Breathing is controlled through the respiratory centre which is formed by a group of nerves in the medulla, the respiratory rhythmicity centre, which controls respiratory pattern (i.e., rate and depth of breathing). An individual can override this when doing activities such as talking, singing, etc. Chemoreceptors within the body respond to changes in the partial pressure of Oxygen and Carbon Dioxide (PO2, Carbon dioxide (PCO2), and blood acidity. If there are slight changes in the partial pressures or acidity levels, this informs the respiratory centre, and signals are sent to alter the respiratory rate. For example, an increased respiratory rate allows for more oxygen supply and removal of carbon dioxide, allowing the balance of partial pressures and acidity to return to normal.
Inspiration occurs through the Diaphragm and External Intercostal muscles contracting. This increases the space within the lungs, decreasing atmospheric pressure. Air flows into the lungs as the atmospheric pressure tries to normalise within the larger space, bringing in Oxygen. On expiration, the Diaphragm and Intercostal muscles relax, causing the lungs to recoil. This increases atmospheric pressure within the lungs, forcing air out. Gaseous exchange occurs within the Alveoli, where capillaries surround the Alveolar structures, allowing the transfer of Oxygen and Carbon dioxide. On normal inspiration, the Tidal Volume (TV (amount of air passing into and out of the lungs during rest)) is around 500 ml.
Through this finely balanced process of respiratory control within the Medulla involving Chemoreceptors measuring blood acidity and PO2/PCO2, and the response of increased respirations through contraction and relaxation of the Diaphragm and Intercostal muscles, homeostasis can be maintained and the body’s requirements met.
Assessing breathing is an important aspect to identify any deficits that may be present, or any worsening symptoms. An initial review of rate, depth, and effectiveness will give you an idea of any potential pathophysiology happening. The clinician can question; is the rate within normal parameters, is it elevated or decreased indicating an imbalance of PO2/PCO2 or acidity? Is it regular or irregular indicating potential issues with the Medulla respiratory centre? Is the depth adequately perfusing the patient, is it shallow breaths meaning potentially poor air entry, is it deep and irregular suggesting possible neurological issues? Is the patients’ breathing effective, is there evidence of cyanosis, excessive intercostal, diaphragm, and/or abdominal use to get air in, are they having use a tripod position to help maintain air entry? Is their Oxygen Saturation (SPO2) maintaining between a healthy normal range, 94-98%, or 88-92% in COPD. All of these questions can help the clinician build an idea if there are potential pathophysiological issues with a patients’ breathing.