page_title: Hypoxemia
section_title: Environmental oxygen
hierarchical_section_title: Hypoxemia / Causes / Ventilation / Environmental oxygen
caption_attribution_description: English: A basic oxyhaemoglobin (oxyhemoglobin) dissociation curve.עברית: עקומת דיסוציאציה בסיסית של אוקסיהמוגלובין
context_page_description: Hypoxemia is an abnormally low level of oxygen in the blood. More specifically, it is oxygen deficiency in arterial blood. Hypoxemia has many causes, and often causes hypoxia as the blood is not supplying enough oxygen to the tissues of the body.
context_section_description: In conditions where the proportion of oxygen in the air is low, or when the partial pressure of oxygen has decreased, less oxygen is present in the alveoli of the lungs. The alveolar oxygen is transferred to hemoglobin, a carrier protein inside red blood cells, with an efficiency that decreases with the partial pressure of oxygen in the air. 
  Altitude. The external partial pressure of oxygen decreases with altitude, for example in areas of high altitude or when flying. This decrease results in decreased carriage of oxygen by hemoglobin. This is particularly seen as a cause of cerebral hypoxia and mountain sickness in climbers of Mount Everest and other peaks of extreme altitude. For example, at the peak of Mount Everest, the partial pressure of oxygen is just 43 mmHg, whereas at sea level the partial pressure is 150 mmHg. For this reason, cabin pressure in aircraft is maintained at 5,000 to 6,000 feet (1500 to 1800 m).
  Diving. Hypoxia in diving can result from sudden surfacing. The partial pressures of gases increases when diving, increases by one ATM every ten metres. This means that a partial pressure of oxygen sufficient to maintain good carriage by hemoglobin is possible at depth, even if it is insufficient at the surface. A diver that remains underwater will slowly consume their oxygen, and when surfacing, the partial pressure of oxygen may be insufficient (shallow water blackout). This may manifest at depth as deep water blackout.
  Suffocation. Decreased concentration of oxygen in inspired air caused by reduced replacement of oxygen in the breathing mix.
  Anaesthetics. Low partial pressure of oxygen in the lungs when switching from inhaled anesthesia to atmospheric air, due to the Fink effect, or diffusion hypoxia.
  Air depleted of oxygen has also proven fatal.  In the past, anesthesia machines have malfunctioned, delivering low-oxygen gas mixtures to patients.  Additionally, oxygen in a confined space can be consumed if carbon dioxide scrubbers are used without sufficient attention to supplementing the oxygen which has been consumed.
caption: Oxygen-Hemoglobin Dissassociation Curve.
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