How much oxygen is present in blood?
22419890#0
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 blood oxygen levels in humans are considered 95–100 percent. If the level is below 90 percent, it is considered low resulting in hypoxemia. 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. 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 air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.
Oxygen saturation (medicine)
3997#20
About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at sea-level pressure is chemically combined with the hemoglobin. About 1.5% is physically dissolved in the other blood liquids and not connected to hemoglobin. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species (for exceptions, see below). Hemoglobin has an oxygen binding capacity between 1.36 and 1.40 ml O per gram hemoglobin, which increases the total blood oxygen capacity seventyfold, compared to if oxygen solely were carried by its solubility of 0.03 ml O per liter blood per mm Hg partial pressure of oxygen (about 100 mm Hg in arteries).
Blood
15272963#7
Oxygen diffuses through membranes and into red blood cells after inhalation into the lungs. They are bound to dioxygen complexes, which are coordination compounds that contain O as a ligand, providing a more efficient oxygen-loading capacity. In blood, the heme group of hemoglobin binds oxygen when it is present, changing hemoglobin's color from bluish red to bright red. Vertebrate animals use hemoglobin in their blood to transport oxygen from their lungs to their tissues, but other animals use hemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters). A liter of blood can dissolve 200 cc of oxygen gas, which is much more than water can dissolve.
Dioxygen in biological reactions
31638472#0
The arteriovenous oxygen difference, or a-vO diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body. The a-vO diff and cardiac output are the main factors that allow variation in the body's total oxygen consumption, and are important in measuring VO. The a-vO diff is usually measured in millilitres of oxygen per 100 millilitres of blood (mL/100 mL).
Arteriovenous oxygen difference
3551251#1
Hemoglobin (Hb) is the primary vehicle for transporting oxygen in the blood. Oxygen is also carried dissolved in the blood's plasma, but to a much lesser degree. Hemoglobin is contained in red blood cells. Under certain conditions, oxygen bound to the hemoglobin is released into the blood's plasma and absorbed into the tissues. Each hemoglobin molecule has the capacity to carry four oxygen molecules. These molecules of oxygen bind to the iron of the Heme group. The binding of the first oxygen molecule induces a conformational change of hemoglobin that increases the affinity for the remaining three oxygen molecules.
Oxygen–hemoglobin dissociation curve
31638472#5
Arterial blood will generally contain an oxygen concentration of around 20 mL/100 mL. Venous blood with an oxygen concentration of 15 mL/100 mL would therefore lead to typical values of the a-vO diff at rest of around 5 mL/100 mL. During intense exercise, however, the a-vO diff can increase to as much as 16 mL/100 mL due to the working muscles extracting far more oxygen from the blood than they do at rest.
Arteriovenous oxygen difference
33209445#6
The ratio of partial pressure arterial oxygen and fraction of inspired oxygen, sometimes called the "Carrico index", is a comparison between the oxygen level in the blood and the oxygen concentration that is breathed. This helps to determine the degree of any problems with how the lungs transfer oxygen to the blood. A sample of arterial blood is collected for this test. A PaO2/FiO2 ratio less than or equal to 200 is necessary for the diagnosis of acute respiratory distress syndrome by the AECC criteria. The more recent Berlin criteria defines mild ARDS at a ratio of <300.
Fraction of inspired oxygen
3997#22
Under normal conditions in adult humans at rest, hemoglobin in blood leaving the lungs is about 98–99% saturated with oxygen, achieving an oxygen delivery between 950 and 1150 ml/min to the body. In a healthy adult at rest, oxygen consumption is approximately 200–250 ml/min, and deoxygenated blood returning to the lungs is still roughly 75% (70 to 78%) saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia). Sustained hypoxia (oxygenation less than 90%), is dangerous to health, and severe hypoxia (saturations less than 30%) may be rapidly fatal.
Blood
42179#140
In May 2007, the Caudwell Xtreme Everest undertook a medical study of oxygen levels in human blood at extreme altitude. Over 200 volunteers climbed to Everest Base Camp where various medical tests were performed to examine blood oxygen levels. A small team also performed tests on the way to the summit. Even at base camp, the low partial pressure of oxygen had direct effect on blood oxygen saturation levels. At sea level, blood oxygen saturation is generally 98–99%. At base camp, blood saturation fell to between 85 and 87%. Blood samples taken at the summit indicated very low oxygen levels in the blood. A side effect of low blood oxygen is a greatly increased breathing rate, often 80–90 breaths per minute as opposed to a more typical 20–30. Exhaustion can occur merely attempting to breathe.
Mount Everest
1144509#12
The calculation of the arterial and venous oxygen concentration of the blood is a straightforward process. Almost all oxygen in the blood is bound to hemoglobin molecules in the red blood cells. Measuring the content of hemoglobin in the blood and the percentage of saturation of hemoglobin (the oxygen saturation of the blood) is a simple process and is readily available to physicians. Using the fact that each gram of hemoglobin can carry 1.34 ml of O, the oxygen content of the blood (either arterial or venous) can be estimated by the following formula:
Fick principle