Definitions of asthma are usually stated in terms that emphasize repeated short-term variations in resistance to airflow in the intrapulmonary airways. The clinical diagnosis of asthma is ordinarily not difficult from history and physical examination, as the history of recurrent attacks of wheezing and shortness of breath with relative freedom from respiratory difficulty between attacks and the finding of inspiratory and expiratory wheezes and relative hyperinflation of the chest during episodes are characteristic. It is, however, valuable to document changes in pulmonary function by objective measurement and, furthermore, occasional patients will present either with severely impaired function or conversely with completely normal function and it becomes necessary to resort to some maneuver to bring out the variability in airflow. Cockcroft (see Chapter 47) reviewed pulmonary function tests and pointed out that FEV1 (forced expiratory volume in one second) and PFR (peak flow rate) are the most easily performed and sensitive tests. The ease of use allows repeated tests to be performed and thus to demonstrate the variability in airways resistance over time. At the same time the severity of the disease may be monitored.
KeywordsCystic Fibrosis Skin Test Bronchiolitis Obliterans Inhalation Challenge Status Asthmaticus
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