Using a cuff that is proportional to the size of the arm is important. If the cuff is too small, the blood pressure reading is too high. If the cuff is too large, the reading is too low. Listening with a stethoscope placed over the artery below the cuff, a health care practitioner inflates the cuff by squeezing the bulb until the cuff compresses the artery tightly enough to temporarily stop blood flow, usually to a pressure that is about 30 mm Hg higher than the person's usual systolic pressure the pressure exerted when the heart beats.
Then the cuff is gradually deflated. The pressure at which the practitioner first hears a pulse in the artery is the systolic pressure.
The cuff continues to be deflated, and at some point, the sound of blood flowing stops. The pressure at this point is the diastolic pressure the pressure exerted when the heart relaxes, between beats. Manual BP measurement devices require the user to inflate the upper-arm cuff to occlude the brachial artery, then listen to the Korotkoff sounds through a stethoscope while the cuff is slowly deflated. When the cuff is slowly deflated, five different sound phases can be heard:.
Practically, the systolic reading is when the Korotkoff sounds are first heard and the diastolic reading is when they disappear. Although portable and generally reliable, manual BP devices require clinical skill and are prone to observer bias Medicines and Healthcare products Regulatory Agency, As a result, these devices are being phased out: their use has already been banned in some European countries, while in the UK a ban on their sale will be introduced from 31 December MHRA, It would, therefore, be prudent for healthcare providers still using mercury sphygmomanometers to start planning to phase these out and to ensure health professionals are competent at using alternative devices.
Health professionals should be trained in:. Although aneroid sphygmomanometers are mercury free and easy to use, wear and tear or mechanical shock to the mechanism can lead to incorrect readings; this means regular calibration checks are required. Electronic sphygmomanometers are prone to observer bias and require clinical skill to use accurately MHRA, Most automated BP measurement devices in current clinical practice use the oscillometric method.
Each arterial pulse wave results in a small rise and fall in the volume of the limb which, in turn, causes an increase then a decrease in the pressure within the encircling cuff Lewis, The oscillometric method relies on detection of variations in pressure oscillations due to arterial wall movement beneath an occluding cuff to calculate the systolic and diastolic BP readings Lewis, It is important to note that some automated oscillometric BP measurement devices are unreliable in patients with cardiac arrhythmia, such as atrial fibrillation AF National Institute for Health and Care Excellence, ; this is because the pulse pressures can vary significantly with each pulse.
In healthy patients, there is usually little difference between lying and standing BP readings. The routine measurement of both lying and standing BP in these groups of patients is, therefore, advisable National Institute for Health and Care Excellence, Postural hypotension, sometimes termed orthostatic hypotension, is when an abnormally low BP occurs when a person suddenly assumes a standing position, typically inducing dizziness and syncope.
The condition is more common in older people and its prevalence increases with age. It can also be caused by a number of medications including diuretics and anti-hypertensive therapy Windsor et al, Postural hypotension can present with a clinical picture of dizziness, syncope and falls on changing position. Measurement of lying and standing BP is part of a multifactorial patient risk assessment Royal College of Physicians, A diagnosis of postural hypotension is indicated when there is a:.
NICE stated that the following groups of inpatients should be considered as at risk of falling in hospital and receive an individualised, multifactorial assessment, including lying and standing BP:. Cuffs and their hoses should be regularly inspected and replaced as necessary; excessive air leakage from damaged cuffs, hoses and tubing connectors may reduce the accuracy of the readings. Faulty devices can lead to inaccurate BP measurements, with significant effects on patient care.
Healthcare providers have a responsibility to ensure adequate maintenance arrangements are in place MHRA, Aneroid devices are particularly prone to inaccuracies Coleman et al, ; the MHRA recommends these are checked and calibrated at least twice a year. For manual sphygmomanometers, the sphygmomanometer blood pressure cuff or machine consists of an inflatable cuff and two tubes; one tube is connected to the pressure hand control bulb and the other tube to the pressure gauge Figure 2.
The size of the patient determines the size of the cuff selected. There are several cuff sizes. When a cuff is too narrow, the blood pressure reading is too high; when the cuff is too large, the reading is too low. The stethoscope , a listening aid that magnifies sound is used with manual devices and consists of two earpieces that are connected by tubes that carry the sound to the earpieces from the end piece, which is placed over the artery Figure 3.
Dental professionals should invest in quality stethoscopes that detect sound easily. Providers should not have to strain to hear sounds. Replace parts to existing stethoscopes or replace entire stethoscope if necessary.
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