Previously we have demonstrated that prolonged exposure to 100% ambient oxygen leads to a marked loss in functional lung volume and lung compliance, hypoxemia, and surfactant system abnormalities similar to acute respiratory distress syndrome (ARDS). However, 50% oxygen administration is believed to be safe in most clinical settings. In the present study, we have evaluated the effects of a 24-h exposure to 50% oxygen in rabbits immediately following experimental gastric acid aspiration. Mild hypoxemia, but no changes in mortality, lung volume, lung compliance, surfactant metabolism, or edema formation occurred after 24 h of normoxia postacid aspiration. Conversely, a relatively short (24-h) exposure to 50% oxygen after acid aspiration results in increased pulmonary edema, physical signs of respiratory distress, and mortality, as well as decreased arterial oxygenation, lung volume, lung compliance, and type II alveolar cell surfactant synthesis. These results suggest that acid aspiration alters the "set point" for oxygen toxicity, possibly by "priming" cells through activation of inflammatory pathways. This pathogenic mechanism may contribute to the progression of aspiration pneumonia to ARDS.

Care of patients who undergo tracheostomy for prolonged mechanical ventilation is expensive. The older the patient, the less satisfactory the outcome from an economic, clinical, and possibly social perspective.

More controlled reimbursements and improved overall survival rates for DRG 483 have contributed to the improved cost per survivor among all age groups over the period. Given the greater proportion of elderly that do not survive or who are placed into residential healthcare facilities, more scrutiny is needed concerning the use of DRG 483 resources so that care is better coordinated for these patients in the inpatient and postacute care settings.

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