Evaluation of Capnography in Nonintubated Emergency Department Patients with Respiratory Distress

Objective: To evaluate the ability of noninvasive capnographic measurement of end‐tidal CO 2 tension (Petco 2 ) to predict artenal CO 2 tension (Paco 2 ) in nonintubated ED patients with respiratory distress Methods: A prospective, nonblind study was performed in a level I trauma centerkommunity teaching hospital ED. Participants included all nonintubated adult patients with respiratory distress requiring measurement of arterial blood gases (ABGs): 29 patients were enrolled Petco z was measured with a capnography monitor. using both baseline tidal volumes and forced expiratory volumes. The bias between Petco ? values and simultaneous measurements of Paco 2 by ABG was assessed Results: Petco, measured with forced expiration, and Pace ? agreed well, with bias (i.e, average difference) = 044 ± 0.52 kPa (33 ± 3.9 torr). Petco 2 measured with the tidal volume breath produced an unacceptably high bias of 0.82 ± 0.70 kPa (6.1 ± 5.2 torr). Levels of agreement between Paco 2 and Petco 2 were similar for smokers and nonsmokers and for men and women. The arterial‐end‐tidal CO 2 tension (Pa‐etco 2 ) difference was not related to Paco 2 Pa‐etco 2 correlated with age (r = 0.473; p = 0.01), and was significantly higher in patients with pulmonary disease (132 ± 0S6 kPa; 99 ± 42 torr) than it was in those without pulmonary disease (0.46 ± 055 kPa, 3.5 ± 4.1 torr, p < 0.001). Conclusions: Noninvasive Petco z monitoring may adequately predict Paco 2 in nonintubated ED patients with respiratory distress who, are able to produce a forced expiration. Petco 2 is less accurate for Paco 2 with tidal volume breathing and in patients with pulmonary disease