From the Guidelines
At high altitudes like the Himalayas, acceptable oxygen saturation (SpO2) levels are typically lower than at sea level, ranging from 75-85% above 3,000 meters (9,800 feet). While 95-100% is normal at sea level, climbers in the Himalayas often function with these lower SpO2 levels as the body adapts to decreased atmospheric oxygen pressure 1. Climbers should monitor for symptoms of altitude sickness rather than focusing solely on SpO2 numbers. If SpO2 drops below 70% and is accompanied by symptoms like severe headache, confusion, or difficulty breathing, supplemental oxygen may be necessary 1.
Key Considerations
- Proper acclimatization is essential, following the "climb high, sleep low" principle and ascending no more than 300-500 meters per day above 3,000 meters.
- Medications like acetazolamide (Diamox) at 125-250mg twice daily can help prevent altitude sickness by accelerating acclimatization, but should be started 24 hours before ascent and continued until descent or full acclimatization.
- The body compensates for lower oxygen levels by increasing respiratory rate and producing more red blood cells over time.
Important Factors
- The BTS guideline recommends a target SaO2 (and SpO2) ≥94% for most hypoxaemic patients to ensure that the actual oxygen level remains above 90% for most of the time with a 4% margin of safety to allow for variability in oxygen saturation levels, their recordings and oximeter error 1.
- Mental functioning becomes impaired if the PaO2 falls rapidly to <6 kPa (45 mm Hg, SaO2 <80%) and consciousness is lost at <4 kPa (30 mm Hg, SaO2 <56%) in normal participants 1.
From the Research
Typical Acceptable SpO2 Levels for Mountain Climbing
- The typical acceptable oxygen saturation (SpO2) level for climbing a mountain like the Himalayas can vary depending on the altitude and individual acclimatization 2, 3, 4, 5, 6.
- At high altitudes, SpO2 levels can drop significantly, with mean values ranging from 68.0% to 85.8% 2, 4, 6.
- A study found that mean SpO2 values of 85.8% in normobaric hypoxia were significantly higher compared to those of 80.2% in hypobaric hypoxia 2.
- Another study suggested that SpO2 levels below 80% may indicate inadequate acclimatization and impending acute mountain sickness (AMS) 3.
- At altitudes above 8,000 meters, SpO2 levels can drop to extremely low values, similar to those of patients with severe respiratory failure, with values as low as 40% recorded during sleep in asymptomatic subjects 6.
Factors Affecting SpO2 Levels
- Acclimatization plays a significant role in maintaining SpO2 levels, with values increasing progressively with acclimatization 6.
- Age, body mass index (BMI), and aerobic capacity can also affect SpO2 levels, with younger individuals and those with higher BMI and aerobic capacity tend to have higher SpO2 levels 3.
- Exercise and physical activity can also impact SpO2 levels, with values decreasing during exercise and increasing with rest 3, 4.