Capnography Accurately Detects Apnea During Monitored Anesthesia Care

Abstract

Apnea and airway obstruction are common during monitored anesthesia care (MAC). Because their early detection is essential, we sought to measure the efficacy of capnography as an indicator of apnea during MAC at a variety of oxygen flow rates compared with thoracic impedance. Anesthesia care providers using standard American Society of Anesthesiologists monitors were blinded to capnography and thoracic impedance monitoring. Ten (26%) of the 39 patients studied developed 20 s of apnea; none was detected by the anesthesia provider, but all were detected by capnography and impedance monitoring. There was no difference in detection rates between the two methods. Higher oxygen flow rates decreased the amplitude of the capnograph but did not interfere with apnea detection. This pilot study revealed that apnea of at least 20 s in duration may occur in every fourth patient undergoing MAC. Although these episodes were undetected by the anesthesia provider, they were reliably detected by both capnography and respiratory plethysmography. Monitoring of nasal end-tidal CO(2) is an important way to improve safety in patients undergoing MAC.

Procedural sedation and analgesia in a Canadian adult tertiary care emergency department: a case series

“…In an effort to identify all such cases, we used an SaO 2 of ≤90% at any stage during the procedure as indication of respiratory depression, while other authors used this saturation level for at least 30 seconds as a definition of desaturation. 29 Soto and colleagues 30 showed that apnea of >20 seconds occurred in 26% of the PSAs performed in their study, all of which were diagnosed by capnography. None were detected by the provider monitoring the patient.…”

“…None were detected by the provider monitoring the patient. 30 While recognizing apnea is important, reacting to very brief periods identified with capnography could induce caregivers to use positive pressure ventilation before oxygen desaturation, which could actually increase the danger of aspiration. If brief apnea was missed in some of our patients, the universally good outcome in our series suggests that detecting such apnea is probably unnecessary.…”

End-tidal capnometry during emergency department procedural sedation and analgesia: a randomized, controlled study

“…[17] Although the jury is still out regarding whether ETC improves patient safety during PSA, there is less of a doubt that apnea is common during the process and that ETC does detect this earlier than PO alone. Soto et al [5] showed that apnea of greater than 20 seconds occurred in 26% (10 of 39) cases of monitored anesthesia care/ sedation, all of whom were diagnosed by capnography, while none was detected by the provider monitoring the patient. Miner et al [1] found that in 74 patients undergoing PSA, 33 were diagnosed with RD, all of whom met the ETC criteria for RD, yet only 11 (33%) were detected by PO.…”

“…The standards are less categorical about the use of ETC in the ED because of the lack of evidence supporting its use. [3,5,6] …”

“…[1][2][3] End-tidal capnometry (ETC) has been shown to identify respiratory depression (RD), airway obstruction, apnea and laryngospasm earlier than PO, and theoretically offers a greater safety margin when monitoring patients. [1,[4][5][6][7][8] Other investigators, using different methods and definitions, found PO to reveal respiratory depression before ETC. [9] The use of combined PO and ETC has been strongly recommended.…”