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Some Notes on Hyperventilation



Hyperventilation is where the lungs are ventilated to the extent that too much carbon-dioxide is flushed out of the body – it is sometimes described as over-breathing. There are two reasons why I feel it is useful to be aware of and understand this potential issue when beginning to develop a breathing or pranayama practice.

One is that it quite common to be a chronic over-breather and this tendency has an effect on mood, muscle tone, energy levels and the respiratory system – all of which have some implications for one’s experience of breathing and pranayama practices.

The other is that some breathing and pranayama practices, at least until one is used to them, have the effect of causing or encouraging hyperventilation. And, given the potential difficulties (and indeed hazards) of this, it is important to be able to recognize the warning signs and understand the appropriate response.

Consequently, these notes attempt to explain what hyperventilation is, its implications, warning signs, how to minimize one’s tendency to hyperventilate, and what to do when one notices one has a tendency to hyperventilate.

What is hyperventilation

Hyperventilation is, literally, over-ventilation of the lungs – with the effect of causing too much carbon-dioxide to be flushed out of the blood in the lung capillaries. The result is that the blood’s level of carbon-dioxide drops.

This may not seem like a problem since we normally think of carbon-dioxide as a waste product (from releasing energy from food) that needs excreting from the body – and this is indeed true. However, it is also true that carbon-dioxide is a crucial component of the blood and, if the level drop too much, the blood functionality suffers. There are several strands to this role of carbon-dioxide in the blood.

One way in which carbon-dioxide acts in the blood is to help with the transfer of oxygen from the hemoglobin in the red blood cells to the tissue cells. Thus, when the carbon-dioxide level in the blood drops too low, the tissues of the body become relatively “starved” of oxygen and thus unable to function so well even though there may well be plenty of oxygen in the blood. [This results because carbon-dioxide, like oxygen, can bind to heamoglobin and, although binding quite weakly, this binding helps the release of oxygen to tissue cells.]

Another role of carbon dioxide is to do with blood pH (a measure of acidity vs. alkalinity). The functionality of blood proteins is highly depended on their shape – that is, the way they are “folded”, and this in turn is highly dependent on blood pH. Thus, if the blood pH moves outside its “normal” range, the blood proteins’ shapes change and they do their jobs lesss well (if at all). The significance of carbon-dioxide in this respect is that, in the absence of other factors, changes in carbon-dioxide levels in a water solution (such as blood) will result in pH changes. In the blood, this issue is partially addressed since we have a very good buffering system that protects against pH changes when carbon-dioxide levels rise to high levels. Unfortunately, this buffering system does not protect well against extremely low blood levels of carbon-dioxide. [In solution, carbon dioxide is a weak acid and thus tends to lower pH.]

Another effect (and perhaps the most important) relates to the role of carbon-dioxide as a vasodilator. In the small arteries and arterioles, the presence of carbon-dioxide acts like a local hormone to encourage the muscles of the blood vessel walls to relax, so causing the bore size of the blood vessels to increase. One of the benefits of this set-up is that when some body tissue increases in metabolic activity (e.g. leg muscles when one starts to run), it releases more carbon-dioxide. This in turn causes a local increase in blood supply helping ensure the tissues receive enough oxygen and nutrients to maintain the level of metabolic activity. However, when blood levels of carbon-dioxide levels drop very low, the small arteries and arterioles tend to constrict, causing a reduction in the blood supply to body tissues. This is particularly problematic for the brain and spinal cord, where the blood supply (and therefore the oxygen and energy nutrient supply) can become insufficient to support the nervous tissue.

Extreme hyperventilation (and the extremely low carbon-dioxide blood levels that result) can cause loss of consciousness – even death. The good news is that death from hyperventilation is fairly rare. What is common is mild and chronic hyperventilation and this can have wide ranging effects on one’s well being – ranging from increased muscular tension, irritability or increased feelings of stress through to fatigue and feelings of lethargy.

Chemoreceptors and breathing centres

Given the importance of blood levels of carbon-dioxide, one might think that our bodies would have system for monitoring and regulating this – and indeed this is the case.

We have chemoreceptors that monitor both oxygen and carbon-dioxide levels in the blood as well as blood pH (i.e. how acid or alkaline the blood is). These receptors are part of the sensory aspect of the autonomic nervous system (which acts to maintain the internal conditions of the body as appropriate for the activity at hand).

There are peripheral chemoreceptors in the main aorta and in the carotid bodies of the arteries of the neck, which monitor blood pH and oxygen levels. These chemoreceptors cause (via the breathing centers) a rapid response to substantial reductions of arterial oxygen or increasing blood acidity (i.e. lowering of pH) to stimulate lung ventilation. In short, they help to ensure that when the need for oxygen increases (say as a result of increased muscular activity), the breathing increases to ensure that we get the necessary oxygen. However, small decreases in blood oxygen cause little effect – so, if one is only a little short of oxygen, instead of the breath increasing one may find oneself feeling a little less alert (and under these circumstances some yoga breathing practices may be particularly helpful).

There are also central chemoreceptors located on the surface of the brain stem, which monitor blood levels of carbon dioxide. These are slower to react to changes in the blood than the peripheral chemoreceptors because they are located in cerebrospinal fluid rather than directly in the blood. They are however much more sensitive to small changes in blood concentration.

The act of breathing occurs as a result of the actions of voluntary muscles (such as the diaphragm and intercostal muscles) which receive their nervous “instructions” via the somatic part of the peripheral nervous system and, in particular, via the phrenic and intercostal nerves. As a result, breathing can easily be brought under conscious (and voluntary control) via input from the cerebral cortex. However, normally, the breath is maintained and regulated by breathing centers (or respiratory centers) and these take their cues from sensory input from the autonomic nervous system (for example as discussed above).

There are respiratory centres located in the brain stem (in the medulla oblongata and also in the Pons Varolii). In the medulla oblongata there is an inspiratory centre (dorsal respiratory group) which controls inspiratory movements and their timing. And, also in the medulla, there is an expiratory centre (ventral respiratory group) which controls voluntary forced exhalation and acts to increase the force of inspiration. The signals from these centres (controlling the breathing process) are coordinated (and refined) by signals from the respiratory centres in the Pons. There is the apneustic centre which coordinates transitions between inhalation and exhalation and sends stimulatory impulses to the inspiratory centre and so activates and prolongs inhalation (causing long deep breaths). In the Pons there is also the pneumotaxic centre which coordinates the transition between inhalation and exhalation and sends inhibitory impulses to the inspiratory centre. This centre plays a vital role in fine tuning the lung ventilation rate and control from here overrides that from the apneustic centre to end inspiration.

Together (in an integrated way), these respiratory centres work primarily to maintain lung ventilation rates are so as to maintain blood carbon-dioxide levels within a healthy range – with oxygen blood levels becoming a significant factor only when the oxygen level drops well below normal levels. When carbon-dioxide levels start to become a bit low they act to inhibit lung ventilation – in the first instance by reducing the signals for the inspiratory breathing muscles to contract during inhalation and slowing the breathing rate. If this fails to work (or does not work sufficiently well), perhaps due to overriding impulses from the cerebral cortex, then indirect approaches to reducing lung ventilation are likely to be employed. One is the contraction of the air passages (via the parasympathic aspect of the autonomic nervous system) to increase the resistance to air flow in and out of the lungs and thus slowing the rate of air flow in and out of the lungs.

Some reasons why regulation of blood carbon-dioxide may not be fully successful

Given the importance of regulating the blood levels of carbon dioxide and the complex systems for regulating the breathing process it might seem strange that hyperventilation is possible. However this apparent weakness also gives a great deal of freedom to adapt and change our breathing according to circumstance and conscious desires.

An obvious reason why breathing rate might not match what is needed to keep carbon-dioxide levels within healthy range is conscious control of the breathing – impulses from the cerebral cortex overriding those of the respiratory centres. This can be very useful (for example, when speaking or singing, and indeed with yoga breathing practices) but can also frustrate attempts to reduce hyperventilation (and this is often a particular factor in prolongation of asthma and panic attacks).

Another reason is that the autonomic nervous system needs to regulate many different aspects of the body’s internal environment to ensure that the body is ready for the type and degree of activity we choose to engage in. Blood carbon dioxide levels are just one of these. Furthermore the autonomic nervous system is to some extent anticipatory. A good example of this is the flight-or-fight reaction – here the body gets prepared for action as a result of exciting or fear-inducing stimuli before the decision to act occurs. And one aspect of this preparation is to speed (and also deepen) the breath –if one then decides not to act (i.e. not to run or fight) then the lung ventilation has been increased without the corresponding increase in carbon-dioxide release from body tissues. (This is often the cause of panic attacks and some types of asthma attacks).

Another factor which can be relevant is environmental. An example of this is trying to breathe at high attitudes where the air level of oxygen is low. Because the of low oxygen level, the ventilation of the lungs has to increase to ensure the blood oxygen levels are sufficient – but increasing the lung ventilation also has the effect of reducing blood carbon-dioxide levels. [Where this is an issue, the body has to find a way to acclimatize to being able to cope with lower blood levels of carbon-dioxide.]

Hyperventilation implications for well-being

It seems relevant to comment at this point that very mild degrees of hyperventilation can be pleasant (or at least interesting in a non-negative sense). Very mild hyperventilation can give one feelings of having a “clean” or clear mind or of having a spacious open mind. This is what I have experienced during natural and spontaneous breath suspension following a few rounds of kapalabhati practice. It is important to note that in addition to the degree of hyperventilation being very mild, I was also in a very calm and peaceful mental / emotional state and furthermore that I was sufficiently non-grasping of the breath to allow breath suspension to occur without concern. Without these 3 key qualities (mildness, calmness and non-grasping of the breath), the experience of hyperventilation is likely to be unpleasant and detrimental for one’s sense of well-being.

The direct effect of hyperventilation is to reduce the blood carbon-dioxide level with the following effects:-
Of course it is important to note that many of these signs of hyperventilation can be caused by other factors. There are also indirect effects of hyperventilation due to the body attempting to reduce the degree of lung ventilation. These may include one or more of the following:

Panic attacks and asthma

In a panic attack one’s breathing rate (and heart beat rate) has increased due to being scared or frightened. This can become self-perpetuating as the feelings of rapid breathing increase the sense that there is reason to be scared and so physiological response to the scare is ramped up. One of the potential problems is that rapid breathing can cause hyperventilation – with all the associated problems. If one is sitting or standing then one should either lie down or lean forwards from a sitting position on the floor – to reduce the risk of falling over should one start to feel dizzy or faint. Consciously slowing the breathing down will help the panic attack to pass more quickly – e.g. exhaling through pursed lips, or counting the length of the exhalation. Also helpful will be drawing your awareness more to exhaling (rather than inhalation) and bringing your awareness more to the abdominal area (away from the thoracic region). If hyperventilation has occurred to a significant degree then placing your hands in a cupped way over your nose (and mouth) for a small number of breaths can help by getting you to breathe in the carbon-dioxide you have just breathed out.

In an asthma attack the airways have become constricted – the feeling is of not being able to breathe – feeling short of breath and not being able to get enough breath. In addition to being scary, it has the potential to be fatal for some forms of asthma attack. I think it is helpful to distinguish between allergy-induced asthma attacks and stress-induced asthma attacks.

In allergy-induced asthma attacks the airways become narrower as a result of the tissue of the linings of the airways swelling due to an allergic reaction. The danger here is of hypoventilation – that the difficulty of drawing air into the lungs and squeezing it out is such that one can’t ventilate the lungs sufficiently to maintain adequate blood oxygen levels. Fortunately, with modern treatment (nebulizers) for asthma attacks, this is now rarely fatal – it is however usually unpleasant and frightening. Mild allergy-induced asthma attack can, as a result of a panic attack reaction to the situation, turn into a stress-induced type of asthma attack.

In stress-induced asthma attacks the airways are constricted by their smooth muscles – in an attempt to reduce lung ventilation in response to blood levels of carbon-dioxide falling too far. The experience is one of being unable to inhale – due to the respiratory centres doing what they can to inhibit the inspiratory process. Consciously, one feels one can’t breathe in and so tends to do all one can to consciously inhale – the cerebral cortex trying to over-ride the signals from the respiratory centre. The result is a feeling of grasping unsuccessfully at the air. During this sort of asthma attack, letting go of the breathing process (and in particular the inhalation) and heeding the above advice for a panic attack will be helpful is aiding the passing of the asthma attack. The problem for most asthma sufferers is that their asthma attack might not be due to hyperventilation (in which case accepting temporary cessation of breathing is helpful) – but due to an allergy (where there is a real risk of insufficient ventilation of lungs) where continuing to breathe is very important. So normally they will use medication to help reduce the asthma attack.

Yoga practices and hyperventilation

Some breathing practices in yoga (e.g. kapalabhati and Bhastrika) explicitly and indeed deliberately take one in the direction of hyperventilation. This is part of the point of them – by taking one to the edge of hyperventilation, natural breath suspension with a corresponding tendency for mind fluctuations (thoughts) to become suspended. These moments of mental calm and stillness are a major aim of yoga practice. But it should be noted that even here the yogi is not trying to hyperventilate, but just go to the edge of hyperventilation – and care and practice is needed to learn how to use these practices well for this purpose.

Most yoga breathing practices are not intended to deliberately take one in the direction of hyperventilation, but can sometimes take one in that direction - usually through inexperience / poor practice. Below I give examples of some thing we often attempt in yoga breathing that can inadvertently take one toward hyperventilation.

Learn to breathe more efficiently. A great thing to do as it reduces effort for breathing, allowing the effort to go elsewhere. However, if more gaseous exchange occurs with each breath, then, unless the breath rate also slows, one’s breathing is also being moved in the direction of hyperventilation.

Prolongation of the exhalation. A useful practice that tends to encourage greater calmness or relaxation. However, the longer the exhalation, the greater in general the emptying of the lungs – which means the ventilation of the lungs tends to increase a lot per breath. To some extent this will be compensated for by each breath taking a bit longer – but not always sufficiently.

Deepening the breath, increasing the volume of air breathed in/out per breath. This is a bit like the above, but the emphasis is on using more of the lung volume with each breath rather than lengthening the exhalation. One reason for doing this is it increases one’s capacity for aerobic activity. Another is due to the idea (in yoga) that one is born with a fixed number of breaths to breath and once one has breathed them one dies – here the idea is to reduce the number of breaths one needs to take per minute and hence lengthen the length of one’s life. Taken to its limit what we are taking about here is the Yoga Complete breath – but, with all approaches to deepening the breath, unless this is also accompanied by sufficient slowing of the breathing rate, it will take one in the direction of hyperventilation.

Breathing more abdominally (as opposed to thoracically). This is a really good idea as abdominal breathing, in addition to being more efficient, is also is a much more calming peaceful breathing pattern. However, since the lower lungs are better supplied with blood during normal levels of activity (when the trunk is up-right), breathing more abdominally leads to more gaseous exchange for the same amount of lung ventilation. Thus, unless the breath either becomes slower or shallower, breathing more abdominally can take one in the direction of hyperventilation.

For these sort of reasons, one should, when first learning a new breathing practice or approach to breathing practice, be open to observing early warning signs of hyperventilation which are: - And, if these symptoms are not noticed, then one might start to feel woozy, faint or dizzy.

If any early warning signs of hyperventilation are noticed (as a result of breathing / pranayama practices) you should: - Stop the practice. - Make sure you are in a position where there is little risk of falling over – and, even if sitting on the floor, you might well want to lie down. - Pause and rest without any conscious control of the breath – if spontaneous breath suspension occurs then allow this to happen. Unless you are distressed, there should not be further need to do anything consciously for the carbon-dioxide levels to return to normal within a few minutes. - Let your yoga teacher know you have experienced hyperventilation and discuss with him/her how your practice might be adapted to make the hyperventilation less likely to occur again. In a general sense, whenever you notice that a practice causes hyperventilation, you should be looking to make the practice less intense, and usually either slower or do less rounds (or both).

Long term approaches to reduce tendency to hyperventilate

Many students have habitual breathing patterns that either lead to them being almost constantly in some degree of hyperventilation or increase their tendency to hyperventilate. The sort of habitual breathing patterns that take one in this direction are: The good new is that breathing habits can be changed with a little practice of appropriate breathing practices. A few minutes of practising a particular routine can make one’s breathing pattern more healthy for even several hours afterwards. The benefits to one’s sense of well-being and health are, indeed, much more than just reducing a tendency to hyperventilate.

Two main approaches to breathing are likely to be helpful:-

And, if you don’t feel like practising breathing, then you can try singing or mantra work instead, as both of these tend to encourage more abdominal breathing and a slower breath. The best thing is to discuss what to do with regard to breathing with your yoga teacher – he / she will most likely be delighted to give you advice and guidance that suits your particular needs.

Another approach to reducing a hyperventilation tendency is to train one’s body to be able to cope with lower levels of carbon-dioxide - those wishing to be active at high attitudes have to take this sort of approach, but it can also be used by those living at sea level. This seems to be a component of the Buteyko method – which many who suffer from asthma have found helpful. And one of the benefits of practices such as kapalabhati and Bhastrika is that there is some acclimatization to coping with lower blood levels of oxygen.

My personal view is that, unless one needs to train for being active at high attitudes, the better approach (at least for one’s emphasis) is that of improving one’s breathing habits. The reason is that the benefits of improving one’s breathing habits are more than just reducing a tendency to hyperventilate.

Recommended Reading

Reading Material What It Offers
Chapter 2 : Breathing in “Anatomy of Hatha Yoga” By H. David Coulter Body and Breath Inc. ISBN 0-9707006-0-1

This gives an excellent explanation of many aspects of the breath including a discussion of the nervous system, regulation of the breath and hyperventilation.

Wikipedia (the internet encyclopedia : http://en.wikipedia.org/wiki/HomePage?HomePage )
        - Hyperventilation
        - Control of Respiration
          (plus other topics depending on your interest)

This in some ways gives more detail than I have in these notes (and certainly in more technical language - whilst still being easily understandable). Information is given in brief note format, so does not take long to read.