In what situation can decreased compliance lead to hypoxemia?

• A. When tidal volumes decrease significantly
• B. When FiO2 is too low
• C. When PEEP is inadequate
• D. When there is left ventricular failure

Answer: (A)

Decreased compliance in the lungs refers to the reduced ability of the lung tissue to expand during inhalation. This situation can lead to hypoxemia, which is a deficiency of oxygen in the blood, particularly when tidal volumes decrease significantly.

When compliance is low, a larger effort is required to achieve adequate ventilation. If tidal volumes drop, less air reaches the alveoli, thereby reducing the amount of oxygen that can diffuse into the bloodstream. This inadequate ventilation subsequently leads to hypoxemia since there is insufficient oxygen exchange occurring at the alveolar-capillary interface.

In contrast, the other options highlight different mechanisms or causes that do not directly link decreased compliance with tidal volume and subsequent hypoxemia. For example, having a low fraction of inspired oxygen (FiO2) affects oxygen availability but does not stem from compliance issues. Similarly, inadequate positive end-expiratory pressure (PEEP) or left ventricular failure can influence oxygenation and hemodynamics, but these factors are distinct from the direct relationship between lung compliance and tidal volume during mechanical ventilation.