Bronchoprovocation Testing

Bronchial hyperresponsiveness is a constant feature of asthma even when airflow obstruction is absent. Detecting nonspecific bronchial hyperresponsiveness is useful when the diagnosis of asthma has not been confirmed or when a patient describes symptoms of cough, chest tightness, and dyspnea that cannot be ascribed to other causes. Also, because wheezing is a symptom of other disorders, inhalation challenge tests can be useful in defining its cause when reversible airflow obstruction has not been documented. A number of easy and safe techniques are available to detect nonspecific bronchial hyperresponsiveness. The histamine and methacholine challenge have had the most widespread use in the clinical pulmonary function laboratory. The exercise and cold air challenges are limited by expense. The osmotic challenge may gain more acceptance as experience with this technique grows. These different agents have the advantage of simplicity, reproducibility, a low number of adverse effects, and a high degree of specificity and sensitivity. A limited number of asthmatics show bronchial hyperresponsiveness to specific agents such as chemical sensitizers in the workplace, aeroallergens, aspirin, nonsteroidal anti-inflammatory agents, and sulfiting agents. Bronchoprovocation testing with these agents is usually reserved for the hospital laboratory because severe or delayed reactions may occur. These tests, however, can be extremely useful in defining a population of sensitive asthmatics.