Ventilation and pulmonary gas exchange at rest and during exercise in boys with bronchial asthma.

During symptom-free periods pulmonary ventilation and alveolar gas exchange was determined in 14 boys with bronchial asthma during submaximal and maximal exercise. In six of these boys studies were also made at rest. At rest there was slight hyperventilation as indicated by decreased PCO2. There was also a lowering of the arterial PO2 and all boys had an increased alveolar-arterial oxygen tension difference. During exercise, there was a sharp increase in pulmonary ventilation with values similar to those encountered in trained healthy boys; there was also a tendency towards normalization of the arterial blood gases and alveolar-arterial oxygen tension difference. This indicates either more even pulmonary ventilation and better distribution of pulmonary perfusion or more even distributions of ventilation and perfusion during physical work in sitting position. Thus, boys with bronchial asthma show good respiratory adaptation to heavy exercise. One boy developed a severe asthmatic attack during exercise and, before the symptoms developed, had a dramatic fall in the arterial PO2 with an unchanged PCO2. The possibility of a sudden drop in arterial PO2 should be kept in mind when children with bronchial asthma perform physical exercise.