Blood pressure measurement

Monitoring a client’s blood pressure forms part of the assessment of vital signs and assists nursing and medical staff in determining the client’s cardiovascular status, general health and well-being. The only pieces of equipment needed are an appropriate device and a stethoscope (if required).

It is recommended that you use an electronic device for infants and children as the pulse is generally difficult to hear. The most commonly used devices are:

• manual mercury sphygmomanometer, which measures blood pressure using mercury
• manual aneroid sphygmomanometer, which measures blood pressure using air
• electronic automated devices, which measure the sound of the blood as it passes through the artery, and then display the pressure on a monitor.

All the devices measure in millimetres of mercury, usually expressed as mmHg. Remember, machines can and do malfunction; if the reading seems too high or low given the client’s overall condition and demeanour recheck the measurement either by using another machine or by checking it manually. All devices should be inspected and calibrated annually.

The procedures are outlined below.

Procedure	Rationale
Explain procedure and ensure adequate understanding	To ensure informed consent and obtain client’s co-operation
Before proceeding check that the client is rested, and has not been consuming alcohol or nicotine, and advise them not to talk during the procedure	To ensure an accurate reading
Ensure client is positioned correctly	To ensure accuracy of reading. Blood pressure readings should be taken in the same position and on the same limb each time if possible. The dominant side is recommended if at all possible. It is therefore good practice to document position to ensure continuity of care, e.g. lying, standing, sitting, and whether you have used the left or right limb. In some instances it may be necessary to record both lying and standing blood pressure, in which case it is important to distinguish between the two as per local preferences
Ensure correct-size cuff	Correct cuff size must be used for accurate reading. Size and instructions are usually printed on the inside of cuff
Apply the cuff 2.5 cm above the antecubital fossa with the client’s palm upwards, ensuring that the cuff is level with the sphygmomanometer and the client’s heart	To ensure accuracy of reading. Inaccurate readings occur if equipment is not in correct alignment. NB Do not use a limb receiving intravenous therapy and make sure that clothing above the cuff is not restrictive otherwise the accuracy of the reading will be questionable
If using an automated device commence the reading	This reading provides a rough estimate of the systolic blood pressure and reduces the possible discomfort arising from hyper inflation of the cuff
If undertaking the measurement manually, locate the radial pulse on the cuffed arm then inflate the cuff until the pulse is no longer felt – note the point at which this happens on the sphygmomanometer scale
Deflate the cuff for 30 seconds ensuring that all air has been released	To allow circulation to return to the limb
Locate the brachial artery and place the stethoscope over the pulse	Locating the artery prior to inflating the cuff ensures that the strongest point of the pulse can be identified and heard during the reading
Inflate the cuff again to approximately 20–30mmHg above the estimated systolic reading	To apply pressure to the artery in order to then hear and record the blood pressure
Deflate the cuff, slowly, at approximately 2–3mmHg per second and listen	Whilst slow deflation may be uncomfortable for the client, deflating too quickly will not allow time to hear the blood pressure sounds and mean that the procedure has to be repeated
Listen for and note the first sound that you hear (systolic); this will be followed by the other sounds listed. Note the point at which the sound disappears (diastolic)	To the attuned, five different sounds can be heard, known as Korotkoff sounds: 1 The first clear tapping sound = systolic 2 A swishing sound 3 An intense clear tap 4 A muffled sound 5 Sounds disappear altogether = diastolic
Compare reading with client’s previous reading and normal range and note any abnormality or improvement. If necessary repeat the reading but allow the client to rest the limb between attempts	Normal range: Newborn                   80/40 mmHg 1–7 years                  100/65 mmHg 8–12 years                100/70 mmHg Adult                          120/80 mmHg Elderly                       systolic 100 + age                                   In the elderly the diastolic                                   may rise also
Record blood pressure measurement on appropriate documentation (see Figure 4.1) and report any abnormalities	Legal requirement to maintain documentation and safeguard client through effective communications
Remove and clean equipment	To reduce the risk of cross-infection. NB Automated machines should not be used on clients being nursed in isolation
Wash hands thoroughly