Validation of a measurement to predict upper airway collapsibility during sedation for colonoscopy

Techniques to quantify the effects of sedation on upper airway collapsibility have been used as research tools in the laboratory and operating room. However, they have not been used previously in the usual clinical practice environment of colonoscopy sedation. The propensity for upper airway collapsibility, quantified as the critical pharyngeal pressure (P(crit)), was hypothesized to correlate with the need for clinical intervention to maintain ventilation. Twenty patients scheduled for colonoscopy with sedation were prospectively recruited to undergo measurement of upper airway collapsibility using negative airway pressure (NAP) provocation with a minimum pressure of -18 cmH(2)O. The P(crit) was the negative pressure that collapses the airway, either directly or by extrapolation from the pressure-flow relationship. An exponential transformation was applied to the P(crit) data for statistical analysis. A clinical intervention score (CIS) was used to quantify required interventions by the sedation nurse. The measurement of the P(crit) during sedation was significantly larger (less negative) than both the baseline ("awake") (P = 0.0029) and late recovery (P = 0.01) values. The CIS was not predicted by the transformed baseline or sedated P(crit) with or without including demographics associated with sleep apnea syndrome. Although the NAP technique showed the expected changes with sedation in this clinical situation, we did not find that it predicted the need for clinical intervention during endoscopy. Our study was not large enough to test for subpopulations in which the test might be predictive; further studies of these particular groups are needed to determine the clinical utility of the NAP measurement.