Respiratory arrest in near-fatal asthma BACKGROUND AND METHODS. The majority of asthma-related deaths occur outside the hospital, and therefore the exact factors leading to the terminal event are difficult to ascertain. To examine the mechanisms by which patients might die during acute exacerbations of asthma, we studied 10 such patients who arrived at the hospital in respiratory arrest or in whom it developed soon (within 20 minutes) after admission. RESULTS. The characteristics of the group were similar to those associated in the literature with a high risk of death from asthma, including a long history of the disease in young to middle-aged patients, previous life-threatening attacks or hospitalizations, delay in obtaining medical aid, and sudden onset of a rapidly progressive crisis. Extreme hypercapnia (mean [+/- SD] partial pressure of arterial carbon dioxide, 97.1 +/- 31.1 mm Hg) and acidosis (mean [+/- SD] pH, 7.01 +/- 0.11) were found before mechanical ventilation was begun, and four patients had hypokalemia on admission. Despite the severe respiratory acidosis, no patient had a serious cardiac arrhythmia during the resuscitation maneuvers or during hospitalization. We observed systemic hypertension and sinus tachycardia in eight patients, atrial fibrillation in one, and sinus bradycardia in another. In both patients with arrhythmia the heart reverted to sinus rhythm immediately after manual ventilation with 100 percent oxygen was begun. The median duration of mechanical ventilation was 12 hours, and all patients had normocapnia on discharge from the hospital. CONCLUSIONS. We conclude that at least in this group of patients, the near-fatal nature of the exacerbations was the result of severe asphyxia rather than cardiac arrhythmias. These results suggest that undertreatment rather than overtreatment may contribute to an increase in mortality from asthma. 