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Ability of new lung function tests to assess methacholine-induced airway obstruction in infants
M R Benoist1, J J Brouard, P Rufin
1Pulmonary Function Testing Laboratory, Necker Hospital for Sick Children, Paris, France.
Insights
Innovative lung function tests, including maximal flow at functional residual capacity (VmaxFRC), effectively detect airway obstruction in infants. These noninvasive methods show promise for assessing bronchial challenges and disease.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Diagnostic Medicine
Background:
- Recurrent wheezing in infants often indicates underlying airway issues.
- Accurate detection of bronchial obstruction is crucial for timely intervention.
- Existing methods may have limitations in assessing subtle airway changes in infants.
Purpose of the Study:
- To evaluate novel noninvasive lung function tests for detecting methacholine-induced bronchial obstruction.
- To assess the sensitivity of tests like VmaxFRC and Fpet in wheezy infants.
- To determine the utility of these tests in identifying airway hyperresponsiveness.
Main Methods:
- Fifty-five infants with recurrent wheezing underwent baseline lung function tests.
- Forty-two infants completed a methacholine bronchial challenge.
- Measurements included maximal flow at functional residual capacity (VmaxFRC), respiratory system compliance (Crs) and resistance (Rrs), breathing patterns, and transcutaneous oxygen tension (PtCO2).
Main Results:
- Forty-one of 42 infants responded to methacholine challenge, indicating bronchial obstruction.
- Significant changes were observed in VmaxFRC, Crs, Rrs, respiratory rate (RR), Ti/Ttot, Tme/Te, and PtCO2.
- VmaxFRC and Fpet demonstrated particular sensitivity to airway obstruction.
Conclusions:
- Noninvasive lung function tests, particularly VmaxFRC and Fpet, can reliably detect minor to moderate airway obstruction in infants.
- These tests offer a valuable tool for assessing bronchial challenges and airway hyperresponsiveness.
- Further research is warranted to establish their role in managing bronchial diseases and treatment efficacy.
Abstract:
We assessed the ability of innovative lung function tests to detect bronchial obstruction induced by methacholine bronchial challenge. Fifty-five recurrently wheezy infants (mean age 16 +/- 5.2 months) free of respiratory symptoms underwent baseline lung function tests. Forty-two completed the methacholine challenge. Maximal flow at functional residual capacity (VmaxFRC) was obtained using the squeeze technique; compliance and resistance of the respiratory system (Crs, Rrs) was measured with the passive expiatory flow volume technique; tidal volume breathing patterns were analyzed from recordings of respiratory rate (RR), tidal volume (VT), and inspiratory time divided by total cycle of duration (Ti/Ttot). Expiratory tidal flow volume (V/VT) curves were described with multiple indices such as the ratio of expiratory time necessary to reach peak tidal expiratory flow (Fpet) to expiratory time (Tme/Te). Transcutaneous oxygen tension (PtCO2) was measured as an indicator of response to methacholine challenge. Of 42 infants 41 responded to methacholine by a change > or = 2 standard deviations from baseline values. The mean SD unit changes were 9.8 in PtCO2, 3.7 for VmaxFRC, 2.8 for Crs, 2.09 for Rrs, 3.1 for RR, 1.6 for Ti/Ttot, 2.2 for Tme/Te 3.9 for PFVt. We conclude that these noninvasive lung function tests, especially VmaxFRC and Fpet, can be used to detect minor or moderate airway obstruction. Further studies are needed to determine the value of the tests in assessing bronchial disease and effects of its treatment.