Examples of impaired gas exchange in the following topics:
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- It is characterized by inflammation of the lung parenchyma leading to impaired gas exchange with concomitant systemic release of inflammatory mediators causing inflammation, hypoxemia, and frequently resulting in multiple organ failure.
- This adds up to the impaired oxygenation which is the central problem of ARDS, as well as to respiratory acidosis, which is often caused by ventilation techniques such as permissive hypercapnia which attempt to limit ventilator-induced lung injury in ARDS.
- The result is a critical illness in which the 'endothelial disease' of severe sepsis/SIRS is worsened by the pulmonary dysfunction, which further impairs oxygen delivery.
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- Pulmonary edema is fluid accumulation in the air spaces and parenchyma of the lungs and it leads to impaired gas exchange which may cause respiratory failure.
- Low oxygen saturation and disturbed arterial blood gas readings support the proposed diagnosis by suggesting a pulmonary shunt.
- In the case of cardiogenic pulmonary edema, urgent echocardiography may strengthen the diagnosis by demonstrating impaired left ventricular function, high central venous pressures, and high pulmonary artery pressures.
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- Low lung compliance is commonly seen in people with restrictive lung diseases, such as pulmonary fibrosis, in which scar tissue deposits in the lung making it much more difficult for the lungs to expand and deflate, and gas exchange is impaired.
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- The partial pressure gradients for gas exchange are also decreased, along with the percentage of oxygen saturation in hemoglobin.
- Humans can survive at high altitudes with impaired short-term functions that eventually adjust in the long term.
- Additionally, the peripheral chemoreceptors cause sympathetic nervous system stimulation, which causes the heart rate to increase while stroke volume decreases, and digestion is impaired.
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- Henry's law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas.
- The main application of Henry's law in respiratory physiology is to predict how gasses will dissolve in the alveoli and bloodstream during gas exchange.
- Oxygen has a larger partial pressure gradient to diffuse into the bloodstream, so it's lower solubility in blood doesn't hinder it during gas exchange.
- Therefore, based on the properties of Henry's law, both the partial pressure and solubility of the oxygen and carbon dioxide determine how they will behave during gas exchange.
- Explain the way in which Henry's law relates to gas exchange in the respiratory system
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- The primary function of the respiratory system is gas exchange between the
external environment and an organism's circulatory system.
- As gas exchange occurs, the acid-base
balance of the body is maintained as part of homeostasis.
- At the molecular level, gas exchange occurs in the alveoli—tiny sacs
which are the basic functional component of the lungs.
- Alveolar Ventilation (VA): The amount of gas per unit of time that reaches the alveoli (the functional part of the lungs where gas exchange occurs).
- It is defined as tidal volume minus dead space (the space in the lungs where gas exchange does not occur) times the respiratory rate.
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- The first is the exchange
of gasses between the bloodstream and the tissues.
- Gas
exchange occurs in the alveoli so that oxygen is loaded into the
bloodstream and carbon dioxide is unloaded from the bloodstream.
- The factors that influence tissue gas exchange are similar to the factors of alveolar gas exchange, and include partial pressure gradients between the blood and the tissues, the blood perfusion of those tissues, and the surface areas of those tissues.
- Each of those factors generally increase gas exchange as those factors are increased (i.e., more oxygen diffusion in tissues with more blood perfusion).
- Regarding the partial pressure gradients in systemic capillaries, they have a PaO2 of 100mmHg and a PaCO2 of 40mmHG within the capillary and a PaO2 of 40 mmHg and PaCO2 of 45 mmHg inside issue cells, which allows gas exchange to occur.
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- This empirical law was observed by John Dalton in 1801 and is related to the ideal gas laws.
- In the lungs, the relative concentration of gasses determines the rate at which each gas will diffuse across the alveolar membranes.
- For the purposes of gas exhange, O2 and CO2 are mainly considered due to their metabolic importance in gas exchange.
- These pressure differences explain why oxygen flows into the alveoli and why carbon dioxide flows out of the alveoli through passive diffusion (just as a similar process explains alveolar and arterial gas exchange).
- While inhaled air is similar to atmospheric air due to Dalton's law, exhaled air will have relative concentrations that are in between atmospheric and alveolar air due to the passive diffusion of gasses during gas exchange.
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- Alveolar ventilation (VA):
The amount of gas per unit of time that reaches the alveoli and becomes involved in gas exchange.
- Dead space ventilation (VD):
The amount of air per unit of time that is not involved in gas exchange, such as the air that remains in the conducting zones.
- Differences in partial pressures of gasses between the alveolar air and the blood stream are the reason that gas exchange occurs by passive diffusion.
- Recall that gasses travel from areas of high pressure to areas of low pressure, so the greater pressure of oxygen in the alveoli compared to that of the deoxygenated blood explains why oxygen can passively diffuse into the bloodstream during gas exchange.
- The partial pressure, and thus concentration of carbon dioxide, is greater in the in the capillaries of the alveoli compared to the alveolar air, so carbon dioxide will passively diffuse from the bloodstream into the alveoli during gas exchange.
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- Alveoli are hollow cavities in the lung that perform gas exchange with the blood.
- The alveolar membrane is the gas-exchange surface.
- The large surface area makes gas exchange with the bloodstream more efficient.
- However, alveoli that are injured and can no longer contribute to gas exchange become alveolar dead space.
- Physiological dead space is the sum of normal anatomical dead space and alveolar dead space, and can be used to determine the rate of ventilation (gas exchange) in the lungs.