Accuracy of respiratory inductive plethysmography for the diagnosis of upper airway resistance syndrome

Objective: To determine the sensitivity and specificity of quantitative respiratory inductive plethysmograph (RIP) compared with the "gold standard," nocturnal esophageal pressure (Pes) measurement, in the diagnosis of upper airway resistance syndrome (UARS) in adults. Methods: Fourteen consecutive patients without obstructive sleep apnea and suspected of having UARS underwent simultaneous measurement of Pes with a catheter and standard nocturnal polysomnography along with RIP. UARS events (RERAs, respiratory effort-related arousals) were identified by observing crescendo changes in Pes with a Pes nadir less than or equal to -12 cm H2O, followed by an arousal or microarousal, UARS was defined as greater than or equal to 10 RERAs per hour. For each patient, the ratio of peak inspiratory flow to mean inspiratory flow (PIFMF) measured by RIP was performed during quiet wakefulness and with 40 randomly selected breaths in the supine position for two conditions: stage 2 sleep, immediately prior to arousals in any sleep stage. The mean PIFMF (wake-sleep) was calculated for each condition. Results: The sensitivities and specificities, respectively, of RIP to distinguish UARS patients from non-UARS patients are from stage 2 sleep (67%, 80%), immediately prior to arousals (100%, 100%). For breaths occurring immediately prior to arousals, the mean PIFMF (wake-sleep) is greater than or equal to 0.13 for UARS patients and < 0.13 for non-UARS patients. Conclusion: The PIFMF measured by RIP allows for the most accurate identification of UARS patients when breaths are selected for analysis immediately prior to arousals.