Emergency Medical Technician (EMT) Intermediate Practice Exam

Which factor would likely exacerbate pulmonary edema?

1. Decreased cardiac preload

2. Increased cardiac preload

3. Decreased fluid intake

4. Increased heart rate

The correct answer is: Increased cardiac preload

Pulmonary edema is a condition characterized by excess fluid in the lungs, often resulting from heart failure or conditions that affect the heart's ability to pump effectively. The primary mechanism at play is the balance between hydrostatic pressure in the pulmonary capillaries and the oncotic pressure in the surrounding tissues. An increase in cardiac preload refers to the volume of blood in the ventricles at the end of diastole. When preload increases, there is more blood being returned to the heart, which can lead to elevated pressures in the chambers of the heart, particularly in the left atrium and left ventricle. This elevated pressure can then be transmitted backward into the pulmonary circulation, increasing the hydrostatic pressure within the pulmonary capillaries. When this pressure exceeds the oncotic pressure–the pressure drawing fluid back into the capillaries–fluid begins to seep into the alveoli, leading to pulmonary edema. In contrast, decreased preload would alleviate the pressure in the pulmonary circulation, and conditions that result in decreased fluid intake would not contribute to fluid buildup in the lungs. Increased heart rate does not directly cause pulmonary edema but may be a compensatory mechanism in response to existing heart failure or overload. Therefore, increased cardiac preload significantly contributes to the worsening of pulmonary edema