Neonatal bronchial hyperresponsiveness precedes acute severe viral bronchiolitis in infants.
BACKGROUND
Respiratory syncytial virus and other respiratory tract viruses lead to common colds in most infants, whereas a minority develop acute severe bronchiolitis often requiring hospitalization. We hypothesized that such an excessive response to respiratory tract viral infection is caused by host factors reflected in pre-existing increased bronchial responsiveness.


OBJECTIVE
We sought to compare bronchial responsiveness and lung function in 1-month-old neonates who later develop acute severe bronchiolitis with those who do not.


METHODS
We measured infant lung function (n=402) and bronchial responsiveness to methacholine (n=363) using the raised-volume rapid thoracoabdominal compression technique before any respiratory symptoms in 1-month-old neonates from the Copenhagen Prospective Study of Asthma in Childhood birth cohort born to mothers with asthma. The children were prospectively monitored for respiratory symptoms and given a diagnosis of acute severe bronchiolitis according to a fixed algorithm.


RESULTS
Thirty-four (8.5%) infants had acute severe bronchiolitis before 2 years of age, 21 (62%) were hospitalized, and 23 (67%) of the cases were associated with respiratory syncytial virus. Children who later had acute severe bronchiolitis irrespective of viral species had a 2.5-fold increased responsiveness to methacholine (provocative dose of methacholine producing a 15% decrease in transcutaneous oxygen pressure [PD(15)]) at age 1 month compared with control subjects (median PD(15) in cases vs control subjects, 0.13 vs 0.33 μmol; P=.01), whereas differences in baseline airflow were not significant for forced expiratory volume at 0.5 seconds (mean z score for cases vs control subjects, -0.18 vs -0.01; P=.36) and forced expiratory flow at 50% of forced vital capacity (mean z score for cases vs control subjects, -0.37 vs -0.09; P=.13).


CONCLUSIONS
Bronchial hyperresponsiveness in at-risk neonates precedes acute severe bronchiolitis in response to infections with respiratory tract virus.
Copenhagen Prospective Studies on Asthma in Childhood, Health Sciences, University of Copenhagen and Danish Pediatric Asthma Centre, Copenhagen University Hospital, Gentofte, Denmark.
Bo L K
BL
Chawes
Porntiva
P
Poorisrisak
Sebastian L
SL
Johnston
Hans
H
Bisgaard
D000208:Acute Disease; D016535:Bronchial Hyperreactivity / Q000150:complications / Q000276:immunology* / Q000821:virology; D001985:Bronchial Provocation Tests; D001990:Bronchiolitis, Viral / Q000150:complications / Q000276:immunology* / Q000821:virology; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016210:Methacholine Chloride / Q000276:immunology; D011446:Prospective Studies; D012129:Respiratory Function Tests; D018357:Respiratory Syncytial Virus Infections / Q000150:complications / Q000276:immunology* / Q000821:virology; D012136:Respiratory Syncytial Viruses / Q000276:immunology; D012720:Severity of Illness Index; D013997:Time Factors
D016210:Methacholine Chloride