Abnormal Airway Function in Individuals with the Acquired Immunodeficiency Syndrome: Methods

A standard approach was employed in the assessment of forced expiratory flow rates. Flow rates were considered to be abnormally low if either the ratio of forced expiratory volume in 1 s (FEVJ to the forced vital capacity (FVC) or the mean forced expiratory flow during the middle half of the FVC (FEF 25-75%) was more than 1.65 standard deviations below the age-sex-height specific predicted value for that individual. Because individuals with abnormally low lung volumes also have low maximum expiratory flow rates, only the FEVj/FVC ratio was considered in the evaluation of obstruction for individuals whose FVC was below 80 percent of predicted. Although a low FVC does not necessarily indicate restrictive impairment, we reasoned that in cases in which the FVC was reduced secondary to air trapping, as would occur with significant airflow obstruction, the FEV/FVC ratio also would be reduced. Thus, we assumed that individuals with reduced FVCs but normal FEV^FVC ratios had restrictive disease irrespective of low instantaneous maximum expiratory flows. Individuals were evaluated prior to and 15 min after two inhalations of an aerosolized albuterol solution (Proventil inhaler, Schering Corp., Kenilworth, NJ). The response to inhaled bronchodilators was considered significant if the FEVt increased by at least 12 percent, or if the FEF 25-75% increased by at least 25 percent while the vital capacity changed less than 10 percent.

To correlate abnormal function with clinical events, the medical records of all individuals were reviewed with the aid of a specially prepared questionnaire. The presence or absence of lower respiratory tract infection was substantiated in each case by results of diagnostic fiberoptic bronchoscopy, chest x-ray film, and a compatible clinical illness. Respiratory tract involvement with Kaposi’s sarcoma was documented by: (a) a characteristic radiologic pattern including the presence of diffuse parenchymal nodules, or pleural disease and/or interstitial infiltrates associated with hilar or mediastinal adenopathy in the absence of microbial pathogens in respiratory secretions; and (b) direct visualization of characteristic violaceous endobronchial masses during bronchoscopy. Chi-square tests were used to assess the strength of observed associations; results were considered significant at the 0.05 probability level.

Category: Airways

Tags: AIDS, airway function, pulmonary, respiratory