Airway Response to a Bronchodilator in Healthy Parents of Infants With Bronchiolitis: Materials and Methods
From January through March 1992, we have studied 132 adults (66 males and 66 females) in good past and present health at least 4 weeks after any upper respiratory tract infection. Informed consent was obtained before participation in the study. In particular, these adults should have had a negative health history for chronic bronchitis, asthma, and allergy. None used inhaled bronchodilators. None had skeletal deformities such as kyphoscoliosis. All came from the same geographic area, with similar exposure to environmental pollution. Socioeconomic conditions and level of education also were similar in the two groups. All subjects had normal values for expiratory airflow and lung volume ([FVC], FEV,, and mean forced expiratory flow during the middle half of FVC [FEF25-75%] >80 percent of predicted) at baseline forced expiratory maneuver. We used the prediction equations of Knudson and coworkers.
There were 66 parents (two by two) of 35 children (2 pairs of twins) affected by bronchiolitis (age, 30.9 ±5.9 years; height, 167.1 ± 8.6 cm). Only 20 (30.3 percent) (13 males and 7 females) were smokers (> 10 cigarettes a day). The second group was composed by 66 parents of children without bronchiolitis (33 males and 33 females) who were almost the same age (30.4 ± 3.9 years), height (169.5 ± 10.3 cm), and percentage of smokers (28.7 percent); 9 were male and 10 female. canadian health&care mall
Subjects were tested with an automated instrument (pneumotachograph Multispiro-PC, Burke & Burke, Wurzburg, Germany). The lung function protocol is based on American Thoracic Society recommendations. In particular, each subject performed baseline forced expiratory maneuvers from maximal inspiration until 3 technically acceptable tests were obtained: of these, 2 comparable flow volume loops should have FEV, and FVC values that did not differ more than 5 percent. The maximum FVC and the maximum FEV, were chosen among each set of spirometry values. The FEF25-75 percent was recorded from the spirometry with the maximum sum of FVC and FEV,.
Parents of infants with bronchiolitis performed pulmonary function tests before and after 15 min inhalation, using a metered-dose inhaler, either of salbutamol (200 Jig) or of a placebo, within 2 subsequent days (double-blind). Parents of infants without bronchiolitis performed pulmonary function tests only before and after 15 min of inhalation of salbutamol. Use of the inhaler with an open mouth technique was demonstrated by an investigator.
The change from baseline after placebo or salbutamol in selected spirometric measurements was expressed as a percentage of variation from the initial value. Consistently with the recommendations of most authorities, we have used at least a 12 percent increase in FEV, from the baseline value in order to obtain a meaningful response. Recommended criteria for response to a bronchodilator in adults are as follows: Intermountain Thoracic Society—FVC, 15 percent; FEV,, 12 percent; FEF25-75% 45 percent; American Thoracic Society— FVC, 12 percent, FEV,, 12 percent. When the postbronchodilator FVC value did not change, a significant improvement in FEF25-75% also ( > 45 percent) was taken into account.
Two-tailed paired and unpaired Student’s t tests were used for group comparisons where appropriate. Statistical significance was chosen at a probability level of less than 0.05.
Category: Respiratory Symptoms
Tags: bronchodilator, bronchodilator response, hyperreactivity, hyperresponsiveness, infants bronchiolitis, lung function