Blood pressure measurement is a basic but very significant skill for nurses and other healthcare professionals in gaining vital information about a patient’s health which is fundamental for the purposes of diagnosis, monitoring and treatment. Blood pressure is essentially the force exerted by the blood on the internal wall of the blood vessels. This is the force that keeps blood circulating in the body and moving from high to low pressure areas (Marieb, 2015). The heart, blood vessels and kidneys are required to work collectively with the brain to regulate normal blood pressure (Marieb, 2015). Blood pressure is therefore one of the vital signs just as important as respiratory rate, oxygen saturation, heart rate and temperature. Blood pressure is universally measured in mmHg (millimetres of mercury) with two different readings, namely the systolic and diastolic figures. The systolic figure articulates the pressure in the blood vessels in synchronicity of when the heart beats and the diastolic figure articulates the pressure in the blood vessels while the heart rests between the heartbeats.
The average resting blood pressure in a healthy adult is considered to be in the range of between 110-149 mmHg systolic and 70/80 mmHg diastolic (Marieb and Hoehn, 2010). High blood pressure (Hypertension) is when the systolic figure is higher than the average range, which is usually the warning indicator for cardiovascular disease, or the side-effects of some medications and also caused by trauma. On the other hand, low blood pressure (Hypotension) is when the systolic figure is lower than the average range, thus indicative of hypovolaemia, cardiogenic trauma or septic shock.
Blood pressure can be measured manually using Sphygmomanometers either electrically with an automated device or via auscultation with a stethoscope. The known manual blood pressure measuring devices are mercury Sphygmomanometers and aneroid Sphygmomanometers. In recent years clinical staff have been dependent on automated blood pressure measuring devices. The accuracy and reliability of these devices however have been debated, particularly in patients with arrhythmias (Cork, 2007). This is supported by NICE guidelines who suggest that blood pressure should be measured manually using direct auscultation over the brachial artery if automated devices cannot gauge patient blood pressure accurately due to pulse irregularity (arrhythmia) (NCGC, 2011). The Medicine and Healthcare Products Regulatory Agency (MHRA, 2013), still consider the manual BP measurement as the ‘gold standard’ in measurement accuracy. The argument now arises regarding fully depending on automatic devices and thus the loss of manual BP measurement skills amongst healthcare professionals. However, an alternate viewpoint exists which suggests that in order to gain an accurate BP reading, it is less of an importance whether manual or automatic measurements are taken and more important to use an appropriate cuff size (British Hypertension Society (BHS), 2009). This article will demonstrate the nurse’s skilled role in measuring blood pressure manually and the challenges faced while performing the measurement.
Correct Tools and techniques
The reliable manual equipment and ‘gold standard’ mercury Sphygmomanometers was withdrawn from standard practice due to health and safety concerns regarding the toxic element of mercury (UKEA, 2007). However, MHRA suggest that aneroid auscultatory devices are similar to mercury Sphygmomanometers but tend to rely on a bellows system linked to a needle to signify the pressure on a dial (MHRA 2003). These aneroid auscultatory devices require regular calibration, at least every six months to maintain clinical reliability (BHS, 2013). In clinical practice, when BP is measured manually, an aneroid sphygmomanometer is used together with a cuff connected to a bladder, tubing and bulb along with a stethoscope. As a nurse, it is important to explain the procedure to the patient and gain consent before taking a BP measurement (NMC, 2004). It is necessary to make sure appropriate equipment is available and in good working condition. These include; a validated and calibrated sphygmomanometer, a stethoscope, an appropriate size cuff (BHS, 2009), NEWs (National Early Warning) score chart to record the reading, hand decontamination items (soap or gel) and detergent wipes. Before the procedure, it is essential to decontaminate hands with soap or alcohol gel. To achieve an accurate reading it is essential to ensure that the patient is rested at least 5 to 10 minutes prior to taking the reading (Nikolic et al, 2013) and the environment is serene. Research studies have established that blood pressure generally settles when an individual is at rest (Hijorskov et al, 2004). It is important to visually check or enquire regarding the patients arm to determine if any complications exist and recommended that blood pressure should not be taken in a patient’s affected arm, e.g. If the patient has a venous cannula in situ (Hatchett, 2015). It is important to ensure that the patient is sitting comfortably, their back supported and feet rested flat on the floor without the legs crossing (Adiyaman et al (2007). The correct cuff size is essential to gain an accurate blood pressure reading (NCGC, 2011). The arm should be exposed with no obstruction to placing the cuff and stethoscope, since any resultant muscle contraction may raise blood pressure (Frese et al, 2011). Thus, it is necessary to make sure the arm is supported. The equipment (dial) should be positioned at eye level to enable clear sight of the column. The arrow on the cuff must line up with the brachial artery and the cuff should be level with the heart regardless of the patients position (Monica et al, 2013). Nurses must wrap the cuff around the patients exposed arm approximately 2-3cm above the brachial artery and ask patients not to move or even talk. The NCGC (2011) recommended that an estimate of the systolic pressure be taken before getting hold of the arterial bp with the stethoscope, as knowing the estimated value will assist in establishing the auscultatory gap and thereafter inflating the cuff and listening to the Korotkoff sounds. This helps to avoid an underestimation of the systolic pressure and any discomfort caused to the patient by preventing high inflation of the cuff. (NCGC, 2011). The diaphragm of the stethoscope ought to be placed over the brachial artery to listen the Korotkoff sounds – commonly described as a pounding, whooshing or thudding sounds (BHS, 2016). For controlling the spread of infections it is imperative to clean ear pieces and the head of the stethoscope before and after direct contact with the patient’s skin. NCGC recommended that, after 15-30 second to inflate the cuff to 20-30mmHg above the estimated systolic pressure and then deflate the cuff using the valve on the bulb at a steady rate of 2-3 mmHg per second while keeping the head of the stethoscope on the antecubital fossa (NCGC, 2011). The Korotkoff sounds will be audible while the cuff gradually deflates. The first loud thudding sound is known as systolic pressure K1 and when these become muffled prior to the final sound it is known as diastolic pressure K4.The last sound itself is called second diastolic K5 which is recommended to note as the patients diastolic pressure (Monica et al, 2013; NCGC, 2011). The patient can then be informed that the procedure is finished whilst removing the cuff from the patient’s arm. Finally, it is crucial for nurses to decontaminate the hands and clean the equipment with detergent wipes for infection control purposes. Ultimately, it is fundamental to document the measurement reading in NEWs chart neatly and accurately (NMC, 2015). As a nurse it is good practice to compare previous readings and inform medical staff if there are significant differences in the readings.
Challenges that affect blood pressure readings
When blood pressure measurements are taken, there are significant factors that can influence the reading. These usually include the equipment used, the observer, the patient and environmental factors. According to established literature, taking blood pressure measurements and achieving an accurate reading depends on efficient equipment and precise knowledge by any individual taking a measurement (Hatchett et al 2015). These include selecting a correct size cuff since inappropriate cuff dimensions are a serious error in clinical practice (O’Brien et al, 2003). A very well documented study found that despite the availability of a range of cuffs, they remain largely under used and only 7% of nurses in the study followed the correct procedure of selecting adequate cuff for each individual patient (Veiga et al, 2003).The incorrect selection of cuff size for those patients can result not only in misdiagonosis of hypertension and subsequent incorrect treatment but can also lead to the incorrect analyses of the physiological state of a patient not limited to exercise and smoking habits, emotional state and even antihypertensive drugs control, thus compomising patient care.
The nursing profession regulator Nursing and Midwifery Council (NMC, 2015) is fundamentally based around promoting patient wellbeing, preventing ill health, and meeting patients alternating health care needs. The NMC identified that all nurses need to be able to perform clinical skills safely (NMC, 2004) such as the ability to measure and record vital signs accurately, including blood pressure which was actually acknowledged as one of the essential skills. To obtain a precise reading, nurses should make sure to use appropriate equipment, maintain and standardize the environment before taking a patient blood pressure measurement (NICE 2011a). Tortora and Dirricson (2011) suggested that factors such as a person’s age, activities (eating, drinking), sleep, emotion (fear, worry), positioning (standing, sitting), physical condition and fitness can alter BP readings. According to NCGC, it is ideal that the patient should not eat or drink just before the BP measurement (NCGC, 2011).
Linking theory and practice
Research on nurses gaining knowledge of measuring blood pressure has almost completely focused on the use of manual equipment. However, in the clinical practice automated equipment are actually used more readily to measure blood pressure with osciliometry and therefore clinical staff are now losing the skills of taking manual BP measurements (MHRA 2006). As a result, student nurses also have less of an opportunity to practice taking manual blood pressure readings since the supervisors may have become de-skilled themselves as manual BP equipment are also not often available. A study has evidenced this dilemma that takes when there is a detachment between the process of education and actual practice of nursing (Watkin, 2000). This has been termed as theory-practice gap. Castledine (2006) coherently argued that there is a theory and practice gap as nurses are not practicing what they were taught. Moreover, to close that gap he recommended educational institutes should keep a strong link with practice placement for student nurses to form a close connection to nursing care.
The research argues that properly validated automated devices should replace manual equipment, as automated devices are more reliable and less prone to observer error (Markandu et al, 2000). In contrast, a 2008 study found that, automated BP measuring devices produced an unreliable diastolic BP reading and should not be used for patients with hypertension and hypotension (Heinemann et al 2008). However, the nursing and midwifery council (2010), identified, the measurement of BP as an essential skill, that all nurses must be able to undertake it both manually and using automatic devices.
Additional studies should be undertaken to establish why many nurses do not carry out manual blood pressure measurements in clinical practice. A basic manual BP measurement step by step guide should be developed and made available for all healthcare professional. Education is important to improve knowledge and skills and thus there needs to be an appropriate guidelines set by those involved in clinical practice and universities to ensure that the measurement of blood pressure taken manually is taught in the correct manner with a sound rationale for the skill. This study highlighted the need for practical education in manual BP measurement towards reaching the end result of achieving accurate readings and suggests that both types of equipment be readily available for nurses to choose from. An informed decision about which to use will ultimately benefit the patient.