Increasing PEEP in mechanical ventilation primarily lowers arterial blood pressure by which mechanism?

Increasing PEEP in mechanical ventilation primarily lowers arterial blood pressure by which mechanism?

• A. Decreasing venous return
• B. Decreasing systemic vascular resistance
• C. Increasing preload
• D. Increasing heart rate

Answer: (A)

Increasing PEEP raises intrathoracic pressure, which directly reduces venous return to the heart by compressing the vena cava and increasing right atrial pressure. With less filling (lower preload), stroke volume falls via the Frank-Starling mechanism, so cardiac output declines and arterial blood pressure drops. This preload-reduction effect is the primary reason for the BP decrease with higher PEEP. The other options don’t fit as the main mechanism. Systemic vascular resistance isn’t the primary driver of the BP change with PEEP, preload isn’t increased (it’s reduced), and a rise in heart rate would be a compensatory response rather than the cause of the blood pressure drop.

Increasing PEEP raises intrathoracic pressure, which directly reduces venous return to the heart by compressing the vena cava and increasing right atrial pressure. With less filling (lower preload), stroke volume falls via the Frank-Starling mechanism, so cardiac output declines and arterial blood pressure drops. This preload-reduction effect is the primary reason for the BP decrease with higher PEEP.

The other options don’t fit as the main mechanism. Systemic vascular resistance isn’t the primary driver of the BP change with PEEP, preload isn’t increased (it’s reduced), and a rise in heart rate would be a compensatory response rather than the cause of the blood pressure drop.