Lesson 1: Indirect BP

Lesson 1: Indirect Blood Pressure Measurement

Auscultation Method

• Relies on Korotkoff sounds.

• SBP: measured at the first sound.

• DBP: measured when the last sound disappears.

• MAP: must be calculated.

Oscillometric Method

• Monitors pressure fluctuations as cuff pressure is released.

• SBP: measured when oscillations first appear.

• DBP: measured at minimum pressure of oscillations.

• MAP: most accurate measurement.

• Note: Requires pulsatile flow; unsuitable for patients on cardiopulmonary bypass or with left ventricular assist devices.

Factors Affecting Accuracy

• Bladder Size:

  • Ideal length: 80% of extremity circumference.

  • Ideal width: 40% of extremity circumference.

• Cuff Location:

  • SBP is lowest at aortic root, highest at dorsalis pedis.

• Arm Positioning:

  • BP changes by 7.4 mmHg for every 10 cm change in height.

Complications of NIBP Measurement

• Pain

• Neuropathy

• Measurement errors

• Limb ischemia

• Bruising

• Avoid cuff placement over PICC lines, fractures, or AV fistulas.