Yoga Physiology

Yoga physiology, anatomy and movement science

Hyperventilation: Why breathing more isn’t necessarily better (Part 1)

This is part one of a series of posts I plan to write on the physiology of hyperventilation.

Recently, when I was in California I spent an evening practicing holotropic breathwork. I didn’t know much about this beforehand, and you might not either, so I’ll just set the scene. There were about 20 or so of us in a circle, along with a facilitator (whose instructions generally only increased my mystification). After a rambling introduction, he switched on some music, and we divided into pairs. One member of each pair was to be a sitter, whose only job was to observe. The others—the breathers—lay supine on a bed of cushions and blankets. That was me.

Our job as breathers was to breathe as rapidly and deeply as possible, preferably making lots of noise. As a physiology geek, this was an interesting experiment to me, so I was diligent in trying to stay with it. It was much harder than it might sound, though, particularly since we had to keep it up for well over an hour. The longer it went on the more spaced out I became, and the more difficult it became to remember what I was supposed to be doing. Eventually I started to experience muscle spasms; my arms and legs began to jerk about uncontrollably.

In the end, I couldn’t sustain it. Despite the urging of the facilitator, who periodically came around to rally me with loud whooshing breathing sounds, I found myself falling into longer and longer periods of almost involuntary apnea (cessation of breathing). My friend who was observing told me afterward that my reactions were mild compared to others’. “It was like an exorcism,” she said: thrashing limbs, clenching fists, loud crying and sobbing.

My purpose isn’t really to write about holotropic breathwork, which, as I said, I don’t know much about anyway. My point here is that the effects I felt—mental fogginess, involuntary muscle contractions, long spells of apnea—are typical physiological responses to hyperventilation (defined as breathing in excess of physiological needs).

So what does this have to do with yoga? I’ll get to that, but for now I’ll just note that many yoga practitioners and teachers—naively, I think—believe that when it comes to breathing, more is better. As you’ll see, however, that’s not necessarily the case; in fact, over breathing can have very deleterious effects.

You might think the problem is too much oxygen. But in healthy people arterial blood leaving the lungs is already nearly fully saturated with oxygen, even during quiet breathing. In other words, you can’t take in too much oxygen.

Rather, the problem with hyperventilation comes from blowing off too much carbon dioxide. In normal breathing, small amounts of incoming air are mixed with a much larger volume of air remaining within the alveoli (the air sacs in the lungs where gas exchange with the blood takes place). This has the effect of maintaining an internal atmosphere within the lungs that contains a much higher percentage of CO2 than does the air outside (carbon dioxide makes up only a very small percentage of atmospheric air). CO2 levels in the bloodstream closely reflect the composition of this internal atmosphere, so that during hyperventilation, as more carbon dioxide is expelled from the alveoli, CO2 levels in the blood also fall.

We tend to see CO2 as a waste product, something to be disposed of. But in fact we need to keep  CO2 in the blood within a certain range, because it plays an important role in maintaining blood pH. As CO2 levels drop during hyperventilation, the result is a higher, or more alkaline, pH.

Because of this rise in blood pH, hyperventilation has an effect that might at first seem paradoxical—by over breathing, we actually reduce the amount of oxygen getting to the brain, a situation termed cerebral hypoxia.

This became an issue during World War II. Hyperventilating military pilots tended to become confused and disoriented. Researchers studying conscientious objectors in the laboratory were able to confirm that hyperventilation led to a reduction in blood flow to the brain, which had long been suspected. Their supposition was this was due to constriction of cerebral blood vessels. This has subsequently been shown to be the case, and although the exact mechanism is still debated, it’s clear that a rise in blood pH  triggers arterial constriction.

What’s worse is that when blood becomes more alkaline, hemoglobin (the molecule that transports oxygen in the red blood cells) tends to hold on more tightly to oxygen. This makes sense in the context of allocating oxygen to the tissues that need it most: metabolically active tissues that have consumed a lot of oxygen and need to replenish it will have also produced a lot of CO2. This creates a more acidic local environment, which in turn causes hemoglobin to release more oxygen. The reverse is true when conditions are more alkaline; tissues don’t get as much oxygen, because hemoglobin hangs on to it.

Thus, the brain gets hit with a double whammy during hyperventilation—less blood flow, plus less oxygen being released from the blood. No wonder those World War II pilots were so disoriented, or that my brain was so foggy that evening in California.

In the next installment of this series, I’ll discuss more physiological effects of hyperventilation.


Kety SS & Schmidt CF. The effects of active and passive hyperventilation on cerebral blood flow, cerebral oxygen consumption, cardiac output, and blood pressure of normal young men. J Clin Invest. 25:107-19, 1946

Raichle ME & Plum F. Hyperventilation and Cerebral Blood Flow. Stroke. 3:566-575, 1972

Tomashefski JF, et al. Carbon dioxide and acid-base transients during hyperventilation. J Appl Physiol. 17(2): 228-232, 1962


6 responses to “Hyperventilation: Why breathing more isn’t necessarily better (Part 1)

  1. Pingback: Yoga: Art+Science | Blog

  2. DAVID SCHAUWEKER July 15, 2013 at 10:53 pm

    Interesting. I recently did a session of holotropic breathing at the Unity Church of the (Cleveland) Heights. Results among the participants was extremely varied. Some people felt they had the equivalent of an enlightenment experience or saw God. Others experienced little. Here is my own experience:
    The session basically involves breathing slightly more rapidly than normal, with no pause between the inbreath and outbreath. One is lying down while doing this in a darkened room with one’s eyes closed. Loud music that gradually changes as it progresses through the chakras was played during the session.
    I guess the goal in the session I attended was some sort of consciousness expansion or increase of self awareness. The session lasted about an hour and a half and results among the participants were varied, extremely varied. Some people said they had extremely powerful, even life-changing spiritual experiences equivalent to an enlightenment experience or meeting God. Some had experiences that one can only describe as extremely strange, such as being a Viking and being transported to Valhalla during battle. Others experienced not much of anything out of the ordinary.
    Personally, I guess my experience fell somewhere in the middle. It was more bodily-oriented and contained no mental images. At a point probably about halfway through the session, I noticed that I could sense the music vibrating just above my eyebrows. Then I had a sense that I was gradually moving from my mind more intimately into my body. Then it seemed that my throat and belly seemed sensitive to the music as well as my brow. Then I started experiencing muscular contractions in my stomach area, as sometimes happens when I meditate. Then I started shouting AAAAAAAAAAA on the outbreath in a rather loud voice (this was not screaming, and, by the way, the music was LOUD, so I don’t think I disturbed anyone). Then I stopped shouting and was in a quiet state where I made the decision to stop controlling my breathing in any way as I intuited that this would interfere with the natural unfolding of the rest of the session. The feeling that I was moving into the body in a more intimate way continued for a while, then stopped, at which point I decided to continue exploring bodily sensations and tensions. Then my mind gradually quieted down even further and I just relaxed. Shortly thereafter, the session ended.
    Following the session, we shared our experiences, and the leader of the session commented upon them. I think it was a very positive experience for most of us. For me personally, I think some tension was released from my throat. If you look at it in terms of the traditional chakras, the throat chakra is associated with self-expression. As for those who had negative experiences during the session, it seems one is able to look upon such experiences as if from a distance, so that they do not affect one.
    In general, I guess I look upon such techniques (and there are probably a lot of them, including some that are fakes) as tools for personal and spiritual transformation which are now available to the average person, just as the Internet is wonderful tool for information gathering.
    As for Joe Miller’s friend’s comment: “It was like an exorcism,” she said: thrashing limbs, clenching fists, loud crying and sobbing,” – these reactions also could be viewed as a release of long-held tensions. I am a regular meditator, and I usually meditate upon awakening, paying attention to the feeling-tone with which I awake, without trying to analyze my feeling, put them into categories, or remember any dreams which may have caused the feelings. I have experienced significantly more material surfacing upon awakening, and even disturbing my rest, causing me to awaken and meditate on these feelings in the middle of the night.

    • Joe Miller July 16, 2013 at 9:53 am

      Hi David. Thanks for your commentary. Very interesting range of experiences — a reminder of the amount of individual variability there is in our phsysiological and psychological responses.

  3. DAVID SCHAUWEKER September 1, 2013 at 10:09 pm

    Just want to make a few final comments about the holotropic breathing session I attended. We shared our experiences after the session, and I think the general feeling was that we were energized and positive, not foggy or confused. The participants seemed to relate their experiences with great vigor and conviction. Those with the most extreme visions and experiences did definitely not seem at all confused, and related their experiences with great directness and energy.

  4. Mardi Storm December 11, 2013 at 6:47 pm

    I agree with David- if you felt foggy or confused it actually sounds like something else going on, like somatic memory of anesthesia- which causes a person to stop breathing during breathwork. Joe, were you born under anesthesia? This is not uncommon for either people who’ve been under anesthesia a lot in their life or during birth. It sounds like you had a big group and not a lot of personal trained attention to work through what was coming up for you in the group. It might just be the Holotropic approach, I’ve heard that from a few people. I do a much gentler form of breathwork, Awake! Breathwork which comes out of Rebirthing, the focus isn’t on flailing about and emoting so much or breathing really hard and fast. We’re more interested in accessing core wound material to heal it, not just release or act it out. The other thing, Joe, that might have happened is if you exhaled forcibly your carbon dioxide levels might have changed drastically causing a real different reaction. I coach people to have an even inhale and exhale. It could be worth experimenting with a different kind of breathwork! I have likewise led yoga training groups and have had it be a really positive opening experience for the participants. It sounds like maybe this style doesn’t work as well for you, and keep in mind its not all the same!

  5. DAVID SCHAUWEKER January 18, 2014 at 3:14 pm

    Well, here I am again, so my final comments above are not so final. Did another session of HB. This time I picked up from the facilitator the fact that one should keep doing the special breathing throughout the session regardless of the mental states on passes through. I had a similar session to the last one, except that muscular contractions began almost immediately and lasted almost throughout the session. Subsequent to the session, subconscious material has continued surfacing even more strongly at night.
    Mardi, I wonder at your characterization of Awake! Breathwork, as opposed to HB, as “the focus isn’t on flailing about and emoting so much or breathing really hard and fast.” In the two HB sessions I have attended at the Unity Center of the Heights, in Cleveland Heights, Ohio, there was no emphasis on emoting, flailing, acting out, or breathing really hard and fast, although one does breath faster than normal, as after a moderate workout.. The sessions take place in the dark, and loud music is playing, so one doesn’t know what other people are doing.
    As I mentioned previously, people’s reactions differ widely. Some people have very blissful sessions, while I myself experience a lot of muscular contractions and some vocalization. Also, some people mention that they have moved from past sessions of angry shouting to currently more blissful sessions, so I definitely feel there is some healing going on.
    Joe, this is response to your viewing the reduction of oxygen to the brain as a result of HB with alarm. There is another way of looking at this phenomenon. I just reread “The Doors of Perception” by Aldous Huxley. In it he restates William James and Henri Bergson’s idea that the brain functions as a reducing valve on conscious rather than its generator. In this sense, having the brain partially disabled by chemical changes in the brain brought about by hyperventilation, various drugs and disciplines, etc., can be a good thing, allowing access to different and wider aspects of consciousness. I think you would Huxley’s essay interesting.

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