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Flow limitation during tidal expiration in symptom-free infants and the subsequent development of asthma
S Young1, J Arnott, P N Le Souef
1Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, Western Australia.
Insights
Infants with early expiratory flow limitation, often linked to family history of asthma, show persistent lung function issues and increased airway responsiveness, predicting later asthma diagnosis.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Asthma Research
Background:
- Longitudinal studies are crucial for understanding infant lung development.
- Early identification of respiratory abnormalities can inform long-term health outcomes.
- Family history and environmental factors influence infant respiratory health.
Purpose of the Study:
- To investigate the long-term respiratory outcomes of infants with early expiratory flow limitation.
- To assess the association between early lung function abnormalities and later asthma development.
- To determine predictors of lower respiratory tract illness in infancy.
Main Methods:
- Longitudinal follow-up of 252 infants from 1 month to 2 years of age.
- Measurement of maximal flow at functional residual capacity (VmaxFRC) and tidal breathing patterns (Tme/Te ratio).
- Histamine challenge for airway responsiveness, respiratory system compliance and resistance, and parental questionnaires for risk factors.
Main Results:
- Infants with flow limitation at 1 month (n=19) had reduced VmaxFRC, Tme/Te, compliance, and increased resistance.
- These infants showed persistent lung function deficits and increased airway responsiveness at 6 and 12 months.
- Early flow limitation significantly predicted physician-diagnosed asthma by age 2 (OR 7.4).
Conclusions:
- Early expiratory flow limitation in infants is associated with persistent lung dysfunction and airway hyperresponsiveness.
- Abnormal infant lung function may indicate a genetic predisposition to asthma or airway issues.
- Findings highlight the predictive value of early respiratory assessments for long-term asthma risk.
Abstract:
During a longitudinal study of lung function and airway responsiveness in a cohort of healthy infants, we identified a subgroup of symptom-free infants at the age of 1 month with flow limitation during tidal expiration. We report a 2-year follow-up of 252 infants who were first studied at 1 month of age. Maximal flow at functional residual capacity (VmaxFRC) was measured from a forced expiratory flow-volume curve by the rapid thoracic compression technique. The pattern of tidal breathing was assessed with the ratio of the time to reach maximal expiratory flow during expiration to the total expiratory time (Tme/Te ratio). Histamine inhalation challenge was used to determine the level of airway responsiveness. Compliance and resistance of the total respiratory system were measured from a passive expiration after occlusion at end inspiration. Data regarding the family history of asthma, atopy, and parental smoking were obtained by questionnaire. Flow limitation was considered present when the forced expiratory flow did not exceed tidal flow at functional residual capacity. Nineteen infants were identified with flow limitation at 5 weeks of age; all had a family history of asthma, atopy, and/or parental smoking. These 19 infants were compared with 35 infants with no family history of asthma or parental smoking and 38 gender-, history-, and age-matched control infants without flow limitation during tidal expiration. At the age of 1 month, the flow-limited group had reduced VmaxFRC, Tme/Te, and respiratory compliance and increased respiratory resistance. At 6 and 12 months of age, although no longer flow limited, these infants still had significantly reduced lung function and increased airway responsiveness. Flow limitation in early life was also significantly associated with the development of physician-diagnosed asthma by the age of 2 years (odds ratio, 7.4; 95% confidence interval, 1.4 to 35.2). Infants with abnormal lung function soon after birth may have a genetic predisposition to asthma or other airway abnormalities that predict the risk of subsequent lower respiratory tract illness.