Comparison of exogenous surfactant and positive end-expiratory pressure therapies in a model of human breast milk-induced acute lung injury in rabbits

To evaluate surfactant and positive end-expiratory pressure (PEEP) as poten tial therapies for the acute lung injury after tracheal instillation of 0.8 ml kg(-1) human breast milk (HBM) acidified to pH 1.8, adult white rabbits were anaesthetized, tracheostomized, ventilated and randomized to (six rab bits per treatment): (i) no treatment after HEM (control); (ii) exogenous B ovine surfactant (100 mg kg(-1)) 1 h after HEM; (iii) PEEP-pre (0.5 kPa PEE P) before and after HEM; or (iv) PEEP-post (0.5 kPa PEEP) after HEM. A fift h group of six rabbits received no tracheal instillate (no aspirate). The a lveolar to arteria[ oxygen tension gradient (A-aDO(2)) and dynamic complian ce were measured pre-injury and hourly for 4 h. At post-mortem, the lungs w ere examined histologically. A-aDO(2) in all four HEM-injured groups increa sed to a maximum at 1 h post-injury; A-aDO(2) then returned towards the bas eline in the surfactant and PEEP-post groups, but remained increased in the PEEP-pre and control groups. Dynamic compliance decreased in all four HEM- injured groups. A-aDO(2) and compliance were unchanged in the no aspirate g roup. Bronchoalveolar architecture after surfactant therapy was normal. We conclude that surfactant is a more effective therapy for HEM-induced lung i njury than either 0.5 kPa PEEP-post or PEEP-pre injury.