#hypoxic drive

[er-cryptid]

Hypoxic Drive

-- back-up system to the carbon dioxide drive

-- there are specialized sensors that monitor oxygen levels

-- these sensors are in the brain, the aorta, and the carotid arteries

-- low oxygen levels stimulate breathing

-- less effective than the carbon dioxide drive

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[firstaid101]

Hypoxic Drive! :D

WOOT! Its time for a small lesson on the hypoxic drive now that I'm back! The hypoxic drive is the bodies backup system to control respiration. When the oxygen level falls, this system will also simulate breathing. Areas in the brain, the walls of the aorta, and the carotid arteries act as oxygen sensors. These sensors are easily satisfied by minimal levels of oxygen in the arterial blood which means that it is not as powerful as the carbon dioxide sensors in the brain stem. (Click Here to learn more on the Carbon Dioxide system) When the carbon dioxide sensors in the brainstem fail, this is when the hypoxic drive kicks in.

[blue-lights-and-tea]

What is the danger of oxygen therapy in CO2 retaining patient?

A patient that is chronically retaining CO2 is a typical A+E patient that comes in with an exacerbation of COPD.

Uncontrolled use of oxygen can cause apnoea. So beware the drowsy COPD pt who is becoming drowsy.

How does it happen?

Loss of hypoxic drive (yes we all know it, but lots of us forget it in the chaos that is a busy shift). Patients with a chronically raised CO2 rely on HYPOXIA to stimulate respiration. So start off with a low % of oxygen via a Venturi mask (such as 24%), watch their sats, check an aBG and see how they are responding. If needs be, change upwards.

Abolition of hypoxia with oxygen therapy can reverse the compensatory hypoxic pulmonary vasoconstriction - leading to a much worse V/Q mismatch.