The effect of PEEP on lungmechanics and bloodgases in mechanically ventilated newborn infants

Because little is known about the effect of small PEEP changes on bloodgases and lungmechanics and its impact on respiratory care in the individual patient, we investigated the effect of PEEP of 2, 4 and 6 cm H2O on compliance of the respiratory system(Crs) and bloodgases in 17 mechanically ventilated neonates(GA 28-39 wks, BW 600-3400 g, mainly one day old). The PEEP levels were randomly altered after half an hour, keeping other variables constant. At each PEEP level compliance was measured as described by Simbruner G (J Pediatr 1986; 108:589) and pO2, pCO2 determined from an arterial blood sample. PEEP increased pO2 (10 mm Hg/cm H2O). In 11/17 patients a PEEP 2 yielded the highest, and in 8/17 PEEP of 6 cm H2O yielded the lowest Crs. At PEEP settings, yielding the highest Crs [optimal PEEP]. Crs was on the average 36% (in individuals up to 100%) higher and CO2 2 mm Hg (in individuals up to 10 mm Hg)lower compared to those PEEP levels, yielding the lowest Crs[worst PEEP]. We conclude that small PEEP changes can significantly influence Crs of individual patients. Setting optimal PEEP in individals would allow gas exchange at lower pressures without much decrease of pO2. In future Crs would have to be referred to the PEEP level at which it was measured.