Patterns of recovery of airflow obstruction in severe acute asthma

The speed and patterns of recovery of airflow obstruction were analysed in 209 patients receiving a standard therapeutic regime for severe acute asthma. Initial rates of recovery were rapid. Three-quarters of the patients had achieved 50% of their total improvement in peak expiratory flow rate (PEFR) within 24 hr. The time taken to reach eventual maximum PEFR was very much longer, 50% of the patients taking one week or more. Diurnal variation of moderate or severe degree was seen in 78% of patients. Length of history of asthma, time of deterioration and other measures of the severity of attack on admission did not differ in faster and slower responders. The rise of PEFR within 4 hr of starting treatment was highly significantly correlated with a higher PEFR at 24 hr and a shorter time to full recovery. Although the mean arterial PCO2 was higher (P less than 0.01) in the slower responding group and they were slightly older (P less than 0.05) and had lower mean FEV1 (P less than 0.02) and FVC (P less than 0.05) these differences were less helpful in predicting which patients responded fastest.