The application of positive pressure for a patient with left ventricular failure is beneficial because of which effect?

• A. Decreases preload to the heart
• B. Increases afterload
• C. Increases cardiac output
• D. Raises systemic vascular resistance

Answer: (A)

When you apply positive pressure, intrathoracic pressure rises and venous return to the heart is reduced. That lowers the left ventricular preload (the amount the ventricle fills before it pumps). In left ventricular failure, high preload worsens congestive symptoms by increasing filling pressures and pulmonary edema. By decreasing preload, the left-sided pressures drop, pulmonary congestion improves, and forward flow can become more effective. This is why the beneficial effect is the reduction of preload to the heart.