Ventilation‐perfusion abnormalities in the preterm infant with hyaline membrane disease: A two‐compartment model of the neonatal lung

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Abstract
Arterial-alveolar differences for oxygen, carbon dioxide, and nitrogen were measured in 7 non-distressed preterm infants and 21 ventilator-dependent preterm infants with hyaline membrane disease. The preterm infants with hyaline membrane disease had a significantly lower average arterial pH (7.34 vs. 7.44; P < 0.001), and significantly higher arterial-alveolar differences for oxygen (286 mm Hg vs. 34 mm Hg; P < 0.005) and nitrogen (118 mm Hg vs. 7 mm Hg; P < 0.005). Both groups had elevated arterial-alveolar differences for P (9 mm Hg in infants with hyaline membrane disease, 5 mm Hg in nondistressed infants; P < 0.2). When acute changes in mean airway pressure were produced in 14 distressed infants, arterial-alveolar CO2 and N2 differences moved in opposite directions in 11 infants. This observation suggests that changes in mean airway pressure do not acutely recruit atelectatic alveoli, but cause redistribution of ventilation within alveoli already ventilated. Pediatr Pulmonal 1990; 9:206–213.