Blood pressure monitoring

Blood pressure measurement plays a vital role in the assessment, diagnosis, monitoring and management of an illness. Variations in blood pressure can be a signal for changes in an individual's health status, aiding healthcare practitioners in tracking the advancement or regression of medical conditions. This includes both extended monitoring for chronic diseases and short-term surveillance during acute episodes, such as trauma or the management of hypertension.

Blood pressure measurement is usually a non-invasive technique, although in the intensive care unit, for example, constant blood pressure monitoring is often important, and may involve monitoring via invasive means to provide real-time readings.

The purpose of blood pressure measurement depends on the situation and the patient's needs, and can involve:

• setting a baseline (eg prior to surgery)
• monitoring high blood pressure (hypertension)
• monitoring low blood pressure (hypotension)
• assessing fluid status (eg postural hypotension)
• monitoring recovery from illness
• monitoring deterioration (eg as part of

Nurses should be familiar with various methods of measuring blood pressure, since different disease states may preclude them from using certain methods (eg electronic monitoring). Nurses must also consider the body shape and size of the person, as this may determine the choice of cuff size.

Nurses must also understand the impact of some activities and settings on blood pressure, and take these into account when measuring the blood pressure. For example, most people have a higher blood pressure in the doctor’s surgery or hospital than they do at home – this is called the 'white coat effect'. Such considerations, alongside the patients presenting complaint and physical abilities, are used to dictate how and where blood pressure is monitored. For example, home-based monitoring of hypertension is becoming increasingly common (Staessen et al, 2017), is known to contribute to better hypertension control and is often preferred over in-office monitoring (Stergiou et

The equipment will depend on the situation in which the nurse is working and the equipment that is available to them. In the majority of cases, blood pressure is monitored using a sphygmomanometer (or a blood pressure monitor), which refers to the Greek 'sphygmos', which means 'beating of the heart', and 'manometer', which is a device for measuring pressure. 

In other circumstances, for example for a patient with atrial fibrillation, a manual sphygmomanometer (which may be aneroid or mercury, although the latter are increasingly rare) may be more appropriate to use (National Institute for Health and Care Excellence, 2022). Blood pressure is measured and recorded in millimetres of mercury (mmHg). 

The Medicines and Healthcare products Regulatory Agency (MHRA, 2021) emphasised that, whatever form of blood pressure measurement is used, the machines require periodic calibration. Poor or absent calibration will invariably lead to inaccurate reading, which may impact patient care.  

The nurse should ensure they gain consent before taking a blood pressure by explaining the nature of the procedure and why it is being undertaken to the patient. Nurses should undertake hand hygiene prior to taking a blood pressure to minimise the risk of transmitting infection.

The patient should be rested and comfortable, and the nurse should address any privacy and dignity issues associated with the procedure. The European Society of Hypertension guidelines recommended that a patient should not drink caffeine at least 30 minutes before or smoke at least 15 minutes before a blood pressure measurement is taken, as these activities temporarily increase blood pressure (Williams et al, 2018).

The cuff should be placed on the upper arm, never over clothing, 2–3 centimetres above the brachial pulse (Park et al, 2019) with the range finder at the centre of the cuff bladder placed directly over the brachial artery –

There are no significant risks associated with a correctly undertaken blood pressure measurement, aside from potentially causing anxiety to the patient. Nurses with limited experience may struggle to attain accurate readings by, for example, failing to address issues such as cuff size and ensuring the patient is sufficiently rested. Manual readings can be complicated for those who are inexperienced in using a stethoscope (Park et al, 2019).

Where there is risk of infection, it is good practice to maintain a blood pressure cuff for single use and clean the equipment between patients where this is possible. The nurse should adhere to their local protocols when minimising risk of infection.

Nurses should be familiar with 'normal' blood pressure readings for different individuals, diseases, ages and during and after different procedures, and be able to respond to abnormal readings appropriately. The nurse must also ensure they are familiar with manufactures instructions and the need for servicing of equipment.

Where blood pressure measurement is part of ongoing disease monitoring, nurses need to be aware of the guidelines regarding blood pressure management in different disease states and ensure they report any findings to an appropriate clinical professional.

Nursing and Midwifery Council: standards of proficiency for registered nurses

Part 1: Procedures for assessing people’s needs for person-centred care

2. Use evidence-based, best practice approaches to undertake
the following procedures:

2.1 take, record and interpret vital signs manually and via
technological devices

2.5 manage and interpret cardiac monitors, infusion pumps,
blood glucose monitors and other monitoring devices

Bilo G, Sala O, Perego C et al. Impact of cuff positioning on blood pressure measurement accuracy: may a specially designed cuff make a difference? Hypertens Res. 2017;40(6):573-580. https://doi.org/10.1038/hr.2016.184

Carvalho F, Breen E-C, Bullock Z et al. Observations. In: Lister S, Hofland J, Grafton H and Wilson C (eds). The Royal Marsden manual of clinical nursing procedures. 10th edn. Chichester: Wiley Blackwell; 2021: 719-800

Cook N, Shepherd A, Boore, J. Essentials of anatomy and physiology for nursing practice. London: Sage; 2020

Dobson C, Simpson T. Clinical measurement. In: Delves-Yates C (ed). Essentials of nursing practice. 3rd edn. London: Sage; 2022

Ellis P, Standing M. Patient assessment and care planning in nursing. 4th edn. London: Sage; 2023

Gilani A, Juraschek SP, Belanger MJ, Vowles JE, Wannamethee SG. Postural hypotension. BMJ. 2021;373:n922. https://doi.org/10.1136/bmj.n922

Irving G, Holden J, Stevens R et al. Which cuff should I use? Indirect blood pressure measurement for the diagnosis of hypertension in patients with obesity: a diagnostic accuracy review. BMJ Open. 2016;6:e012429.