INFANT RESPIRATORY-FUNCTION AFTER RSV-PROVEN BRONCHIOLITIS

The mechanisms underlying the increased risk of wheezing in early chil dhood following acute bronchiolitis in infancy remain unclear. Previou s studies have reported significant abnormalities in infant respirator y function after clinical recovery from bronchiolitis, but are difficu lt to interpret because of the frequent omission of a concurrent compa rison group. Respiratory function was compared within pairs of previou sly healthy full-term caucasian infants admitted with a first episode of acute bronchiolitis to an inner London hospital, and age- and sex-m atched control infants without prior wheezing, asthma, or lower respir atory illness who were recruited from local general practices. Respira tory function was measured in 29 control and 29 asymptomatic index Inf ants, with measurements in the latter done at a median interval of 36 wk (range: 16 to 49 wk) after admission, when 16 (55%) had experienced subsequent wheezing. Index infants tended to be autumn-born and of sh orter gestation than control infants, to have younger mothers, and to have been exposed to tobacco smoke. There were no statistically signif icant differences in plethysmographic FRC, initial inspiratory airway resistance (Raw), or respiratory system compliance (mean [index minus control] within-pair difference [95% confidence interval]: -11 mi [-29 , 7 mi]; -0.2 kPa/L/s [-0.7, 0.4 kPa/L/s]; -8 ml/kPa [-21, 4 ml/kPa], respectively), but respiratory rate and time to peak tidal flow as a p roportion of total expiratory time (t(PTEF):t(E)) were significantly d iminished in index as compared with control infants (-4.0 breaths/min [-7.6, -0.4 breaths/min], versus -0.035 [-0.066, -0.005], respectively ). These findings suggest a better prognosis for infant lung function after acute bronchiolitis than reported previously. Longitudinal studi es are needed to clarify whether subclinical alterations in airway fun ction precede acute bronchiolitis.