How We Breathe

Introduction

Breathing is one of our most crucial functions and is central to health.[1] Respiration refers to the movement of oxygen into the body and the removal of carbon dioxide. It is essential in the metabolisation of energy.[2]

Breathing affects the entire body. It has a significant role in ensuring that allostasis is maintained, as well as being involved in biomechanical and postural stability, as well as mobility of the trunk and spine.[3] Van Dixhoorn summarises the key functions of breathing as follows:

  1. Gas exchange and respiratory function, which includes smell and speech
  2. Musculoskeletal movement, which includes the movement of body fluids, organ function, mobility and trunk stability
  3. The connection of conscious awareness with the state of the body.[1]

An optional breath is usually defined as a three-dimensional abdominal breath that results in expansion of the lower ribs.[3]. However, while essential for survival, this pattern can be disrupted by a number of factors. This disruption results in dysfunctional breathing. Factors that may interrupt optimal breathing include biomechanics, biochemistry and psychophysiology. Moreover, breathing patterns can, in turn, influence these functions.[2]

History of Breathing Pattern Disorders[edit | edit source]

One of the earliest discussions of the symptoms that are now associated with breathing pattern disorders was a report by Dr Jacob M Da Costa in 1871. He noted that a number of American civil war soldiers complained of a specific set of symptoms that mimicked those of heart disease: fatigue on exertion, palpitations, sweating, chest pain and shortness of breath[1][4] Da Costa’s syndrome became known as Soldier’s Heart or Irritable Heart although he noted that similar features often presented in typical private practice as well.[1][5]

The term “hyperventiltation” was coined by Kerr and colleagues in 1937 and has been in common use since. Essentially, hyperventilation refers to someone who breathes in excess of his or her metabolic demands, which results in hypocapnia.[1] While it has had many different names, Hyperventilation Syndrome was initially used to describe a state of anxiety that existed alongside other cardiovascular and emotional symptoms; patients were seen as neurotic and their condition was not given serious consideration.[1]

More recently, research on breathing pattern disorders has explored a range of symptoms associated with the influence of psychology on breathing, including anticipation, suppressed emotions, association and conditioned responses.[1] Research has also explored the impact that the musculoskeletal system has on breathing - in particular Leon Chaitow’s work which has found that a change in one system will invariably have an impact on the other.[1]

Definitions[edit | edit source]

There is no formal definition of dysfunctional breathing, but the term is used to refer to a group of irregular breathing patterns that result in chronic changes in breathing patterns.[6][2] The primary symptom of dysfunctional breathing is dyspnoea, but it is also associated with other non-respiratory symptoms, including dizziness and palpitations.[7] These occur in the absence of, or in excess of, a related physiological condition (cardiac or respiratory).[2][6]

Hyperventilation is the most widely recognised form of dysfunctional breathing.[6] It refers to breathing that is disproportionate to bodily functions. Overbreathing reduces the levels of carbon dioxide in the bloodstream, causing respiratory alkalosis.[2]

Breathing disorders are defined as inappropriate breathing, which is persistent enough to cause symptoms with no clear organic cause[8] - although an organic disorder (asthma, COPD, diabetes, anaemia) may be present.[2]

Epidemiology[edit | edit source]

Hyperventilation Syndrome is thought to affect 6-10% of the general population - in an asthmatic population, these rates may be as high as 29%.[6] A recent study by Vidotto and colleagues reports that Dysfunctional Breathing is identified in all age ranges. In adults presenting in primary care settings in the United Kingdom, prevalence rates are around 9.5%.[7] Again, they reported higher rates in patients with asthma: one third of women with asthma, and one fifth of men have dysfunctional breathing patterns.[7]

However, breathing pattern disorders remain poorly understood, so it is thought that this condition is likely underdiagnosed or misdiagnosed.[7] Moreover, it is impossible to determine the exact prevalence of dysfunctional breathing as there is no gold standard diagnostic criteria.[6] While diagnosis is made after other organic pathologies have been ruled out, the Nijmegen Questionnaire is usually used as a diagnostic tool. However, it may not be valid in certain circumstances.[6]

Basics of Breathing[edit | edit source]

Internal and External Respiration[edit | edit source]

The lungs play an essential role in providing cells with oxygen via the blood and cardiovascular system, which enables cells to produce energy.[9]

On inhalation, oxygen enters the lungs and diffuses into the blood. The heart receives this oxygenated blood and pumps it to the cells.[9]

Carbon dioxide waste diffuses back into the blood at the cell level and is transported to the lungs, where it is expelled on exhalation.[9] The exchange of gases in the lungs is called external respiration and the exchange of gases in the cells is referred to as internal respiration.[9]

Conduction and Respiratory Zones[edit | edit source]

The conduction zone refers to the areas where air is transported to the lungs from the external environment. These are the:[9]

  • Nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi and bronchioles

The nasal cavities and turbinates play an important physiological function as they humidify, moisten, warm and filter air.[2] The paranasal sinuses produce nitric oxide (NO), which diffuses to the lungs and bronchi, particularly during nasal breathing. NO has a vasodilatory and bronchodilatory effect.[10][11]. It plays a significant role in nasal patency, oxygen uptake, sterilisation of the lungs and airways.[2]

The vocal cords are situated in the pharynx. The upper portion of the pharynx is the nasopharynx, which plays an important role in pressure control. The vocal folds sit at the top of this pressure canister and are important for vocalisation. Dysfunctions related to vocal folds include vocal cord dysfunction, and Exercise-Induced Laryngeal Obstruction and should be considered when exploring breathing pattern disorders.[2]

After air travels to the bronchioles, it passes on to the alveoli and this is where ventilation and perfusion takes place (ie the respiratory zone).[2][9]

Respiratory Muscles[edit | edit source]

There are three groups of respiratory muscles:[12]

  • diaphragm
  • rib cage muscles
  • abdominal muscles

The diaphragm is the main musculoskeletal muscle involved in respiration. When the diaphragm contracts, the abdomen and lower part of the rib cage expand.[12]

The rib cage muscles, including the intercostals, the parasternals, the scalene and the neck muscles, are involved in inspiration and expiration. They mostly act on the upper part of the rib cage.[12]

The abdominal muscles are expiratory and they act on the abdomen and the abdominal rib cage.[12]

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Clifton‐Smith T, Rowley J. Breathing pattern disorders and physiotherapy: inspiration for our profession. Phys Ther Rev. 2011; 16: 75–86.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Clifton-Smith T. How We Breathe Course. Physioplus. 2020.
  3. ↑ 3.0 3.1 Hansen-Honeycutt J, Chapman EB, Nasypany A, Baker RT, May J. A clinical guide to the assessment and treatment of breathing pattern disorders in the physically active part 2, a case series. Int J Sports Phys Ther. 2016;11(6): 971-979.
  4. ↑ Paul O. Da Costa's syndrome or neurocirculatory asthenia. Br Heart J. 1987;58(4): 306-315.
  5. ↑ Pollard HB, Shivakumar C, Starr J, et al. "Soldier's Heart": A Genetic Basis for Elevated Cardiovascular Disease Risk Associated with Post-traumatic Stress Disorder. Front Mol Neurosci. 2016;9:87.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Boulding R, Stacey R, Niven R, Fowler SJ. Dysfunctional breathing: a review of the literature and proposal for classification. European Respiratory Review. 2016; 25: 287-294.
  7. ↑ 7.0 7.1 7.2 7.3 Vidotto LS, Carvalho CRF, Harvey A, Jones M. Dysfunctional breathing: what do we know?. J Bras Pneumol. 2019; 45(1): e20170347.
  8. ↑ Bradley H, Esformes J. Breathing pattern disorders and functional movement. Int J Sports Phys Ther. 2014; 9(1): 28-39.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Cedar SH. Every breath you take: the process of breathing explained. Nursing Times [online]. 2018; 114(1): 47-50.
  10. ↑ Martel J, Ko YF, Young JD, Ojcius DM. Could nasal nitric oxide help to mitigate the severity of COVID-19?. Microbes Infect. 2020; 22(4-5):168-171.
  11. ↑ Lundberg JO, Settergren G, Gelinder S, Lundberg JM, Alving K, Weitzberg E. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans. Acta Physiol Scand. 1996;158(4): 343-347.
  12. ↑ 12.0 12.1 12.2 12.3 Aliverti A. The respiratory muscles during exercise. Breathe (Sheff). 2016; 12(2):165-168.
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