devices and eventually VAL, DL dropped substantially over the 3 periods (Table 12). As such, it was credited with successfully securing the airway in only one-fourth of Period C encounters. VAL, electively or as rescue, was responsible for two-thirds of the total in Period C. Period B experienced a considerable rise in the deployment of accessory devices. This buoyed DL-related multiple attempts, as they were used early on following DL difficulty/failure.
The analyzed data provided thus far have confirmed that NOREI can be fraught with complexities and complications. The recommendations put forth by the ASA guidelines were a springboard for organizing and deploying airway management equipment with the goal of improving patient safety. The value of the guidelines is evident in the marked reduction in airway- and hemodynamic-related alterations.
Is providing such airway management equipment the primary influence on improving patient safety? Certainly, immediate access to such equipment is valuable, but are there any other important factors that may influence patient safety? Team training through simulation-based crisis management, lectures, hands-on workshops, practice using accessory devices in the OR, and other factors will all affect patient care.
Position of MO Patients for NOREI
Patient positioning has been mentioned as an extremely important factor for patient management in and outside the OR. This is particularly true for the obese population. Optimizing the position of an acutely ill patient may be relegated the least attention, but the effort may reap significant benefits for the patient as well as the airway team. Moreover, there is little downside besides the consumed time (30-90 seconds). It is time well spent if it benefits patient safety. Ramping, reverse Trendelenburg, 25- to 40-degree head-of-bed elevation, HELP, with or without head and neck extension, or a combination of these maneuvers—depending on the patient’s anatomy, needs, and tolerance—have all been shown to benefit pulmonary mechanics and airway management (ventilation, laryngoscopy, intubation, improved mandibular hinging to increase access to the mouth, improved landmark identification and manipulation within the sternomental area, and a move away from the entrapped feeling an obese patient may experience when supine).
To evaluate the effect of positioning during NOREI in the MO population, first-pass success rate, the need for 3+ attempts, airway- and hemodynamic-related complications, and the need for deployment of accessory device rescue equipment were assessed based on either the supine or ramped positions.
Head-of-bed elevation 25 to 40 degrees combined with neck extension.
Flattening of the auditory canal to sternum line, much more submental room to provide access to neck structures, marked improvement in mandibular hinging (mouth opening), improved oral access for instrumentation, and less interference from torso structures.
Improves respiratory mechanics and patient comfort, provides room between chin and torso, augments mouth opening and provides neck extension depending on towel placement. It is imperative to undo hair buns or tied-up hair that is located posteriorly (a major impediment to extending patient’s head during management of the airway). Note leveling of auditory canal and sternum.
Provides similar attributes as the ramped and head of bed elevation positions for improving respiratory mechanics, maximizing oxygenation, improving mask ventilation, and facilitating tracheal intubation. As observed in this pictorial, simply placing the patient in reverse Trendelenburg may assist pulmonary function but, without enabling some degree of neck extension, airway management may be difficult. Simply moving the towels from under the head to under the neck may be sufficient. Moreover, extension of the end of the OR table may suffice. This situation can be problematic with a hospital bed that does not have extension capabilities; thus, rolls or towels under the neck to allow extension may assist positioning.
Modified Cormack-Lehane Grade View with Laryngoscopy
DL: Grade 1 10.9% 29.0%
Grades 1, 2 38.4% 60.6%
Grade 3 40.4% 28.5%
Grade 4 20.9% 15.5%
Grades 3, 4 61.6% 39.4%
VAL: Grade 1 57.1% 72.5%
Grades 1, 2 90.9% 95.1%
Grade 3 7.4% 4.1%
Grade 4 1.7% 0.8%
Grades 3, 4 9.1% 4.9%
The significant improvement in airway management and the commensurate reduction in serious consequences over 3 time periods are in large measure due to the utilization of advanced accessory devices and adhering to the equipment recommendations of the ASA guidelines. Another notable difference over the 3 periods is the increased use of nonsupine positioning in the MO group: Period A (12.7%)<2192>Period B (24.5%)<2192>Period C (47.4%). Thus, positioning may be an important contributing factor to improved patient safety in the MO group. Previously, the attributes of ramping were presented (Table 1). Ramping may provide several important advantages over the supine position beyond its influence on the view obtained with laryngoscopy (DL, VAL). Analysis of the MO group suggests that the views obtained with DL and VAL were influenced by positioning (Table 13). Intubation success, attempts required and subsequent complications were reduced in those patients ramped for NOREI.
The first-pass success for DL varied immensely between the supine and rampedpositions. Only 943 patients of 1,999 DL encounters that were positioned supine were intubated successfully (47.1% vs 71.6% ramped). Stated differently, over half of the DL patients relied on accessory device rescue to achieve successful intubation (52.8%). Conversely, the DL encounters that were ramped and required an accessory device for rescue numbered 28.4%. Management with VAL had a much higher success rate than DL. The effect of ramping was evident but less so than the supine position. Patients positioned supine with primary VAL intervention were successful at a much higher rate than DL (88%) as opposed to the ramped VAL approach, which had a higher success rate (96%). NOREI airway- and hemodynamic-related complications in the MO group were reduced when in the ramped position.
Although the ramped position has been widely described, individual practitioner nuances likely influenced the ramped position obtained for NOREI. The acute setting combined with the available personnel and their efforts, as well as the patient’s anatomical characteristics (height, weight and its distribution, neck length and circumference, torso size) combined with bed and mattress factors will undoubtedly influence how one replicates best positioning efforts. In essence, although ramping is not entirely uniform, its application and execution are in the eyes of the beholder. The upshot of the positioning issue is that making a concerted effort to position the patient (reverse Trendelenburg, HELP, head-of-bed elevation, ramping, foam support, air baffle support, towel support) appears to be warranted and certainly better than expending no effort and leaving the patient supine (barring contraindications to positioning).
Topical Local Anesthesia Preparation and MO Patients
Topical local anesthesia (TLA) with or without sedation is a time-tested method of approaching the known or suspected difficult airway patient.35 While this preparation is typically equated with an awake FOB approach, any primary or rescue technique can be employed with adequate TLA preparation. Of late, asleep VAL has become a popular substitute for awake FOB. Many practitioners have curtailed deployment of FOB and migrated toward a VAL-based approach for the known or suspected difficult airway patient. This move transforms a previously awake approach to one typically reliant on induction of anesthesia. However, adequate TLA preparation affords a VAL-based intubation while maintaining an awake (with or without mild sedation) spontaneously ventilating patient.
Providing TLA in the acute setting can be accomplished relatively quickly by the application of 4% lidocaine to the oral cavity, oropharynx, and hypopharynx. Gargling is preferable for maximal distribution, but many patients are incapable of such a task. Use of a malleable atomizer to spray the tonsillar pillars, valleculae and supraglottic tissues can be performed in a timely manner.
4% lidocaine solution with a malleable MADgic atomizer (Teleflex) or other similar device to distribute the local anesthetic. The malleable atomizer affords better directional distribution as it can be angled to spray the tonsillar pillars and hypopharynx. More random shotgun spraying from a syringe alone or syringe with an attached IV catheter may be adequate in a pinch.
Application of lidocaine jelly or ointment on the tongue can augment coverage, and testing the area with a tongue depressor will assist with assessing the patient’s tolerance. Equally, the disposable blade cover of the VAL with the applied jelly/ointment (with or without video baton in place) can be gently advanced into position to perform two tasks: to distribute TLA, and to assess the patient’s tolerance. If accepted by the patient, the video baton can be placed within the blade cover and intubation can follow.
TLA preparation involved 719 MO patients (15% of total MO group), which is 50% higher than the remaining non-MO database (10.2%). Approximately 70% of these patients had TLA alone, while the remaining patients received a small dose of a supplemental sedative-hypnotic or anxiolytic (eg, <0.75 mg/kg propofol [20-40 mg], or 0.02-0.04 mg/kg midazolam [1-3 mg]). The acute circumstances precipitating the need for a controlled airway presented a wide array of clinical conditions accompanied by a variable mental/neurologic status. Application of the TLA was based on the airway team’s assessment of airway characteristics and the clinical conditions of the patient. The patient was positioned either supine (377; 52%) or ramped (342; 48%). Of the ramped patients, 55 were actually positioned upright (>60-90 degrees) for FOB-guided intubation under TLA. Overall, 112 of the 342 ramped patients underwent FOB-assisted intubation (32.7%), which relegated DL (19.5%), bougie (1.2%), or SAD (1.8%) to less prominent roles. FOB was used in only 6.3% of the supine MO patients with TLA.
VAL was equally deployed in both the supine and ramped groups (45%). The need for a surgical airway was markedly reduced when ramping the patient (1.9%<2192>0.3%) compared with the supine position. Further differences in patient care were noted in the supine versus ramped group under TLA preparation (first-pass success, 40.6% vs 65%; 3+ attempts, 38.5% vs 14.6%; success with a single airway device, 61% vs 87.4%; bradycardia, 5.2% vs 1.6%; esophageal intubation, 11.3% vs 1.5%; regurgitation, 1.6% vs 0.6%; aspiration, 1.3% vs 0.3%; cardiac arrest, 3.2% vs 0.6%; any hypoxia SpO2 <90%, 23.7% vs 16.7%; and severe desaturation <80%, 10.6% vs 8.2%).
TLA appears to have advantages for patient care. Relatively easily applied at the beside under hurried conditions, this noncontrolled, nonrandomized analysis suggests that it provides an improved margin of safety in the MO group, particularly if combined with the ramping position. The upright position (40-90 degrees) is excellent for FOB, particularly if the operator stands in front of the patient, rather than approaching from over his/her head. This may be difficult in a hospital bed. The awake VAL approach in the upright position is challenging from over the patient’s head but can be accomplished if a safe, elevated step for the operator can be assembled. Conversely, if the hospital bed precludes positioning in front of the patient, two operators—one performing the laryngoscopy and the other performing the intubation—can be used. The narrow OR table would allow the awake VAL method to be performed by a single operator positioned from the side. This technique is best practiced in the simulation lab to allow one to gain confidence and skill in its application.36,37
This review has focused on the MO population: those with a BMI greater than 35 kg/m2. However, the range of BMI is as large as the BMI values are themselves (35-99 kg/m2). Though the majority of patients lie within the BMI range of 35-50 kg/m2 (n=3,508, 77.2%), over one-fifth of patients are above 50 kg/m2 (50-75 kg/m2: n=935, 20.5%; 75-100 kg/m2: n=107, 2.2%). A BMI value greater than 50 kg/m2 is often referred to as super MO (SMO). Beyond this designation, there does not appear to be any further categorization for the higher BMI patient. The 1,042 patients with a BMI greater than 50 kg/m2 were compared to the 35- to 50-kg/m2 BMI group. Patient positioning differed significantly between MO groups. The ramp rate for MO was 38.5%. However, if the SMO patients are evaluated separately (BMI 50-75 kg/m2 and BMI >75 kg/m2) from the overall MO group, the ramp rate differs significantly (33.9% in MO vs 51.4% in BMI 50-75 kg/m2 vs 74.8% in BMI >75 kg/m2). Figures 20 and 21 depict a marked improvement in airway access when an SMO patient is ramped versus supine. Patient preparation with TLA differed (15.1%, overall MO vs 21.4%, SMO; P<0.02). The use of accessory airway devices in both groups to manage the airway was similar with the bougie (8.1% vs 8.1%) and VAL (41% vs 40%), but the lower use of DL (37.3%, MO vs 30%, SMO) was offset by a significant increase in FOB utilization (7.9%, MO vs 18.2%, SMO). The first-pass laryngoscopy success differed (59.1%, MO vs 49%, SMO; P<0.02), but 3+ attempts were 50% higher (15.7%, MO vs 23.7%, SMO; P<0.01). Desaturation of any level (SpO2 <90%) was similar (21.2%, MO vs 25.6%, SMO), but reductions of SpO2 <80% differed by 50% (9.7%, MO vs 13.4%, SMO; P<0.02). Bradycardia, regurgitation, aspiration, new-onset dysrhythmia, and cardiac arrest rates differed little between both MO groups.
In further detailed analysis of the SMO group, comparing the complications and airway management trends between those who were positioned supine versus ramped revealed continued support for the ramped position. First-pass success differed significantly (41%, supine vs 60.5%, ramped; P<0.002), as did 3+ attempts (27.3% vs 18.5%; P<0.02). Overall success of DL differed between both positions (37.6%, supine vs 55.7%, ramped; P<0.001). The overall use of accessory airway devices (non-DL) was the same (71.7%, supine vs 70.7%, ramped), but the need to utilize a rescue device differed significantly (52.9%, supine vs 23.2%, ramped, P<0.02). The rate of VAL use was much lower in the supine group (31% vs 48.6%), but that may reflect the less popular and less often used ramp position in time Periods A and B (VAL not available). The rate of successful VAL-assisted intubation—when used alone—differed (82.5%, supine vs 92.5%, ramped). The overall VAL success rate rose to 93.8% (supine) vs. 95.5% (ramped) when accessory adjuncts were used with VAL (combined VAL + FOB or VAL + bougie-assisted endotracheal tube [ETT] advancement when the ETT tip was “hung-up” on the anterior tracheal wall–cricoid ring).
The rate of airway management maladies for the SMO group was likely held in check by the effort put forth to ramping this larger-sized patient group. The above reported complications and intubation trends would have suffered further if the majority of patients in the SMO group had been managed in the supine position. Conversely, if the rate of ramping of the MO group (39.4%) was more reflective of the positioning of the SMO group, the number of complications and intubation trends for the MO group likely would have been reduced.
In summary, effort expended to improve positioning of MO and SMO patients appears warranted and justified. The advantages of the ramped position appear to be numerous, and are reflected in a reduction in the rate of airway- and hemodynamic-related complications as well as an improved first-pass success rate, fewer attempts and less reliance on emergency deployment of accessory airway devices. In many cases, MO and SMO patients can be managed with conventional laryngoscopy in the supine position (eg, with pear-shaped individuals with minimal difficult airway characteristics). Not all ramped patients are straightforward, nor are supine MO patients necessarily difficult to manage, but the likelihood of intubation difficulty and its consequences are reduced in the ramped MO patient population undergoing NOREI.
NOREI is fraught with patient safety concerns. With considerable effort, time, and expense focused on implementation of the equipment recommendations put forth by the ASA guidelines, it appears that the patient safety profile has undergone significant transformation toward lowering airway- and hemodynamic-related complications for patients undergoing NOREI. The MO population appears at much higher risk for intubation consequences than the lean population, although we have made great strides toward improving airway management for both groups. The MO group has benefited greatly from immediate bedside deployment of accessory airway devices and EtCO2equipment. Practice trends indicate that elective use of DL has declined significantly in favor of VAL or other accessory devices, for example, FOB, as a primary approach for securing the airway. Moreover, since the introduction of VAL, the use of other accessory airway devices (bougie, SAD, FOB, etc) has fallen significantly since their previous roles in Plans B and C. This use of VAL followed DL difficulty or failure. Nonetheless, these accessory devices remain prominent in a backup role for not only DL but now for VAL.
Positioning of MO patients is an important component of NOREI care. Effort spent to place MO patients in a nonsupine position may be rewarded with improved respiratory mechanics and improved airway intervention and its management. The ramped position is particularly advantageous when deploying DL, but VAL will also benefit. TLA alone or combined with light dosing of a sedative-hypnotic or anxiolytic induction appears to offer a superb safety profile and allows the practitioner to address the airway with a variety of primary and secondary approaches.
The SMO group (BMI >50 kg/m2) appears to benefit greatly from the combination of ramping and TLA preparation for intubation. These improvements in patient safety during NOREI are based on the incorporation of accessory airway devices in accordance with the suggestions put forth by the ASA Task Force on Management of the Difficult Airway. A reduction in those requiring 3+ attempts is key to reducing complications. Aggressively incorporating accessory airway devices appears to be warranted toward improving patient safety. Obese, MO, and SMO populations, as with other patient populations, should experience enhanced safety when accessory airway devices are readily available by experienced personnel.
1. Obesity-associated comorbidities potentiate complications in the perioperative period. Nearly every aspect of respiratory mechanics is affected. Decreased chest wall compliance with accessory muscle use, decreased FRC, and a hypermetabolic state contribute to higher rates of hypoxia with more rapid desaturation.
2. It remains unclear whether obesity and higher BMI lead to more difficulty with intubation in the elective setting. It would appear that NOREI in the MO population is more difficult. Conversely, obesity does not make airway management easier. A widened neck circumference, Mallampati class III or IV score, and OSA are predictors of potential difficult intubations and ventilation.
3. The prevalence of obesity is increasing, as is the degree of obesity, with more patients in higher BMI categories. Management schema and access to advanced airway adjuncts should be stepped up to meet these challenges inside and outside the OR.
4. Optimizing patient positioning prior to airway manipulation is imperative. Aligning the ear canal at or above the level of the sternum is a reasonable goal that can be achieved with—singly or in combination—reverse Trendelenburg, ramping, HELP, or head-of-bed elevation combined with neck extension. Positioning can be achieved with towels, preformed supports, air baffle supports, bed position adjustments, or a hybrid approach with a combination of several methods to customize positioning for variable body shapes and sizes.
5. Advantages of the ramped position include improved pulmonary mechanics, improved alignment of the 3 axes for airway management, improved access to the submental–neck area, improved mouth opening and access to the oral cavity, and improved ability to mask ventilate.
6. Overall, non-OR emergency intubations have a significantly higher rate of complications compared with their elective counterparts in the OR. Management difficulties and complications were highest prior to the institution’s advanced preparation to ensure bedside access to airway equipment, in accordance with the ASA guidelines (Period A-DL was the primary mode). Marked improvements in patient safety were ushered in following implementation of guidelines recommendations outside the OR (Period B). The effect of limiting DL attempts combined with earlier use of accessory airway devices (SAD, bougie, and FOB) was impressive. Management difficulties and complications have decreased further with the advent and ubiquitous distribution of VAL (Period C).
7. Despite advances in airway management, there are differences between lean and obese patients in the emergency non-OR setting. The obese group had a lower first-pass success rate, a higher rate of 3+ attempts with DL, more instances of desaturation, and a marked increased requirement for accessory devices to secure the airway. Overall, however, the advancement in airway management has decreased the incidence of airway and hemodynamic complications in both the lean and obese groups (Periods A<2192>B<2192>C).
8. A marked decline in airway- and hemodynamic-related complications in MO patients has been achieved. Ready access to advanced equipment and its deployment are important contributing factors. Moreover, a progressive shift away from supine positioning over the 3 time periods (Period A, 12.7% ramped<2192>Period C, 47% ramped) also should garner credit. MO patients in the supine position experienced a far higher failure rate with DL compared with those ramped, a marked increase use of accessory airway equipment, and a commensurate increase in airway- and hemodynamic-related complications. Furthermore, first-pass success with VAL was more successful in the ramped group.
9. Topical anesthesia with awake (±) light sedation has significant advantages in a suspected or known difficult airway patient. Primarily, this burns few bridges and maintains a spontaneously breathing patient who can be managed with most airway adjuncts, most notably FOB and VAL. Topicalization of local anesthesia to the airway can be accomplished fairly quickly in the NOREI setting with minimal provisions.
10. TLA combined with the ramped position in MO patients was associated with higher first-pass success and a markedly reduced instance of regurgitation, aspiration, significant hypoxia, cardiac arrest, and the need for a surgical airway.
11. Departmental and institutional efforts focused on improving the safety record of NOREI have benefited greatly from the recommendations offered by the ASA’s guidelines. Our database suggests we have greatly reduced the airway- and hemodynamic-related complications in NOREI and improved patient safety.
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