Acute mountain sickness (AMS) refers to health issues affecting people who ascend rapidly to high altitudes. The root cause is reduced barometric pressure, which lowers the availability of oxygen absorbed with each breath—a condition known as hypobaric hypoxia. This decrease causes symptoms like headache and fatigue, typically starting above 8,200 feet (2,500 meters). Supplemental oxygen is a highly effective treatment that directly counteracts hypoxia by increasing the inhaled oxygen concentration. While acclimatization is the long-term solution, oxygen provides immediate relief and stabilization when symptoms arise. This guidance focuses on administering supplemental oxygen in an altitude setting.
When Supplemental Oxygen is Necessary
The decision to use supplemental oxygen depends on symptom severity. Mild AMS is often managed by resting or descending slightly, though oxygen can speed recovery. More serious symptoms indicate life-threatening conditions like High Altitude Cerebral Edema (HACE) or High Altitude Pulmonary Edema (HAPE), where oxygen provides immediate stabilization. HACE symptoms include severe headache, confusion, and lack of coordination. HAPE often involves a persistent dry cough, chest tightness, and shortness of breath even while resting.
A pulse oximeter provides an objective measure for oxygen need, but readings must be interpreted considering altitude. While sea level blood oxygen saturation (SpO2) is typically 95% to 100%, this range naturally drops at higher elevations. For someone showing altitude illness symptoms, a reading consistently below 90% strongly indicates supplemental oxygen is necessary. For severe cases, medical guidance recommends using oxygen to achieve an SpO2 reading greater than 90% for stabilization prior to descent.
Understanding Oxygen Delivery Systems
Travelers to high altitudes have access to different types of oxygen equipment. The most accessible option is the small, disposable canister, often marketed as recreational oxygen. These cans contain highly concentrated oxygen (around 95% pure) and are sold without a prescription. However, they offer a very limited supply, providing only a few minutes of use designed for short, temporary bursts of relief, not sustained treatment.
For prolonged treatment, two main medical-grade options are available: pressurized oxygen tanks and oxygen concentrators. Pressurized tanks contain regulated, medical-grade oxygen and require a prescription. Oxygen concentrators filter ambient air to produce a continuous stream of concentrated oxygen, meaning they do not run out as long as they have a power source. Both systems provide a continuous, adjustable flow rate, making them appropriate for treating moderate to severe altitude sickness.
Practical Steps for Administering Oxygen
Medical-grade systems offer precise control over the flow rate. For portable tanks or concentrators, oxygen is typically delivered through a nasal cannula—a tube with two small prongs that fit into the nostrils. Once secured, the flow rate is set using the regulator dial. For mild to moderate AMS symptoms, a continuous flow rate of 1 to 2 Liters Per Minute (LPM) is often sufficient.
In severe cases, such as HACE or HAPE, a higher flow rate is temporarily applied to rapidly increase blood oxygen saturation. A flow rate between 2 to 4 LPM is commonly used to quickly raise the SpO2 above 90%. Since a nasal cannula mixes oxygen with room air, the effective concentration changes based on the person’s breathing rate. After initiating oxygen, symptoms and SpO2 levels should be monitored every few minutes to stabilize the condition.
Recreational oxygen cans operate differently, lacking a continuous, regulated flow rate. Users press a button to release a short burst of oxygen, inhaled directly from the mouthpiece or mask. They are best used for intermittent relief, such as taking a few breaths every few minutes, rather than continuous therapy. For medical-grade systems, duration varies from intermittent 30-minute periods to continuous use while sleeping, which can significantly reduce altitude sickness symptoms.
The Critical Importance of Descent
Supplemental oxygen is an immediate and effective treatment, but it serves primarily as stabilization, not a definitive cure. Oxygen supports the body against hypoxia but does not remove the underlying cause: high altitude. It is a temporary measure designed to improve the person’s condition for a safer descent.
If symptoms, particularly those indicative of HACE or HAPE, do not improve rapidly despite correct oxygen administration, immediate descent is the only complete remedy. Delaying descent hoping oxygen alone will resolve the condition is dangerous. The protocol for severe altitude illness is to begin oxygen therapy and necessary medications immediately, while preparing for and executing a descent to a lower elevation as soon as safely possible.