Nasal cannula with graphic display of respiratory rate and pattern is the most sensitive detector of respiratory depression during therapeutic endoscopy

Background: Previous studies have suggested that measurement of transcutaneous CO₂ (TCO₂) is the most accurate indicator of oversedation during upper endoscopy. However, TCO₂ is cumbersome and not practical for clinical use. Purpose: To determine if a nasal cannula with a sidestream CO2 detector is a more sensitive indicator of oversedation than standard monitoring techniques. Methods: Patients having therapeutic upper endoscopy underwent standard monitoring. Additionally, nasopharyngeal carbon dioxide measurements were obtained using a sidestream CO₂ detector and a nasal cannula as a sampling device. This method provides graphic display of respiratory rate and pattern as well as continuous CO₂ monitoring. Both endoscopist and nursing personnel were blinded to the CO₂ values and graphic display. Apnea was defined as the absence of respiration for > 10 seconds. The occurrence of apneic episodes was compared to the frequency with which pulse oximetry, CO₂ monitoring, and nursing personnel detected a compromise in the patient's respiratory status. Results: A total of 47 apneic episodes occurred in four of eight patients with a mean duration of 24.6 seconds (range 10-100 seconds, median 19 seconds). Total No. Apneic Episodes No. Episodes Detected by Pulse Oximetry (%) No. Episodes Detected by Co₂ Monitor (%) No. Episodes Detected by Nursing Personnel (%) 47 2 (4%) 0 (0%) 2 (4%) Ten apneic episodes 40 seconds or greater in duration were not detected by nursing personnel, pulse oximetry and CO₂ monitoring. Conclusions: 1) Apneic episodes occur frequently during therapeutic upper endoscopy 2) Current monitoring techniques for sedation and analgesia are inadequate to detect apnea. 3) Graphic display of the respiratory rate and pattern is a more sensitive indicator of respiratory depression than CO₂ monitoring.