The Stanford 25

An Initiative to Revive the Culture of Bedside Medicine

BP & Pulsus Paradoxus 

In addition to attending as a cardiologist, Dr. Ronald Witteles conducts research into heart failure and serves as Associate Director of the CCU and Co-Director, Stanford Amyloid Center. In the video below, he demonstrates his technique for measuring blood pressure and evaluating pulsus paradoxis.

Introduction: Few realize that the measurement of blood pressure is highly skill dependent. A practiced technique allows a physician to take an accurate reading when the result may guide clinical decision making.

Technique:

  • Position
    • Recognize that BP normally rises with activity/exertion. Therefore, BP should never be taken shortly after ambulation, such as when a patient first walks into clinic. If checking orthostatic vital signs, the individual should ideally be in the position (supine, sitting, or standing) for at least 60 seconds before the measurement is recorded.
      • Caveats: BP norms are taken from quiet patients sitting with back support. Speaking may elevate BP by 8-15mmHg (Arch Intern Med 153:2741), sitting w/o back support may elevate BP by 5-10mmHg (J Gen Intern Med 10:223).
  • Equipment
    • Cuff size: Bladder length should be 80% and bladder width should be at least 40% of the circumference of the upper arm.
      • A too small cuff will overestimate, too large will be ineffective.
  • Technique
    • Inflate the bladder quickly to 20 mmHg above the pressure at which radial pulse is blocked.
    • Deflate the bladder 3 mmHg/sec, record the pressure at which the first Korotkoff sound is heard as the systolic pressure.
      • Do NOT use upward deflections on the manometer to measure systolic pressure.
    • Continue deflating, record the disappearance of Korotkoff sounds as the diastolic pressure.
    • If the Korotkoff sounds are weak, have the patient raise the arm, open and close the hand five to ten times, and then inflate the bladder quickly.
  • Recordings
    • Note the pressure, patient position, arm, and cuff size:
      • e.g. 140/90, seated, right arm, large adult cuff.

Findings:

Pulsus Paradoxus: On inspiration, a drop in systemic arterial pressure greater than 10mmHg.

  • Measurement:
    1. Inflate the cuff beyond the point where you hear any Korotkoff sounds.
    2. Slowly deflate the cuff until you start hearing any sounds. At the highest BP when you hear sounds intermittently (rather than with every heart beat), note the blood pressure. (This corresponds to the higher systemic blood pressure which is occurring during expiration).
    3. Keep slowly deflating the cuff until you reach the highest BP in which you hear sounds every beat.
    4. The difference between #2 and #3 is the “pulsus paradoxus.” If it is >10 mmHg, it is considered significant.
    • Clinical Pearl: One does not have to be watching the patient’s respirations. Rather, one might listen to the sounds.
  • Ddx: moderate to severe cardiac tamponade, occasionally constrictive pericarditis or COPD.
  • Physiology — Inspiration is performed by decreasing intrathoracic pressure.  Because the heart is in the thorax, this pressure is transmitted to the heart and causes a bigger gradient between the pressure in the veins outside of the thorax and the right atrium/ventricle.  As such, with each inhalation, more blood flows into the right side of the heart. When this occurs, the interventricular septum subtly bulges into the LV cavity, lowering LV filling, and therefore lowering systemic stroke volume/BP.  Because the ventricle can normally also expand outward, this septal shift is usually small, and the difference in the blood pressure is therefore small between inspiration and expiration (<10 mmHg). In states in which the ventricle cannot expand outward (e.g. tamponade) or in which the drop in intrathoracic pressure with inspiration is profound (e.g. status asthmaticus), the septal shift is exaggerated and the difference in BP is larger.
  • Other signs of cardiac tamponade
    • Beck’s Triad
      • Low arterial blood pressure.
      • Jugular venous distention that rises on inspiration (Kussmaul’s sign).
      • Distant, muffled heart sounds.
    • Friedreich’s sign: exaggerated drop in diastolic central venous pressure
    • Clear lungs (usually).

Further Reading:

Bailey RH, Bauer JH. “A review of common errors in the indirect measurement of blood pressure” Arch Intern Med. 1993 Dec 27;153(24)

Baker RH, Ende J. “Confounders of auscultatory blood pressure measurement.” J Gen Intern Med. 1995 Apr;10(4)

Embedded Videos & Links (Not produced by Stanford, click through for credit and source).

Image credit: wrongdiagnosis.com

Source via wrongdiagnosis.com: Springhouse “Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series”Lippincott Manual of Nursing Practice Series, Copyright © 2007 Lippincott Williams & Wilkins.

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Written by stanford25admin

June 7, 2010 at 3:58 pm

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