Clinical usefulness of end-tidal CO measured using a portable capnometer in patients with respiratory disease.

INTRODUCTION

This study aimed to evaluate the correlation and agreement between end-tidal CO (EtCO ) measured with the novel portable capnometer (CapnoEye®) and partial pressure of arterial carbon dioxide (PaCO ) levels in patients with respiratory diseases and to compare the efficacy of EtCO and PvCO in predicting PaCO levels.

METHODS

We analyzed the correlation and the agreement between EtCO and PaCO and between PvCO and PaCO using Pearson's moment correlation coefficient in patients with type 1 and type 2 respiratory failure and both groups overall.

RESULTS

A total of 100 samples were included that comprised 67 men (67%). The mean age of the subjects was 77 ± 13 years. Chronic obstructive pulmonary disease (COPD) (43%) was the most common disease. There was a high correlation between EtCO and PaCO (r = 0.88; p < 0.0001). Sixty-six PvCO samples were obtained, and there was a high correlation between PvCO and PaCO (r = 0.81; p < 0.0001). Regarding type 2 respiratory failure, there was a high correlation between EtCO and PaCO (r = 0.81). The Bland-Altman analysis between PaCO and EtCO revealed a bias of 5.7 mmHg, with limits of agreement ranging from -5.1 mmHg to 16.5 mmHg. In contrast, the analysis between PaCO and PvCO revealed a bias of -6.8 mmHg, and the limits of agreement ranged from -22.13 mmHg to 8.53 mmHg.

CONCLUSION

EtCO measured by CapnoEye® was significantly correlated to PaCO levels in patients with respiratory diseases. Moreover, CapnoEye® may be more useful for predicting hypercapnia conditions in which respiratory diseases are compared with measure PvCO .