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Transmission of pressure across the chest wall during the rapid thoracic compression technique in infants
1Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, West Australia.
Insights
Chest compression pressure transmission in infants is lower at functional residual capacity due to passive chest wall mechanics, not muscle activity. This finding is crucial for understanding infant resuscitation techniques.
Area of Science:
- Pediatric Resuscitation
- Cardiopulmonary Physiology
- Thoracic Mechanics
Background:
- The rapid thoracic compression maneuver is used in infant resuscitation.
- Pressure transmission during this maneuver varies with lung volume.
- Previous studies suggest respiratory muscle activity might influence this variation.
Purpose of the Study:
- To determine if passive chest wall characteristics, rather than respiratory muscle activity, explain reduced pressure transmission at lower lung volumes.
- To quantify pressure transmission across the infant chest wall at different lung volumes.
Main Methods:
- Assessed pressure transmission across the chest wall in nine anesthetized, muscle-relaxed infants and young children.
- Measured esophageal and airway occlusion pressure during chest compressions at varying lung volumes.
- Analyzed the relationship between distending pressure (lung volume) and transmitted pressure.
Main Results:
- A linear relationship was observed between distending pressure and the proportion of pressure transmitted to the airway (r2=0.80) and esophagus (r2=0.85).
- Reduced pressure transmission at lower lung volumes (functional residual capacity) was consistent under both static and dynamic conditions.
- This pressure transmission pattern occurred independently of respiratory muscle activity.
Conclusions:
- Reduced pressure transmission during chest compressions at lower lung volumes in infants is primarily due to the passive mechanical properties of the chest wall.
- Findings suggest that lung volume, influenced by passive chest wall compliance, is a key determinant of pressure transmission efficiency during resuscitation maneuvers.
- This understanding can help optimize thoracic compression techniques in neonatal resuscitation.
Abstract:
During the rapid thoracic compression maneuver in infants, the transmission of pressure from compression jacket to pleural space and airway is less at functional residual capacity than at end inspiration. To examine whether reduced pressure transmission at functional residual capacity vs. higher lung volumes is explained by passive characteristics of the chest wall rather than by respiratory muscle activity, we assessed the pressure transmitted across the chest wall in nine anesthetized infants and young children after muscle relaxation. We measured esophageal and airway occlusion pressure during chest compressions at different lung volumes determined by varying distending pressure. In six subjects studied under static conditions, there was an approximately linear relationship between distending pressure and the proportion of pressure transmitted to the airway and esophagus from the compression jacket. The mean r2 value (95% confidence interval) was 0.80 (0.09) for pressure transmission to the airway and 0.85 (0.04) for pressure transmission to the esophagus. This relationship between lung volume and pressure transmission observed under static conditions was also demonstrated dynamically. Thus the reduced transmission of pressure from compression jacket to airway and pleural space at low lung volumes occurs independently of respiratory muscle activity.