Single lung transplantation (SLT) is emerging as definitive therapy for end-stage pulmonary disease of varying etiology, yet a complete description of the hemodynamic properties of the transplanted lung has not been reported. In this study, Fourier analysis was used to calculate the pulmonary arterial (PA) impedance spectrum before and immediately after SLT to define precisely the pulmonary pressure-flow relationship. Median sternotomies were performed in 18 dogs (donors): an ultrasonic flow probe was placed around the PA and micromanometers were placed in the PA and left atrium (LA). Control PA pressure and flow (PAQ) and LA pressure were measured during transient occlusion of the right PA. The lungs were harvested using cold modified Euro-Collins solution for preservation. After thoracotomy and pneumonectomy, left SLT was performed in 18 recipient dogs with a mean ischemic time of 179 ± 6 min. After reperfusion for 1 hr, PA pressure and flow data were again collected. Characteristic impedance (Z0), a measure of resistance to pulsatile flow, was compared to input resistance (Rin), a measure of resistance to mean flow, and pulmonary vascular resistance (PVR), the conventional index. Rin is defined as the zeroth harmonic of the impedance spectrum and Z0 as the mean of impedance moduli from 2-12 Hz. All recipients survived transplantation. Both PVR and Rin increased significantly after transplantation (11 ± 1 vs 19 ± 3 Wood U, P < 0.05, and 1352 ± 121 vs 1964 ± 244 dyne · sec · cm-5, P < 0.05). Moreover, Z0 increased 144% after transplantation (377 ± 51 vs 918 ± 134 dyne · sec · cm-5, P < 0.05), indicating a proportionately greater change in resistance to pulsatile blood flow than to mean blood flow. These data suggest that characteristic impedance may be a more sensitive indicator of pathologic changes in the pulmonary vasculature secondary to transplantation. Furthermore, this study demonstrates the feasibility of impedance measurements in a lung transplant model which may be useful in evaluating preservation techniques and pharmacologic interventions. © 1992.
