II. Clinical Application

The sensitivity of all cells to damage by ionizing radiations is related to the oxygen tension around them at the time of irradiation. In all types of neoplasm there may be areas of low oxygen tension resulting either from the type of tumour structure or inadequate circulation or both. Cells in these areas are protected from injury during conventional radiotherapy and may survive to cause recurrence of the growth. The oxygen tension around these cells may be increased by the inspiration of additional oxygen. On account of the mechanism of oxygen transport to the cells the use of high pressure of oxygen in the inspired gases is necessary to affect the cells of tumours with a poor circulation. Oxygen at high pressure for patients involves the use of a pressure chamber, a general anaesthetic to eliminate the danger of convulsions and bilateral myringotomies to prevent damage to the middle ear. Special techniques are necessary to safeguard and observe the patient during treatment. The enhanced effect of radiation in human patients breathing oxygen at 3 atmospheres pressure has been demonstrated histologically. More than 40 patients have been treated without mishap or complication due to the technique. All had inoperable neoplasms and were considered to have little if any chance of cure by conventional radiotherapy. The results of the treatment of 35 patients are presented and discussed.