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Improving Clinical and Consumer Use of 
Blood Pressure Measuring Devices

National Institutes of Health
Consensus Development Conference Statement
April 26-27, 1979

Conference artwork, a blood pressure measuring device on a purple background.

This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus http://www.nlm.nih.gov/medlineplus/.

This statement was originally published as:Improving Clinical and Consumer Use of Blood Pressure Measuring Devices. NIH Consens Statement 1979 Apr 26-27;2(4):23-27.

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Improving Clinical and Consumer Use of Blood Pressure Measuring Devices. NIH Consens Statement Online 1979 Apr 26-27 [cited year month day];2(4):23-27.


Introduction

A National Institutes of Health Consensus Development Conference on Improving Clinical and Consumer Blood Pressure Measuring Devices was held at NIH on April 26-27, 1979.

The purpose of the conference was to bring together representatives of the medical profession, engineering, consumer groups, and government in an effort to help develop language for proposed national voluntary guidelines for the use and manufacture of sphygmomanometers--blood pressure measuring devices. At NIH, biomedical research scientists, practitioners, legal experts, industry representatives, consumers, and others, meet at consensus development conferences in an attempt to reach general agreement on the safety and efficacy of medical technologies.

This consensus development meeting was scheduled in view of the recent availability of blood pressure measuring devices to consumers without the existence of guidelines to cover the accuracy and lifespan of the sphygmomanometers or the manner in which the public should use them. Coin-operated blood pressure measuring devices have been introduced to drugstores, airports, and other public locations in the past two years, while "take-home" blood pressure kits have been on the market for approximately three years.

During the meeting, seven workshops dealt with various aspects of proposed national voluntary guidelines and developed recommendations. The topics addressed included scope and labeling, performance requirements, and test methods of validation procedures for either automated or nonautomated sphygmomanometers, and needs of special patients, such as the elderly and children. The Association for the Advancement of Medical Instrumentation draft guidelines for sphygmomanometers served as the focal point for discussions. Following are the key conclusions drawn by the groups:

Workshop A

This group discussed scope and labeling for nonautomated devices.

The outer container for the sphygmomanometer should be properly labeled to include information needed by the "end-user." Product literature should accompany the device, and it should include a list of precautions. Among these are the manufacturer's recommendations for calibration checks, cleaning and care of the instrument, hazards of prolonged overinflation of the device's bladder, methods for determining malfunctioning of the display device, and, when required, recommended sterilization procedures and methods for dealing with mercury spills.

The literature should include both adequate operating and use instructions, including the need to consult with a physician for interpretation of pressure measurements. Manufacturers should not attempt to tell an individual how to interpret his or her measurements and, in fact, should be active in encouraging that the user consult with a physician.

Labeling language should require warranty information and identify available service centers. In addition, the cuff should be labeled or prominently marked as to the intended limb diameter or circumference. The size of the cuff has a very important bearing on the accuracy of the reading. It would be very useful to have information on the cuff itself--some means of identifying what particular kind of size limit the device would have.

There was a recommendation to include several terms for definition in the glossary section.

Workshop B

This group dealt with performance requirements for nonautomated sphygmomanometers.

Any part that is labeled conductive should also be labeled with a precaution that the conductivity is useless if the part is not used with other components that are conductive.

It was generally agreed that instead of relating the width of the bladder to the diameter of the patient's arm, it should be related to arm circumference, which is easier to measure or estimate.

On the aneroid dial, no decision was reached on the method of specifying durability, but the workshop recognized the need to determine that such a method be included in guideline requirements or be included in the guidelines test methods section. It was suggested that on the mercury-gravity manometer, the requirement state that a space below zero be visible so that if the mercury is below zero, there would be a visible reading.

It was agreed for the calibrated tube that a minimum wall thickness as well as a minimum diameter be specified. An alternative would be to have the test methods section cover the breakability of the glass tube. Preferably, language concerning wall thickness and the withstanding of breakage tests should both be included in the guidelines.

It was agreed that the accuracy requirements for manometers, within specified temperature ranges, should be re-examined.

Workshop C1

This group dealt with test methods or validation procedures for nonautomated sphygmomanometers.

The question of accuracy and system reliability was raised during the discussion of testing. It was the consensus that a test arm for checking the accuracy of nonautomated sphygmomanometers would be of great assistance. There was consensus that there should be some type of life testing of devices to ensure that the consumer does not obtain a device, use it a few times, and then discover that it no longer functions. Such testing should be part of the guideline requirements.

It was suggested that various tests be combined and others be done in sequence so that the test procedures are simplified and follow one another in a more organized fashion.

There was consensus to enter into some type of field testing of clinical accuracy of blood pressure measuring devices. It was also suggested that a statement be included regarding accuracy verification in the labeling of manometers.

It was also suggested that labeling instructions should urge that the blood pressure measuring device be checked against the patient's physician's mercury unit. The label should also suggest that the device be sent back to the manufacturer periodically to ensure that the unit continues to be accurate (i.e., calibrated).

Workshop C2

This group dealt with scope and labeling of automated/electronic sphygmomanometers.

Participants agreed that the draft scope document was adequate. The group agreed that some additions should be made to the labeling document language.

When the devices are used in a nonclinical setting, a statement should be prominently displayed on the device that states: "For interpretation of results, a physician should be consulted."

A workshop member asked to define "longevity" of devices, but the group agreed that it would be extremely difficult to develop specific language. In order to give users some basis on which to judge longevity, information on product warranty and exclusions should be included in all documentation accompanying sphygmomanometers. In this way, the manufacturer would advise a consumer on how long the warranty period might be.

It would be quite helpful to include a comprehensive glossary with any guidelines in order to be sure everyone is using the same set of definitions regarding use and manufacture of blood pressure measuring devices.

Workshop D

This group dealt with performance requirements for automated/electronic sphygmomanometers.

Among the items discussed were methods of verifications of operations and concerns about coin-operated blood pressure measuring devices.

Test methods and testing cycles generated considerable discussion. The existing document basically requires only one test--there is no mention of the need for a device to meet the requirements over a certain number of cycles. Such language should be part of any guidelines to ensure that the device has some long-term stability.

There was a suggestion that testing tolerances be changed from "plus or minus" to "ranges greater than and less than." This was urged because the ranges, not the specific numbers, are most important.

The minimum voltage and frequency requirements for line-operated equipment should be reinserted in the proposed guidelines. At present, the proposed guidelines state that these are parametric and specified by the manufacturer.

There was some concern for indicating on coin-operated devices that their ability is limited. It was felt that more data should be present on what possible applications the device is intended for, such as arm size.

Workshop E

This group discussed test methods of validation procedures for automatic/electronic sphygmomanometers.

Much discussion centered upon the problem of system verification versus the defective instrument. There was some concern that it would be quite helpful if there were a means of verifying in the field if an instrument were working properly. The subject of the use of an artificial arm for testing device accuracy arose. The group agreed that it was not the place of guidelines to require the use of an artificial arm for testing. It might, however, be appropriate that a recommendation for future research state that for design and verification and for field evaluation, such a test arm would be extremely desirable.

Considerable discussion surrounded the three methods of design verification: comparison with the auscultatory technique, comparison against intra-arterial pressure, or comparison against another instrument which has been verified against intra-arterial methods. Several workshop participants considered the verification by auscultatory methods unacceptable. Another group, however, felt this method was to be preferred. In general, the group agreed that all three methods would be acceptable and that the method chosen would depend upon which device was being tested and into which market or usage segment it was placed.

Workshop F

This group dealt with sphygmomanometers and special patients such as the elderly and children.

There appears to be some evidence that the cuff sizes should be wider for children than has been recommended by the American Heart Association. In addition, it would be very useful to have a greater variety of cuff sizes available for young people. It would also be helpful to have a more reliable method for diastolic pressure detection in younger people.

It was pointed out that in the older population, problems exist that can confound blood pressure readings more than with other groups. Atrial fibrillation is one example of such a problem. With older patients, then, averaging a number of readings may be more important than a given reading. In certain situations (e.g., aortic valve disease), the fourth phase may be more useful than the fifth phase for diastolic indications.

Recent data from Canada report the inaccuracy of the blood pressure measurements that may be caused by stiff wall arteries. Errors on the high side of up to 50mm Hg have been shown in some older patients. Verification of these findings could have a significant impact on treatment for patients with stiff wall arteries.

On the question of testing, development of a test arm drew support. Looking to the future, use of a family of test devices to check sphygmomanometers could prove quite helpful. This is an area in which government or independent investigators could lend support.

A requirement for periodic testing of coin-operated blood pressure measuring devices should be inserted in any set of guidelines.

At the final plenary session, recommendations from each of the workshops were considered and were endorsed without change.
 

Workshop Leaders

William A. Baum, Jr.
Association for the Advancement of Medical Instrumentation
Alan S. Berson, Ph.D.
National Institutes of Health (two workshops)
V.R. McCall
Association for the Advancement of Medical Instrumentation
Maynard Ramsey III, M.D., Ph.D.
Association for the Advancement of Medical Instrumentation
William N. Reining
Association for the Advancement of Medical Instrumentation
Stephen S. Richman
Association for the Advancement of Medical Instrumentation

Conference Sponsors

American College of Cardiology
American Heart Association
American Medical Association
Association for the Advancement of Medical Instrumentation (AAMI)
Food and Drug Administration
National Bureau of Standards
National Heart, Lung, and Blood Institute, NIH

Supplemental Information for NIH Consensus Statement on Improving Clinical and Consumer Use of Blood Pressure Monitoring Devices

Since the NIH Consensus Statement on Improving Clinical and Consumer Use of Blood Pressure Monitoring Devices was issued, additional information has become available that supplements the original statement.

The 1979 NIH Consensus Development Conference on Improving Clinical and Consumer Use of Blood Pressure Monitoring Devices was convened with the primary objective of determining the need for instrument standards. The consensus panel recognized the need for standards, recommended that standards be developed, and provided a list of specifics to be addressed in the standards.

The Association for the Advancement of Medical Instrumentation (AAMI), which played a leading role in the consensus development conference, subsequently established two committees to develop standards, one for non-automated sphygmomanometers and the other for electronic or automated sphygmomanometers. The standards developed by the committees were released as American National Standards (Non-Automated Sphygmomanometers: ANSI/AAMI SP9-1985 and Electronic or Automated Sphygmomanometers: ANSI/AAMI SP10-1987) and are available from the AAMI at a nominal cost. They specify performance and safety requirements such as labeling, environmental stability, inflation source and pressure control, accuracy and repeatability, and procedures for statistical validation of performance.

The Non-Automated Sphygmomanometer standard was updated in 1994 and is available as ANSI/AAMI SP9-1994. The Electronic or Automated Sphygmomanometer standard was updated in 1992 and is available as ANSI/AAMI SP10-1992. This updated version incorporates requirements and recommendations for ambulatory blood pressure measurements. An amendment to the latter standard completed in 1996 addresses devices intended for neonates.

For copies of the current standards and amendment, contact:
Association for Advancement of Medical Instrumentation
3330 Washington Boulevard, Suite 400
Arlington, Virginia 22201-4598
(703) 525-4890

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