Author: Michael Vlessides
Accurate screening for obstructive sleep apnea (OSA) may be possible using a point-of-care ultrasound screening (PoCUS) tool, which would help avoid the pitfalls of OSA screening questionnaires.
“We currently have several screening tools to help identify people with OSA,” said Mandeep Singh, MD, an assistant professor of anesthesia at the University of Toronto. “But the problem is that these tools are all questionnaires, which tend to have a high percentage of false positives. And these high false-positive rates end up being a drain on health care costs and resources, due to increased monitoring and specialized postoperative care that may have been otherwise avoided.
An Ongoing Effort
Dr. Singh and his colleague Vincent Chan, MD, are leading a multidisciplinary team of experts in anesthesiology, PoCUS, sleep medicine and clinical epidemiology. At the time of study presentation at the 2019 annual meeting of the Canadian Anesthesiologists Society (abstract 638231), the researchers had enrolled 87 patients in the trial, all of whom were scheduled to undergo elective, noncardiac surgery. All participants had a previous diagnosis of OSA and were either noncompliant with treatment or deemed to be high risk (STOP-Bang score, >3).
Patients underwent preoperative clinical and airway examinations, as well as OSA screening with the STOP-Bang questionnaire. Each patient also underwent surface airway ultrasound scanning of the upper airway and head/neck structures.
A variety of dimensions were measured, including:
Clinicians rated the quality of ultrasound image acquisition and ease of performance on a 5-point Likert scale.
Dr. Singh said 243 patients were prescreened in the preoperative clinic, of whom 87 completed ultrasound scanning (mean age, 52.3±14.0 years; 38 were female). The majority of the patients were scheduled to undergo orthopedic surgery, general surgery or bariatric procedures, and their median STOP-Bang score was 5 (range, 3-8).
Refining the Parameters
Although the study is ongoing, analysis to date found that data acquisition was completed for all predefined dimensions in the preoperative period. The total time required for a complete ultrasound examination using the point-of-care tool was 29±7 minutes, and most individual parameters could be captured within one to three minutes.
“Our ultimate goal for the ultrasound tool is that it won’t take longer than 15 minutes. If there is good diagnostic performance compared to the current gold standards, then we’ll have an alternative point-of-care tool,” Dr Singh said.
Clinicians’ qualitative assessment of image acquisition and ease of performance was rated as either good or very good for tongue base thickness, upper airway length, mandible-to-hyoid distance, thyrohyoid membrane and subcutaneous fat tissue thickness at the hyoid bone. Their assessment was fair for distance between the lingual arteries, internal carotid artery intimal media thickness and anterior neck soft tissue thickness at the hyoid bone. Finally, image acquisition and ease of performance for pharyngeal air passage and lateral pharyngeal wall thickness were rated as either difficult or very difficult.
These preliminary data will help determine the feasibility of performing preoperative PoCUS screening for OSA within half an hour. However, the investigators acknowledged that the potential clinical applications of the novel tool remain unclear and require further validation.
“We are also going to look into how the point-of-care ultrasound tool performs when we combine it with the current OSA screening tools, such as the STOP-Bang questionnaire, and what additional information it provides,” Dr. Singh said.
“I think this is a very important study,” commented David T. Wong, MD, a professor of anesthesia at the University of Toronto, who was not involved in the study. “I think if you begin with an OSA questionnaire, then you can add this ultrasound test for added value. Because if patients are deemed to be high risk on the STOP-Bang criteria, then they should be treated as if they have OSA. But this test will increase the certainty of OSA diagnosis.”
Dr. Wong also urged the investigators to simplify their ultrasound test to make it more user-friendly. “You are currently measuring quite a few parameters,” he said. “I think you need to make it simpler and boil it down to the three or four that are the most useful.”