Five patients with respiratory insufficiency secondary to muscular weakness developed oxygen pneumonitis. During treatment with pressure-cycled ventilators attached to endotracheal tubes (IPPB), these patients developed diffuse, patchy infiltrates in the lung fields. Despite use of the ventilators' air-mix controls, expired oxygen concentrations ranged from 83% to 91%. All had abundant tracheal secretions. Atelectasis, pulmonary infections, and anemia were frequent complications.
The alveolar-to-arterial oxygen gradients (A-a O2 gradient) were markedly elevated. One patient died, and the lungs showed changes characteristic of severe pulmonary oxygen toxicity. In the other four patients the mean expired oxygen concentration was reduced from 87% to 40%. Within 2 to 5 days they could be weaned from the ventilators. Pulmonary infiltrates decreased in 1 to 4 weeks and disappeared in 3 to 7 weeks. Diffusing capacity, spirometry, and the A-a O2 gradient were normal in one patient studied 11 weeks later.
The above findings indicate that these patients developed pulmonary oxygen toxicity. The oxygen-induced pneumonitis gradually resolved once the expired oxygen concentration was reduced to levels of 45% or lower. Inspired or expired oxygen concentration should be measured frequently during administration of supplementary oxygen.