Which maneuver is NOT effective in decreasing preload?

The correct answer is that squatting from a standing position is not effective in decreasing preload.

To understand this, it is important to recognize the role of preload in the cardiac cycle. Preload refers to the volume of blood in the ventricles at the end of diastole, just before contraction. A decrease in preload reduces the workload on the heart and can be beneficial in certain clinical situations, such as managing heart failure or conditions characterized by volume overload.

The Valsalva maneuver, which involves forced exhalation against a closed airway, effectively decreases venous return to the heart, thus reducing preload. During this maneuver, intrathoracic pressure increases, impairing venous return and leading to a temporary reduction in preload.

Sudden standing from a sitting position can also decrease preload. This change in position causes blood to pool in the lower extremities due to gravity, which can momentarily lead to decreased venous return to the heart and reduced preload.

Nitroglycerin is a vasodilator that decreases venous return by dilating veins, which leads to a reduction in preload. By decreasing the volume of blood returning to the heart, nitroglycerin alleviates stress on the cardiac muscle, making it particularly useful in