The correlation and level of agreement between arterial blood gas PCO2 and end-tidal CO2 in patients with chronic obstructive pulmonary disease exacerbation

Chronic Obstructive Pulmonary Disease (COPD) represents a major public health problem. The course of COPD is characterized by episodic periods of worsening symptoms، termed exacerbations. Supplemental oxygen should be given to patients with COPD exacerbation without causing CO2 retention. Arterial blood gas sampling is the gold standard for monitoring adequate oxygenation and for assessing CO2 retention. Capnography is a noninvasive method based on measurement of end tidal carbon dioxide (ETCO2)، which in this article we aim to evaluate the relationship between end-tidal carbon dioxide pressure (ETCO2) and arterial partial pressure of carbon dioxide (PaCO2) in patients with COPD exacerbation.

This was a cross-sectional study carried out in 75 patients with COPD exacerbation between the ages of 41 and 85 who required hospitalization in second half of year 2010. Measurements of ETCO2 and PaCO2 were taken by ABG and capnography simultaneously: 1) at admission، 2) 30 minutes after treatment with supplemental oxygen and bronchodilators.

There was a significant correlation between ETCO2 and PaCO2 at both stages (correlation coefficient: 0. 773 and 0. 783، respectively). The mean (SD) difference for PaCO2 and ETCO2 were: 9. 99 (7. 17) and 9. 97 (6. 84) mmHg، respectively. Further analysis with Bland-Altman showed agreement between results of capnography and ABG in both stages of this study.

In this study we found strong correlation and agreement between arterial blood gas pco2 and end-tidal co2 results in patients with Chronic Obstructive Pulmonary Disease exacerbation.