The effects of profound cryotherapy upon the pulmonary parenchyma

Cryotherapy, the application of supercool temperatures to living tissue, has proved successful in the treatment of many superficial neoplasms. Recent clinical studies have suggested the efficacy of an aggressive surgical excision of multiple pulmonary metastatic nodules. The current experiments were designed to study the effects of profound cryotherapy upon the pulmonary parenchyma as a preliminary to the use of this modality clinically in patients in whom further pulmonary resection is impossible. Six dogs were subjected to temperatures of -120 degrees C on the visceral pleural surface of the lingula for three successive freeze/thaw cycles. Serial roentgenograms were obtained on all animals and surviving animals were killed between 4 and 28 days following cryotherapy. Radiographically, an infiltrate developed in the region of cryotherapy within 3 to 5 days, clearing completely by 28 days. There was no instance of delayed pneumothorax developing. Histologically, a subpleural hemorrhagic infarct developed in the region of cryotherapy with mesothelial proliferation on the overlying pleural surface. Within 28 days the infarct had resolved to a subpleural fibrous scar with normal surrounding pulmonary parenchyma. These studies demonstrate the safety of profound pulmonary cryotherapy and suggest cautions clinical trials.