The importance of respiration can be viewed in the context of the integrated model of joint function. It illustrates the interplay between the active, passive, neural and emotional components in joint function. Respiratory alkalosis is known to cause increased contraction of smooth muscle cells. Smooth muscle cells are located in collagen within intervertebral discs, ligaments, fascia and menisci. Thus alterations in breathing mechanics may affect the function of the passive system. Furthermore, respiratory alkalosis alters neuronal excitability, muscle function and emotional state (Chaitow 2004). Through these mechanisms respiratory rate may at times affect the function of the entire musculoskeletal system.
Nasal vs. mouth breathers
Breathing mechanics may affect dentofacial and craniorofacial structure. Harari et al (2010) retrospectively analysed the changes in 116 paediatric patients, 55 of which showed signs and symptoms of nasal breathing and 61 controls that were normal nasal breathers. Mouth breathers demonstrated considerable backwards and downward rotation of the mandible, increased overjet, increased mandible plane angle, a higher palatal plane and narrowing of both the upper and lower arches compared to nasal breathers. This occurs as the mouth adapts to more closely resemble a nose. In this position, the mandible may not contact the maxilla causing unrestricted alveolar development and posterior tooth eruption. Thus, altering occlusion. Furthermore, a posterior cross bite was more prevalent in the mouth breathers at 49% compared with 26% in controls. As was an abnormal lip to tongue seal, 56% in mouth breathers as opposed to 30% in controls. This could be viewed as the CNS prioritising respiration over the stomatognathic system.
Mouth breathing and the kinetic chain
Mouth breathing is also associated with compensatory changes throughout the kinetic chain. In children, mouth breathers have been found to have significant increases in cervical protraction and thoracic curvature in the sagittal plane measured with biophotogrammetry (Lima et al 2004). These changes lead to measureable reductions in thoracic rotation and winging scapula. At the lumbar spine extension coupled with an anteriorly rotated pelvis is a typical but not statistically significant compensation, as some patients compensate with a posterior pelvic tilt (Lima et al 2004). In the lower limb the knees hyperextend and the ankles dorsiflex. These findings suggest the CNS is sacrificing the spine and limbs to achieve cervical protraction and open up the oral airway to improve respiration.
The importance of nasal breathing highlights the need to assess whether patients are breathing nasally or orally, as well as any contributing factors such as deviated septums, nasal polyps and allergies. Oral breathing can normally be easily detected on assessment. In addition, mouth-breathing patients may report ptyalism (drooling) during the night on questioning.
Respiratory system and posture
The respiratory function of muscles is prioritised over their stabilisation function. The postural and respiratory function of the diaphragm is co-coordinated with the respiratory and postural inputs summated at the phrenic motorneurons (Hodges et al 2001). Further integration of respiratory and postural roles has been demonstrated for the transversus abdominis and the intercostals. Hodges et al (2001) assessed the effects of increasing respiratory demand on the postural function of the diaphragm. Six participants had to oscillate an arm whilst breathing through a tube, which increased dead space in the lungs for four minutes. As participants reached the final minutes, their respiratory rates increased and CO2 levels had decreased. Their results showed that as respiratory demand increased, the postural function of the diaphragm declined. They concluded:
“To maintain homeostasis, the CNS must prioritise respiratory drive over other functions of the respiratory muscles, such as postural control” (Hodges et al 2001, p. 1006).
The clinical application of this statement is clear. Patients need to be cleared for respiratory dysfunctions, such as breathing pattern disorder or chronic hyperventilation, to inform management clinically. Patients with respiratory dysfunctions may need treatment for their respiratory dysfunction or a palliative solution prior to achieving long-term resolution of chronic pain symptoms.
Want to learn more about breathing mechanics?
Kieran’s course, A Practical Approach to Mastering The Art of Breathing, is running on 25th April in Middlesex.
About Kieran
Kieran is a physiotherapist, nutritional therapist and exercise specialist who is passionate about getting people out of chronic pain and back to what they do best.
He has worked in the health, exercise and rehabilitation industry since 2004, starting as a personal trainer and sports massage therapist. Kieran work works extensively with golfers and back pain.
References
Chaitow, L., 2004. Breathing pattern disorders, motor control and pain. Journal of osteopathic medicine, 7 (1), 34-41.
Harari, D., Redlich, M., Miri, S., Hamud, T., Gross, M., 2010. The effect of mouth breathing versus nasal breathing on dentofacial and craniofacial development in orthodontic patients. Laryngoscope, 120 (10), 2089-93.
Hodges, P., Heijnen, I., Gandevia, S.C., 2001. Postural activity of the diaphragm is reduced in humans when respiratory demand increases. Journal of physiology, 537 (3), 999-1008.
Lima, L.C.O., Baruna, M.A., Sologurem, M.J.J., Canto, R.S.T., Gastaldi, A.C., 2004. Postural alterations in children with mouth beathing assessed by computerized biophotogrammetry. Journal applied oral science, 12 (3), 232-237.
