Rasvahapot valtimotaudin vaaran arvioinnissa

Blood pressure measurement - EHES

September 21, 2010

Antti Jula

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Developed Countries Deaths in 2000 Developed Countries Deaths in 2000 Attributable to Attributable to Selected Leading Risk FactorsSelected Leading Risk Factors

Number of deaths (000s)

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Hypertension as a cardiovascular risk factor

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Systolic and diastolic blood pressure and mean arterial pressure in different parts of circulation

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What is blood pressure?

• Systolic blood pressure, higher of the two values, represents the pressure while the heart contracts to pump blood to the body

– First appearance of a clear repetitive sounds (Phase I)

• Diastolic blood pressure, lower of the two values, represents the pressure when the heart relaxes between beats

– Disappearance of the repetitive sounds (Phase V)

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Factors affecting the accuracy of BP measurementFactors affecting the accuracy of BP measurement

• Measurement circumstances

• Patient dependent factors

• Observer dependent factors

• Measurement technique– Auscultatory technique– Oscillometric technique

• Devices– Accuracy of the measurement device– Cuff size

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Factors affecting BP variability• Respiration – beat to beat oscillation• Emotions – sympathetic stimulation – white coat effect• Exercise• Meals• Tobacco• Caffeine• Alcohol• Temperature• Bladder distension• Pain• Diurnal variation

– Sleep, posture, BP-lowering medication

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Average effects on blood pressure of commonly occuring activites relative to BP while relaxing

• Meetings +20.2/+15.0 mmHg

• Work +16.0/+13.0 mmHg

• Walking +12.0/+9.2 mmHg

• Dressing +11.5/+9.5 mmHg

• Telephone +9.5/+7.2 mmHg

• Eating +8.8/+9.6 mmHg

• Talking +6.7/+6.7 mmHg

• Reading +1.9/+2.2 mmHg

• Sleeping -10.0/-7.6 mmHg

Clark LA et al. J Chronic Dis 1987;40:671-9

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Inter-room difference

with sphygmomanometer

8.7/3.5 mmHg

Kumpusalo et al. J Human Hypertens 2002;16:725-728

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Inter-room differences measured by patients with Omron IC device

5.9/2.8 mmHg

2.9/1.1 mmHg3.0/1.7 mmHgKumpusalo et al. J Human Hypertens 2002;16:725-728

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Watson et al, J Hypertens 1987, 5:207–11

Paired BP readings without careful preceding procedures and measurement techniques

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Jula et al, Hypertension 1999, 34:261–6

Paired BP readings with careful preceding procedures and measurement techniques

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Univariate correlates with the left ventricle and albuminuriaJula, Puukka, Karanko, Hypertension 1999;34:261-266

Systolic BP LVM LVMI LUA

Clinic 0.38*** 0.40*** 0.34***

Home 0.45*** 0.47*** 0.32***

Ambulatory awake 0.41*** 0.45*** 0.32***

Ambulatory asleep 0.32*** 0.35*** 0.26***

Ambulatory 24-hour 0.40*** 0.44*** 0.32***

*** P <0.001. LVM = left ventricular mass, LUA=log uri-nary albumin

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Univariate correlates with the left ventricle and albuminuriaJula, Puukka, Karanko, Hypertension 1999;34:261-266

Diastolic BP LVM LVMI LUA

Clinic 0.43*** 0.37*** 0.25***

Home 0.44*** 0.44*** 0.28***

Ambulatory awake 0.32*** 0.35*** 0.21**

Ambulatory asleep 0.31*** 0.32*** 0.17*

Ambulatory 24-hour 0.35*** 0.37*** 0.23**

*** P <0.001, ** P <0.01, * P <0.05. LVM = left ventricular mass, LUA=log urinary albumin

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Interarm differences

• BP measured from the right arm is 2.3/0.5 mmHg higher than that measured from the left arm (unpublished findings from 493 subjects aged 25-74 years, The Finrisk 2007 study)

• If reproducible differences greater than 10 mmHg are observed, the measurements should be done from the arm with higher readings

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Three categories of observer errorRose G et al. Lancet 1965; 1: 673-4.

1. Systematic error that leads to both intraobserver and interobserver error

2. Terminal digit preference, which results in the observer rounding of the pressure reading to a digit of his or her choosing, most often to zero

3. Observer prejudice or bias, whereby the observer adjust the pressure to meet his or her preconceived notion of what the pressure should be

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Mismatching of bladder and arm

Maxwell ym. Lancet 1982;2:33-36

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Use appropriate cuff size

• A too small cuff overestimates and a too large cuff underestimates BP

• Optimal size of the cuff: width >40% and length >80% of the arm circumference

• Finnish guidelines:

– Cuff width 13 cm (arm circumference 26-32 cm)– Cuff width 15 cm (arm circumference 33-41 cm)– Cuff width 18 cm (arm circumference > 41 cm)

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Different BP measurement devices

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Oscillometric vs auscultatory measurement technique

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Regression Equation for Converting Auscultatory to Automated Oscillometric (Omron M6) Systolic Blood Pressure

Finriski 2007, unpublished findings, n=493

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Regression Equation for Converting Auscultatory to Automated Oscillometric (Omron M6) Diastolic Blood Pressure

Finriski 2007, unpublished findings, n=493

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Corresponding oscillometric BP of five auscultory measured BP level

Auscultatory BP

120/80

140/90

160/100

180/110

200/120

Oscillometric BP

122.4/79.4

141.6/89.3

160.7/99.1

179.9/108.9

200.2/118.7

Finrisk 2007, junpublished findings, n=493

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Summary of the measurement I

• Participant conditions– Posture: the participant should sit queitly for 5 min

with the cuff around the arm, arm baired and supported at the level of the heart and the back resting againts a chair

• Circumstances– The participant should avoid a heavy meal, smoking,

heavy exercise and drinking caffeine containing beverages at least within 30 minutes preceding the reading

– A quiet, warm setting

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Summary of the measurement II

• Equipment– Appropriate cuff size– Either a mercury, a validated and recently calibrated aneroid or

validated electronic device– The bell of the stetoscope should be used (avoid excess bell

pressure!)

• Technique– At least two measurements (3) 1-2 minute apart of each other– Avoid observer error by training observers in the proper

technique of auscultatory BP measurements (manuals, binaural stethoscope, audio-tape training methods, video-films etc.)