Final answer:
The causes of hypoxemia include ventilation/perfusion mismatch, alveolar hypoventilation, and diffusion impairment. These lead to inadequate oxygenation of the blood due to issues with lung function or tissue characteristics. Increased inspired O2 is not a cause but a treatment for hypoxemia.
Step-by-step explanation:
The causes of hypoxemia, which is a low level of oxygen in the blood, include ventilation/perfusion (V/Q) mismatch, alveolar hypoventilation, and diffusion impairment. These conditions lead to insufficient oxygenation of the blood, with the following mechanisms:
- V/Q mismatch occurs when there is an imbalance between the air that reaches the lungs (ventilation) and the blood that reaches the lung capillaries (perfusion). This mismatch can be due to anatomical or physiological issues causing dead spaces where there is no effective gas exchange.
- Alveolar hypoventilation means that the lungs are not getting enough air, leading to low partial pressure of oxygen in the alveoli and subsequently in the blood.
- Diffusion impairment happens when transfer of oxygen from the alveoli to the blood is hindered, which can occur in diseases like fibrosis where the lung tissue becomes stiff and thickened.
In contrast, increased inspired O2 is not a cause of hypoxemia but rather a treatment or intervention to increase the amount of oxygen in the blood. Hence, the correct answer to the question "Which of the following are causes of hypoxemia?" is c. 1, 2, and 3.