Hyperventilation and Asthma

In an article entitled Hyperventilation Syndrome and Asthma, Demeter notes: “Hyperventilation whether spontaneous or exercise induced, is known to cause asthma” [1]. Demeter offers an explanation as to why hyperventilation syndrome receives very little attention in the treatment of asthma. Firstly, he explains that it is very difficult to make a diagnosis of hyperventilation in laboratory tests and secondly “no mention is made of any link” between hyperventilation syndrome and asthma [1]. For a paper by Elshout et al, which was published in the highly respected medical journal Thorax, a study was done to determine what happens to airway resistance when there is an increase of carbon dioxide (hypercapnia) or a decrease (hypocapnia) [2]. It was found that an increase of carbon dioxide determined by measuring end tidal CO2 resulted in a “significant fall” in airway resistance in both normal and asthmatic subjects. This simply means that an increase of carbon dioxide caused the airways to become less restricted, resulting in a reduction of asthma symptoms.

In another paper, entitled The mechanism of bronchoconstriction due to hypocapnia in man, Sterling writes that “hypocapnia (loss of carbon dioxide) due to voluntary hyperventilation in man causes increased resistance to airflow”. Furthermore, when subjects inhaled an air mixture containing 5% carbon dioxide “bronchoconstriction was prevented, indicating that it had been due to hypocapnia, not to mechanical factors associated with hyperventilation” [3]. The following is a quotation from a paper entitled Demonstration and treatment of hyperventilation causing asthma: “Hyperventilation, leading to airways cooling, will cause bronchoconstriction in vulnerable individuals” but, “because attacks of asthma are accompanied by hyperventilation of physiological origin, the role of hyperventilation in causing asthma attacks may be overlooked”. The article concludes that “this case demonstrates that training in controlled breathing can help patients who hyperventilate to avoid some attacks of asthma” [4].

Prolonged hyperventilation
When hyperventilation occurs over a small period of time, it’s not a problem. In this situation, the respiratory centre senses the decrease of carbon dioxide and so automatically reduces or stops the breathing process to enable it to restore to preset levels [5]. In this situation therefore, hyperventilation is only a short-term phenomenon. However, if overbreathing is prolonged over a long period of time, physiological changes occur in the body resulting in hyperventilation becoming a more permanent state [5]. Demeter also supports this when he states “prolonged hyperventilation (for more than 24 hours) seems to sensitize the brain, leading to a more prolonged hyperventilation” [1]. Hyperventilation becomes habitual or long term, so even when the primary cause is removed, the behaviour is maintained. Let’s amalgamate this with Buteyko’s theory.

The lifestyle of modern man increases breathing volume which in turn causes a loss of carbon dioxide, resulting in asthma for persons genetically predisposed. As increased respiratory volume is a common symptom of an attack [6], asthma plays a role in increasing hyperventilation and therefore symptoms. Simply because an asthma attack can occur over a relatively long period of time, the respiratory centre can become used to accepting a lower level of carbon dioxide. In turn, this leads to increased breathing volume over the long term [1,5]. One feeds the other; hyperventilation leads to an increased breathing volume, and this in turn leads to further hyperventilation.

Water and heat loss
Another area not altogether separate from prolonged hyperventilation is that of exercise-induced asthma (EIA). Exercise-induced asthma affects up to ninety per cent of asthmatics. While the main theories explaining EIA are water loss or cooling of the airways [7,8,9], Buteyko and others [2,12] cite loss of carbon dioxide. On commencement of physical exercise, the volume of breathing increases. The airways are therefore required to condition a greater volume of air and this causes the dehydration and cooling effect which plays a primary role in producing asthma symptoms. According to Anderson, the greater the volume of ventilation, the greater the loss of water and cooling of the airways and so the greater the severity of broncho-constriction [10]. It is very interesting to note that similar effects to EIA can be reproduced by voluntary hyperventilation.

In other words, asthmatic symptoms similar to those caused by exercise can be produced by taking in large volumes of air through the mouth over the course of a few minutes [11,12,13]. Therefore, it can be accepted without question that the volume of air inhaled and the condition of this air plays a noteworthy role in producing symptoms. It is also logical to state that the airways become dryer and cooler with a greater volume of air passing through. This is not just solely applicable to people undergoing exercise; it also relates to the volume of air inhaled during rest. Bearing this in mind, it is most important that asthmatics never breathe through their mouth. Please click here to purchase supporting book Asthma Free Naturally by Patrick McKeown.

KEY REFERENCES

1. Demeter & Cordasco, ‘Hyperventilation Syndrome and Asthma’, The American Journal of Medicine, (1986), vol 81 pp 989.

2. FJJ van den Elshout, CLA van Herwaarden, HTM Folgering, ‘Effects of hypercapnia and hypocapnia on respiratory resistance in normal and asthmatic subjects’, Thorax, (1991), vol 46, pp 28-32.

3. GM Sterling, ‘The Mechanism of Bronchoconstriction due to hypocapnia in man’, Clin Sci, (1968), vol 34, pp 277-285.

4. G Hibbert & D Pilsbury, ‘Demonstration and treatment of hyperventilation causing asthma’, British Journal of Psychiatry, (1988), vol 153, pp 687-689.

5. EB Brown, ‘Physiological effects of hyperventilation’,The American Physiological Society, (1953), vol 33 (4), pp 445- 461.

6. McFadden & Lyons, ‘Arterial blood gases in asthma’, The New England Journal of Medicine, (1968), vol 278 (19), pp 1027-1032.

7. IA Gilbert & JM Fouke, et al, ‘Intra-airway thermodynamics during exercise and hyperventilation in asthmatics’, J Appl Physiol, (1988), vol 64, pp 2167-2174, 1988.

8. IA Gilbert & ER McFadden, ‘Airway cooling and rewarming. The second reaction sequence in exercise-induced asthma’, J Clin Invest, (1992), vol 90, pp 699-704, 1992.

9. ER McFadden & BM Pichurko, ‘Intra-airway thermal profiles during exercise and hyperventilation in normal man’, J Clin Invest, (1985), vol 76, pp 1007-1010, 1985.

10. Anderson & Holzer, ‘Exercise induced asthma is the right diagnosis in elite athletes’, Journal Allergy Clin. Immunol, (2000), vol 106, pp 419-28.

11. RR Rosenthal, ‘Simplified eucapnic voluntary hyperventilation challenge’ J Allergy Clin Immunol, (1984), vol 73(5 Pt 2) pp 676-9.