PEEP DOES NOT IMPROVE PULMONARY MECHANICS IN INFANTS WITH BRONCHIOLITIS

Positive end-expiratory pressure (PEEP) may improve pulmonary mechanic s, work of breathing, and gas exchange in some patients with respirato ry failure. These beneficial effects do not occur consistently, howeve r, and side effects, such as gas trapping due to expiratory flow limit ation, may be exacerbated. We determined the effects of PEEP (0, 3, 6, and 9 cm H2O applied in random order) on the expiratory airway resist ance and static compliance of nine infants mechanically ventilated for acute bronchiolitis. We also noted the presence of inadvertent PEEP ( PEEPi) to determine its influence on the response to applied PEEP. App lied PEEP at any level failed to consistently improve passive expirato ry airway resistance or increase compliance from baseline (PEEP = 0 cm H2O, resistance = 92 +/- 32 cm H2O/L/s; compliance = 0.71 +/- 0.19 ml /cm H2O/kg). Increases in end-expiratory lung volumes ranged from 18 t o 40% of the tidal volume at maximal PEEP. Although all infants had PE EPi (5 +/- 2 cm H2O), PEEPi had no influence on the response of mechan ics to applied PEEP other than that peak inspiratory pressures increas ed when PEEP > PEEPi. We conclude that the routine use of PEEP in infa nts with bronchiolitis does not consistently improve passive expirator y pulmonary mechanics and may increase the risk of barotrauma from gas trapping.