Fatal asthma and the environment

Abstract

The human immune system has evolved over millions of years to protect against pathogenic invaders in the environment, especially microbes. The immunoglobulin E (IgE)-mediated immune response is adept at defending against helminthic parasitic infections. In allergic disease, however, this same system can kill the host organism in a matter of minutes. Anaphylaxis and upper airway obstruction caused by soft tissue swelling are two dramatic examples of potentially fatal allergic reactions to substances that have been injected, ingested, or inhaled. Asthma is another example of a potentially fatal maladaptive response to environmental stimuli that is mediated in large part through IgE-related mechanisms. Asthma represents a persistent tendency of the bronchi—large and small—to narrow excessively in response to triggers in the environment. This narrowing can result from smooth muscle contraction in the airway, bronchial wall swelling, and filling of bronchial lumens with mucus and inflammatory debris. It can develop gradually over days to weeks or rapidly over minutes to hours. The potential consequence of an extreme generalized asthmatic reaction is asphyxiation and death. Fatal asthma is not a unique, biologically predetermined form of asthma. It is a disastrous and, for the most part, preventable outcome of a very severe asthmatic attack. All persons with asthma are vulnerable to asthmatic attacks. Factors affecting the severity of an attack include the degree of underlying hyperresponsiveness of the airways and the intensity of the stimulus that triggers the attack. These factors are influenced by environmental exposures. The outcome of severe asthmatic attacks also is determined by the availability of intensive medical care to treat the attack. Key determinants of the outcome of severe asthmatic attacks are recognition (by the patient or medical provider) of the seriousness of the illness and rapid transfer of the patient to a setting where intensive medical treatment can be administered.