Breathing, also know as Pulmonary Ventilation is a physiological process consisting of two phases:

1. 1. Inspiration: air is taken into the lungs.
   2. Expiration: air is passed out of the lungs.

Source: E. Marieb & L. Smith. “Human Anatomy & Physiology Laboratory Manual, 10th Edition”. 2014

The Nervous System is in charge of controlling the respiratory rhythm. It is mainly kept at 15-25 respirations/min. However, there is no doubt that physical phenomena (talking, singing, walking, exercising…) can affect and alter the rate of respiration. In a similar manner, chemical factors like changes in Oxygen or Carbon dioxide contentions in the blood can also modify the respiratory rate.

Oxygenation occurs when oxygen molecules enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the inhaled air and into the blood. Cells in the body need oxygen to function, and the protein responsible to transport it from the lungs to the rest of the body is hemoglobin which is present in the blood. Oxygen binds with this protein and thus can be transported with the blood and supplied to different tissues in the body through the vascular system.

Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood.

The human body requires and regulates a very precise and specific balance of oxygen in the blood.

• • Normal arterial blood oxygen saturation levels in humans are 95–100%.
  • Hypoxemia occurs when the level is below 90%. This means that not enough oxygen is entering the body.
  • Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels.