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Interaction between chest wall motion and lung mechanics in normal infants and infants with bronchopulmonary
J L Allen1, J S Greenspan, K S Deoras
1Department of Pediatrics, St. Christopher's Hospital for Children, Philadelphia, PA 19134-1095.
Insights
Thoraco-abdominal asynchrony (TAA) in infants with lung disease indicates abnormal breathing mechanics. This study found TAA correlates with lung resistance and compliance, suggesting its use as an indicator of lung function in infants.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Infant Health
Background:
- Infants with lung disease often exhibit asynchronous chest wall motion.
- Thoraco-abdominal asynchrony (TAA) has been shown to improve after bronchodilator treatment.
- The cross-sectional utility of TAA as an indicator of baseline lung function is not well-established.
Purpose of the Study:
- To investigate the correlation between TAA and baseline lung mechanics in infants.
- To determine if TAA can serve as a cross-sectional index of lung function in infants with bronchopulmonary dysplasia (BPD).
Main Methods:
- Respiratory inductive plethysmography was used to measure TAA during sleep in infants with BPD and controls.
- The phase angle (phi) between rib cage and abdominal motion quantified TAA.
- Lung resistance (RL) and compliance/kg (CL/kg) were calculated from pressure, volume, and flow measurements.
Main Results:
- Infants with BPD showed significantly higher TAA (phi = 102 +/- 16 degrees) compared to controls (phi = 8 +/- 3 degrees).
- TAA was significantly correlated with increased RL (r = 0.773) and inversely correlated with CL/kg (r = -0.67).
- A wide range of TAA was observed in BPD infants, with some showing near-synchronous motion.
Conclusions:
- In infants of similar weight, TAA is a useful cross-sectional indicator of lung function.
- TAA reflects both the resistive and elastic properties of the lungs in infants.
- The degree of TAA provides insights into the severity of lung disease in infants.
Abstract:
Asynchronous or paradoxic motion between the rib cage and abdomen may be seen in infants with lung disease. We have recently shown that after bronchodilator administration, the degree of asynchrony decreases proportionately to the improvement in lung mechanics. However, whether such thoraco-abdominal asynchrony (TAA) is a useful indicator of lung function in a cross-sectional population, i.e., whether asynchrony correlates with baseline lung mechanics, is unknown. Therefore, we quantitated the degree of TAA using respiratory inductive plethysmography during quiet sleep in ten infants with bronchopulmonary dysplasia (BPD) and six weight-matched control infants. We displayed abdominal wall (AB) and rib cage (RC) motion on an X-Y recorder, and from the tidal breathing loop we calculated a phase angle phi, between 0 degrees and 180 degrees as an index of asynchrony (synchronous RC/AB motion = 0 degrees, paradox = 180 degrees). Lung resistance (RL) and compliance/kg (CL/kg) were calculated from esophageal and mouth pressure, tidal volume, and tidal flow. As expected, BPD infants had abnormally high RL, and low CL/kg when compared to controls. All infants with BPD displayed marked thoraco-abdominal asynchrony (phi = 102 +/- 16 degrees, mean +/- SEM; range 35 degrees-160 degrees) with controls displayed synchronous chest wall motion (phi = 8 +/- 3 degrees, range 0 degrees-15 degrees) (P less than 0.001). The degree of TAA was significantly correlated with RL (r = 0.773, P less than 0.001) and inversely correlated with CL/kg (r = -0.67, P less than 0.01). We conclude that in infants of similar weight, TAA may be used as a cross-sectional index reflecting both resistive and elastic properties of the lungs.