What is the primary characteristic of hypoxemic respiratory failure?

The primary characteristic of hypoxemic respiratory failure is low oxygen levels in the blood. Hypoxemia, which is a deficiency in the amount of oxygen reaching the tissues, occurs when the lungs are unable to adequately oxygenate the blood. This can result from various conditions such as pneumonia, acute respiratory distress syndrome (ARDS), or pulmonary edema, where the ability of the alveoli to facilitate gas exchange is impaired.

In this context, while elevated carbon dioxide levels might indicate hypercapnia, which is often associated with another type of respiratory failure (ventilatory failure), it is not a characteristic of hypoxemic respiratory failure. Similarly, increased heart rate and reduced blood pressure can occur as compensatory mechanisms or responses to stress but do not define hypoxemic respiratory failure itself. The hallmark of this condition remains the inadequate oxygenation leading to low oxygen levels, which is critical for cellular metabolism and function.