Risk of Sleep Apnea During Sedation for Endoscopy: Are Current Diagnostic Guidelines Useful?

Abstract

Safety is a major goal in outpatient open access endoscopy centers for patients undergoing colon cancer screening. Sleep apnea is a concern for patients receiving sedation due to predisposition to upper airway obstruction, particularly when using propofol for sedation. Various risk assessment methods have been promoted in the anesthesia literature to aid risk stratification of patients for probability of apnea resulting from upper airway collapse. However, none of these tools are well validated. Aim: To determine the predictive value of all currently recommended sleep apnea screening methods, in patients undergoing endoscopic procedures. Methods: A prospective study was performed in patients undergoing outpatient colonoscopy. Patients known to have sleep apnea were excluded. Each patient was given a survey including the Berlin Questionnaire, Epworth Sleepiness Scale, and Stanford Sleepiness Scale. A physical examination was performed to determine each subject's “modified neck circumference,” (Flemons et al in 2002) “modified Mallampati grade,” and “tonsil grade.” Patients were carefully evaluated by an anesthesiologist and by portable sleep monitoring while undergoing colonoscopy. All studies were read by a board certified sleep medicine physician blinded to the results (JG). Results: Of the 20 patients enrolled in the study, 16 studies were complete enough to be included in data analysis. Seven patients were found to have positive studies (>5 apneas/hypopneas), and 9 had negative studies. In the positive sleep study group, 43% by Berlin questionnaire, 43% by Epworth, and 40% by Stanford score were determined to be at high risk for sleep apnea. In the negative study group, 33% by Berlin questionnaire, and 0% by Epworth and Stanford scores were determined to be at high risk. Modified Mallampati and Tonsil grades had no significant differences between the groups. The average BMI was identical in both groups (28.4 vs 28.4), and average modified neck circumference were similar (46.2 cm vs 45.6 cm). Inter-test comparability showed poor correlation between the six different screening tools. Conclusion: Risk assessment prior to sedation is critical in determining who may safely undergo colonoscopy in an outpatient ambulatory setting. This is the first study to evaluate the predictive value of various risk assessment methods for screening patients prior to colonoscopy. Our data suggests that Epworth and Stanford Scales may have good negative predictive values. However no risk assessment method revealed a high positive predictive value. Although our data is limited, we are currently evaluating these methods in a larger population.