Monitoring blood pressure

Blood pressure is the pressure exerted on resisting artery walls as blood is forced through from the heart.

Monitoring a client’s blood pressure measurements helps nursing and medical staff to establish the ability of the client’s arteries to fill with blood, the efficiency of the heart as a pump, and the volume of circulating blood.

It is normally taken using the arm but the thigh can also be used if required.

There are two types of blood pressure:

  • systolic – the highest pressure reached during contraction of the heart
  • diastolic – the pressure remaining in the ventricles when the heart is resting between contractions

Factors that may influence blood pressure include:

  • high body temperature
  • exposure to heat/cold
  • stress
  • obesity
  • smoking
  • alcohol
  • heart disease
  • haemorrhage.

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



  • Explain procedure and ensure adequate understanding
  • 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
  • Ensure client is positioned correctly
  • Ensure correct-size cuff
  • Apply the cuff 2.5 cm above the antecubitalfossa with the client’s palm upwards,ensuring that the cuff is level with the sphygmomanometer and the client’s heart
  • If using an automated device commence the reading
  • 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
  • Locate the brachial artery and place the stethoscope over the pulse
  • Inflate the cuff again to approximately 20–30mmHg above the estimated systolic reading
  • Deflate the cuff, slowly, at approximately 2–3mmHg per second and listen
  • 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)
  • 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
  • Record blood pressure measurement on appropriate documentation and report any abnormalities
  • Remove and clean equipment
  • Wash hands thoroughly