Mean airway pressure--significance during mechanical ventilation in neonates

Variations in PEEP with concomitant changes of DPP while MAP, PIP, flow, FIO2, and ventilator rate remained constant were investigated in nine neonates with RDS during the first and second days of life. After stabilization on baseline ventilator settings, PEEP was increased by 3 cm of H2O and DPP decreased in order to maintain balance MAP. Following a return to baseline settings, the PEEP was decreased by 3 cm of H2O and DPP increased sufficiently to maintain constant MAP. Arterial PaO2, PaCO2, pH, blood pressure, heart rate and a/APO2 ratios were measured before, during, between, and after the experimental conditions. Analysis revealed no significant changes in PaO2, a/APO2, blood pressure, or heart rate during baseline or experimental conditions. PaCO2 decreased significantly when PEEP was decreased and DPP increased, both on day 1 (37.2 +/- 2.4 vs 41.4 +/- 2.3 torr; P less than 0.025) and day 2 (42.1 +/- 2.6 vs 46.8 +/- 2.0 torr; P less than 0.05). Changes in pH were inversely related to PaCO2 changes. This study confirms the importance of MAP in determining oxygenation in newborn infants with RDS. However, ventilation was significantly affected by variation in PEEP and DPP despite a constant MAP.