Valdidating Blood Pressure Monitors

Following six years of continuous use, a study has validated the accuracy of the ambulatory blood pressure (ABP) monitors of Spacelabs Medical (Issaquah, WA, USA).

The researchers used a simulator to routinely check the accuracy of 15 Spacelabs ABP devices (most were model 90207) in use at the Cardiovascular Risk Clinic at the Western General Hospital in Edinburgh (UK) from 1998-2004. The protocol was designed to test the devices over a range of low, normal, and high pressures. The records were examined to assess the long-term consistency and reliability of the devices.

Out of the 1,920 sets measured, only one was outside the generally accepted limits of the pressure expected from the Spacelabs records with the simulated waveforms, and that one exceeded the limits by only 1 mmHg. The criteria for consistency call for the standard deviation of the systolic, diastolic, and mean arterial pressures recorded to be within 3 mmHg, with at least two-thirds within 2 mmHg. In the test, nearly 90% of the average pressures recorded by any device remained within 2 mmHg of their recordings at successive test intervals. Most differences were less than 1 mmHg.

"At the Western General Hospital each patient referred to the Cardiovascular Risk Clinic has 24-hour ambulatory blood pressure monitoring prior to their first clinical consultation,” explained Sister Gough, a physician at the Cardiovascular Risk Clinic. "Spacelabs ambulatory blood pressure monitors are used exclusively at our clinic. The monitors are programmed to record blood pressure measurements at 30-minute cycles over a 24-hour period and patients are encouraged to continue with their normal daily activities while wearing the monitor. We achieve a monitoring success rate in excess of 95%.”

Maintenance records at the Western General Hospital showed that most blood pressure monitoring devices required breakdown maintenance less than once every three years, with no devices requiring repair more than once a year.





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