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Blood pressure measurement
Make it clearer
Measuring blood pressure means measuring how hard the blood pushes against the wall of the arteries, which is why the result comes as two numbers instead of one.
The top one is the systolic pressure: the peak, the moment the ventricle of the heart contracts and sends the blood out. The bottom one is the diastolic: the lowest, the pressure left between beats, when the heart is in diastole, meaning it is relaxing. With the auscultatory method, the one that uses a stethoscope, the cuff squeezes the arm until the flow stops and is then slowly released; the moment the Korotkoff sounds are first heard marks the systolic, and the moment they can no longer be heard marks the diastolic.
And the fit of the cuff is no small detail: too large and the reading comes out falsely low, too small and it comes out falsely high.
In brief
The two numbers mean different things: systolic pressure reflects the peak pressure in the arteries during ventricular systole, and diastolic pressure the lowest pressure during diastole.
With the auscultatory method, the onset of the Korotkoff sounds marks the systolic pressure and their disappearance marks the diastolic.
Technique matters here: a cuff that is too large may produce falsely low readings, while one that is too small may yield falsely elevated values.
Sources (1)
- National Center for Biotechnology InformationBlood Pressure Measurement. StatPearls
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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