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The mechanism often quoted is the “ hypoxic drive to breath “. The idea is that COPD patients tend to have chronically elevated levels of carbon dioxide due to the nature of their illness. As such, administering oxygen to these patients with COPD can be dangerous.
Hypoxia induces a breathing pattern of rapid and shallow breaths with a relatively higher increase in respiratory rate than tidal volume. The aim is to decrease the cost of breathing by avoiding the need to overcome the lungs' higher elastance at high volumes.
In patients with COPD, hypoxic pulmonary vasoconstriction is the most efficient way to alter the Va/Q ratios to improve gas exchange. This physiological mechanism is counteracted by oxygen therapy and accounts for the largest increase of oxygen-induced hypercapnia.
The hypoxic drive is a form of respiratory drive in which the body uses oxygen chemoreceptors instead of carbon dioxide receptors to regulate the respiratory cycle. Normal respiration is driven mostly by the levels of carbon dioxide in the arteries, which are detected by peripheral chemoreceptors, and very little by the oxygen levels. An ...
One of the most clinically interesting and least understood theories in respiratory medicine is the hypoxic-drive theory. This holds that people who chronically retain carbon dioxide lose their hypercarbic drive to breathe.
Excessive oxygen administration can lead to hypercapnic respiratory failure in some COPD patients. COPD patients with more severe hypoxemia are at higher risk of CO2 retention from uncontrolled O2 administration.
Hypoxia is a life-threatening condition that is treatable with prompt medical attention. If you have a heart or lung condition that puts you at risk for hypoxia, talk to your healthcare provider about the signs and symptoms to look for and what to do if you think your oxygen is too low.
When hypoxemia exists with chronic hypercapnia, the central response to carbon dioxide is blunted, and the primary stimulus to breathe is mediated through hypoxic stimulation of the peripheral chemoreceptors. This is known as the hypoxic drive, and it is real.
The mechanism proposed initially and still being taught in the medical school is the hypoxic drive theory. According to this theory, COPD patients depend on hypoxic ventilatory drive as the hypercapnic drive is blunted in chronically hypercapnic COPD patients.
Hypercapnia and shift of normal respiratory drive to hypoxic drive to maintain respiratory hemostasis: Carbon dioxide is the main stimulus for the respiratory drive in normal physiological states. Carbon dioxide increases the hydrogen ions, which lowers the pH.