Certified Emergency Nurse (CEN) Test 2025 – 400 Free Practice Questions to Pass the Exam

Preload refers to the degree of stretch of the heart muscle fibers at the end of diastole, which is directly influenced by the volume of blood returning to the heart. When fluid volume increases, it leads to an increase in blood returning to the right atrium, thereby increasing the preload. This enhanced filling of the heart results in a greater volume of blood being pumped out during systole, as dictated by the Frank-Starling law of the heart.

In contrast, vasodilation decreases preload by allowing blood to pool in the peripheral vasculature, reducing the volume of blood returning to the heart. An increased respiratory rate does not directly affect preload; however, it may be associated with various physiological changes but does not contribute to the volume of blood returning to the heart. A decreased heart rate might allow more time for ventricular filling, but if fluid volume does not increase, preload will not be significantly affected. Therefore, increasing fluid volume is the primary factor that enhances preload in a patient.