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Bronchial responsiveness and lung function in infants with lower respiratory tract illness over the first six months
J R Clarke1, A Reese, M Silverman
1Department of Paediatrics and Neonatal Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London.
Insights
Infant bronchial responsiveness to histamine, a measure of airway sensitivity, was assessed early in life. This study found that airway sensitivity in infants is not linked to early lower respiratory tract illnesses.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Lower respiratory tract illness (LRTI) in infancy, characterized by wheeze or cough, is common.
- Infant respiratory health and the development of conditions like asthma are significant concerns.
Purpose of the Study:
- To investigate the association between increased bronchial responsiveness to histamine and infant lower respiratory tract illness.
- To determine if airway hyperresponsiveness in early life predicts subsequent respiratory symptoms.
Main Methods:
- Pulmonary function testing was performed on 45 normal newborn infants (median age 6.5 months) with at least one atopic parent.
- Maximum flow at functional residual capacity (VmaxFRC) was measured using partial forced expiratory flow volume curves.
- Bronchial responsiveness to histamine was quantified by the provoking concentration causing a 30% decrease in VmaxFRC (PC30).
Main Results:
- Symptomatic infants (with a history of LRTI) exhibited lower length-adjusted VmaxFRC compared to control infants before histamine challenge.
- No significant difference in histamine PC30 was observed between infants with and without a history of LRTI.
- Bronchial responsiveness to histamine was present in most infants early in life and appeared independent of LRTI history.
Conclusions:
- Increased bronchial responsiveness to histamine in infancy is not significantly associated with a history of lower respiratory tract illness.
- Airway hyperresponsiveness to histamine is a common finding in early infancy and may not be a predictor of LRTI.
- Further research is needed to understand the long-term implications of early bronchial responsiveness.
Abstract:
The aim of this study was to determine whether increased bronchial responsiveness to histamine is associated with lower respiratory tract illness (one or more episodes of wheeze or cough, or both) in infancy. Fifty four normal newborn infants who had at least one atopic parent were recruited. At a median age of 6.5 months, 45 infants, 23 with a history of lower respiratory tract illness, and 22 without, underwent pulmonary function testing during a symptom free period. The maximum flow at functional residual capacity (VmaxFRC) was calculated from partial forced expiratory flow volume curves using the squeeze technique. Bronchial responsiveness to increasing doses of histamine was assessed by determining the provoking concentration which caused a 30% decrease in VmaxFRC (PC30). The length adjusted VmaxFRC was lower for symptomatic infants before the challenge (median 125 ml/s; 95% confidence intervals (CI) 85 to 164 ml/s) compared with control infants (median 215 ml/s; 95% CI 159 to 298 ml/s). There was no significant difference in PC30 between symptomatic infants (median 10.3 g/l; 95% CI 2.8 to 23.8 g/l) and control infants (median 16.5 g/l; 95% CI 2.4 to 27.9 g/l). Bronchial responsiveness to histamine can be shown in most infants early in life and is independent of lower respiratory tract symptoms including wheezing.