where is the partial pressure of oxygen the greatest? course hero

Once oxygen has reached the arteries, the difference in pressures (gradient of pressure) between the capillary to the cytosol of surrounding cells results in a steep diffusion gradient, the greatest in the body reaching more than 42% [ 4 ]. The average partial pressure in the tissue is called the tissue partial pressure of oxygen (PtO 2) [ 10 ].

Full Answer

What is the partial pressure of oxygen in the blood?

Throughout the process of oxygen consumption by various tissues, the oxygen content of blood drops such that the 100 mm Hg in the arterial blood decreases to 40 mm Hg in venous blood. [2] Clinical Significance The primary measurement used to evaluate the partial pressure of oxygen is arterial blood gas.

How does the human body maintain a suitable level of oxygen?

Conclusions The human body is a complex living organism, which has developed mechanisms to keep oxygen levels in a suitable level as to cover the metabolic demand, while avoiding excessive oxygen pressure. The partial pressure of oxygen varies in the different structures of the organism.

What is the atmospheric pressure of oxygen at sea level?

The pressure of all of the gases you breathe (oxygen, nitrogen, carbon dioxide) is roughly 760 millimeters of mercury (mm Hg) at sea level. At higher altitudes, increases in atmospheric pressure result in a drop in the pressure of your blood gases, including the partial pressure of oxygen.

What is the partial pressure of oxygen in the dermal papillae?

Dermal papillae at 45 to 65 micrometers depth typically have an 18 to 30 mm Hg partial pressure of oxygen, and at the subpapillary plexus of 100 to 120 micrometers depth, the partial pressure of oxygen is approximately 27 to 43 mm Hg.

What is diffusion limitation?

What is the driving force for the diffusion of oxygen across the alveolar membranes?

What is the difference between PAO2 and PCO2?

How is PAO2 measured?

Why is oxygenation important?

What is the composition of air?

What is hypoventilation in obesity?

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Partial Pressure Calculator - How to calculate partial pressure

Partial Pressure Formula: Uptill now many theories have been published for calculating partial pressure in a gas mixture. Some of the important gas laws that are widely used to calculate the partial pressure are as follows:

What is the partial pressure of oxygen in atmosphere? - Quora

Answer (1 of 8): Since inspired air is 21% oxygen and atmospheric pressure is 760 mmHg (at sea level), the partial pressure of oxygen is 0.21 x 760 mmHg = 160 mmHg. As air moves into the alveoli, water vapor and carbon dioxide are added, and that reduces the partial pressure of oxygen to about 10...

What is Partial Pressure of Oxygen and How Do You Calculate It?

In this article, we will address the definition of partial pressure, the physics behind it, how you calculate partial pressure and how to convert the oxygen partial pressure into volumetric content for those interested in oxygen concentration.

Partial pressure of oxygen in the human body: a general review

The human body is a highly aerobic organism, in which it is necessary to match oxygen supply at tissue levels to the metabolic demands. Along metazoan evolution, an exquisite control developed because although oxygen is required as the final acceptor of electron respiratory chain, an excessive level …

What is diffusion limitation?

Diffusion limitation exists when the movement of oxygen from alveoli to pulmonary vasculature is impaired. This etiology is characterized by fibrosis of the lung and parenchymal destruction of alveoli leading to a decreased surface area of alveoli tissue. Often diffusion abnormalities are coexisting with V/Q mismatching and are most prevalent under exercise conditions. During rest, blood flow through the lung arterioles is slow enough to allow for proper diffusion regardless of an increased A-a gradient. However, under exercise conditions, cardiac output increases. When this occurs, there is less time for oxygenation to occur in the lung, which leads to transient hypoxia. Examples of limited diffusion disease include lung fibrosis and chronic obstructive pulmonary disease. The result is a normal partial pressure of oxygen in the alveolar space but a low partial pressure of oxygen in the arterial space. [6][7][8]

What is the driving force for the diffusion of oxygen across the alveolar membranes?

This alveolar partial pressure of oxygen is the driving force for diffusion of oxygen across the alveolar membranes, through pulmonary capillary walls, and into the arteriolar blood flow and erythrocytes for transport throughout the body into peripheral tissues. The diffusion gradient from alveolar space into the capillary is quantified via the A-a gradient calculated as:

What is the difference between PAO2 and PCO2?

While PAO2 is the partial pressure of oxygen in the alveoli, Patm is the atmospheric pressure at sea level equaling 760 mm Hg. PH2O is the partial pressure of water equal to approximately 45 mm Hg. FiO2 is the fraction of inspired oxygen. PCO2 is the carbon dioxide partial pressure in arteries , which in normal physiological conditions is approximately 40 to 45 mm H g, and the RQ (respiratory quotient). FiO2 is directly related to the percent composition of oxygen in the inspired air. Without support at sea level, this is 21% or 0.21. However, each liter of supplemental oxygen in the inspired air increases this value by approximately 4% or 0.04. Therefore 2 liters of supplemented oxygen increase the FiO2 at sea level by 8% or 0.08 to 29% or 0.29. The value of RQ can vary depending upon the type of diet and metabolic state of the person. A standard value of 0.82 for the typical human diet. At sea level without supplemented inspired oxygenation, the alveolar oxygen partial pressure (PAO2) is:

How is PAO2 measured?

PaO2 is measured using an arterial blood gas , and PAO2 is calculated as above. A larger gradient indicates pathology is hindering the transfer of oxygen into the capillary, which impacts the available partial pressure of oxygen throughout the body. The necessary partial pressure of oxygen throughout tissues is variable depending on the metabolic demands of the tissues. The brain has been found to require a partial pressure of oxygen of at least 35 mm Hg below. Mental functions become impacted because the aerobic metabolism of glucose for energy production cannot occur efficiently. The skin typically has a partial pressure spectrum based on the depth of the skin layer from the surface. The superficial region of the skin at 5 to 10 micrometers depth is approximately 5.0 to 11 mm Hg partial pressure of oxygen. Dermal papillae at 45 to 65 micrometers depth typically have an 18 to 30 mm Hg partial pressure of oxygen, and at the subpapillary plexus of 100 to 120 micrometers depth, the partial pressure of oxygen is approximately 27 to 43 mm Hg. The intestines also have a variable partial pressure of oxygen, with the serosal portion of the small bowel being 53.0 to 71.0 mm Hg. Liver partial pressures of oxygen have been studied with somewhat variable results such that two separate groups were found to have median values of 42.04 mm Hg and 34.53 mm Hg. The kidneys make up another organ system that has a high oxygen requirement due to the high energy and subsequent metabolic demand involved in the active transport processes of the nephron reabsorption systems. As such, the medullary partial pressure of oxygen is 10 to 20 mm Hg, and the cortex requires 52 to 92 mm Hg. Muscular demand for oxygen is highly variable depending on the activity intensity and duration of the muscle. At baseline, muscular partial pressures of oxygen are 27 mm Hg to 31 mm Hg. Throughout the process of oxygen consumption by various tissues, the oxygen content of blood drops such that the 100 mm Hg in the arterial blood decreases to 40 mm Hg in venous blood. [2]

Why is oxygenation important?

Oxygenation of tissues is one of the most important processes that occur within the human body. Without proper oxygenation of tissues, metabolic processes cannot function efficiently, and cellular functions will falter. With such importance for the survival of an organism, it is understandable that the process of extracting oxygen from environmental air is tightly regulated physiologically. All gases follow chemical laws that, when mixed, will each have a partial pressure equal to the hypothetical pressure when the same gas homogeneously occupies the same volume at the same temperature as the original mixture. [1]

What is the composition of air?

The composition of environmental air is approximately 78% nitrogen, 21% oxygen, 1% argon, and trace percentages of carbon dioxide, neon, methane, helium, krypton, hydrogen, xenon, ozone, nitrogen dioxide, iodine, carbon monoxide, and ammonia. Therefore, at sea level, where atmospheric pressure is known to be 760 mm Hg, the partial pressures of the various gases can be estimated to have partial pressures of approximately 593 mm Hg for nitrogen, 160 mm Hg for oxygen, and 7.6 mm Hg for argon. However, these partial pressures are not accurate reflections of the partial pressures available for diffusion within the alveoli of the lung. When air is inhaled through the upper airways, it is warmed and humidified by the pulmonary tract. The result of this process introduces the presence of significant levels of water vapor that then adjusts the partial pressures of the other gases, including oxygen. It is not possible to collect gases directly from the alveoli. The alveolar gas equation is of great help in calculating and closely estimating the partial pressure of oxygen inside the alveoli.  The alveolar gas equation is used to calculate alveolar oxygen partial pressure:

What is hypoventilation in obesity?

Obesity hypoventilation where the excess weight of the chest does not allow for proper inflation

What is the name of the gas that is measured in an arterial blood gas test?

The PaO2 is one of the components measured in an arterial blood gas (ABG) test —which also reports oxygen (O2) saturation, bicarbonate (HCO3), the partial pressure of carbon dioxide (CO2), and the pH level in red blood cells. Science Photo Library / Getty Images.

What is the purpose of a PaO2 test?

Purpose of Test. The PaO2 test can be used to assess the effects of breathing problems on oxygen supply, especially in a hospital setting or during an episode of severe respiratory distress.

Why do we do a repeat PaO2 test?

In some situations, such as when oxygen therapy or ventilation (mechanical breathing support) has been started, a repeat PaO2 test is used to assess whether a respiratory condition is improving or worsening and whether the treatment needs to be adjusted.

What factors can lower PaO2 levels?

A number of factors can lower your PaO2 levels, including: 6 . The partial pressure of oxygen in the air you inhale: At higher altitudes (such as in mountainous areas), the decrease in atmospheric pressure reduces oxygen availability—and oxygen pressure in your lungs.

What is PaO2 in medical terms?

Sanja Jelic, MD, is board-certified in sleep medicine, critical care medicine, pulmonary disease, and internal medicine. The partial pressure of oxygen , also known as PaO2, is a measurement of oxygen pressure in arterial blood.

How to stop bleeding after a blood test?

Once enough blood is collected, the needle is removed and cotton or gauze is placed over the puncture site. Your practitioner will place pressure over the puncture site to help stop the bleeding.

How to clean a puncture site?

The skin around the intended puncture site will be cleaned, usually with an alcohol pad. A small needle, which is attached to a tube, will then be inserted into your artery. The pressure or pain is a bit uncomfortable—more uncomfortable than the pain felt when you have blood drawn from a vein. 3 However, the test is tolerable for most people.

How much oxygen diffusion is there in the alveoli?

The rate of oxygen diffusion across the alveoli-capillary membrane in addition to a faster and easier elimination of CO2, assures that capillary PaO2is almost equal to the alveolar PAO2and during normal conditions (at sea level) it correspond to 75 to 100 mmHg [24].

How does air pressure affect oxygen?

Once air is warmed and humidified in the nose and upper respiratory tract, the pressure of oxygen decreases while concentration of H2O increases, thus altering effective PO2in this gas mixture. Therefore, oxygen partial pressure within the upper airway is noted inspired PO2(PiO2) [15]. The reduction of pressure of oxygen is caused by the addition of water vapour (humidification) to the entire mixture of gases, thus reducing the pressure of the other gases [4]. The pressure of water vapour is constant at 47 mmHg at normal body temperature (37°C), and it is strongly temperature dependent [11]. This results in an effective reduction at the alveolar level in the partial pressure of oxygen (PAO2) from 159 to 149 mmHg that is not likely to be physiologically relevant at sea level, because only represents about 6% of the total AtmPO2[16]. However, when the BP is already low, such as at the summit of Mount Everest (altitude 8,848 m), a reduction of 47 mmHg (the water vapour pressure) represents almost 20% of the available AtmPO2, making this reduction life threatening [17,18].

What is the R of 47?

Where R is the respiratory exchange ratio and equals 0.8 most of the time and the 47 correspond to the water vapour pressure at normal body temperature (37°) [4].

How does oxygen travel through the body?

The transport of oxygen from the atmosphere into the entire body is mediated by the rate diffusion as well as the rate of consumption between physiological barriers [29]. Diffusion is based on the kinetic theory that encompasses the rapid movement of molecules, causing a self-generated energy source to rapidly cross membranes [30]. Whereas convective transport refers to the heat transferred and energy-consuming combination of molecules to cause the movement of oxygen in the trachea and the bronchial tree with the surrounding alveoli-capillary circulation [31]. The diffusive transport is the passive movement of oxygen across several barriers, such as the endothelium, the alveolus and the mitochondrial membrane [32]. The amount of diffusive oxygen movement depends on the gradient of partial pressure of oxygen, the available surface area to diffusion, the permeability and thickness of diffusion barriers and the local metabolic demand [33,34].

What is the composition of the troposphere?

The composition of gases within the troposphere is constant at approximately the following ratio: 78.08% nitrogen, 20.95% oxygen, 0.93% argon and finally less than 0.038% for carbon dioxide and other gases [6].

What are the factors that determine the amount of oxygen in a cell?

The amount of dissolved oxygen within the tissues and the cells depends on several factors including: barometric pressure (BP), climatological conditions (temperature, relative humidity, latitude, altitude), as well as physiological, pathological, and physical-chemical processes within the organism itself [4,5].

What is the body's energy source?

The human body is a highly aerobic organism that consumes oxygen according to its metabolic demand [1]. During aerobic respiration the presence of oxygen in addition to pyruvate, produces adenosine triphosphate (ATP), thus yielding energy to the entire organism [2].

What is diffusion limitation?

Diffusion limitation exists when the movement of oxygen from alveoli to pulmonary vasculature is impaired. This etiology is characterized by fibrosis of the lung and parenchymal destruction of alveoli leading to a decreased surface area of alveoli tissue. Often diffusion abnormalities are coexisting with V/Q mismatching and are most prevalent under exercise conditions. During rest, blood flow through the lung arterioles is slow enough to allow for proper diffusion regardless of an increased A-a gradient. However, under exercise conditions, cardiac output increases. When this occurs, there is less time for oxygenation to occur in the lung, which leads to transient hypoxia. Examples of limited diffusion disease include lung fibrosis and chronic obstructive pulmonary disease. The result is a normal partial pressure of oxygen in the alveolar space but a low partial pressure of oxygen in the arterial space. [6][7][8]

What is the driving force for the diffusion of oxygen across the alveolar membranes?

This alveolar partial pressure of oxygen is the driving force for diffusion of oxygen across the alveolar membranes, through pulmonary capillary walls, and into the arteriolar blood flow and erythrocytes for transport throughout the body into peripheral tissues. The diffusion gradient from alveolar space into the capillary is quantified via the A-a gradient calculated as:

What is the difference between PAO2 and PCO2?

While PAO2 is the partial pressure of oxygen in the alveoli, Patm is the atmospheric pressure at sea level equaling 760 mm Hg. PH2O is the partial pressure of water equal to approximately 45 mm Hg. FiO2 is the fraction of inspired oxygen. PCO2 is the carbon dioxide partial pressure in arteries , which in normal physiological conditions is approximately 40 to 45 mm H g, and the RQ (respiratory quotient). FiO2 is directly related to the percent composition of oxygen in the inspired air. Without support at sea level, this is 21% or 0.21. However, each liter of supplemental oxygen in the inspired air increases this value by approximately 4% or 0.04. Therefore 2 liters of supplemented oxygen increase the FiO2 at sea level by 8% or 0.08 to 29% or 0.29. The value of RQ can vary depending upon the type of diet and metabolic state of the person. A standard value of 0.82 for the typical human diet. At sea level without supplemented inspired oxygenation, the alveolar oxygen partial pressure (PAO2) is:

How is PAO2 measured?

PaO2 is measured using an arterial blood gas , and PAO2 is calculated as above. A larger gradient indicates pathology is hindering the transfer of oxygen into the capillary, which impacts the available partial pressure of oxygen throughout the body. The necessary partial pressure of oxygen throughout tissues is variable depending on the metabolic demands of the tissues. The brain has been found to require a partial pressure of oxygen of at least 35 mm Hg below. Mental functions become impacted because the aerobic metabolism of glucose for energy production cannot occur efficiently. The skin typically has a partial pressure spectrum based on the depth of the skin layer from the surface. The superficial region of the skin at 5 to 10 micrometers depth is approximately 5.0 to 11 mm Hg partial pressure of oxygen. Dermal papillae at 45 to 65 micrometers depth typically have an 18 to 30 mm Hg partial pressure of oxygen, and at the subpapillary plexus of 100 to 120 micrometers depth, the partial pressure of oxygen is approximately 27 to 43 mm Hg. The intestines also have a variable partial pressure of oxygen, with the serosal portion of the small bowel being 53.0 to 71.0 mm Hg. Liver partial pressures of oxygen have been studied with somewhat variable results such that two separate groups were found to have median values of 42.04 mm Hg and 34.53 mm Hg. The kidneys make up another organ system that has a high oxygen requirement due to the high energy and subsequent metabolic demand involved in the active transport processes of the nephron reabsorption systems. As such, the medullary partial pressure of oxygen is 10 to 20 mm Hg, and the cortex requires 52 to 92 mm Hg. Muscular demand for oxygen is highly variable depending on the activity intensity and duration of the muscle. At baseline, muscular partial pressures of oxygen are 27 mm Hg to 31 mm Hg. Throughout the process of oxygen consumption by various tissues, the oxygen content of blood drops such that the 100 mm Hg in the arterial blood decreases to 40 mm Hg in venous blood. [2]

Why is oxygenation important?

Oxygenation of tissues is one of the most important processes that occur within the human body. Without proper oxygenation of tissues, metabolic processes cannot function efficiently, and cellular functions will falter. With such importance for the survival of an organism, it is understandable that the process of extracting oxygen from environmental air is tightly regulated physiologically. All gases follow chemical laws that, when mixed, will each have a partial pressure equal to the hypothetical pressure when the same gas homogeneously occupies the same volume at the same temperature as the original mixture. [1]

What is the composition of air?

The composition of environmental air is approximately 78% nitrogen, 21% oxygen, 1% argon, and trace percentages of carbon dioxide, neon, methane, helium, krypton, hydrogen, xenon, ozone, nitrogen dioxide, iodine, carbon monoxide, and ammonia. Therefore, at sea level, where atmospheric pressure is known to be 760 mm Hg, the partial pressures of the various gases can be estimated to have partial pressures of approximately 593 mm Hg for nitrogen, 160 mm Hg for oxygen, and 7.6 mm Hg for argon. However, these partial pressures are not accurate reflections of the partial pressures available for diffusion within the alveoli of the lung. When air is inhaled through the upper airways, it is warmed and humidified by the pulmonary tract. The result of this process introduces the presence of significant levels of water vapor that then adjusts the partial pressures of the other gases, including oxygen. It is not possible to collect gases directly from the alveoli. The alveolar gas equation is of great help in calculating and closely estimating the partial pressure of oxygen inside the alveoli.  The alveolar gas equation is used to calculate alveolar oxygen partial pressure:

What is hypoventilation in obesity?

Obesity hypoventilation where the excess weight of the chest does not allow for proper inflation