Positive end-expiratory pressure and pressure support in peripheral airways obstruction

Abstract

OBJECTIVES: Children with peripheral airways obstruction suffer the negative effects of intrinsic positive end-expiratory pressure: increased work of breathing and difficulty triggering assisted ventilatory support. We examined whether external positive end-expiratory pressure to offset intrinsic positive end-expiratory pressure decreases work of breathing in children with peripheral airways obstruction. The change in work of breathing with incremental pressure support was also tested. DESIGN AND SETTING: Prospective clinical trial in a pediatric intensive care unit. PATIENTS: Eleven mechanically ventilated, spontaneously breathing children with peripheral airways obstruction. INTERVENTIONS: Work of breathing (using pressure-rate product as a surrogate) was measured in three tiers: (a) Increasing pressure support over zero end-expiratory pressure. (b) Increasing applied positive end-expiratory pressure and fixed pressure support. The level of applied positive end-expiratory pressure at which pressure-rate product was least determined the compensatory positive end-expiratory pressure. (c) Increasing pressure support over compensatory (fixed) positive end-expiratory pressure. MEASUREMENTS AND RESULTS: Increases in pressure support alone decreased pressure-rate product from mean 724+/-311 to 403+/-192 cmH2O/min. Applied positive end-expiratory pressure alone decreased pressure-rate product from mean 608+/-301 to 250+/-169 cmH2O/min. The lowest pressure-rate product (136+/-128 cmH2O/min) was achieved using compensatory positive end-expiratory pressure (12+/-4 cmH2O) with pressure support 16 cmH2O. CONCLUSIONS: For children with peripheral airways obstruction who require assisted ventilation, work of breathing during spontaneous breaths is decreased by the application of either compensatory positive end-expiratory pressure or pressure support.