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Hypoxemia is usually defined in terms of reduced partial pressure of oxygen (mm Hg) in arterial blood, but also in terms of reduced content of oxygen (ml oxygen per dl blood) or percentage saturation of hemoglobin (the oxygen-binding protein within red blood cells) with oxygen, which is either found singly or in combination. [2] [5]
Normal arterial blood oxygen saturation levels in humans are 96–100 percent. [1] If the level is below 90 percent, it is considered low and called hypoxemia . [ 2 ] Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed.
Hypoxemic hypoxia is a lack of oxygen caused by low oxygen tension in the arterial blood, due to the inability of the lungs to sufficiently oxygenate the blood. Causes include hypoventilation, impaired alveolar diffusion, and pulmonary shunting. [8] This definition overlaps considerably with that of hypoxic hypoxia.
In medicine, oxygen saturation refers to oxygenation, or when oxygen molecules (O 2) enter the tissues of the body. In this case blood is oxygenated in the lungs, where oxygen molecules travel from the air into the blood. Oxygen saturation ((O 2) sats) measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen ...
A pulse oximeter probe applied to a person's finger. A pulse oximeter is a medical device that indirectly monitors the oxygen saturation of a patient's blood (as opposed to measuring oxygen saturation directly through a blood sample) and changes in blood volume in the skin, producing a photoplethysmogram that may be further processed into other measurements. [4]
The blood can also be drawn from an arterial catheter. An ABG test measures the blood gas tension values of the arterial partial pressure of oxygen (PaO2), and the arterial partial pressure of carbon dioxide (PaCO2), and the blood's pH. In addition, the arterial oxygen saturation (SaO2) can be determined. Such information is vital when caring ...
For example, in high altitude, the arterial oxygen PaO 2 is low but only because the alveolar oxygen (PAO 2) is also low. However, in states of ventilation perfusion mismatch, such as pulmonary embolism or right-to-left shunt, oxygen is not effectively transferred from the alveoli to the blood which results in an elevated A-a gradient.
Arterial blood oxygen tension (normal) P a O 2 – Partial pressure of oxygen at sea level (160 mmHg (21.3 kPa) in the atmosphere, 21% of the standard atmospheric pressure of 760 mmHg (101 kPa)) in arterial blood is between 75 and 100 mmHg (10.0 and 13.3 kPa).