How We Breathe

Original Editor - Tania Clifton-Smith Top Contributors - Jess Bell

Introduction

Breathing is one of our most crucial functions and is central to health - it is the foundation of movement, health, and wellbeing.[1][2] 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 postural stability and mobility of the trunk and spine.[3] Van Dixhoorn summarises the key functions of breathing as follows:[1]

  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, including interference from our thoughts, feelings and past experience.[2] 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

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 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]

However, from these early reports and definitions, research into this condition continued. In the 1950s, Konstantin Pavlovich Buteyko developed the Buteyko method, which uses breathing exercises to treat symptoms associated with low carbon dioxide levels.[2] Then in the 1960s, Dianna Innocenti, Rosemary Cluff and Professor Claude Lum collaborated to develop a series of breathing exercises,[2] now known as the Papworth Method, which have been found to improve respiratory symptoms, dysfunctional breathing and mood.[6]

More recently, research on breathing pattern disorders has explored a range of symptoms associated with the influence of psychology on breathing, including anticipation, the suppression of emotions, association and conditioned responses.[1] Research has also explored the impact that the musculoskeletal system has on breathing (as well as the impact of breathing on the musculoskeletal system.[1]

Definitions

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.[7][2] The primary symptom of dysfunctional breathing is dyspnoea, but it is also associated with other non-respiratory symptoms, including dizziness and palpitations.[8] These occur in the absence of, or in excess of, a related physiological condition (cardiac or respiratory).[2][7]

Hyperventilation is the most widely recognised form of dysfunctional breathing.[7] 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[9] - although an organic disorder (asthma, COPD, diabetes, anaemia) may be present.[2]

While work on classification is continuing, it is important to note that there are many components to breathing dysfunction. An accurate subjective assessment will enable a physiotherapists to determine what is driving the dysfunctional breathing. Is it due to a mechanical dysfunction such as tight accessory respiratory muscles? Or alternatively it may be driven by biochemical factors, such as over-breathing which results in symptoms of low carbon dioxide levels (for a list of symptoms associated with low CO2, please click here). It could also have been caused by a traumatic event or anxiety.

Epidemiology

Hyperventilation Syndrome is thought to affect 6-10% of the general population - in an asthmatic population, these rates may be as high as 29%.[7] 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%.[8] Again, they reported higher rates in patients with asthma: one third of women with asthma, and one fifth of men have dysfunctional breathing patterns.[8]

However, breathing pattern disorders remain poorly understood, so it is thought that this condition is likely underdiagnosed or misdiagnosed.[8] Moreover, it is impossible to determine the exact prevalence of dysfunctional breathing as there is no gold standard diagnostic criteria.[7] 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.[7]

Basics of Breathing

Internal and External Respiration

The lungs play an essential role in providing cells with oxygen via the blood and cardiovascular system, which enables cells to produce energy.[10]

On inhalation, oxygen enters the lungs and diffuses into the blood. The heart receives this oxygenated blood and pumps it to the cells.[10]

Carbon dioxide waste diffuses back into the blood at the cell level and is transported to the lungs, where it is expelled on exhalation.[10] 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.[10]

[11]

Conduction and Respiratory Zones

The conduction zone refers to the areas where air is transported to the lungs from the external environment. These are the:[10]

  • 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.[12][13]. It plays a significant role in nasal patency, uptake of oxygen and the 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][10]

Respiratory Muscles

There are three groups of respiratory muscles:[14]

  • 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.[14]

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.[14]

The abdominal muscles are expiratory and they act on the abdomen and the abdominal rib cage.[14]

Diaphragm

The diaphragm is a dome shaped muscle that is primarily involved in respiration. The superior portion of the diaphragm originates at the xiphoid process anteriorly, the lower six costal cartilages of the thorax laterally and the first two lumbar vertebrae posteriorly. It converges into a central tendon which forms the dome’s crest.[15] The peripheral segment attaches to the chest wall and abdominal cavity.[15]

It is innovated by the right and left phrenic nerves (C3, 4, 5) and has three major openings - the aorta, vena cava and the oesophagus.[15][2]

[16]

The diaphragm and intercostal muscles are the only muscles that are active during quiet inspiration.[2]

The diaphragm contracts and pulls its central tendon down. This increases the negative pressure inside the thoracic cavity, which draws air in. At the same time, the external intercostal muscles raise the anterior chest wall - in a bucket handle action.[15] As the chest cavity becomes larger and wider, air is able to enter from outside the body.[15]

During quiet exhalation, the rib cage and chest wall relax and return to their original position. Concurrently, the diaphragm relaxes and lifts. This movement expels the air from the lungs.[15] The diaphragm of individuals who have hyper-inflated chests (i.e. those with COPD or voluntary hyperinflation) will not be able to return to its natural resting position during exhalation.[2]

The diaphragm has a number of other roles aside from respiration. When it contracts, it works with the anterior abdominal wall muscles to increase intra-abdominal pressure - thus it aids processes such as micturition (urination), defecation, and parturition (giving birth).[15] It is also integral to stability during locomotion.[2]

It also acts essentially as a pump.[2] On inhalation, its descent decreases intrathoracic pressure and improves intra-abdominal pressure. This compresses the inferior vena cava and helps push deoxygenated blood upward into the right atrium. It also compresses abdominal lymph vessels assisting lymph movement.[15] Similarly, on inhalation, cerebrospinal fluid is pumped into the brain and pumped back down on exhalation. Thus, the diaphragm plays a significant role in movement, mobility and cleansing of the whole body.[2]

Accessory Respiratory Muscles

As breathing demands increase, humans require more air in larger volumes. Thus, we start to adopt an apical, as well as a thoracic lateral breathing pattern and our accessory respiratory muscles become involved. The primary accessory muscles are:[2]

  • Scaleni
  • Pectoralis major and minor
  • Sternocleidomastoid
  • Iliocostais
  • Serratus anterior and posterior
  • Latissimus dorsi
  • Trapezius

Transversus abdominus, multifidus and the pelvic floor muscles are also involved. All muscles work together to ensure an efficient breathing pattern.[2] When patients present with neck or shoulder pain, or thoracic outlet problems (peripheral pins and needles etc), it can be beneficial to consider their breathing patterns (ie breathing pattern, respiratory rate, location of breath).[2] Patients with neck pain present with a number of musculoskeletal deficits and respiratory dysfunction.[17] Their respiratory function may be affected due to strength deficits in their respiratory muscles.[18] If they have adopted a more apical breathing pattern, these respiratory muscles will be overworked, which results in increased muscular tension. This can have a significant impact on the neurovascular bundle, which travels under the clavicle, pectoralis minor and down the arm.[2]

  • NB performing a neurodynamic tension test pre- and post- breathing retraining can highlight changes in tension caused by a reduction in accessory muscle work.

Pelvic Floor

The pelvic floor also plays an important role in breathing. It descends on inhalation and returns to its resting position on exhalation.[2] Contractions of the pelvic floor are combined with abdominal muscle activity - they work in conjunction with the anterolateral abdominal muscles and the diaphragm to control / react to changes in intra-abdominal pressure. All three muscle groups work together to protect organs against changes in pressure and contribute to respiratory and postural function.[19][20]

Summary

  • Breathing is essential for survival and it has an impact on many systems, including our biomechanics, biochemistry and psychophysiology
  • Breathing patterns can be disrupted by a number of factors
  • A significant number of people are diagnosed with breathing pattern disorders, but due to a lack of understanding and gold standard diagnostic tool, prevalence rates may be higher than those recorded
  • When assessing breathing pattern disorders, it is essential to understand the physiology and anatomy of respiration, but it is also important to look at biomechanics and the musculoskeletal system. It is impossible to breathe well unless this system is working effectively
    • Consider the whole system, from the nose, vocal folds, diaphragm, pelvic floor and surrounding muscles[2]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Clifton‐Smith T, Rowley J. Breathing pattern disorders and physiotherapy: inspiration for our profession. Phys Ther Rev. 2011; 16: 75–86.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 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.
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  8. 8.0 8.1 8.2 8.3 Vidotto LS, Carvalho CRF, Harvey A, Jones M. Dysfunctional breathing: what do we know?. J Bras Pneumol. 2019; 45(1): e20170347.
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