Effects of positive end-expiratory pressure on hyaline membrane formation in a rabbit model of the neonatal respiratory distress syndrome
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- Sandhar, B.K., Niblett, D.J., Argiras, E.P. et al. Intensive Care Med (1988) 14: 538. doi:10.1007/BF00263527
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Sixteen rabbits were anaesthetized and subjected to saline lavage of the lungs to produce surfactant deficiency. This resulted in an arterial oxygen tension of less than 12 kPa on 100% inspired oxygen and an inflection point on the pressure-volume curve at a pressure of 8–12 mmHg. After lavage the animals were randomly assigned to receive either conventional mechanical ventilation (CMV) with a positive end-expiratory pressure (PEEP) of 1–2 mmHg (group I —low PEEP) or CMV with PEEP equal to the inflection point pressure (group II — high PEEP). Mean airway pressures were kept at 14–16 mmHg in both groups by increasing the inspiratory: expiratory time ratios in the low PEEP group. The 5-h protocol was completed by 4 animals in group I and 6 animals in group II, early death usually being associated with a metabolic acidosis. On 100% oxygen, the mean PaO2 at 2-h post-lavage was 15.2±8.3 kPa in group I and 39.6±21.8 kPa in group II. Group I had much lower end-expiratory lung volumes (3.0±1.5 ml above FRC) than group II (34.9±12.2 ml above FRC). Histological examination of the lungs revealed significantly less hyaline membrane formation in group II (p=0.001). Thus, the prevention of alveolar collapse by the use of high PEEP levels appears to reduce lung damage in this preparation.