Pathophysiology
P-I-17. Methods to measure blood pressure
血圧測定法と正しい測定の実際
Methods to Measure Blood Pressure
Direct (invasive)
- Catheter technique inside the artery; used in intensive care units
- Invasive → not available in everyday practice
Indirect (non-invasive) — widely used
- Oscillometric semi-automatic and automatic monitors
- Korotkoff sound auscultation with validated manometers
- Mercury sphygmomanometers — today used only for calibration
Correct Measurement Technique
- No food, caffeinated drinks, alcohol or smoking for 30 minutes beforehand
- ≥5 minutes rest in quiet, neutral conditions (no emotional/thermal/noise stress, bladder emptied)
- Sitting, back supported, muscles relaxed; upper arm at heart level, elbow slightly bent; legs parallel, feet on the floor
- Cuff centered on the upper arm, lower edge 2–3 cm above the elbow
- Perform at least three times; report the average of the last two readings
- Neither patient nor examiner talks during measurement
- Korotkoff method: inflate
30 mmHg above the pressure that abolishes the radial pulse, then deflate slowly (3 mmHg/sec)
ABPM (overview)
- Ambulatory BP monitoring = automatic measurement several times a day, usually 24 hours
- Detects white-coat hypertension, masked hypertension, and disturbed diurnal rhythm (loss of the normal night-time dip suggests severe, progressive hypertension)
Diagnostic Thresholds
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Medical office | ≥140 | ≥90 |
| Home | ≥135 | ≥85 |
| ABPM — daytime (awake) | ≥135 | ≥85 |
| ABPM — nighttime (asleep) | ≥120 | ≥70 |
| ABPM — 24-hour | ≥130 | ≥80 |
一問一答
▶What is the direct (invasive) method of blood pressure measurement, and where is it used?
An intra-arterial catheter technique, used in intensive care units.
▶What are the main indirect (non-invasive) methods of measuring blood pressure?
Oscillometric automatic/semi-automatic monitors and Korotkoff sound auscultation with validated manometers.
▶What is the role of mercury sphygmomanometers today?
They are now used only for calibration.
▶What should be avoided for 30 minutes before a blood pressure measurement?
Food, caffeinated drinks, alcohol, and smoking.
▶How long should a patient rest before BP measurement, and under what conditions?
At least 5 minutes of rest in quiet, neutral conditions (no emotional/thermal/noise stress, bladder emptied).
▶What is the correct body position for blood pressure measurement?
Sitting with back supported and muscles relaxed, upper arm at heart level with elbow slightly bent, legs parallel and feet on the floor.
▶Where should the cuff be positioned on the arm?
Centered on the upper arm with its lower edge 2–3 cm above the elbow.
▶How many BP readings should be taken, and how is the result reported?
At least three measurements; report the average of the last two readings.
▶Why should neither patient nor examiner talk during measurement?
Talking raises blood pressure and introduces measurement error.
▶In the Korotkoff method, how high should the cuff be inflated and how fast deflated?
Inflate ~30 mmHg above the pressure that abolishes the radial pulse, then deflate slowly at ~3 mmHg/sec.
▶What is ABPM (ambulatory blood pressure monitoring)?
Automatic blood pressure measurement several times a day, usually over 24 hours.
▶What conditions can ABPM detect?
White-coat hypertension, masked hypertension, and disturbed diurnal rhythm (loss of the normal night-time dip).
▶What does loss of the normal night-time BP dip suggest?
Severe, progressive hypertension.
▶What is the office (medical-setting) diagnostic threshold for hypertension?
Systolic ≥140 mmHg or diastolic ≥90 mmHg.
▶What is the home BP diagnostic threshold for hypertension?
Systolic ≥135 mmHg or diastolic ≥85 mmHg.
▶What are the ABPM daytime (awake) thresholds for hypertension?
Systolic ≥135 mmHg or diastolic ≥85 mmHg.
▶What are the ABPM nighttime (asleep) thresholds for hypertension?
Systolic ≥120 mmHg or diastolic ≥70 mmHg.
▶What is the ABPM 24-hour average threshold for hypertension?
Systolic ≥130 mmHg or diastolic ≥80 mmHg.
▶What is white-coat hypertension?
Elevated blood pressure only in the medical office setting, with normal readings elsewhere.
▶What is masked hypertension?
Normal blood pressure in the office but elevated readings outside the clinical setting.