Final answer:
A blood pressure cuff determines systolic pressure by inflating to stop blood flow, then deflating until blood pulsates through the artery, marked by audible Korotkoff sounds.
Step-by-step explanation:
The mechanism by which a blood pressure cuff determines systolic pressure involves several steps. Initially, the clinician wraps an inflatable cuff around the patient's upper arm and inflates it to a pressure that halts blood flow. As the cuff's pressure is slowly released, the first moment blood pulsates through the artery as the heart beats is when systolic pressure is reached. This event is indicated by the Korotkoff sounds, which are audible via a stethoscope when the cuff's pressure is equivalent to the arterial systolic pressure, allowing blood to flow past the cuff. These sounds signal the resumption of blood flow, marking the systolic pressure reading.