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The standard drug treatment of dexamethasone does not alter the hypoxia or the consequent vasoconstriction, but stimulates fluid reabsorption in the lungs to reverse the edema. Additionally, several studies on native populations remaining at high altitudes have demonstrated to varying degrees the blunting of the HPV response.
Many people with chronic obstructive pulmonary disease have a low partial pressure of oxygen in the blood and high partial pressure of carbon dioxide.Treatment with supplemental oxygen may improve their well-being; alternatively, in some this can lead to the adverse effect of elevating the carbon dioxide content in the blood (hypercapnia) to levels that may become toxic.
To be classified as pulmonary heart disease, the cause must originate in the pulmonary circulation system; RVH due to a systemic defect is not classified as pulmonary heart disease. Two causes are vascular changes as a result of tissue damage (e.g. disease, hypoxic injury), and chronic hypoxic pulmonary vasoconstriction. If left untreated, then ...
The physiological responses to high altitude include hyperventilation, polycythemia, increased capillary density in muscle and hypoxic pulmonary vasoconstriction–increased intracellular oxidative enzymes. There are a range of responses to hypoxia at the cellular level, shown by discovery of hypoxia-inducible factors (HIFs), which determine ...
By contrast, in the lungs, the response to hypoxia is vasoconstriction. This is known as hypoxic pulmonary vasoconstriction, or "HPV", and has the effect of redirecting blood away from poorly ventilated regions, which helps match perfusion to ventilation, giving a more even oxygenation of blood from different parts of the lungs. [81]
If lack of oxygenation is proportional to low respiratory effort, then the A–a gradient is not increased; a healthy person who hypoventilates would have hypoxia, but a normal A–a gradient. At an extreme, high CO 2 levels from hypoventilation can mask an existing high A–a gradient. This mathematical artifact makes A–a gradient more ...
These methods can be used to mimic some forms of hypoxic hypoxia and they are currently being studied including the detection of variation in arterial CO 2 tension acting as a quick-response-system for short term (or emergency) regulation.
Pulmonary interstitial pressure (Pi) rises as lung volume decreases due to reduced radial tethering of the lung parenchyma. Pi is highest at the base of the lung due to the weight of the above lung tissue. Pi can also rise due to an increased volume of 'leaked' fluid from the pulmonary vasculature (pulmonary edema). An increase in Pi causes ...