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Effect of chest wall distortion on occlusion pressure and the preterm diaphragm
Insights
Chest wall distortion (CWD) significantly impairs diaphragm function in preterm infants. Increased respiratory effort during high CWD does not translate to effective pressure generation, impacting breathing effectiveness.
Area of Science:
- Neonatal Physiology
- Respiratory Mechanics
Background:
- Preterm infants often experience respiratory challenges.
- Chest wall distortion (CWD) can affect breathing mechanics.
Purpose of the Study:
- To investigate the impact of CWD on transdiaphragmatic pressure (Pdi) and mouth occlusion pressure (Pmo) in preterm infants.
- To assess the relationship between diaphragmatic electromyogram (Edi) and respiratory pressures under varying CWD conditions.
Main Methods:
- Measured Pmo, gastric pressure (Pga), Edi, and rib cage/abdominal motion in seven preterm infants.
- Compared respiratory parameters during periods of minimal and maximal CWD.
- Analyzed Pdi as Pmo - Pga during airway occlusion.
Main Results:
- High CWD abolished the pressure response to increased Edi in four infants.
- Breaths with similar Pmo or Pdi showed significantly higher Edi during maximal CWD compared to minimal CWD.
- Increased Edi was 76% higher for Pmo and 144% higher for Pdi during maximal CWD.
Conclusions:
- Mouth occlusion pressure (Pmo) can be an unreliable indicator of respiratory drive in preterm infants with CWD.
- Chest wall distortion significantly compromises the diaphragm's ability to generate force, impacting respiratory effectiveness.
Abstract:
We studied the effect of chest wall distortion (CWD) on transdiaphragmatic pressure (Pdi) and/or mouth pressure during end-expiratory airway occlusions in seven preterm infants. We measured mouth occlusion pressure (Pmo) with a face mask and pressure transducer, gastric pressure (Pga) with a fluid-filled catheter, diaphragmatic electromyogram (Edi) using surface electrodes, and rib cage and abdominal motion using magnetometers. We reasoned that Pdi = Pmo - Pga on airway occlusion. Periods with maximal and periods with minimal CWD were compared. We found that 1) when CWD was minimal, an increase in Edi produced an increase in Pmo and Pdi in all infants; when CWD was greatest, large increases in Edi produced no increase in Pmo or Pdi in four infants; 2) when breaths with the same Pmo or Pdi from each period in each infant were compared, those from the period with greatest CWD had an increased Edi (mean increase 76%, P less than 0.005, and 144%, P less than 0.01, for Pmo and Pdi, respectively). We conclude that in preterm infants, Pmo can be a poor indicator of respiratory drive, and CWD markedly limits the effectiveness of the diaphragm as a force generator.