How would the Vd/Vt ratio change in a patient experiencing a Pulmonary Embolism?

In the context of pulmonary embolism, the Vd/Vt ratio, which represents the dead space ventilation over the total ventilation, would likely increase.

When a pulmonary embolism occurs, there is obstruction in the pulmonary vasculature, leading to reduced perfusion of the alveoli. This causes some areas of the lung to be ventilated but not perfused, resulting in an increase in the physiological dead space. The rationale is that while the volume of air that reaches the alveoli (Vt) remains the same or may decrease, the amount of air that is effectively contributing to gas exchange is reduced because blood cannot flow to the alveoli that are being ventilated. Thus, the ratio of dead space to tidal volume increases, as more of the inhaled air is not participating in gas exchange.

This phenomenon is crucial in understanding the impact of pulmonary embolism on respiratory physiology and the efficiency of ventilation, making the increase in the Vd/Vt ratio a key indicator of the impairment caused by the embolism.