The Effects of High Altitude on Asthma

A change of scenery is often a welcome break. But for people with asthma, spending time in a high altitude environment can cause unexpected effects. With reduced air pressure at high altitude, the air is thinner and there is less available oxygen to breathe. Air temperature and humidity also tend to be lower at high altitudes. These environmental changes can affect people with asthma. When your respiratory system is adapting to high altitude, this can lead to aggravation of asthma symptoms. Reduced humidity, however, may prove beneficial for those with allergic asthma.

High altitude is generally considered 8,000 or more feet above sea level. As altitude increases and air pressure falls, the amount of oxygen available with each breath decreases. This leads to a fall in the oxygen concentration in your bloodstream and tissues. Your body responds to these changes in various ways. Almost immediately, the rate and depth of your breathing increases. Your heart rate also increases. Other less obvious adaptations occur as well, including increased blood pressure in the lungs. This localized increase in blood pressure may help your lungs pick up more oxygen with each breath, but can lead to problems if excessive.

The changes in your body that occur at high altitude may make your asthma symptoms worse, especially with exercise. Scientific studies have shown that short-term exposure to high altitude can aggravate asthma. A study published in November 2002 in "JAMA Internal Medicine" reported that among travelers who experienced an asthma attack during their trips, 18 percent noted altitude as a trigger and 43 identified trekking. A study published in October 2013 in "Thorax" found that among 18 people with asthma, exposure to high altitude and low temperatures during a climbing expedition led to a small increase in airway obstruction and moderately increased asthma symptoms. However, the researchers concluded that cold weather was likely a more significant contributor to the findings than high altitude.

While short-term exposure to high altitude might make your asthma worse, long-term exposure may lead to improvement of allergic asthma. This is primarily related to the absence of house dust mites at high altitude. A study published in June 1996 in "Thorax" found that after a month living at high altitude, 16 children with allergic asthma experienced reduced airway inflammation and reactivity. Thin, high-altitude air may also promote better airflow through your airways, making breathing feel easier. While this has not been studied at high altitude, a study published in August 1999 in "Chest Journal" showed symptom improvement in people experiencing a severe asthma attack when they breathed a thin helium-oxygen mixture, which is similar to high-altitude air.

There are a variety of precautions you can take if you have asthma and travel to a high altitude area. Guidelines published in the summer of 2009 in "High Altitude Medicine and Biology" recommend that your asthma should be stable and well controlled before high altitude exposure. They also recommend continuing your regular asthma therapy. You should have access to warm, dry rescue drugs, and avoid intense exercise at high altitude. If symptoms occur at high elevation and you do not respond to initial self-treatment, guidelines recommend seeking medical attention right away. Talk with your doctor before traveling to a high altitude, for specific evaluation and recommendations.