The sounds heard during the first phase of blood-pressure measurement are called
One group member puts on a stethoscope, with the earpieces on the headpiece angled forward. The recording end of the stethoscope is twisted, so that the diaphragm and not the bell is activated. This can be tested by tapping lightly on the diaphragm. The diaphragm is placed over the brachial artery in the space between the bottom of the cuff and the crease of the elbow. At this point no sounds should be heard. The cuff pressure is inflated quickly to a pressure about 30 mm Hg higher than the systolic pressure determined by the method of palpation. Then the air is let out of the cuff at a rate such that cuff pressure falls at a rate of about 5 mm Hg/sec.
The sounds are called Korotkoff sounds. The pressure reading at this point gives the diastolic pressure. The subject should now lie on his or her back for five minutes. The systolic pressure and diastolic pressure are recorded. Then the subject stands up, and the pressures are immediately recorded once more. Explanatory NotesThe laminar flow that normally occurs in arteries produces little vibration of the arterial wall and therefore no sounds. However, when an artery is partially constricted, blood flow becomes turbulent, causing the artery to vibrate and produce sounds. >>For a QuickTime video with sound, click here >>For an avi video with sound, click here JNC Classification of blood pressure in adults Classification BP (mm Hg) Normalsystolic: less than 120diastolic: less than 80Pre-hypertension120-139/80-89Stage 1 hypertension140-159 (systolic) or 90-99 (diastolic)Stage 2 hypertensionequal or more than 160 (systolic) equal or more than 100 (diastolic) JNC: Joint National Committee on Prevention, Detection, Evaluation, The cuff is not of the proper size: if the cuff is too small the blood pressure readings may be artefactually high. If the cuff is too big, the readings may be artefactually low. |