National Physical Therapy Examination (NPTE) Practice Exam

What physiological measurement may temporarily decrease when a patient is taking nitroglycerin?

1. Heart rate

2. Respiratory rate

3. Oxygen saturation

4. Blood pressure

The correct answer is: Blood pressure

Nitroglycerin is a medication commonly used to treat angina pectoris and heart failure. It acts as a vasodilator, relaxing blood vessels and thereby increasing blood flow to the heart. When this medication is administered, a notable physiological effect is the decrease in blood pressure. This occurs as the dilation of blood vessels lowers the resistance against which the heart pumps, resulting in a reduction in systemic vascular resistance and consequently lower blood pressure. The temporary decrease in blood pressure can also lead to a compensatory mechanism in the body, which may increase heart rate as the heart attempts to maintain adequate blood flow despite the reduced pressure. However, the primary and most immediate effect of nitroglycerin is on blood pressure due to its significant impact on vascular tone. Other physiological parameters such as respiratory rate and oxygen saturation may not show notable changes in response to nitroglycerin administration directly; instead, variations in respiratory rate might occur due to other factors or conditions unrelated to the medication. Oxygen saturation is often maintained unless there are underlying respiratory or cardiac issues. Therefore, blood pressure is the most relevant measurement that is likely to show a temporary decrease when a patient takes nitroglycerin.