Diffuse and focal oxygen pneumonitis. A preliminary report on the threshold of pulmonary oxygen toxicity in man.

Utilizing hyaline membranes and proliferative pneumonitis as evidence of pulmonary oxygen toxicity, the lung changes in 21 patients (19 injured, two inhaled smoke) who died after oxygen therapy are correlated with the intensity and duration of oxygen administration. Diffuse pneumonitis inducing hypoxaemia was found in 10 (or 11) subjects, and in nine of them it was associated with the breathing of high concentrations of oxygen (60 to 100%) for at least two days. In at least eight subjects the pneumonitis contributed to death, and two others who survived for weeks had extensively fibrosed lungs. The breathing of 40% oxygen for a sufficient time seems to be a threshold for dangerous lung effects, since one patient developed a diffuse pneumonitis and another a partly-diffuse partly-focal pneumonitis while exposed to this concentration. Those respiring oxygen concentrations between 25 and 40% for days developed either subclinical focal lung lesions or had no relevant lung changes.