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.
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