Question

Why might a low V/Q ratio cause pulmonary hypertension?

Answer 1

A low V/Q ratio can lead to pulmonary hypertension due to the body's response to insufficient ventilation in the alveoli. Prolonged vasoconstriction in the pulmonary arterioles, in an attempt to redirect blood to well-ventilated areas, increases resistance in pulmonary circulation, which can cause hypertension.

Step-by-step explanation:

A low V/Q ratio indicates that ventilation (V) to the alveoli is reduced relative to perfusion (Q) by blood in the pulmonary capillaries. This mismatch can be caused by conditions such as infection or edema, which obstruct airflow and create physiological dead spaces or shunts. When alveolar ventilation is insufficient, the partial pressure of oxygen in the alveoli decreases, leading to poor oxygen diffusion across the respiratory membrane. The body responds to a dysfunctional alveolus by constricting the pulmonary arterioles that serve it, attempting to redirect blood flow to better-ventilated alveoli. However, prolonged hypoxia and the resultant vasoconstriction in multiple areas of the lung due to low V/Q can lead to pulmonary hypertension, as the resistance in the pulmonary circulation increases in an effort to maintain adequate oxygenation.

Answer 2

A low V/Q ratio can cause pulmonary hypertension by creating a mismatch between ventilation and perfusion in the lungs, leading to decreased oxygen levels in the blood and vasoconstriction of the pulmonary arterioles.

Step-by-step explanation:

A low ventilation/perfusion (V/Q) ratio can cause pulmonary hypertension because it leads to a mismatch between the amount of air (ventilation) and the amount of blood (perfusion) in the lungs. Pulmonary hypertension occurs when the blood vessels in the lungs constrict and narrow, impeding blood flow. In a low V/Q ratio, the decreased ventilation reduces the amount of oxygen available for diffusion and can result in a decrease in oxygen levels in the blood. This triggers vasoconstriction of the pulmonary arterioles, leading to increased resistance in the pulmonary circulation and ultimately causing pulmonary hypertension.