What causes hand jerking during wrist blood pressure (BP) measurement?

Hand Jerking During Wrist Blood Pressure Measurement

Hand jerking during wrist blood pressure measurement is most likely caused by the oscillometric technique used by wrist monitors, which can stimulate nerves and muscles in the wrist when the cuff inflates and deflates, particularly when the device is positioned incorrectly relative to heart level.

Mechanism of Hand Jerking

The jerking sensation during wrist blood pressure measurement can be attributed to several physiological factors:

1. Nerve Stimulation:

   • The wrist contains several important nerves (median, ulnar, and radial nerves) that can be compressed during cuff inflation
   • Pressure from the cuff can temporarily stimulate these nerves, causing involuntary muscle contractions 1

2. Arterial Compression:

   • Wrist monitors work by detecting oscillations in the radial artery during cuff deflation
   • The radial artery lies just over the radius bone, making the signal very position-sensitive 1
   • Excessive compression can cause discomfort and reflexive muscle movement

3. Hydrostatic Effects:

   • When the wrist is not positioned at heart level, hydrostatic pressure differences can cause the device to inflate to higher pressures than necessary 1
   • This higher pressure can increase discomfort and likelihood of nerve stimulation

Proper Technique to Minimize Jerking

To minimize hand jerking during wrist blood pressure measurement:

• Position the wrist at heart level - This is critical as improper positioning is the most common cause of measurement errors and discomfort 1
• Use devices with position sensors - Some newer wrist monitors only record measurements when the device is held at heart level 1
• Ensure proper fit - The cuff should be snug but not overly tight
• Maintain proper posture - Sit with back supported, feet flat on floor, and arm supported 2
• Rest before measurement - Rest for 3-5 minutes before taking the reading 2
• Avoid movement - Keep the wrist and hand still during measurement

Limitations of Wrist Blood Pressure Monitors

Despite their convenience, wrist monitors have important limitations:

• Lower accuracy - Wrist devices tend to overestimate low blood pressures and underestimate high blood pressures 3, 4
• Position sensitivity - Even small deviations from heart level can cause significant measurement errors 1, 5
• User technique dependence - A 2016 study found that 621 out of 721 subjects had measurement errors of at least ±5 mmHg when using wrist devices at home 5

When to Consider Alternative Measurement Methods

Consider using upper arm blood pressure measurement instead of wrist measurement when:

• Persistent jerking occurs despite proper technique
• Accuracy is critical for clinical decision-making
• Patient has difficulty maintaining proper wrist position
• Significant differences (>10 mmHg) are noted between wrist and upper arm readings 4

Bottom Line

The American Heart Association and European Society of Cardiology recommend upper arm blood pressure measurement as the standard method, with wrist monitors considered only when upper arm measurement is not feasible (such as in very obese patients) 1. If using a wrist monitor, proper positioning at heart level is essential to minimize both measurement errors and the hand jerking sensation.