PurposeThe PRediction of Opioid-induced respiratory Depression In patients monitored by capnoGraphY (PRODIGY) trial was a multicenter prospective trial conducted to develop a risk prediction score for opioid-induced respiratory depressive (OIRD) episodes. Several subjects in the PRODIGY trial developed critical respiratory depressive events, which were qualified as reportable adverse events (AEs). In this study, we determine whether those patients also had an episode of OIRD as detected by continuous capnography and pulse oximetry leading up to the critical clinical event.MethodsBlinded capnography and pulse oximetry data from PRODIGY patients who had critical respiratory depressive AE were reviewed. The occurrence and timing of OIRD episodes were recorded in relationship to the AE.ResultsOf the 1335 subjects in PRODIGY, 7 patients had 8 reportable pulmonary AE and 187 OIRDs (150 apnea episodes, 14 bradypnea episodes, 23 hypoxic episodes) with median 12 (5–19.5) OIRDs per patient. Five patients were monitored before the AE, and multiple preceding OIRD episodes were detected. One patient had 2 AE, the first (hypoxemia) was recognized upon application of pulse oximetry. This patient subsequently had multiple OIRDs until the second AE occurred (somnolence requiring naloxone administration). Another patient’s AE (hypotension and bradypnea) was recognized upon monitor application and subsequently had many OIRD episodes.ConclusionsIn the PRODIGY trial, patients who had a pulmonary AE had multiple preceding OIRDs detected by continuous capnography and pulse oximetry. When monitoring was initiated before the AE, numerous OIRDs, mostly apneic episodes preceded AE, suggesting continuous monitoring of both ventilation and oxygenation may allow for early detection and possible prediction of future clinical decompensation.