Bronchodilator responsiveness in infants with bronchiolitis

Abstract

We evaluated 34 infants with bronchiolitis, (17 of both genders; mean age, 4.6 mos; ranges, 0.7-14.5 mos). The 20 inpatients were significantly younger than the 14 outpatients (2.6 vs. 8.2 months, P < 0.05), and more females were inpatients. Forced expiratory flows at functional residual capacity (VmaxFRC) were obtained at baseline, after aerosolized normal saline (NS), and metaproterenol (0.025 mL/kg in 2 mL NS). Flows were expressed as Z-scores, the difference between the measured and predicted flows, divided by the standard deviation for the predicted value. At baseline, outpatients were more obstructed than inpatients (-1.64 vs. -0.95, P < 0.05), infants > 2 months old were more obstructed than infants < or = 2 months old (-1.54 vs. -0.80, P < 0.05), and males more than females (-1.45 vs. -1.02, P < 0.05). Following NS the whole group had a small but significant decrease in Z-scores (-1.23 to -1.31, P < 0.05). Following metaproterenol, the younger infants had significantly (P < 0.05) higher Z-scores compared to baseline and NS (-0.80 vs. -0.86 vs. -0.59). However, no significant changes occurred in older infants. Females also had an increased flow after metaproterenol and were less obstructed than after NS (-1.11 vs. -0.86, P < 0.015). In males no increased flows occurred after metaproterenol (-1.45 vs. -1.48). Bronchodilator responsiveness did not relate to severity of airway obstruction, history of family asthma, allergy, or passive smoke exposure. We conclude that inhaled metaproterenol improves airway function in a subgroup of infants with bronchiolitis, but the subgroup could not clearly be identified because age and gender were confounding factors.

Aerosolized albuterol improves airway reactivity in infants with acute respiratory failure from respiratory syncytial virus

“…This apparent trend toward a larger response to bronchodilators in younger infants has also been described in a series of 34 infants with bronchiolitis who did not have respiratory failure. 38 Except for three of our patients, the post-treatment VЈmaxFRC values still remained below the normal values for healthy infants, indicating that the airway obstruction was not fully reversible in the patients who responded to albuterol. This finding and a similar one of Mallory et al 16 can be attributed to the pathophysiology of the disease, wherein airway obstruction may be multifactorial, including components of bronchospasm, mucosal edema, and plugging of the airways with mucus and necrotic epithelium.…”

“…17,26,39 However, when the issue of bronchodilator efficacy for a particular disease is the subject of investigation, authors have relied on comparing individual patient values to their predicted, age-based normal range, then analyzing the magnitude of the group response to bronchodilator. 38 As recently as 1996, a widely used textbook of infant pulmonary function still did not have a standard definition of bronchodilator responsiveness. 40 In summary, the attempts to determine whether patients with RSV LRI respond to bronchodilators have been confounded by a lack of constancy between variables studied and a lack of uniformity regarding what degree of change is deemed a positive response to a bronchodilator.…”

Bronchodilator responsiveness testing using raised volume forced expiration in recurrently wheezing infants

“…Many studies have looked at the effect of bronchodilators on forced expiratory measures of lung volume with little evidence of an effect. Tepper et al 21 showed that metaproterenol improved maximal flow at functional residual capacity (V'max,FRC) in only a subgroup of infants with bronchiolitis. Motoyama et al 22 demonstrated an increase in forced expiratory flows by the forced deflation technique in infants with bronchopulmonary dysplasia.…”

Reproducibility of forced expiratory flow and volume measurements in infants with bronchiolitis

“…Previous work has indicated that bronchodilator responsiveness in bronchiolitis may vary between individual infants; responses can range from marked improvement to deterioration of lung function. [4][5][6][31][32][33][34][35] This calls for a special technique to assess individual response following bronchodilator administration. Such evaluations have been hampered in the past by a lack of techniques with sufficient sensitivity and reproducibility to accurately define the response of an individual patient.…”

“…Rapid thoracoabdominal compression (RTC) techniques are used for generating forced expiratory maneuvers; of these, the "squeeze-technique" (ETRTC technique) is most widely practiced. 1 Forced expiratory flow measurement with this method (maximum expiratory flow rate at functional residual capacity ‫ס‬ VЈ maxFRC ) has extended the understanding of airway physiology and lung growth in infancy, 2 has contributed to the development of treatment concepts for acute airway obstruction, [3][4][5][6] and furthermore has been used to study the mechanisms underlying recurrent wheezing and development of obstructive lung disease in infancy. 7 A substantial disadvantage of this technique, however, is the large intraindividual variability of the measurements.…”