How fast should I deflate my sphyg during measurement?
The AHA recommends a deflation rate of 2 – 3mmHg per second. During routine measurement, the system is typically inflated to about 180mmHg and deflated to about 60mmHg to a range of 120mmHg (the actual range is determined by the patient’s expected blood pressure). At a deflation rate of 2-3mmHg/sec, it should take 40 to 60 seconds to deflate the cuff correctly. Excessive deflation rates are one of the most common causes of measurement error – often distorting readings by 10mmHg to as much as 20mmHg. When the deflation rate is too quick, the observer’s reaction time – much slower than the rapid deflation rate – may result in gross underestimation of blood pressure. On the other hand, because of a phenomenon known as mercury lag, excessive deflation COULD result in an overestimation of blood pressure when measured on a mercurial sphyg.
