Patterns of recovery of airflow obstruction in severe acute asthma

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Abstract
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 h. The time taken to reach eventual maximum PEFR was very much longer: 50% of the patients taking 1 wk 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 PEFH within 4 h of starting treatment was highly correlated with a higher PEFR at 24 h and a shorter time to full recovery. Although the mean arterial PCO2 [CO2 partial pressure] was higher (P < 0.01) in the slower responding group and they were slightly older (P < 0.05) and had lower mean FEV1 [forced expiratory volume in 1 s] (P < 0.02) and FVC [forced vital capacity] (P < 0.05), these differences were less helpful in predicting which patients responded fastest.