Arterial Blood Gases in Bronchial Asthma

Abstract

Abstract Arterial blood gases were analyzed more than once on 63 patients with bronchial asthma during various phases of asthmatic attacks. The degree of airway obstructive change was quantified by measuring the one-second forced expiratory volume (FEV 1 ) and expressing this measurement as a percentage of the predicted FEV 1 . Measurements performed on 13 normal adults were used as controls. Pco 2 did not change much until a very severe degree of airway obstruction was encountered, in which case Pco 2 tended to increase. Despite the maintenance of a normal Pco 2 in most of the subjects, there was a linear fall in Po 2 with increasing severity of airway obstruction. So 2 showed almost no changes when the degree of airway obstruction was not marked but decreased significantly when the degree became severe. The pH remained fairly constant, but when the degree of airway obstruction became severe, it tended to decrease. From these results, it appears that alveolar ventilation is maintained at a normal level during most asthmatic attacks, but the Po 2 falls in relation to the degree of obstruction, probably because of uneven ventilation. An elevated Pco 2 during an asthmatic attack appears to be an ominous sign.