Abstract
Twenty six premature infants, mean BW 1480 g, mean gestational age 32 wks. who needed mechanical ventilation because of respiratory failure were studied. Spontaneous respiration was suppressed by slight hyperventilation. Chest wall compliance was calculated by dividing tidal volume (VT) by the change in esophageal pressure (Pes) obtained at different peak inspiratory pressures.
Changes in Pes reflect the amount of airway pressure transmitted to the pleural space. Means for VT and Pes measurements were:
The results indicate that there is a linear correlation between VT and Pes (r=0.95) up to maximal inflation of the lung. The slope of the regression was 6.4 m]/cmH20×kg, which is the value of chest wall compliance. No linear correlation was found between airway pressure and Pes because the pressure volume curve of the lung is not linear but becomes progressively flatter at high volumes. Because chest wall compliance is four to six times higher than the normal lung compliance, no more than a sixth to a fourth of the airway pressure can be transmitted to the esophagus during positive pressure ventilation. Transmission will be even smaller when lung compliance is decreased as it occurs in hyaline membrane disease or when the tidal volume reaches the flatter part of the pressure volume curve of the lung. This poor transmission may protect the cardiovascular system from the effects of positive pressure.
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Gerhardt, T., Bancalari, E. 1182 CHEST WALL COMPLIANCE IN PREMATURE INFANTS. Pediatr Res 12 (Suppl 4), 561 (1978). https://doi.org/10.1203/00006450-197804001-01188
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DOI: https://doi.org/10.1203/00006450-197804001-01188