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Blackdamp is encountered in enclosed environments such as mines, sewers, wells, tunnels and ships' holds. It occurs with particular frequency in abandoned or poorly ventilated coal mines. Coal, once exposed to the air of a mine, naturally begins absorbing oxygen and exuding carbon dioxide and water vapor.
A ventilation perfusion scan or lung scintigraphy can be used to diagnose areas of lungs being ventilated but not adequately perfused. This results in a raised Alveolar-arterial (A-a) gradient which is responsive to supplemental oxygen. In conditions with right to left shunts, there are also ventilation perfusion defects with high A-a gradients.
By redirecting blood flow from poorly-ventilated lung regions to well-ventilated lung regions, HPV is thought to be the primary mechanism underlying ventilation/perfusion matching. [1] [2] The process might initially seem counterintuitive, as low oxygen levels might theoretically stimulate increased blood flow to the lungs to increase gas exchange.
FILE - A health worker uses a pulse oximeter to check the oxygen saturation level of another after administering COVID-19 vaccine at a hospital in Gauhati, India, Jan. 21, 2021.
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]
Colorimetric capnography is a qualitative measurement method that detects the presence of carbon dioxide (CO2, a relatively acidic gas) in a given gaseous environment. From a medical perspective, the method is usually applied by exposing litmus paper/film to an environment containing a patient's airway gases (i.e. placing it into their breathing circuit/airway circuit), where it will then ...
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Hypoventilation is not synonymous with respiratory arrest, in which breathing ceases entirely and death occurs within minutes due to hypoxia and leads rapidly into complete anoxia, although both are medical emergencies. Hypoventilation can be considered a precursor to hypoxia, and its lethality is attributed to hypoxia with carbon dioxide toxicity.