Sudden-onset severe acute asthma: clinical features and response to therapy

To characterize patients with sudden onset of severe acute asthma (SAA) and to examine whether this presentation is associated with rapid recovery.

Retrospective cohort study of ED visits to a teaching hospital. Subjects were aged 18-64 years, with SAA (n = 225), defined as initial peak expiratory flow rate (PEFR) < or =40% of predicted. Visits for sudden-onset SAA (< or =3 hours of symptoms) were characterized and multivariate logistic regression was used to examine the association between sudden onset and rapid recovery.

Patient visits for sudden-onset SAA had different triggers as compared with those for the slower-onset group (p = 0.006). The sudden-onset patients were less likely to report an upper-respiratory-tract infection (17% vs 40%) and more likely to have an unidentifiable trigger (40% vs 19%). In the multivariate logistic regression model, sudden onset was a strong independent predictor of rapid response [odds ratio (OR) 4.3, 95% confidence interval (CI) 1.6-11.6]. Sudden-onset visits were less likely to lead to admission (23% vs 43%, p = 0.03).

These data suggest that different triggers may be involved in sudden-onset SAA and that sudden onset of symptoms is independently associated with rapid recovery. In their rapid deterioration and rapid response, these subjects share certain characteristics with "sudden asphyxic asthmatics" and may constitute a population suitable for further study of factors contributing to that condition. While these visits led to admission less frequently, prospective studies are necessary to provide information on duration of response and risk for relapse.