When measuring blood pressure, when should the medical assistant read the diastolic pressure?

The correct answer is when the second sound disappears. In the process of measuring blood pressure, the diastolic pressure is identified by the point at which the last Korotkoff sound is heard during deflation of the blood pressure cuff. This sound indicates the transition from diastolic pressure to no sound, which reflects complete vasodilation and the cessation of blood flow turbulence in the arteries.

When the healthcare professional observes that the sounds have stopped, it marks the diastolic pressure; this is critical for accurate blood pressure readings. Understanding the sounds produced by blood flow can help differentiate between systolic and diastolic pressures, making this identification crucial for proper diagnosis and management of blood pressure.

The other options do not correctly identify the point at which diastolic pressure is measured. The first sound marks systolic pressure, while reading at zero or when the cuff is fully deflated would not accurately reflect diastolic pressure, as these are not related to the hemodynamics actively being assessed. By focusing on the disappearance of the second sound, the medical assistant ensures an accurate reading of the diastolic pressure.