Role of venous blood gases in hypercapnic respiratory failure chronic obstructive pulmonary disease patients presenting to the emergency department

Abstract

Background: Many patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) have type 2 respiratory failure (T2RF). Often arterial blood gases are not performed and correlation with venous blood gases (VBG) is controversial. The venous pH and bicarbonate (HCO₃ ) are useful, but VBG pCO₂ (PvCO₂ ) is considered too unpredictable.

Aim: To examine the utility of VBG in this cohort of patients.

Methods: A prospective study of AECOPD patients with T2RF presenting to the emergency department was performed. Patients being considered for non-invasive ventilation and who required an arterial blood gas were invited to participate. A subsequent VBG was also taken, and Bland-Altman plots were used for analysis.

Results: Sixty-three patients were included in this study. The limits of agreement for pH and HCO₃ were narrow. Wider limits of agreement with a systematic bias of 7.7 mmHg were noted with pCO₂ .

Conclusions: The utility of VBG pH and HCO₃ was again demonstrated. VBG pCO₂ in this cohort of patients may have a role in the assessment of patients with AECOPD. Further study is needed on the possible role of VBG in the management of such patients with T2RF particularly those using non-invasive ventilation.

Keywords: COPD; arterial blood gas; type 2 respiratory failure; venous blood gas.