Distribution of pulmonary blood flow in the perfluorocarbon-filled lung

Objective:Partial liquid ventilation (PLV) improves gas exchange in animal studies of lung injury. Perfluorocarbons (PFCs) are heavy liquids and are t herefore preferentially delivered to the most dependent areas of lung. We h ypothesised that improved oxygenation during PLV might be the consequence o f a redistribution of pulmonary blood flow away from poorly ventilated, dep endent alveoli, leading to improved ventilation/perfusion (V/Q) matching. T his study investigated whether partially filling the lung with PFC would re sult in a redistribution of pulmonary blood flow. Design: Prospective experimental study. Setting: Hospital research institute laboratory. Participants: Six anaesthetised pigs without lung injury. Interventions: Animals were anaesthetised and ventilated (gas tidal volume 12 ml/kg, PEEP 5, FIO2 1,0, rate 16). Whilst the pigs were maintained in th e supine position, regional pulmonary blood flow was measured during conven tional gas ventilation and repeated during PLV. Flow to regions of lung was determined by injection of radioactive microspheres (Co-57, Sn-113, SC46). Measurements were performed with ventilation held at end-expiratory pressu re and, in two PLV animals only, repeated with ventilation held at peak ins piratory pressure. Results: During conventional gas ventilation, blood flow followed a linear distribution with the highest flow to the most dependent lung. In the lung partially filled with PFC a diversion of blood flow away from the most depe ndent lung was seen (p = 0.007), resulting in a more uniform distribution o f Row down the lung (p = 0.006). Linear regression analysis (r(2) = 0.75) a lso confirmed a difference in distribution pattern. On applying an inspirat ory hold to the liquid-containing lung, blood flow was redistributed back t owards the dependent lung. Conclusions: Partially filling the lung with PFC results in a redistributio n of pulmonary blood flow away from the dependent region of the lung. Durin g PLV a different blood flow distribution may be seen between inspiration a nd expiration. The clinical significance of these findings has yet to be de termined.