The first half of the book examines breathing methods for improving health. Nestor focuses extensively on nose breathing versus mouth breathing and on various “under-breathing” techniques which are said to make dramatic differences to chronic lung conditions such as asthma and emphysema, as well as promoting general good health and increased endurance and athletic performance. Nestor spends some time discussing his experiment in solely mouth-breathing for two weeks (his nostrils were physically blocked for the duration) followed by two weeks of solely nose breathing. He taped his lips shut at night so he would not mouth-breath while asleep.  He took extensive measurements of physiological indicators and other factors, such as time spent snoring. Mouth breathing resulted in substantially worse health and mental states, as well as higher blood pressure and heart rates. Nose breathing resulted in dramatic improvements. He also reviews a lot of research and ancient knowledge supporting these conclusions.

This half of the book was fascinating, and I’ll certainly experiment with some of the techniques. Although he warned that breathing methods will not cure cancer or make an embolism go away, this part of the book still reminded me of books I’ve read where the author claims their diet, exercise, or whatever, will cure all your health problems and turn you into a high-functioning human.

The second part of the book looked at breathing techniques which are more extreme and claimed to be radically transformative. These include various forms of breathwork which affect the autonomous nervous system and can improve immune system function and the ability to withstand extreme cold. Wim Hof breathwork is a well-known form of this and Nestor spends quite some time reviewing studies of it, and investigating the biological mechanisms involved.  He does practice some Wim Hof breathwork with an instructor, but as far as I could tell, did not actually include cold exposure training.  He much more briefly discusses holotropic breathwork and his discussions with Stan Grof and other holotropic breathwork instructors.  He did one holotropic breathwork session early in his exploration of breathing methods and did not experience much at all. He is dismissive of other participants who had dramatic experiences, noting that their breathing did not appear much more intense than his and that their experience came on very quickly. He largely dismisses the effects of holotropic breathwork as psychosomatic (due to set or setting rather than the breathing technique).

I was disappointed in the inadequacy of his approach to understanding it. My experience is that the results of holotropic and other forms of breathwork is very dependent on your willingness to open to rather than resist the experience (yes, set is important). To a greater extent than in psychedelic drug trips, the holotropic breather is largely in control the intensity of the experience. In my first transformational breathing session, I held back from allowing the bodily energy and emotions full expression due to embarrassment, but later I found that I would very rapidly start to experience powerful emotions and bodily energy in a breathwork session.  Nestor’s description struck me as that of someone who had held back in their first and only holotropic session.

A third type of breathwork covered in the second part of the book involves drastically increasing the concentration of carbon dioxide in the air breathed. Normal outdoor air concentration of CO₂ is around 0.04% and carbon dioxide therapy involves breathing a mixture of 15-35% CO₂ with normal air. Although blood oxygen levels do not change significantly, the very high concentration of CO₂ induces an intense fear of not being able to take another breath and arises from chemoreceptors in the brainstem. It is a much more primitive and uncontrollable biological reaction than fear mediated by the amygdala. I recently met someone who told me he had purchased a cylinder of CO₂ and was experimenting with breathing mixtures involving around 7% CO₂.  He claimed that this invoked a very intense fear of death which enabled him to break through to deep unconscious fears and address them. At the time I had not read this book and thought he was a nutcase. Nestor claims that this form of conscious breathwork (a much more intense version of breath-holding practice) allows the practitioner to develop much greater chemoreceptor flexibility and tolerance. In effect, it vaccinates the practitioner against excessive stress responses to events in their life. Hmm, its an extremely unpleasant experience, and I think I will pass.

While I was disappointed at Nestor’s lack of interest in exploring holotropic and related forms of transformational breathwork, I did learn a lot and enjoyed reading the book overall. I can see why it was a bestseller in the pandemic period, when no doubt many people were stuck in lockdown with time to experiment. Anyway, I’m heading to the bathroom now to shave off my moustache so I can tape my mouth shut tonight.