Our intervention with oxygen, though aimed at rectifying, can exacerbate lung injury akin to the adverse effects observed in cases of acute respiratory distress syndrome (ARDS).
The administration of high concentrations of oxygen leads to a cascade of biological responses, including the overproduction of reactive oxygen species (ROS), which, in turn, precipitates cellular damage and inflammation within the pulmonary parenchyma . This process is quantitatively significant; for instance, the exposure of lung tissue to an FiO2 of 1.0 can lead to discernible cellular toxicity within as little as 24 hours in healthy lungs. Increased ROS production with diminished antioxidant defenses results in significant pulmonary injury.
The onset of symptoms such as tracheobronchitis and absorptive atelectasis, following even short-term exposure to elevated oxygen levels, reminds of the delicate balance we must maintain in oxygen therapy. It should be noted that absorptive atelectasis, a condition where high FiO2 leads to the washout of alveolar nitrogen, results in alveolar collapse. This reduces lung volumes and, ironically, worsens hypoxemia. The anesthesia provider must adjust FiO2 to achieve target oxygenation levels without tipping the scales towards hyperoxia, mindful of the diminishing returns and potential for adverse outcomes associated with excessive oxygen supply.
| Population or setting | Principal concern | Practical approach |
|---|---|---|
| Neonates | Retinopathy of prematurity, and bronchopulmonary dysplasia with epithelial hyperplasia, squamous metaplasia, and fibrosis | Judicious oxygen management; infants with bronchopulmonary dysplasia may endure months of respiratory distress and require prolonged supplemental oxygen. |
| Adults on long-term oxygen therapy | Nasal dryness, irritation, and nosebleeds; less frequently, facial and upper airway burns, heightened in the presence of cautery | Water-based lubricants or humidification devices; long-term oxygen therapy should not be withheld when clinically indicated. |
| Post-cardiac arrest | A "two-hit" injury — hypoxic-ischemic insult followed by a reperfusion surge of reactive oxygen species plus hyperoxia-induced vasoconstriction; PAO2 greater than 300 mm Hg is associated with diminished survival | Monitor and adjust oxygen to maintain saturation within a physiologically normal range. |
| Post-myocardial infarction | Coronary blood flow falls by up to 29 percent for a gain in oxygen content of only about 7 to 8 percent | Reserve supplemental oxygen for instances of clinically evident hypoxia. |
| Acute lung injury and ARDS | Overproduction of reactive oxygen species with diminished antioxidant defenses; an FiO2 of 1.0 can cause discernible cellular toxicity within as little as 24 hours in healthy lungs | A conservative target of FiO2 below 0.6, complemented by strategies that minimize the need for high FiO2. |
| Mechanical ventilation for respiratory failure | Highest risk of oxygen toxicity, especially with FiO2 above 0.6 for extended periods; risk is influenced by FiO2, exposure duration, and sensitizing agents such as certain drugs or radiation | Minimize FiO2 to the lowest effective level that achieves target oxygenation, personalized to the patient. |
