Acute severe asthma. A prospective study of the precipitating factors in 40 children.

A prospective study was undertaken to determine the factors precipitating acute severe asthma in children attending the Red Cross War Memorial Children's Hospital, Cape Town. A comparison in terms of recent exposure to possible precipitating factors was made between 40 known asthmatics presenting with acute severe asthma and 40 known asthmatics who were clinically well. Exposure to known allergens had occurred in 7 cases. The time of onset of symptoms bore no relationship to meteorological changes in temperature, humidity or average pressure. Drug compliance in both groups was of the order of 50%. The majority of severe asthma attacks were associated with infection of the respiratory tract. The importance of infection as a precipitating factor in a severe asthma attack is discussed with reference to the cholinergic, adrenergic and immunological mechanisms.