PERSISTENT AIRWAYS OBSTRUCTION AND BRONCHODILATOR RESPONSIVENESS IN INFANTS FOLLOWING LOWER RESPIRATORY INFECTION (LRI)

Abstract

LRIs during infancy have been found to be associated with increased respiratory symptoms and impaired pulmonary function in later years. We measured maximal flows at functional residual capacity, VmaxFRC, in 10 hospitalized infants (age 1-16 mo) using the rapid thoracic compression technique. FRC was measured by helium dilution technique. Eight of 10 infants had follow-up testing while asymptomatic at 1-3.5 months post discharge. 110 normal babies of similar age were used for comparison. During the initial testing 6/10 LRI infants had abnormal VmaxFRC. At the time of follow-up 4/8 patients had low VmaxFRC but all had normal lung volumes, and 4/6 infants tested with inhaled metaproterenol demonstrated an increase in VmaxFRC. The slope of the regression equation of VmaxFRC vs. length for the normals was significantly greater (p<.05) than for the LRI infants when asymptomatic at follow up (5.81 vs. 1.70). We also studied 4 infants prior to their first LRI (mean age=1.8 mo) and at least 6 months following their LRI (mean age=9.4 mo);of these, 3 demonstrated an abnormally small increase in flows with growth despite a normal increase in lung volume. We conclude that infants with LRIs have evidence of either persistent airways obstruction or abnormal airway growth several months following an acute LRI and that some respond to an inhaled bronchodilator even when clinically asymptomatic. (Supported by NHLBI SCOR Grant #14136).