Body and Breath - Yoga Shop Talk

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Yoga shoptalk, March, 2003

I'm scheduled for an upcoming trip to mountainous regions of Nepal and Tibet, and will be staying at altitudes ranging from 10,000 to 19,000 feet for about a month. I live on the east coast of the US, and my only real experience with mountains was in Colorado, where I stayed in Estes Park for two weeks and at one point in time during my stay made a climb to the summit of Long's Peak. I had moderate headaches for the first few days in the environs of Estes Park, and felt pushed to my limit climbing Long's Peak. Are there any yogic breathing exercises that can help acclimate me to the altitudes I will be experiencing in Nepal and Tibet?

Answer: The elevation in Estes Park is about 7,500 feet, and the elevation at the summit of Long's Peak is about 14,250 feet, so you have a good chance of not running into problems at the altitudes you will be experiencing in the Himalayas, especially if you do not plan on remaining at the highest altitudes in your plan (18,000 to 19,000 feet) for prolonged periods. Better safe than sorry, however, and there are several precautions you should take. And yes, there are breathing exercises that can help you, but more on that later.

First, you should travel in a group in which at least one or two individuals are medical professionals who have been trained to be aware of the dangers of high altitude sickness and to know how to treat its symptoms. Even moderate altitudes of 10,000 to 15,000 feet can be life-threatening to certain individuals under stressful circumstances, and in an emergency their survival may depend on proper medical treatment and evacuation to a lower altitude.

In order to illustrate physiological aspects of breathing exercises, I comment indirectly on a few high altitude questions in chapter two (breathing) of Anatomy of Hatha Yoga. The essential problem, at least in its most simplified form, is that you will need to breathe much faster and more deeply at high altitudes in order to get enough oxygen into your blood supply, especially if you are exercising, as you would be doing on a climb. And you can best train for doing that by extensive practice of the bellows breath at ordinary altitudes. The problem associated with deep and rapid breathing, however, is that your blood carbon dioxide is lowered substantially, and this can cause difficulties with the circulation of blood to the brain. Quoting from chapter two of Anatomy of Hatha Yoga:

". . . vigorous practice of bellows breathing brings up the question of hyperventilation, or overbreathing, and this, paradoxically, can create a deficit in the supply of oxygen for the cells of the central nervous system where we need it the most.

"Let's say you are hyperventilating during the course of an extreme bellows exercise. If this involves breathing in and out a tidal volume of 500 ml three times per second, you will end up with an alveolar ventilation of 180 breaths per minute times 350 ml per breath, which equals 63,000 ml per minute, or fifteen times the norm of 4,200 ml per minute. If you were in world-class athletic condition and running full speed up forty flights of stairs, this would be fine. During heavy exercise your body will use all the oxygen it can get, and it will also need to eliminate a heavy overload of carbon dioxide. It's not, however, a good idea for an ordinary person to breathe in this way. Extreme hyperventilation when you are not exercising strenuously skews the blood gases too much.

"Our first thought is that hyperventilation must drive too much oxygen into your tissues, but this is inaccurate. Except for a few special circumstances, such as breathing 100% oxygen for prolonged periods, or breathing oxygen at high pressure in deep-sea diving, you can't get too much, and the increased oxygen in the blood that results from hyperventilation is certainly not harmful.

"The problem with hyperventilation is not that it increases arterial oxygen but that it decreases arterial carbon dioxide, and that can have an unexpected side effect. What happens is that a substantial reduction in arterial carbon dioxide constricts the small arteries and arterioles of the brain and spinal cord. The way this happens, or at least the end result, is very simple: an arteriole acts crudely like an adjustable nozzle on the end of a garden hose that can open to emit a lot of water or clamp down to emit only a fine spray. As carbon dioxide in the blood is reduced, the arterioles clamp down and the blood supply to the tissue is restricted until there is so little blood flowing to the brain that it doesn't matter how well it is oxygenated. Not enough blood (and therefore not enough oxygen) can get through the arterioles to the capillary beds and adequately support the neurons.

"Hyperventilating vigorously enough to dramatically lower blood carbon dioxide doesn't necessarily result in death or even obvious clinical symptoms, but it can cause more general complaints such as fatigue, irritability, lightheadedness, panic attacks, or the inability to concentrate. It's not illogical that the folk remedy for panic attacks, which is still routinely administered by triage nurses in emergency rooms, is to have someone who is in such a state breathe into a paper bag. Rebreathing our exhaled carbon dioxide increases carbon dioxide levels in the blood and opens the cerebral circulation. There are better solutions, however, and triage nurses who have also had some training in relaxed yogic breathing practices would be more imaginative, perhaps suggesting something as simple as having the patient lie supine and breathe abdominally with their hands or a moderate weight on the abdomen.

"Extremely low blood levels of carbon dioxide can cause you to pass out. Children at play sometimes hyperventilate, hold their breath after a deep inhalation, and then strain against a closed glottis. If they do this for only 3-4 seconds they will drop to the floor like stones. Increasing intrathoracic pressure from straining will have diminished the venous return to the heart (and thus the cardiac output) immediately after the cerebral circulation has been partially occluded by hyperventilation, and these two ingredients combined cut off enough of the blood supply to the brain to cause an immediate but temporary loss of consciousness. The danger of passing out from constricted brain arterioles is also why lifeguards do not allow swimmers to hyperventilate vigorously before swimming underwater. Hyperventilating followed by holding the breath after a deep inhalation is not harmful to children on a grassy lawn who will begin to breathe normally as soon as they lose consciousness, but it is deadly under water.

"One of the most demanding tests of aerobic capacity is mountain climbing without bottled oxygen at altitudes higher than 25,000 feet. Superbly conditioned athletes are able to meet this standard and reach the summit of Mount Everest by hyperventilating the oxygen-poor atmosphere (42 mm Hg at 29,000 feet) all the way to the top. They can jam enough oxygen into their arterial blood to survive (about 40 mm Hg), and that's good; but the hyperventilation also drives their alveolar carbon dioxide down to less than 10 mm Hg, and that's not so good. They have to train rigorously at high altitudes to adapt the cerebral circulation to such extremely low levels of carbon dioxide. If most of us were transported unprepared to such an altitude (as would happen if we suffered a sudden loss of cabin pressure in an airliner cruising at 29,000 feet), we would experience so much reflex hyperventilation and subsequent constriction of the cerebral circulation that without supplemental oxygen we would pass out in about two minutes and die soon thereafter. Beginning hatha yoga students who practice the bellows breath excessively may experience some adverse symptoms of hyperventilation, especially irritability. But if they continue the practice over a period of time, the cerebral circulation gradually adapts to decreased levels of carbon dioxide in the blood, and they can intensify their practice and safely gain the benefits of alertness and well-being associated with higher levels of blood oxygen."

Getting back to your trip, the best possible low-altitude preparation is extensive practice of the bellows. Start moderately, as instructed in Anatomy of Hatha Yoga, and then gradually increase your capacity, finally working up to several minutes of enthusiastic practice several times a day. Your system will gradually become acclimated to lower levels of carbon dioxide, and when you are required (at high altitudes in the Himalayas) to breathe faster and more deeply to get enough oxygen, your brain arteries will not shut down from dramatic decreases in carbon dioxide. For more background and technical details, see chapter two of Anatomy of Hatha Yoga. And have a great trip.