Objective: To evaluate bronchial hyperresponsiveness (BHR) early after recovery from acute severe asthma (ASA).
Design: Prospective study including all patients admitted to the intensive care unit (ICU) for ASA over a 12-month period.
Setting: University teaching ICU and pneumonology department.
Patients: 41 consecutive patients admitted to the ICU for ASA. Results were compared with those of a control group with stable asthma and no history of ASA or steroid therapy, matched for sex and age.
Measurement and results: Of the 41 patients, 40 completed respiratory function tests 10 days after ICU admission, and the minimal dose of acetylcholine inducing a fall in forced expiratory volume in 1 s (FEV1) of 20% or more (PD AC) could be determined safely by a novel method in 26 patients with an FEV1 above 60% predicted. PD AC (micrograms) was found to be significantly lower in ASA than in control patients. Very severe BHR (PD AC < or = 100 micrograms) was found in 18 ASA patients, but not in the control patients; 5 ASA versus 12 control patients had marked BHR (100 > PD AC < or = 500 micrograms); and 3 ASA versus 14 control patients had moderate BHR (> 500 micrograms). A similar level of BHR was found in ASA patients with progressive or acute worsening. No correlation was found between PD AC and admission PaCO2 value, admission peak expiratory flow (PEF) value, delay in improvement of PEF, delay in PD AC determination, or prechallenge FEV1 value.
Conclusion: BHR measurement is safe soon after an episode of ASA if done with caution. At this time, patients who are free of clinical symptoms and have no significant objective bronchial obstruction appear to have severe bronchial hyper-responsiveness.