Head elevation before direct laryngoscopy may substantially increase the likelihood of obtaining a better laryngeal view, making it the ideal starting point when difficult visualization is expected, research has shown.
A research team led by Mohammad El-Orbany, MD, professor of anesthesiology at the Medical College of Wisconsin, in Milwaukee, studied the effects of head elevation on 167 patients scheduled to undergo elective surgery with endotracheal intubation.
Patients who had their heads raised 6 cm by the pillow—the so-called sniffing position—showed better glottic exposure before direct laryngoscopy than simply positioning the patient’s head flat on the operating table. The study also found that in most cases, an “elevated sniffing position” (in which the back of the head is raised 10 cm by an inflatable pillow) proved to be superior for visualization in most cases.
The authors also found that in no case did head elevation actually worsen the laryngeal view.
“We should revisit the traditional head position,” Dr. El-Orbany said. “This study proved that even more elevation [than the traditional sniffing position] improves the view and that maybe this is a better starting position before direct laryngoscopy.”
Doctors at Illinois Masonic Medical Center, in Chicago, performed direct laryngoscopy on each of the patients, alternating through the three different head positions—flat, sniffing and elevated sniffing—to assess the views that best exposed the glottis.
An inflatable pillow, designed by Dr. El-Orbany and his team to provide various degrees of head elevation, was used during the study. A Macintosh blade, size 3 or 4, was used during the procedures, the researchers explained.
The order in which each patient was put through the three different head positions was selected at random, with “computer-generated, sealed envelopes containing one of six possible sequences,” Dr. El-Orbany noted.
Other safeguards were also taken. The three laryngoscopists who performed the procedures at Illinois Masonic Medical Center went through special training to minimize a factor that could have skewed the results—given that greater exertion might improve the view of the glottis on its own, the doctors practiced using the same exact lifting force with the laryngoscope blade in each head position.
In the majority of the cases studied, the best laryngeal views were obtained in patients whose heads were elevated either 6 or 10 cm.
More than 46% of patients whose heads were elevated by 10 cm offered the best view possible of their glottises; specifically, a 1a on the Cormack-Lehane classification system, as modified by Benumof. All of the patient’s vocal cords, including the anterior commissure, could be visualized, Dr. El-Orbany noted.
Of the patients whose heads were elevated by 6 cm, 34% scored in this top category compared with 24% of patients whose heads were not elevated. In fact, nearly all the patients whose heads were elevated earned either the top or next best viewing grade on the scale.
Of patients with no head elevation, 33% were grade 2 and only the arytenoids could be seen, with the vocal cords hidden from view. By comparison, only 15.6% of patients in the sniffing position and 6% of those in the elevated sniffing position were judged to be in this obstructed-view category.
The most significant group is the difficult laryngoscopy group in whom only the epiglottis could be visualized (grade 3); 8.4% of patients in the head-flat position fell into this category. This incidence decreased to 2.4% for patients in the sniffing position and 1.2% for those in the elevated sniffing position.
Other Studies Flawed
This study is the most comprehensive to date and provides strong support for head elevation after years of contradictory reports on the issue, Dr. El-Orbany said. “One of the strengths of our study was the sample size,” he said. “It was large enough to draw meaningful conclusions. It was not [just] seven or 10 patients.”
Previous studies have been clouded by a number of limitations and errors, he explained. A study by Hubert J. Schmitt, MD, and Harald Mang, MD, reported that relatively poor laryngeal views improved in 19 of 21 patients when their heads were elevated beyond the sniffing position (J Clin Anesth 2002;14:335-338). But the researchers also used external laryngeal manipulation and increased lifting force, making it difficult to isolate the role played solely by elevating the patients’ heads.
A 1999 study found better laryngeal views with head elevation (Ann Otol Rhinol Laryngol 1999;108:715-724). But the researchers used an uncommon laryngoscope blade, and the nomenclature they used for each head position was confusing when applied to the accompanying illustrations, Dr. El-Orbany wrote.
A 2003 study analyzed the effects of head elevation on laryngeal view using seven fresh human cadavers, the results of which were videotaped (Ann Emerg Med 2003;41:322-330). Richard M. Levitan, MD, and his team found that head elevation improved the view in all seven cadavers. But the head positions were not chosen at random and the head-flat position revealed 30% of the vocal cords, casting into doubt the value of this maneuver for a true difficult laryngoscopy situation, in which no vocal cords can be seen, according to Dr. El-Orbany.
More recently, a South Korean team compared laryngoscopic views on patients in the head-flat position with those propped up with 3-, 6- and 9-cm pillows (J Anesth 2010;24:526-530).
The study reported that the highest head elevation yielded the most favorable results. But the researchers had to remove and insert various pillows before examining each view, which could have “altered the final blade’s position during each attempt,” Dr. El-Orbany said.
An earlier study found no advantage to elevating patients’ heads after working with eight fully conscious volunteers (Anesthesiology 2001;94:83-86). Their heads, however, were not placed in a proper sniffing position, nor was laryngoscopy performed on any of the volunteers, Dr. El-Orbany noted.
“All those studies had some flaws in the methodology, or the sample size, or the conclusions,” he said. “The strength of our study is that it isolated the effect of head elevation on laryngeal exposure in a large number of subjects.”