An attempt to determine the optimal duration of hospital stay following a severe attack of asthma.

The optimal duration of hospital stay following admission for acute severe asthma is difficult to determine. An asthmatic is at particularly high risk of sudden death in the 6-12 weeks after admission, and too early hospital discharge may add to this risk. Thirty patients hospitalised for severe asthma recorded peak flows thrice daily for 8 weeks following discharge. Peak flow charts were reviewed at monthly intervals, and dips were divided into 'minor' (peak flow less than 75% of the patient's best), 'major' (less than 50%) and 'catastrophic' (less than 30%). Fourteen of the 30 patients had major dips (including 4 who had catastrophic dips as well). Four of these 14 patients were readmitted with acute severe asthma during the 8 weeks follow-up period; in contrast, none of the 16 patients without major dips required readmission. The only in-hospital factor that correlated with and was predictive of (p less than 0.001) multiple major dips post-discharge was the peak flow variability in the 24 hours before discharge, defined as [(highest-lowest peak flow)/highest] x 100. Thirteen of the 14 patients with major dips had pre-discharge peak flow variation greater than 20% compared with only 2 of the 16 without major dips. We believe it is unwise to discharge asthmatics from hospital until the diurnal variation in their peak flow is below 20%. Discharging them before this target is reached puts them at increased risk of further severe attacks of asthma requiring re-hospitalisation.