Pulmonary function after prolonged mechanical ventilation with high concentrations of oxygen

Area of Science:

• Pulmonary Medicine
• Critical Care Medicine
• Toxicology

Background:

• Mechanical ventilation with high inspired oxygen concentrations is common in critically ill patients.
• Potential risks include oxygen toxicity and impaired lung function.
• The clinical significance of oxygen toxicity in this setting requires further investigation.

Purpose of the Study:

• To investigate the mortality and morbidity associated with high concentrations of inspired oxygen during mechanical ventilation.
• To assess the long-term lung function in patients who survived prolonged mechanical ventilation with supplemental oxygen.

Main Methods:

• Retrospective review of clinical and postmortem findings in 91 patients requiring mechanical ventilation for pulmonary disease.
• Prospective lung function studies in 16 patients who survived prolonged mechanical ventilation with high oxygen concentrations.

Main Results:

• In patients with fatal respiratory failure, oxygen toxicity was unlikely to be a major contributor to mortality.
• In survivors, prolonged mechanical ventilation with high oxygen concentrations was associated with significant long-term defects in lung function (ventilation/gas transfer).
• Oxygen toxicity was considered a likely or possible cause in a minority of these patients.

Conclusions:

• Adverse effects of oxygen on alveolar epithelium are rarely clinically significant in hypoxemic patients requiring mechanical ventilation.
• Disturbance to pulmonary defenses against infection may be a more important complication.
• The fear of oxygen toxicity should not prevent adequate treatment of arterial hypoxemia in ventilated patients.