The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [471]
With an aneroid scale, the eye level should be equal with the centre of the gauge (O’Brien et al. 2003, E).
6 Ensure the cuff is the correct size for the arm. The cuff bladder length should be 80% of the arm circumference and its width 40% (BHS 2006). Small cuffs give falsely high readings and large cuffs give falsely low readings (Williams et al. 2004, E).
7 Check the patient’s arm is free from clothing, supported and placed at heart level (midsternal level) (Bickley and Szilagyi 2009, NICE 2006, O’Brien et al. 2003). Their legs should be uncrossed with feet flat on the floor (Turner et al. 2008). See Figure 12.12. If the arm is lower than heart level it can lead to falsely high readings, and vice versa (O’Brien et al. 2003, E). Diastolic pressure can increase by up to 10% if the arm is unsupported (O’Brien et al. 2003, E). Blood pressure results can be falsely high if the patient has their legs crossed (van Groningen et al. 2008, R).
Procedure
8 Wrap the cuff of the sphygmomanometer around the arm, with the bladder centred over the artery and superior to the elbow (Marieb and Hoehn 2010, Patton and Thiobodeau 2009). The lower edge of the cuff should be 2–3 cm above the brachial artery pulsation (O’Brien et al. 2003). To obtain an accurate reading (BHS 2006, C), and so that the artery can easily be palpated (NICE 2006, C).
9 Ask the patient to stop talking, eating and so on, during the procedure. Activity can cause a falsely high blood pressure (BHS 2006, C).
10 Palpate the brachial artery while pumping air into the cuff using the bulb. Once the pulse can no longer be felt rapidly inflate the cuff for further 20–30 mmHg (Bickley and Szilagyi 2009, NICE 2006). Inflating the cuff to only 20/30 mmHg above the predicted systolic level prevents undue discomfort (Bickley and Szilagyi 2009, E). The brachial pulse is advocated rather than the radial pulse (NICE 2006, C) and doing this locates the correct position for stethoscope placement (VallerJones and Wedgbury 2005, E).
11 Deflate the cuff and the point at which the pulse reappears approximates the systolic blood pressure (BHS 2006, NICE 2006, O’Brien et al. 2003). This provides an indication of systolic pressure and can ensure accurate results in those who have an auscultatory gap (Curran 2009, E; BHS 2006, C).
12 Deflate the cuff completely and wait 15–30 seconds (Bickley and Szilagyi 2009). To allow venous congestion to resolve (O’Brien et al. 2003, E).
13 The stethoscope should be firmly, but without too much pressure, placed on bare skin over the brachial artery where the pulse is palpable (O’Brien et al. 2003). The bell of the stethoscope may hear the tone of the Korotkoff sounds better (Bickley and Szilagyi 2009). However, the diaphragm has a larger surface area and is easier to hold in place (O’Brien et al. 2003). If the stethoscope is in contact with material it may distort the Korotkoff sounds (O’Brien et al. 2003, E).
Applying pressure with the stethoscope may partially occlude the artery (O’Brien et al. 2003, E).
14 Inflate the cuff again to 20–30 mmHg above the predicted systolic blood pressure (Bickley and Szilagyi 2009, NICE 2006). To ensure an accurate measurement (NICE 2006, C).
15 Release the air in the cuff slowly (at an approximate rate of 2–3 mmHg per pulsation) until the first tapping sounds are heard (first Korotkoff sound). This is the systolic blood pressure (Patton and Thiobodeau 2009). The cuff should not be deflated too quickly as this may result in inaccurate readings being taken (O’Brien et al. 2003, E).
16 Continue to slowly release the air, listening to the Korotkoff sounds; the point at which the sounds disappear is the best representation of the diastolic blood pressure (fifth Korofkoff sound). Continue to deflate the cuff slowly until you are sure the sounds have disappeared (after another 10–20 mmHg) (Bickley and Szilagyi 2009). To ensure an accurate diastolic blood pressure and that you note any irregularities