What does hyperoxia (high oxygen levels) in the lungs signify?

From the Guidelines

Hyperoxia in the lungs signifies a potentially harmful condition. High oxygen levels in the lungs, also known as hyperoxia, can occur with supplemental oxygen therapy, such as administering oxygen via nasal cannula or ventilator 1. This condition can lead to oxygen toxicity, causing diffuse alveolar damage, haemorrhage, alveolar collapse, infiltration of inflammatory cells, necrosis, apoptosis, and injury to the endothelium and epithelium in the lungs 1.

• Prolonged exposure to high oxygen tensions, exceeding 24 hours, may increase the risk of oxygen toxicity, necessitating careful monitoring and adjustment of oxygen therapy 1.
• The British Thoracic Society guideline recommends careful consideration of oxygen therapy, as uncontrolled supplemental oxygen can be harmful to patients at risk of hypercapnic respiratory failure, especially if the PaO2 is raised above 10 kPa 1.
• Key mechanisms involved in oxygen physiology include the transport of oxygen in the blood, either dissolved in plasma or bound to haemoglobin, and the regulation of oxygen levels by the carotid body and kidneys 2.
• Normal oxygen saturation levels range from 95-98% in healthy adults at sea level, and supplemental oxygen therapy should aim to maintain a target saturation range of 94-98% to avoid hypoxic tissue injury 2.

From the Research

Hyperoxia in the Lungs

Hyperoxia, or high oxygen levels, in the lungs can signify several things, including:

• Potential for absorption problems in the lungs, middle ear, and paranasal sinuses, particularly if the inspired oxygen fraction (FIo₂) is greater than 80% and small airways, Eustachian tubes, or sinus passages are blocked 3
• Risk of pulmonary oxygen toxicity and direct oxidative injuries, although this is unlikely in flight and has not been found when the partial pressure of oxygen (Po₂) is less than 55 kPa 3
• Constriction of blood vessels, changes in blood pressure control, and reduced response to low blood sugar 3
• No improvement in gas transport and oxygen delivery with healthy lungs, even with increased Po₂ 3

Clinical Implications

Hyperoxia can have significant clinical implications, including:

• Increased risk of hypercapnia, particularly in patients with chronic obstructive pulmonary disease (COPD), morbid obesity, asthma, and other conditions 4, 5
• Association with worse clinical outcomes, including increased mortality and reduced ventilator-free days, in patients with acute respiratory distress syndrome (ARDS) 6
• Potential for harm, including increased risk of serious adverse events and mortality, when using higher fractions of inspired oxygen or targets of arterial oxygenation in adults admitted to the intensive care unit (ICU) 7

Oxygen Therapy

Oxygen therapy should be used judiciously, with consideration of the potential risks and benefits, including:

• Monitoring of peripheral oxygen saturation (SpO₂) and titration of oxygen therapy to maintain SpO₂ within a target range 4
• Avoidance of hyperoxia, particularly in patients at risk of hypercapnia or with ARDS 4, 6
• Use of lower fractions of inspired oxygen or targets of arterial oxygenation, particularly in adults admitted to the ICU 7