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Overpumping Can be Hazardous to Your Sphyg's Health

Written By: 
Marc Blitstein / President & CEO

The cuff on a manual sphyg is inflated with the help of a squeeze bulb. On average it takes 3 compressions of the bulb to inflate an adult cuff to 180-200mmHg, the typical target on most patients (for hypertensive patients, the level could be much higher). We say “on average” because the number of compressions will vary a bit with the circumference of the patient’s arm and the size of the practitioner’s hand. On larger cuffs it takes considerably more squeezes which is why, on the largest cuffs, we provide an oversized bulb with greater volume.

But for the smaller cuffs (small adult, child, and infant) it takes far fewer bulb compressions. As such, care must be taken to prevent accidental over-inflation which risks patient discomfort or even injury; and damage to the delicate movement of the manometer (the gauge portion of the instrument). On a mercury instrument, over-inflation even risks blowing the mercury out through the top of the instrument creating a nasty environmental hazard.

Below is the average number of compressions required on the three smaller cuffs we offer:

  • On a small adult cuff roughly 2 full compressions will fully inflate the instrument to 300mmHg.
  • On a child cuff, just 1 full compression will fully inflate the instrument to 300mmHg.
  • On an infant cuff, you need to be even more careful compressing the bulb minimally. A single full squeeze can overinflate the cuff.

What happens when you over-inflate? Besides subjecting your patient to unnecessary discomfort and possibly even injury, you risk crippling damage to the manometer.

The mercury in the column may bubble if overinflated and can even be forced through the top filters designed to contain the liquid but allow air to move through the tube. On ADC aneroid sphygs, we utilize a very robust movement that can withstand over-inflation to about 340 mmHg but beyond that and/or if over-inflated repeatedly the movement may be damaged requiring free, but inconvenient recalibration.

Remember to watch the manometer as you squeeze the inflation bulb to ensure rapid, but appropriate inflation of the cuff. And never inflate it past 300mmHg. Besides a very angry patient you may be looking at an instrument in need of service.