Acute respiratory failure induced by bleomycin and hyperoxia

Bleomycin, a chemotherapeutic agent, and oxygen at concentrations greater than 20%, induce acute pulmonary damage separately and when administered together. The interaction of 5 U/kg intratracheal bleomycin and 24 hours of exposure to 80% oxygen in hamsters produces delayed onset acute respiratory distress syndrome three days after treatment. As little as 12 hours of 80% O2 exposure, after intratracheal bleomycin, induces severe pulmonary damage. Lung lesions are characterized as diffuse alveolar damage. Significant pulmonary edema, measured by iodine-125-bovine serum albumin and technetium-99m-diethylenetriaminepentaacetate, occurs 72 hours after treat-ment. Lesions progress from focal mild alveolar interstitial and air-space macrophage and granulocyte infiltrates at 24 hours to marked infiltrates and severe interstitial and air-space edema with hemorrhages and hyaline membranes at 96 hours. Significant changes measured by electron microscopy morphometry are increases in volume fractions of neutrophils, alveolar tissue and mononuclear leukocytes. Morphological changes in alveolar capillary endothelial cells detected by electron microscopy are focal attenuations, overlapping cell junctions, gaps between cells or in cell cytoplasm, and focal segmental cell necrosis. Surfactant assay of bronchoalveolar lavage fluid shows a marked decrease in the lecithin/sphingomyelin ratio at 72 hours. Proposed mechanisms of bleomycin and hyperoxia synergism include enhanced production of superoxide radicals either directly or indirectly by increasing neutrophil activity or numbers, or by alteration of cell mediators. The pulmonary edema, without evidence of severe morphological changes, may be secondary to alterations of transalveolar transport mechanisms.