ETCO2 and Mental Status

Monitoring Mental Status

In an article in the October 2006 American Journal of Emergency Medicine, Noninvasive capnometry for continuous monitoring of mental status: a tale of 2 patients, authors Davis and Patel describe how capnography was used in the case of two similar unresponsive drug overdose patients to aid in the decision to intubate or not.

One patient with a stable ETCO2 was observed for three hours during which she eventually regained consciousness. The other patient had an initial ETCO2 of 33 that gradually rose to 41 over 45 minutes when the decision to intubate was made. That patient remained obtunded for three days.

The authors write: “In each of these cases of suspected overdose with nearly identical presentations, continuous noninvasive capnography was successfully used to monitor the depth of sedation and assist in the decision regarding intubation for airway protection. In the first case, the consistency in ETCO2 values correctly indicated a less severe overdose, with return to normal consciousness in the ED. In the second case, a gradual rise in ETCO2 suggested a decreasing level of consciousness despite the absence of a clear trend in GCS scores. The decision to perform intubation appeared to be justified by her prolonged obtundation...”

The bottom line of this case report is the suggestion that ETCO2 trending is a valuable indicator of the depth and direction of consciousness. While it has previously been used to monitor patients receiving medical sedation to prevent them from lapsing into hypoventilation, it can also be used to monitor EMS patients to gauge the depth and trend of their responsiveness.