EXPERIMENTAL STUDIES ON HETEROTOPIC LUNG TRANSPLANTATION DURING TEMPORARY PULMONARY-INSUFFICIENCY

Survival from reversible forms of severe pulmonary insufficiency remai ns dismal despite the development of artificial oxygenators. We hypoth esized that an intraabdominal heterotopic lung could help maintain ade quate oxygenation during acute pulmonary insufficiency. Five mongrel d ogs underwent an acute heterotopic lung transplant (HLT). The left atr ial cuff was anastomosed to the inferior vena cava, and the left pulmo nary artery was anastomosed to the abdominal aorta. The trachea was ex teriorized, intubated, and ventilated with a volume-controlled ventila tor. Ventilation to the native lungs was discontinued. The heterotopic lung was then ventilated at a rate of 20/min, tidal volume of 15 ml/k g, and inspired concentration (FIo(2)) of 50 percent. Partial pressure of oxygen (Po-2) and mixed venous oxygen saturation (SvO(2)) were mai ntained at 53 +/- 5.2 mm Hg and 71 +/- 12 percent, respectively. Flow through the HLT was approximately 20 percent of the systemic cardiac o utput and did not vary with changes in FIo(2), respiratory rate, or po sitive end-expiratory pressure (PEEP). Four separate animals underwent HLT and were studied 2 to 3 days later. The FIo(2) was reduced in the native lungs to 10 percent until SaO(2) was less than 90 percent. The HLT was then ventilated at a tidal volume of 300 ml, an FIo(2) of 50 percent, and a respiratory rate of 10. Arterial Po-2 increased from 62 +/- 4 mm Hg to 75 +/- 2 mm Hg, and SvO(2) increased from 75 +/- 2 per cent to 82 +/- 3 percent (p<0.05). Flow through the HLT increased slig htly to 27 percent of the systemic cardiac output. We conclude that a HLT can augment oxygenation after induction of moderate hypoxemia, but cannot serve as the sole source for gas exchange because now through the HLT is limited to less than 30 percent of the cardiac output.