Capnographic Monitoring of Extubated Postoperative Patients

Abstract

Postoperative respiratory monitoring of surgical patients requires assessment of both oxygenation and ventilation. Arterial blood gas (ABG) measurements traditionally have been used to detect elevated arterial carbon dioxide (Paco₂) concentrations. The recent availability of a noninvasive technique for end-tidal CO, measurements (Etco₂) may allow substitution of this real-time modality for the more cumbersome blood gas determinations. This study examines 41 extubated postoperative patients monitored with both modalities and evaluates whether capnography can replace routine blood gas determinations in selected patients. Paired ABG and Etco₂ measurements were obtained at 30 and 90 min afer admission to the recovery room. A new nasopharyngeal catheter was employed to obtain exhaled gas samples for Etco₂ measurement. Overall, Etco₂ was lower than Puco₂ by 2.8 torr (p <. 05), with a precision of ± 2.6 torr. Correlation between Etco₂ and Paco₂ was excellent (r = 0.87, p <. 01). We conclude that on-line Etco₂ measurements provide a useful substitute for routine ABG determinations of Paco₂ in selected patients. The nasopharyngeal catheter provides both a patent airway and undiluted gas for evaluation. This methodology can improve patient comfort and safety considerably while decreasing cost and discomfort.

Key Words:

• monitoring
• capnometry
• carbon dioxide