Blood pressure measurement by mercury sphygmomanometer - background information

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Blood pressure measurement by mercury
sphygmomanometer- background information

• EHES Training Material

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Hypertension as a cardiovascular risk factor
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What is blood pressure?

• Systolic blood pressure (higher value),
  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 value),
  represents the pressure when the heart relaxes
  between beats
• Disappearance of the repetitive sounds (Phase V)

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Risk factors of elevated blood pressure

• Salt intake
• Obesity
• Alcohol use
• Sedentary lifestyle
• Smoking
• Fat contents of the food

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Factors affecting blood pressure levels

• Measurement environment
• Noise, temperature
• Factors related to the participant
• Factors related to the measurer
• Measurement device
• Cuff size

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Factors related to the participant

• Emotions white coat hypertension
• Exercise
• Eating before measurement
• Smoking
• Use of caffeine containing drinks
• Alcohol use
• Full bladder
• Pain
• Daily variation
• Medication

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Average magnitude of the effects (1/3)
Effect Systolic bp (mmHg) Diastolic bp (mmHg)
Full bladder ? 10-15 mmHg, even up to 50 mmHg if bladder uncomfortably distended ? 10 mmHg, even up to 40 mmHg if bladder uncomfortably distended
Not resting 3 to 5 minutes before measurement ? 10-20 mmHg ? 14 mmHg
Back / feet unsupported ? 5-15 mmHg ? 6 mmHg
Supine posture instead of sitting posture ? 3-10 mmHg ? 1-5 mmHg
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Average magnitude of the effects (2/3)
Effect Systolic bp (mmHg) Diastolic bp (mmHg)
Legs crossed ? 5-8 mmHg ? 3-5 mmHg
Participant talks during the measurement ? 10-15 mmHg ? 6-10 mmHg
Arm below heart level ? 10 mmHg ? 10 mmHg
Physical exercise before measurement ? 22 mmHg ? 7-8 mmHg
Left arm instead of right arm ? 1-3 mmHg ? 1 mmHg
Arm unsupported during the measurement ? 1-7 mmHg ? 5-11 mmHg
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Average magnitude of the effects (3/3)
Effect Systolic bp (mmHg) Diastolic bp (mmHg)
Diaphragm of the stethoscope instead of bell ? 2 mmHg ? 0-2 mmHg
Cuff too small ? 3-12 mmHg ? 2-8 mmHg
Cuff too large ? 10-30 mmHg ? 10-30 mmHg
Cuff over clothing ? up to 5 mmHg
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Three categories of observer error

• Systematic error that leads to both
  intra-observer and inter-observer error
• 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
• Observer prejudice or bias, whereby the observer
  adjust the pressure to meet his or her
  preconceived notion of what the pressure should
  be

Rose G et al. Lancet 1965 1 673-4
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Acknowledgements

• Slides
• Hanna Tolonen