Measuring reduced cytochrome aa3 in cadaveric lungs using near-infrared spectroscopy

Researchers are investigating the use of cadaveric lungs to make up for the shortage of donors. However, no method to enable accurate evaluation of cadaveric lung viability has been established. We designed the present study to evaluate the viability of cadaveric lung tissue using near-infrared spectroscopy (NIRS). Male Lewis rats were anesthetized, mechanically ventilated, and subjected to a left thoracotomy. After cardiac arrest induced by an injection of sodium pentobarbital, we continued mechanical ventilation using oxygen (Group 1, n = 16) or nitrogen (Group 2, n = 20). Using NIRS, we monitored the redox state of cytochrome aa3 at intervals of 20 minutes for a period of 5 hours. We harvested the lung tissues of each group at 2 and 5 hours post-mortem and performed pathologic examination. The reduced cytochrome aa3 in Group 2 increased from 2 hours post-mortem. We observed no significant changes in Group 1. We found and scored the formation of hyaline membranes, intra-alveolar edema, edema around bronchioles and small vessels, and congestion in the cadaveric lungs. In Group 1, histologic findings were mild to moderate. In Group 2, findings were moderate at 2 hours post-mortem but became much more severe at 5 hours post-mortem. The measurement of reduced cytochrome aa3 using NIRS may reflect the histologic condition of cadaveric lung tissue. We expect that this evaluation method will be advantageous for lung transplantation in the future.