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Short-term variability of pulmonary function tests in infants with bronchopulmonary dysplasia
B G Nickerson1, D J Durand, L C Kao
1Department of Pulmonary Medicine, Children's Hospital, Oakland, CA 94609.
Insights
Short-term lung function tests in infants recovering from bronchopulmonary dysplasia (BPD) show significant variability. Understanding this variability is crucial for accurate interpretation of pulmonary function in these vulnerable infants.
Area of Science:
- Pediatric Pulmonology
- Neonatal Medicine
- Respiratory Physiology
Background:
- Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants.
- Assessing pulmonary function is vital for managing BPD, but short-term variability can complicate interpretation.
Purpose of the Study:
- To determine the short-term variability of various pulmonary function parameters in infants recovering from BPD.
- To inform clinical interpretation of pulmonary function tests in this population.
Main Methods:
- Sixteen infants recovering from BPD underwent pulmonary function testing twice within 4-8 days during clinical stability.
- Measurements included forced expiratory flow (Vmax FRC), expiratory time constant (tau), thoracic gas volume (TGV), airway resistance (Raw), specific airway conductance (SGaw), and dynamic pulmonary compliance (Cdyn).
- Testing utilized modified rapid thoracic compression and whole-body plethysmography.
Main Results:
- Variability (SD of % change) ranged from 12% for TGV to 72% for total specific airway conductance (SGawT).
- Significant variability was observed for Vmax FRC (30%), tau (23%), RawM (20%), RawT (35%), SGawM (25%), and Cdyn (23%).
- Total specific airway conductance (SGawT) exhibited the highest variability at 72%.
Conclusions:
- Pulmonary function tests like Vmax FRC, SGaw, and Cdyn are valuable for assessing infants with BPD.
- The inherent short-term variability of these tests must be considered when monitoring infants with BPD.
- Accurate interpretation of pulmonary function requires accounting for test-retest variability.
Abstract:
We determined the short-term variability of pulmonary function in infants recovering from bronchopulmonary dysplasia. Sixteen infants with birth weight of 1,231 +/- 929 grams (mean +/- SD) and gestational age of 29 +/- 4 weeks were studied twice at 17 +/- 8 weeks postnatally at intervals of 4 to 8 days during a period of clinical stability. The infants were still on supplemental oxygen but were off diuretics and bronchodilators. We used a modification of the rapid thoracic compression method to measure forced expiratory flow (Vmax FRC) and the time constant (tau) of expiratory flow at functional residual capacity. Thoracic gas volume (TGV), mean and total airway resistance (RawM and RawT), and mean and total specific airway conductance (SGawM and SGawT) were measured in a whole body pressure plethysmograph. An esophageal balloon was used to measure dynamic pulmonary compliance (Cdyn). Variabilities were defined as the standard deviation of percent changes between the first and second tests. They were 30% for VmaxFRC, 23% for tau, 12% for TGV, 20% for RawM, 35% for RawT, 25% for SGawM, 72% for SGawT, and 23% for Cdyn. All these tests are useful in assessing pulmonary function of infants with BPD; however, their variability must be taken into account when interpreting short-term changes.