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Definitions

Respiration

The major function of the respiratory system is to supply the cells of the human body with oxygen and to remove carbon dioxide, to ensure the cells can function effectively (Tortora and Derrickson [199]). Respiration is composed of four processes:
  • pulmonary ventilation: movement of air into and out of the lungs to continually refresh the gases there, commonly called ‘breathing’
  • external respiration: movement of oxygen from the lungs into the blood, and carbon dioxide from the blood into the lungs, commonly called ‘gaseous exchange’
  • transport of respiratory gases: transport of oxygen from the lungs to the cells, and of carbon dioxide from the cells to the lungs, accomplished by the cardiovascular system
  • internal respiration: movement of oxygen from blood into the cells, and of carbon dioxide from the cells to the blood (Marieb and Hoehn [110]).

Pulse oximetry

Pulse oximetry provides continuous and non‐invasive monitoring of the oxygen saturation from haemoglobin in arterial blood (Peate and Wild [157]). Pulse oximetry is an effective method of monitoring for hypoxaemia and detecting a fall in arterial oxygen saturation, often even before any obvious symptoms are displayed (Marini and Dries [112]). It also provides useful information about heart rate (Tait et al. [194]).
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