Physiology and Pathophysiology of Hypoxia and Hypercapnia

Definition and Classification of Hypoxia

Hypoxia is defined as an insufficient oxygen supply to the tissues, leading to cellular dysfunction. It can be classified into four major types:

• Hypoxemic Hypoxia: Caused by decreased arterial oxygen concentration due to respiratory diseases or high altitude.
• Anemic Hypoxia: Results from reduced hemoglobin levels or impaired hemoglobin function.
• Circulatory Hypoxia: Occurs due to inadequate blood flow, often seen in conditions such as heart failure.
• Histotoxic Hypoxia: Caused by toxins that prevent oxygen utilization at the cellular level, such as cyanide poisoning.

Pathophysiology of Hypoxia and Hypercapnia

Both hypoxia and hypercapnia significantly impact physiological functions. Hypoxia leads to compensatory mechanisms such as increased cardiac output and erythropoiesis, while severe cases may cause tissue necrosis. Hypercapnia, characterized by excessive carbon dioxide levels in the blood, affects respiratory drive, causing symptoms such as dyspnea and confusion.