Continuous negative extrathoracic pressure versus positive end-expiratory pressure in piglets after saline lung lavage

Recent reports have suggested that substituting continuous negative extrathoracic pressure (CNEP) for positive end-expiratory pressure (PEEP) may result in clinical benefits to infants with pulmonary disease. Other studies have suggested potential hemodynamic advantages. We compared the effects of CNEP and PEEP in 13 mechanically ventilated newborn piglets after acute lung injury induced by saline lavage. The piglets were instrumented, salinelavaged, and exposed to 15 minute periods of incremental CNEP (–3, –6, –9, –12 cmH₂O) (n = 7) or PEEP (3, 6, 9, 12 cmH₂O) (n = 6). We measured and/or calculated dynamic lung compliance (C_Ldyn), lung resistance (R_L), end-expiratory lung volume (EELV), blood gases, cardiac output (CO), heart rate (HR), transmural vascular pressures, and pulmonary and systemic vascular resistance. Pulmonary function abnormalities after saline lavage included decreased P_ao2, C_Ldyn, EELV, and increased P_aco₂ and R_L (P < 0.05). Except for decreased CO, lung inflation with both CNEP and PEEP resulted in large increases in P_aO₂ without major pulmonary or hemodynamic effects. Other than differences in EELV at 3, 6, and 9 cmH₂O distending pressure, there were no differences in pulmonary function or hemodynamics between sequences of incremental CNEP and PEEP. We conclude that CNEP and PEEP are physiologically equivalent in this model of acute lung injury. Pediatr Pulmonol. 1994; 17:161–168. © 1994 Wiley-Liss, Inc.