Rapid-onset asthma attack: a prospective cohort study about characteristics and response to emergency department treatment.

STUDY
OBJECTIVES: (1) To determine the frequency of rapid-onset asthma attacks (ROAAs) and slow-onset asthma attacks (SOAAs) in adult patients with acute, severe disease (18 to 50 years old), who presented to an emergency department (ED); and (2) to establish whether ROAA patients differ from SOAA patients in terms of clinical and spirometric characteristics; and (3) in terms of the response of treatment. SUBJECTS AND METHODS: Four hundred three patients (with peak expiratory flow [PEF] or FEV(1) of < 50% of predicted value) with acute exacerbations of asthma were enrolled in the trial using a prospective cohort study. Asthma attacks were classified as an ROAA (< 6 h of symptoms) or an SOAA (> or = 6 h). All patients were treated with albuterol, four puffs at 10-min intervals (100 microg per actuation), delivered by metered-dose inhaler with a spacer device during 3 h.
RESULTS: On the basis of previously determined criteria, 11.3% of patients were classified as having a ROAA. Male patients comprised 53.6% of the ROAA group (p = 0.03). In ROAA patients, the exacerbation was less likely to be attributed to respiratory tract infection (p = 0.001) and more likely to have no identifiable cause (p = 0.0001). Also, ROAA patients had lower pulmonary function (FEV(1)) at presentation (mean difference, - 0. 13; 95% confidence interval [CI], - 0.22 to - 0.04 L; p = 0.04) than SOAA patients. At the end of treatment, ROAA patients had an overall 48.0 L/min (95% CI, 14.1 to 81.8 L/min) greater improvement in PEF and a 0.31 L (95% CI, 0.08 to 0.54 L) greater improvement in FEV(1) than SOAA patients. Also, ROAA patients presented with less accessory muscle use (p < 0.05) and higher oxygen saturation (p = 0. 005). Finally, SOAA patients showed an increased incidence of hospital admission (relative risk, 3.89; 95% CI, 1.01 to 15.0).
CONCLUSIONS: Data from this study support the notion that ROAAs constitute a distinct but uncommon acute asthma ED presentation, with a predominance of male patients. Upper respiratory tract infection was not believed to be a significant trigger factor in these patients, and ROAA patients had rapid deterioration of their conditions followed by a more rapid response to treatment and a lower hospital admission rate than SOAA patients. Thus, we have identified a subgroup of patients who appear to have common characteristics with patients with sudden-onset near-fatal/fatal asthma.