Gas Exchange Abnormalities in Mild Bronchitis and Asymptomatic Asthma

Abstract

Alveolar arterial tension differences for oxygen, and ratios of physiologic dead space to tidal volume measured at rest, were significantly greater in eight patients with mild bronchitis and seven with asymptomatic asthma as compared to normal controls. Routine pulmonary-function tests, including pulmonary resistance, gave normal or only minimally abnormal results. On exercise, oxygen tension differences became normal in three patients with bronchitis and four with asthma but remained abnormal in the others. Ratios of dead space to tidal volume were normal on exercise in only one bronchitic and three asthmatic patients. Abnormalities of ventilation distribution and gas exchange occur before other abnormalities of lung function become apparent.