Capnography monitoring in nonintubated patients with respiratory distress

ObjectiveThe objective was to assess agreement between end-tidal carbon dioxide values measured by a handheld capnometer (Petco2) and values measured by a blood gas analyzer (Paco2) in nonintubated patients with respiratory distress in an out-of-hospital setting.MethodsThis prospective study compared Petco2 values obtained by an end-tidal capnometer (Microcap Plus; Oridion Capnography Inc, Needham, Mass) to Paco2 values by the Bland and Altman statistical method.ResultsA total of 50 patients were included. Continuous Petco2 monitoring was easily performed in all 50 patients during ambulance transport, but blood gas analysis failed in 1 patient. Agreement between the 2 methods was poor with a bias (mean difference) between Petco2 and Paco2 measurements of 12 mm Hg and a precision (SD of the difference) of 8 mm Hg. The gradient between Petco2 and Paco2 was greater than 5 and 10 mm Hg in 41 and 25 patients, respectively.ConclusionsPetco2 measurements poorly reflected Paco2 values in our population of nonintubated patients with respiratory distress of various origins.