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Bronchial responsiveness and lung function in recurrently wheezy infants
S M Stick1, J Arnott, D J Turner
1Department of Respiratory Medicine, University of Western Australia, Perth.
Insights
Wheezy infants show lower baseline airflow but do not exhibit increased bronchial responsiveness (BR) to histamine compared to healthy infants. This suggests different underlying mechanisms for infant wheezing versus childhood asthma.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Allergy and Immunology
Background:
- Infant wheezing is common but often unresponsive to asthma treatments.
- Pathologic mechanisms causing wheezing in infants remain poorly understood.
- The link between wheezing and bronchial responsiveness (BR) in older individuals is well-established.
Purpose of the Study:
- To investigate if the association between wheezing and BR observed in older subjects is also present in infants.
- To compare bronchial responsiveness to inhaled histamine in wheezy infants versus healthy controls.
Main Methods:
- Study included 19 recurrently wheezy infants and age-, height-, weight-, and sex-matched controls.
- Bronchial responsiveness (BR) assessed using inhaled histamine challenge.
- Maximal flow at functional residual capacity (VmaxFRC) measured via partial expiratory flow-volume curves; PC40 (provocative concentration causing 40% fall in VmaxFRC) determined.
Main Results:
- Wheezy infants had significantly lower median baseline VmaxFRC (100.0 ml/s) compared to controls (182.0 ml/s, p < 0.01).
- No significant difference in PC40 was found between wheezy infants (2.1 g/L) and control infants (2.3 g/L).
- This indicates similar bronchial responsiveness despite differing baseline airflow.
Conclusions:
- Recurrent wheezing in infants is associated with reduced baseline airflow but not increased bronchial responsiveness to histamine.
- The findings suggest that wheezing in infancy may stem from different pathophysiological mechanisms than those in older asthmatic individuals.
- Further research is needed to elucidate the specific mechanisms driving wheezing in this age group.
Abstract:
Although most wheezy infants are considered asthmatic, they generally respond poorly to antiasthma treatment, and there is inadequate knowledge about the pathologic mechanisms that cause wheezing at this age. The aim of this study was to determine whether the strong association between wheezing and bronchial responsiveness (BR) seen in older subjects was also present in infants. We compared BR with inhaled histamine in 19 recurrently wheezy infants with a group of age-, height-, weight-, and sex-matched control infants. Maximal flow at FRC (VmaxFRC) was determined from partial expiratory flow-volume curves generated using the "squeeze" technique. Histamine was delivered during 1 min of tidal breathing in doubling concentrations from 0.125 g/L to a maximum of 8 g/L or until VmaxFRC fell by 40% (PC40). The median baseline VmaxFRC for the wheezy infants was 100.0 ml/s compared with 182.0 ml/s for the control infants (p less than 0.01). However, there was no significant difference in the PC40 between the two groups (2.1 versus 2.3 g/L).