Along with body temperature and weight, blood pressure is the most common measurement taken in a doctor's office, and it serves as a key diagnostic tool. High blood pressure indicates, for example, a patient at risk for a stroke, heart attack, or other cardiovascular problems.
An estimated 50 million Americans have high blood pressure, according to the American Heart Association. In response, almost 100 pressure-reducing drugs are now on the market.
For many decades, the mercury manometer—the long tube with the rising column of silvery metal—has been the gold standard for measuring blood pressure. It requires little maintenance and provides reliable, consistent readings.
The trouble is that manometers occasionally break and spill. Mercury spills are toxic, and mercury exposure in humans can lead to birth defects and other health problems. In 1998, the U.S. Environmental Protection Agency and the American Hospital Association agreed to eliminate as much mercury waste as possible from hospitals by 2005.
This week, University of Washington Medical Center continues to join the nonmercury generation by phasing out many of its remaining 300 mercury blood pressure devices (100 have already been replaced).
But some health professionals, including experts at the National Institutes of Health and the American Heart Association, argue that the new technology may not be as reliable as the old. They warn that inaccuracies could lead to false diagnoses and inappropriate treatments.
Area hospitals that have switched from mercury manometers to newer spring-type and digital devices say that they've had no problems.
But anecdotal evidence from around the country argues otherwise, say critics of the new technology. They say it's time for a pause in the campaign to switch blood pressure monitoring devices.
"It is a public health concern," says Edward Roccella, coordinator of the national high blood pressure program at the National Heart, Lung, and Blood Institute.
Newer, aneroid blood pressure monitors go out of kilter and provide improper readings more often than mercury devices, detractors say. That's bad news for physicians as well as patients.
A reading that's too low by five points (120/80, say, as opposed to a true 125/85) could result in a misdiagnosis, says Daniel Jones, a professor of medicine at the University of Mississippi Medical School and a spokesperson for the American Heart Association.
"If someone is misdiagnosed and they are actually hypertensive, then they miss the protection of making lifestyle changes and drug treatments which result in fewer strokes and heart attacks," says Jones. "This is a large concern."
He says he knows of several cases of misdiagnosed blood pressure owing to faulty aneroid devices, including one case in which a patient died.
Proponents of the new devices argue that they are accurate as long as they are calibrated regularly. Jones and Roccella agree.
But they say that what's proved problematic is getting hospitals to adopt a regular calibration schedule. What's more, there are no federal regulations governing how often blood pressure devices should go into the shop for service.
Local physicians think both the NIH and the American Heart Association are overreacting—and that the move to new technology should continue.
"Are we jumping on a bandwagon too fast?" says Marshall Corson, chief of cardiology at Harborview Medical Center. "My sense is that we're getting rid of a hazard, and we have good alternatives."
Harborview, which is operated by UW as part of its medical school, replaced all its mercury devices in 1999. Corson says that there have been no problems with the new devices and that the hospital follows an annual calibration schedule.
Other area hospitals report similar experiences. Children's Hospital, Group Health Cooperative, and Virginia Mason and Swedish medical centers have either completely switched to new aneroid devices or mix those devices with mercury ones. Officials at each facility say they've had no problems with the new devices.
So why the concern from back East?
Corson attributes it to doctors simply being more comfortable with older technology.
Keith Jesse, manager of clinical engineering at UW, says that the AHA, in particular, is obsessed with keeping mercury manometers in circulation.
"I just can't explain it," he says. "I wish I could."