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Pulmonary function in technology-dependent children 2 years and older with bronchopulmonary dysplasia
Isaac Talmaciu1, Clement L Ren, Susan M Kolb
1Division of Pediatric Pulmonology, St. Christopher's Hospital for Children, Philadelphia, Pennsylvania, USA. italmaciu@aol.com
Insights
Most children with bronchopulmonary dysplasia (BPD) improve by age two. However, some require ongoing support, showing similar pulmonary function tests despite needing mechanical ventilation or oxygen.
Area of Science:
- Pediatric Pulmonology
- Neonatology
- Respiratory Medicine
Background:
- Bronchopulmonary dysplasia (BPD) often resolves by age two, but a subset of children require prolonged respiratory support.
- Technology dependence in BPD beyond two years suggests persistent respiratory compromise.
Purpose of the Study:
- To compare pulmonary mechanics in technology-dependent children with BPD (2+ years) versus those who are normoxemic.
- To test if standard pulmonary function indices reflect hypoxemia in older children with BPD.
Main Methods:
- Pulmonary mechanics were measured in 21 ventilator/oxygen-dependent children (BPDO2 group) and 19 weaned controls (age 2+ years).
- Techniques included esophageal catheter for lung mechanics and rapid thoracic compression for flow-volume measurements.
- Functional residual capacity (FRC) was determined by nitrogen washout.
Main Results:
- Most pulmonary mechanics indices were not significantly different between the BPDO2 and control groups.
- Maximal flow at FRC normalized to FRC (V'(maxFRC)/FRC) was significantly lower in the BPDO2 group compared to controls (0.34 vs. 0.81 sec(-1), P<0.003).
Conclusions:
- Standard pulmonary function tests may not adequately reflect the need for ongoing respiratory support in children with BPD aged two years and older.
- Lung elastic recoil and ventilation/perfusion distribution tests might be more sensitive indicators for differentiating hypoxemic and normoxemic children with BPD.
Abstract:
Somatic and pulmonary growth coincide with resolution of hypoxemia by 2 years of age in most children with bronchopulmonary dysplasia (BPD). However, a distinct subgroup of children with BPD continue to require mechanical ventilation and/or supplemental oxygen beyond 2 years of age. This study tested the hypothesis that indices of pulmonary function would be significantly worse in children with BPD 2 years and older who remained technology-dependent secondary to hypoxemia, compared to those of age-matched children with BPD who were normoxemic. We measured pulmonary mechanics in 21 oxygen- or ventilator-dependent children with BPD 2 years and older (BPDO2 group; mean age+/-SD, 30.2+/-6.5 months) and in 19 children with BPD who had been weaned off mechanical ventilation and supplemental oxygen for at least 6 months (control group; mean age, 30.1+/-5.5 months). Respiratory rate and tidal volume were measured after sedation with chloral hydrate, and dynamic compliance and expiratory conductance were calculated using the esophageal catheter technique. Maximal flow at FRC (V'(maxFRC)) and ratio of forced-to-tidal flows at midtidal volume were obtained by the rapid thoracic compression technique. FRC was determined by nitrogen washout. There were no statistically significant differences in most measured indices of pulmonary mechanics between the BPDO2 and control groups. However, V'(maxFRC)/FRC was higher in controls compared to subjects in the BPDO2 group (0.81+/-0.40 sec(-1) vs. 0.34+/-0.21 sec(-1), P<0.003). We conclude that most indices of pulmonary function in children with BPD 2 years and older do not reflect the need for mechanical ventilation or supplemental oxygen. We speculate that measurements of lung elastic recoil and tests of distribution of ventilation and pulmonary perfusion may be more sensitive in differentiating normoxemic and hypoxemic children with BPD 2 years and older.