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Partial forced expiratory flow-volume curves in young children during ketamine anesthesia
Insights
Maximal flows at functional residual capacity (VmaxFRC) in preschool children correlate with physical size, with anesthesia improving measurement reliability. Dysanapsis appears minimal in this age group, suggesting uniform lung and airway growth.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Biomechanical Engineering
Background:
- Assessing maximal flows at functional residual capacity (VmaxFRC) is crucial for pediatric respiratory health.
- Previous studies faced challenges with awake children's cooperation and volume history control.
- Anesthesia offers a controlled environment for accurate pulmonary function testing in young children.
Purpose of the Study:
- To measure VmaxFRC in preschool children under general anesthesia.
- To investigate the correlation of VmaxFRC with physical parameters like height, weight, and age.
- To evaluate the impact of anesthesia on VmaxFRC measurement variability and compare it to awake measurements.
Main Methods:
- Partial forced expiratory flow-volume (PEFV) curves were obtained from 14 normal preschool children under general anesthesia.
- Rapid chest wall compression using an inflatable jacket generated PEFV curves from end inspiration.
- VmaxFRC was measured in milliliters per second and analyzed for correlations with anthropometric data and functional residual capacity (FRC).
Main Results:
- VmaxFRC showed a linear correlation with height, weight, and age, best described by height^2.47, aligning with wave-speed theory.
- FRC-corrected VmaxFRC averaged 2.42 FRC's/s, with no significant sex-based differences.
- Normalizing VmaxFRC for FRC significantly reduced intersubject variability compared to awake children, suggesting improved measurement reliability under anesthesia.
Conclusions:
- Anesthesia facilitates more reliable VmaxFRC measurements in preschool children by controlling volume history and flow generation.
- Dysanapsis does not appear to be a significant factor influencing VmaxFRC in this age group.
- The similar growth patterns of VmaxFRC and FRC with height support the concept of equidimensional growth in pediatric airways and lung parenchyma.
Abstract:
Maximal flows at functional residual capacity (VmaxFRC) from partial forced expiratory flow-volume (PEFV) curves were obtained in 14 normal preschool children (8 boys, 6 girls) of average age 44 mo, under general anesthesia before elective surgery. PEFV curves were generated from end inspiration by rapid compression of the chest wall with an inflatable jacket. VmaxFRC, expressed in milliliter per second, correlated linearly with height, weight, age, and FRC in milliliter and milliliters per kilogram. The best correlation of VmaxFRC (ml/s) was to height to the power of 2.47, which agrees with the results predicted by wave-speed theory. Mean FRC-corrected VmaxFRC was 2.42 +/- 0.50 (SD) FRC's/s with no significant difference between boys (2.35 FRC's/s) and girls (2.51 FRC's/s). There was no correlation between lung-size corrected VmaxFRC and height, weight, or age, but it tended to decrease with increasing FRC. The intersubject variability for VmaxFRC was reduced by normalizing for FRC, and was significantly better than that reported for awake children. This can be attributed to the greater control over volume history and more reliable maximal flow generation during anesthesia. The intrasubject coefficient of variation (CV) for VmaxFRC was 12.2%, and the intersubject CV was 20.0%. The difference may represent the variability due to dysanapsis. It is concluded that dysanapsis is not a prominent factor in children of this age group. In addition, the similarity of the regression equation for VmaxFRC vs. height to that of FRC vs. height supports the concept of equidimensional growth of the airways and lung parenchyma.