Mechanisms of worsening gas exchange during acute exacerbations of chronic obstructive pulmonary disease

Abstract

This study was undertaken to investigate the mechanisms that determine abnormal gas exchange during acute exacerbations of chronic obstructive pulmonary disease (COPD). Thirteen COPD patients, hospitalized because of an exacerbation, were studied after admission and 38±10(±SD) days after discharge, once they were clinically stable. Measurements included forced spirometry, arterial blood gas values, minute ventilation (V'E), cardiac output (Q̄'), oxygen consumption (V'O2), and ventilation/perfusion (V'A/Q') relationships, assessed by the inert gas technique. Exacerbations were characterized by very severe airflow obstruction (forced expiratory volume in one second (FEV1) 0.74±0.17 vs 0.91±0.19 L, during exacerbation and stable conditions, respectively; p=.0.01), severe hypoxaemia (ratio between arterial oxygen tension and inspired oxygen fraction (Pa,O2/F(I,O2) 32.7±7.7 vs 37.6±6.9 kPa (245±58 vs 282±52 mmHg); p=0.01) and hypercapnia (arterial carbon dioxide tension (Pa,(CO2)) 6.8±1.6 v