Which term signifies low oxygen in the bloodstream?

• A. Oxygen Therapy
• B. Pleural Space
• C. Hypercarbia
• D. Hypoxemia

Answer: (D)

Low oxygen in the bloodstream is called hypoxemia. It means there’s reduced arterial oxygen tension (PaO2) or lower oxygen saturation (SaO2). Clinically, PaO2 below about 80 mmHg at sea level signals hypoxemia, with more severe levels risking tissue hypoxia. Hypoxemia can arise from problems with ventilation (air reaching the lungs), diffusion (oxygen transfer across the alveolar membranes), perfusion (blood flow to the lungs), or a mismatch between ventilation and perfusion, as well as from altitude or certain lung diseases. Oxygen therapy is used to raise blood oxygen levels. The pleural space is just the area around the lungs and does not describe blood oxygen, and hypercarbia refers to elevated carbon dioxide, not reduced oxygen.