Blood Pressure (BP)

Last updated 13.02.13

 

Index

 

Definition

-  Measurement of the pressure within the arterial system during systole & diastole of the cardiac cycle

 

Features

-  Elevated: Hypertension

-  Decreased: Hypotension

-  Mercury sphygmomanometers are most accurate

-  BP instruments need to be regularly validated – no n-murcury every 6 months

-  If first reading then measure both arms & use arm with higher reading from then on

-  24 hour ambulatory measurement or self measurement

-  Common Errors in BP Measurement

-  Cuff placed over clothing

-  Incorrect cuff size

-  Arm elevated above heart

-  Patient not rested before measurement

-  Patient talking during measurement

-  Radial pulse not palpated prior to measurement & therefore missing auscultatory gap

-  Single measurement

 

Equipment

-  Syphgmomanometer: automatic or manual (mercury)

-  Use validated & calibrated device

-  Cuff bladder width should be >40% of circumference of arm

-  Cuff bladder length should be >80% of circumference of arm

-  Stethescope

 

Procedure

-  Patient seated at rest

-  Estimate cuff (Bladder) size

-  Length 80% circumference of mid upper arm

-  Width 40% circumference of mid upper arm

-  If cuff is too small may cause falsely high readings

-  If no larger cuff available consider using on forearm & auscultate radial artery

-  Allow pt to sit quietly for several minutes

-  Preferably not eaten in last 30minutes

-  Not smoked in last 2hrs

-  No caffeine in last 4-6hrs

-  Bare arm supported

-  Sleeve should be loose & above cuff

-  Free of constricting clothing

-  Place cuff on arm

-  Ideally with tubes proximally to free cubital fossa for auscultation

-  Position cuff as close to heart level as possible

-  Center of bladder over brachial artery

-  Lower border of cuff 2cm above cubital fossa

-  Palpate radial pulse & inflate cuff

-  Inflate cuff until pulse is no longer palpable & another 30mmHg

-  Release cuff & note mmHg when radial pulse appears

-  Fully deflate the cuff & wait 30 seconds

-  Inflate cuff to 30mmHg greater than systolic level at loss of pulse

-  Auscultate cubital fossa for brachial artery (medial to bicep tendon)

-  Deflate the cuff slowly: around 2mmHg/second

-  Record pressure at first sounds of turbulent blood flow in artery = SBP

-  Record pressure at the absence of sounds in artery = DBP

-  Take at least 2 measurements spaced by 30sec+

-  Record to the nearest 2mmHg

-  Average readings for recording

-  If different by >10mmHg systolic or >6mmHg diastolic rest for another 5 minutes then repeat

 

Postural Drop/Hypotension

-  Rationale

-  To determine presence of postural hypotension (orthostatic hypotension)

-  Procedure

-  Patient to lie supine for 5 minutes & relax

-  Take BP on arm at heart height

-  Patient to stand – with support as necessary (fall risk)

-  Wait for 2 minutes then repeat BP measurement

-  Interpretation

-  Systolic drop of < 20 mmHg is normal

-  >20 mmHg drop in systolic BP = postural hypotension

-  >10mm Hg drop in diastolic BP = postural hypotension

 

 

 

References

 

Guide to Management of Hypertension 2008, Heart Foundation, 2010