The Role of Bronchodilators in Bronchospastic Disease

Abstract

The role of bronchodilators in lung disease was investigated. It was found that 90% of patients sent for lung function tests have obstructive airways disease. Of these, 75% benefited from inhalation of a bronchodilator, the average improvement being a 26% increase in FEV_1• Examination of the changes in arterial oxygen showed that although there was on the average a small significant drop in arterial oxygen, there were sometimes quite significant rises too. The falls tended to occur from high arterial oxygen pressures, while those who had low resting values showed a small fall, no change or even a rise in Pao₂. These changes correlated with indirectly initiated changes in alveolar ventilation, an increased alveolar ventilation tending to cause a decrease in arterial oxygen and vice versa.The mechanism for this is thought to be part of the control of ventilation perfusion matching, for even in normals made to hyperventilate there is a widening of the alveolar:arterial oxygen gradient as the Paco₂ falls.