What is hypoxaemia?

• A. an abnormally low concentration of oxygen in the blood
• B. the absence of oxygen reaching the tissues
• C. total oxygen deprivation within tissues and organs
• D. a normal oxygen level in air

Answer: (A)

Hypoxaemia means there is less oxygen in the arterial blood than normal. It’s typically defined by a lower-than-normal arterial oxygen tension (PaO2) or lower oxygen content in the blood, which means the blood delivering to tissues isn’t carrying as much oxygen as it should. This is different from hypoxia, which describes tissue oxygen deficiency, and from anoxia, which is a total lack of oxygen. Hypoxaemia can occur even when the animal is breathing room air if there’s a problem with the lungs or blood that impairs gas exchange—for example, ventilation issues, diffusion impairment, a ventilation–perfusion mismatch, or a shunt. Clinically, it is assessed with measurements like PaO2 or via pulse oximetry (SpO2); if levels are low, supplemental oxygen and addressing the underlying cause are key steps.