Positive end-expiratory pressure during KL4 surfactant instillation enhances intrapulmonary distribution in a simian model of respiratory distress syndrome.

Intrapulmonary distribution of a peptide-phospholipid (KL4) surfactant administered through an adapter permitting maintenance of positive end-expiratory pressure was compared with distribution by instillation with disconnection from mechanical ventilation in 10 surfactant-deficient Macaca mullata preterm infants. Animals received KL4 surfactant (200 mg/kg) when the arterial to alveolar (oxygen ratio) (a/Ao2) was < or = 0.22 (approximately 50 min after birth) on mechanical ventilation. Six rhesus infants received bolus instillation of two half doses of KL4 surfactant through an endotracheal tube adapter over 10-15 s while maintaining positive end-expiratory pressure (0.4 kPa) accompanied by turning to the right and left lateral positions for 60 s. In four rhesus premature infants KL4 surfactant was injected as two half-dose boluses through the endotracheal tube with disconnection from mechanical ventilation while positioning the infant rhesus monkey in the right and left lateral positions for 30 s of mechanical ventilation between instillation. Acute effects on oxygen saturation were monitored, and physiologic measures of a/Ao2, mean airway pressure, and the ventilatory efficiency index were monitored over the 12-h study. Intrapulmonary distribution of KL4 surfactant was determined using dye-labeled microspheres or [3H]dipalmitoylphosphatidylcholine-labeled surfactant, measured by colorimetry or by scintillation counting. Lungs of each monkey were processed into 50 +/- 5 pieces to determine distribution of radiolabel or microspheres and for scanning electron microscopy. The drop in oxygen saturation was greater among monkey infants disconnected from the ventilator for surfactant instillation.(ABSTRACT TRUNCATED AT 250 WORDS)