From the Guidelines
A lower target oxygen saturation of 88-92% should be aimed for in patients with chronic obstructive pulmonary disease (COPD) or other conditions at risk of hypercapnic respiratory failure, as stated in the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. This approach is also appropriate for other conditions where patients rely on hypoxic respiratory drive, including some cases of obesity hypoventilation syndrome, neuromuscular disorders with respiratory involvement, and chest wall deformities. The physiological basis for this conservative approach is that some patients with chronic hypercapnia develop reliance on low oxygen levels (hypoxemia) to stimulate breathing. Providing excessive oxygen can remove this stimulus, potentially leading to carbon dioxide retention, respiratory acidosis, and respiratory depression. When administering oxygen to these patients, controlled oxygen delivery methods should be used, such as Venturi masks (set at 24-28%) or nasal cannulas at 1-2 liters per minute, with frequent monitoring of both oxygen saturation and respiratory rate, as recommended in the guideline 1. Blood gas analysis may be necessary to assess carbon dioxide levels in patients showing signs of drowsiness or confusion during oxygen therapy. This cautious approach balances the need to correct hypoxemia while avoiding the potentially dangerous consequences of excessive oxygenation in vulnerable patients, and is in line with the philosophy of the guideline that oxygen is a treatment for hypoxaemia, not breathlessness 1. Key points to consider when aiming for a lower target oxygen saturation include:
- The patient's underlying condition and risk of hypercapnic respiratory failure
- The use of controlled oxygen delivery methods
- Frequent monitoring of oxygen saturation and respiratory rate
- The potential need for blood gas analysis to assess carbon dioxide levels.
From the Research
Target Oxygen Saturation Ranges
When to aim for a lower target oxygen saturation in oxygen therapy depends on various factors, including the patient's condition and age.
- For preterm infants, the recommended oxygen saturation target range is 87% to 94% until vascular maturation of the retina is achieved, as supported by large multicentered, international studies such as BOOST II, COT, and SUPPORT 2.
- In adult patients without COPD or other conditions associated with chronic respiratory failure, a target oxygen saturation range of 92-96% may be preferable to 94-98% 3.
- For patients with COPD exacerbation, European and British guidelines endorse oxygen target saturations of 88%-92%, with adjustment to 94%-98% if carbon dioxide levels are normal 4.
Patient-Specific Considerations
- In preterm infants, the amount of oxygen supplementation and/or invasive ventilation during the first 7 weeks of life or up to 31 weeks postmenstrual age may be associated with the development of severe retinopathy of prematurity, suggesting the need for strict oxygen supplementation strategies during this period 5.
- In patients with COPD receiving supplemental oxygen, oxygen saturations above 92% were associated with higher mortality, and even modest elevations in oxygen saturations above the 88%-92% range were associated with an increased risk of death 4.
Clinical Implications
- Establishing clear target saturation limits according to recommendations and improving bedside compliance can help prevent states of hypoxia and/or hyperoxia in preterm infants 2.
- Automated oxygen regulations have been shown to increase the time that SpO2 is within the target range, which can improve compliance in targeting oxygen saturation in preterm infants 6.
- Treating all patients with COPD with target saturations of 88%-92% can simplify prescribing and improve outcomes 4.