exist for the performance of diffusing capacity testing. As of 1987, however, interlaboratory variability was too great to recommend one set of equations for all laboratories. Rather, laboratories are advised to use internal controls, such as repeated measurements on a normal individual.

Exercise Studies

Exercise pulmonary function studies can be used as part of a clinical evaluation to quantitate exercise-induced bronchoconstriction in asthmatics (Chatham et al., 1982b), and to exclude the diagnosis of asthma in other cases. Often, however, serial peak flow monitoring during normal activities will be sufficient to document exercise-induced asthma. Exercise testing is also used to evaluate an individual with suspected interstitial lung disease. The occurrence of desaturation or a widening alveolar-arterial oxygen gradient suggests significant interstitial disease (Whipp and Wasserman, 1988). Finally, exercise testing can be used as part of the impairment evaluation when symptoms are disproportionate to static lung function due to deconditioning or unrecognized cardiovascular or pulmonary pathology (Engelberg, 1988).

Measures of Upper Airway Function

Measures of upper airway function are primarily used in research settings at present. The one exception is the obtaining of a nasal swab with cytologic examination for the presence and characteristics of inflammatory cells.

For physiologic measurement of nasal airflow (rhinomanometry), the pressure-flow characteristics during panting maneuvers are used to derive nasal airway resistance (Cole, 1982). Ten to 15 percent of patients are unable to perform the maneuver successfully; normal values are problematic because of normal fluctuations in nasal airway caliber. Nasal resistance measures correlate to a variable degree with congestive symptoms. Peak flow measurements of nasal airflow have been made by adapting a standard peak flow meter with a pediatric anesthetic mask (Ahman, 1992). This method is not without its problems or constraints; for example, technical questions remain about whether to record a nasal inspiratory or expiratory maneuver.

Acoustic rhinometry is a new technique that describes the cross-sectional area of the interior of the nose as a function of the distance from the nares. An acoustic pulse is generated, and reflections are recorded by a microphone and analyzed with a computer program using Fourier analysis. Subjects must stop breathing only for approximately half a second; the test is therefore easier to perform than physiological measures of nasal airway



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