Clinical usefulness of end‐tidal CO(2) measured using a portable capnometer in patients with respiratory disease

INTRODUCTION: This study aimed to evaluate the correlation and agreement between end‐tidal CO(2) (EtCO(2)) measured with the novel portable capnometer (CapnoEye®) and partial pressure of arterial carbon dioxide (PaCO(2)) levels in patients with respiratory diseases and to compare the efficacy of EtCO(2) and PvCO(2) in predicting PaCO(2) levels. METHODS: We analyzed the correlation and the agreement between EtCO(2) and PaCO(2) and between PvCO(2) and PaCO(2) 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(2) and PaCO(2) (r = 0.88; p < 0.0001). Sixty‐six PvCO(2) samples were obtained, and there was a high correlation between PvCO(2) and PaCO(2) (r = 0.81; p < 0.0001). Regarding type 2 respiratory failure, there was a high correlation between EtCO(2) and PaCO(2) (r = 0.81). The Bland–Altman analysis between PaCO(2) and EtCO(2) 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(2) and PvCO(2) revealed a bias of −6.8 mmHg, and the limits of agreement ranged from −22.13 mmHg to 8.53 mmHg. CONCLUSION: EtCO(2) measured by CapnoEye® was significantly correlated to PaCO(2) 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(2).