Critique of New York Times Story, Risk Seen in Move to Replace Gauge of Blood Pressure

Critique of New York Times story, “Risk Seen in Move to Replace Gauge of Blood Pressure”

On Sunday, June 16, the New York Times ran a story by Medical Reporter Gina Kolata titled, “Risk Seen in Move to Replace Gauge of Blood Pressure.” In that page 1 piece, Ms Kolata reported on the important problem of inaccuracy in measuring blood pressure and ascribes a single cause of that problem: the phase out of mercury sphygmomanometers for environmental reasons. In creating this simple cause-and-effect story, Ms. Kolata makes four critical mistakes: First, she mischaracterizes the outcome of the meeting on which she bases her report. Second, she inaccurately describes the problem of calibration of blood pressure devices as being limited to devices that do not contain mercury. Third, she fails to mention the serious public health impacts of mercury exposure, which is the motivation for voluntary mercury elimination initiatives. Fourth, and most importantly, she misinforms her readers about the many reasons why their blood pressure reading may not be accurate and what should be done to solve this important problem.

Ms. Kolota’s report is derived from an April 2002 working meeting on Blood Pressure Measurement, sponsored by the National High Blood Pressure Education Program, the National Heart, Lung and Blood Institute and the American Heart Association. The goal of the meeting was, “to examine the science that supports current BP (blood pressure) measurement policies and to identify additional research needed to strengthen policies.” A review of the meeting summary shows the variety of issues Ms. Kolata had to ignore to create the overly simplistic cause-and-effect theme of her article:

 Inadequate or Out-of-Date Training Many physicians and other health care providers don’t know the most recent recommendations on how to properly measure blood pressure. In a year 2000 study, only 5 percent of physicians who responded had read the complete American Heart Association recommendations for blood pressure measurement (50% were not familiar with them). In a pre-test of knowledge, 2 of 3 healthcare providers scored less that 50% on a 16-question test on blood pressure measurement. Errors include improper cuff size selection, positioning and preparation.

 Poor Technique Analysis of national surveys in the United States, Finland, Norway, Australia and England have documented the errors that health care providers make when reading blood pressure. These studies have shown that the most common problems are reading too high or too low, falsification of the numbers, bias towards certain numerical digits and failure to follow the protocol for calibration and technique.

 Patient Variables Accurate reading and interpretation of blood pressure can be impacted by the “white coat effect,” pregnancy, the advanced age of the patient, stiffer arteries and isolated systolic hypertension.

 Cuff Size A 2001 study found that more that 50% of nurses used the wrong cuff size. Studies indicate that increased obesity in the United States is leading to increasing arm circumference, but manufacturers have not yet developed a standard set of larger cuff sizes.

 Equipment Calibration In a variety of studies, both mercury and aneroid blood pressure devices have been found to be inaccurate as a result of poor calibration and maintenance. Some automatic devices may not work in every setting for every patient. Validation, calibration, and regular maintenance must be required of all blood pressure measuring devices.  Mercury Spills “Environmental concerns about mercury are real,” stated meeting participant Sheldon Sheps, M.D., Mayo Medical Center. Mercury BP devices do spill, and costs for cleanup are substantial. In a two-year period at Mayo Medical Center the 50 recorded spills resulted in $26,000 in clean-up costs.

The meeting concluded with the development of consensus recommendations to address the concerns associated with blood pressure measurement. These recommendations include:

1. Blood pressure devices should not be sold without appropriate regulatory approval and with a regulated informational package insert. 2. Blood pressure measurement devices must be manufactured with the ability to accept cuffs interchangeably from a standard set of cuff sizes. 3. A standard system of training, certification and recertification—perhaps linked to license—should be implemented and enforced. 4. Calibration and maintenance programs should be promoted with partners including JCAHO 5. Mercury should be eliminated from the environment and a period of research should be undertaken to devise an adequate replacement for the mercury manometer.

Gina Kolata’s well-placed but selective assessment leaves the reader thinking that all health care providers must do to accurately measure blood pressure is return to mercury-containing devices. It’s just not so. Proceedings of the meeting support the position that, “We don’t have a system in place to ensure the accurate determination of blood pressure,” but this is not due to the “push to get rid of mercury sphygmomanometers.” As Dr. Clarence Grim of the Medical College of Wisconsin wrote in his position paper for the April meetings, “Practice surveys around the world report serious problems in accuracy of sphygmomanometers (aneroids, mercury and electronic) and poor adherence to proper technique.” Health care providers need to improve the accuracy of blood pressure measurements through proper training, upgraded equipment and consistent programs of calibration and validation of all measurement devices. And the Times and Gina Kolata could use some upgrading of their accuracy as well.