Acute lung injury after tracheal instillation of acidified soya-based or Enfalac (R) formula or human breast milk in rabbits

Purpose: The aim of this study was to compare the severity of the acute lun g injury after tracheal instillation of acidified soya-based or Enfalac(R) infant formula, or human breast milk (HBM) in anesthetized rabbits. Methods: Alveolar-arterial oxygen tension gradient (A-aDO(2)) and dynamic c ompliance were measured before (baseline) and hourly for four hours after t racheal instillation of 0.8 ml.kg(-1) soya-based or Enfalac(R) infant formu la or HEM (all acidified to pH 1.8 with hydrochloric acid) or no fluid (con trol) in 24 anesthetized and tracheotomized adult rabbits. The A-aDO(2), th e difference between alveolar and arterial oxygen tensions, was corrected f or barometric pressure and carbon dioxide tension. Dynamic compliance was t he ratio of the expired tidal volume to the peak inspiratory airway pressur e, normalized to body weight, Results: Baseline A-aDO(2) and dynamic compliance were similar among the fo ur groups. In the control rabbits, A-aDO(2) remained unchanged throughout t he four hours, whereas mean A-aDO(2) increased 180 mm Hg in the soya-based group (P < 0.0025) and 350 and 275 mm Hg in the Enfalac(R) and HEM groups r espectively (P < 0.0002). The order of the A-aDO(2) post-instillation was E nfalac(R) approximate to HBM > soya > control (P < 0.0002). Dynamic complia nce decreased 10-12% in the control rabbits during the four post-instillati on measurements compared with baseline (P < 0,033), decreased 20% in the so ya-based group (P < 0.0002) and;40-50% in the Enfalac(R) and HEM groups (P < 0.0002). Conclusion: The severity of the acute lung injury after intratracheal insti llation of infant feeds in a volume of 0.8 ml.kg(-1) and at pH 1,8 in rabbi ts depends in part, on the type of feed: Enfalac(R) approximate to HEM > so ya > control.