After administering sublingual nitroglycerin, which outcome would indicate its effectiveness?

The effectiveness of sublingual nitroglycerin is primarily indicated by a decrease in chest pain. Nitroglycerin acts as a vasodilator, which means it relaxes and widens blood vessels, allowing for better blood flow. This is particularly beneficial for individuals experiencing angina or chest pain due to reduced blood supply to the heart muscle. When the medication takes effect, patients typically report an alleviation or significant reduction in discomfort associated with angina, reflecting effective relief of myocardial ischemia.

Other options may not directly reflect the medication's primary purpose. For example, an increased heart rate may occur as a compensatory mechanism in response to various factors but does not specifically indicate the effectiveness of nitroglycerin. Similarly, while nitroglycerin can lower blood pressure due to its vasodilatory effects, this is not the primary measure of its effectiveness for treating acute chest pain. Lastly, improved breathing could be associated with various factors including anxiety relief rather than a direct consequence of nitroglycerin use. Therefore, decreased chest pain is the most relevant and direct outcome to assess the effectiveness of sublingual nitroglycerin.