MECHANISM OF RESPIRATORY ARREST IN AN ANIMAL-MODEL OF ACUTE FATAL BRONCHOCONSTRICTION

The cause of respiratory arrest in acute asthma is not known. By its n ature, respiratory arrest is difficult to study clinically The possibl e causes of respiratory arrest include cardiovascular dysfunction, res piratory muscle fatigue, and central respiratory failure. We used a do g model of respiratory arrest in acute bronchoconstriction that examin ed the effects of hypoxemia and intrinsic loading in an attempt to est ablish the mechanism. Our hypothesis was that, in a setting of hyperem ia and intrinsic loading similar to human fatal asthma, respiratory ar rest is caused by a central respiratory failure, more specifically, fa ilure of the central rhythm generator. We studied 18 dogs divided into 1) an intrinsically loaded group, 2) a hypoxemic group, and 3) both a loaded and a hypoxemic group. Intrinsic loading was induced with meth acholine combined with selective beta(2)-blockade, and the hypoxemia w as controlled by varying inspired O-2 fraction. Respiratory arrest occ urred only in animals with both hypoxemia and intrinsic loading. We fo und no evidence of hemodynamic instability or respiratory muscle fatig ue. Instead, there was an abrupt cessation of ventilation while the in tensity of the central neural output was maintained. Our results are c onsistent with a failure of the central rhythm generator as the causal agent in respiratory arrest.