Home sphygmomanometers

Home sphygmomanometers

Tekin AKPOLAT, MD

Professor of Internal Medicine

Ondokuz Mayis University School of Medicine

Department of Nephrology

SAMSUN-TURKEY

November 21, 2009 ANTALYA

Plan Introduction

Home sphygmomanometers and features

Validation protocols

Limitations of the validation protocols

Accuracy of sphygmomanometers

Potential role of nephrologists

Conclusions/Summary

References

Purpose of this presentation

Summarize basic features of automated home BP measurement devices

Emphasize the distinction between validation, calibration and accuracy of automated home sphygmomanometers

Discuss some practical points for improvement of BP control in CKD for nephrologists.

Other topics Aneroid and mercury sphygmomanometers

Proper patient preparation

Patient training

BP measurement techniques

Potential advantages of SMBP and 24h ABPM

Automated devices used for 24 hours ABPM or in hospitals will not be discussed

Current situation 1

The introduction of inexpensive, easy-to-use, and automated BP measuring devices, lead to a widespread use of SMBP at home and SMBP at home became a part of clinical practice including CKD.

Current situation 2 According to a nation-wide survey in 2004–

2005 in Japan, 90% of clinicians recommended home blood pressure measurement and 77% of hypertensive patients have a sphygmomanometer at home.

The proportion of patients owning a monitor has increased from 49% in 2000 to 64% in 2005 (USA).

http://www.microlife.com/products/hypertension/automatic/bp-a100-plus/

http://www.microlife.com/products/hypertension/automatic/bp-3ac1-1-pc/

Home sphygmomanometers Mercury, aneroid, automatic, and

semi-automatic Mercury: the gold standard Aneroid: practical difficulties Automated: preferred Measurement of BP with an automated

device is a simple procedure.

Features of automated home

sphygmomanometers 1 Measurement site (upper arm, wrist,

finger)

Appropriate cuff-size

Availability of smaller or larger sized cuffs

One device-two cuffs

Comfort cuff (22-42 cm)


sphygmomanometers 2 Validation status in general

population

Validation status in special groups

Model/type

Accuracy


sphygmomanometers 3 Arrhythmia detection

Consecutive 3 measurements

Avoidance of pumping to too high levels

Multi-user facility

Easy to use

XL size display

Infrared interface


sphygmomanometers 4 Quick measurement Capacity of memory Modern style Small dimensions (suitable for traveling,

handbags…) Equipped with carrying bag Soft case Easy wrap cuff


sphygmomanometers 5 Washable cuff cover

Batteries included

Minimum number of batteries

Low battery indication

Rechargeable battery pack

Enabling PC connectability via USB cable


sphygmomanometers 6 Software for use with a PC

Links to PC separate printer

With printer

Bluetooth output to telemedicine service providers

Blood pressure classification indicator

Hypertension Indicator


sphygmomanometers 7 Hide display function

Advanced Positioning Sensor

Wrist position sensor

Voice speaks readings

Voice speaks orders

Automatic switch off


sphygmomanometers 8 Fully automated deflation

Tracking of morning hypertension

Time and date of measurement

Pulse rate

Provide trend plots

Important/essential features

Measurement site (upper arm, wrist, finger)

Appropriate cuff-size

Validation status in general population/ special groups

Accuracy

Wrist/upper arm Wrist devices are popular

Wrist diameter is little affected by obesity

Strict attention should be paid to having wrist at heart level while operating the device.

Three specific guidelines and two relevant websites recommend upper arm devices

A validated finger device is not available

Appropriate cuff-size Obesity is an increasing problem

Cuff bladder must encircle at least 80% of the arm.

The manufacturer's specifications can be followed

Recommendations: AHA and BSH

Smaller or larger cuff-sizes: Extra payment

Validation/accuracy Validation protocols are objective guides

Two useful websites

All models/types of any trademark or company present in the market are not validated

The validation protocols do not guarantee accuracy of a particular device for an individual patient

Validation protocols 1

AAMI

BHS

International protocol

Japan ISO-WG

Validation protocols 2 The basis of the validation tests is the

comparison of BP measured by the device being tested with measurements made by trained observers, using a mercury sphygmomanometer under control of one or two experts.

BP should be measured with the arm supported at heart level after 10-15 min rest.

Validation protocols 3 Indirect measurement of BP using a

mercury sphygmomanometer is preferred, direct (intra-arterial) or simultaneous measurements have some disadvantages.

A sequential same-arm method was used for comparison of tested automated and mercury sphygmomanometers.

The devices are tested over a wide range of BP categories with a certain number of subjects in each category.

Validation in special groups 1

The BHS protocol described validation procedures for special groups such as pregnant women, children and elderly people

The basis of additional validation testing for elderly population is increased arterial stiffness with aging which is a manifestation of CKD including predialysis period


Arterial stiffness can influence the correspondence between readings taken by mercury sphygmomanometers and oscillometric devices.

Up to now, only one home sphygmomanometer was validated for dialysis patients (Blood Press Monit 2007; 12: 227-232)


Arterial stiffness is also increased in diabetes mellitus which is the most common cause of CKD in most of the countries.

Special patient groups such as early stages of CKD, diabetic nephropathy or patients having extraosseus/vascular calcifications may require specific validation tests.

Blood Press Monit 2002; 7: 313-8.


Gerin et al have addressed the clinically relevant issue of device accuracy in individual patients for the first time.

They planned a theoretical study and made an empirical test to estimate the proportion of persons for whom a BP monitor validated according to existing BHS and AAMI standards would be inaccurate.


They have shown that errors do tend to cluster within persons, and by concentrating solely on the population mean error, the BHS and AAMI protocols allow the approval of monitors that are inaccurate for a substantial proportion of people.

As a result, they concluded that under these validation criteria, it is possible that more than half of patients will have an average error greater than 5 mmHg, and more than one in four will have an average error greater than 10mmHg.

They proposed two stages for validation.

1. The model of the monitor in question should be validated at the population level.

2. The particular monitor unit should be validated in the physician’s office for the intended user.

International protocol

In order to decrease individual inaccuracy, the IP introduced a tertiary phase whereby the device was assessed according to the number of subjects in whom it gives accurate measurements in addition to its overall accuracy.

Blood Press Monit 2008; 13: 187-91

The statistical power of three validation protocols (AAMI, BHS and International) have been compared by Friedman et al and they concluded that the decrease of participants from 85 to 33 in the IP reduced its statistical power from 98 % to 70 %.

Accuracy of sphygmomanometers 1

Validation, accuracy and calibration are different and confusing concepts.

Calibration is a procedure to control accurate BP measurement and it assesses a sphygmomanometer under in-vitro conditions.

For automated sphygmomanometers, calibration is the assessment of the accuracy of the pressure transducer, which requires specialized equipment.


Although calibration of the pressure transducer is essential for an automated device, it does not address the accuracy of BP determination.

Accuracy can only be determined by clinical testing.


The American Heart Association, American Society of Hypertension, Preventive Cardiovascular Nurses Association and European Society of Hypertension guidelines on SMBP emphasized the importance of checking monitors for accuracy in 2008.

Samsun experience 1

We planned a campaign to determine the accuracy of home sphygomanometers in 2006.

The findings have been published in two articles [Blood Press 2008; 17: 34–41 and Blood Press Monit 2009; 14: 26–31.].

Samsun experience 2

We realized that a significant proportion of the devices had individual accuracy problems.

Devices having a difference greater than 4mmHg were considered inaccurate.

After learning that their newly purchased devices were inaccurate, most of the patients returned them to the retailer, who in turn forwarded them to the importer.

Samsun experience 3

The technical service of the importer found that the calibration was normal in almost all of the devices.

The company did not consider inaccuracy a problem and returned the device back to the patient.

The patients came back, there was nothing to do.

Published studies/guidelines

The devices were checked for accuracy using two methods in previous studies: assessment of calibration and sequential measurement.

The percentage of inaccurate automated devices was higher than 40 % in all studies using the sequential method for the evaluation of accuracy

This high inaccuracy rate is the evidence of magnitude of the individual accuracy problem.

Calibration/Accuracy

Calibration and accuracy are different concepts

Accuracy can only be determined by clinical testing: But HOW?

HOW WILL THE INDIVIDUAL ACCURACY BE CHECKED?

The cutoff value for inaccuracy began from greater than 3mmHg; many investigators used at least 5mmHg, and Ali and Rouse [J Hum Hypertens 2002; 16:359–361] considered inaccuracy an error of greater than 10 mmHg.

The relevant guidelines emphasized the importance of checking the individual accuracy, but did not mention how to do it.

Blood Press Monit 2009; 14: 208-

215.


This study described a method for the assessment of individual accuracy in details.

The three pivots of this method are sequential measurement, the number of BP measurements and cutoff values for assessment.


The test has three stages

Sequential measurement of BP similar to validation protocols (mercury, tested device, mercury..) was used for the first time for the assessment of individual accuracy.

The tested devices were categorized into 4 groups

Potential role of nephrologists

Recommendation for purchase of a validated device (trademark and model/type)

Checking of the device of the patient for accuracy

Teaching of BP measurement technique

Observation of the patient while operating the device

Practical points Two useful websites Measurement of arm circumference Supplementation with CD, video,

easily readable booklets, brochures… The PA.NET International Quality

Certification Protocol (Blood Press Monit 2008; 13: 285-9)

Conclusions/Summary 1

Inaccuracy of home sphygmomanometers is a common, neglected and ignored problem.

Measurement site, cuff-size, validation status, and accuracy are the most important features.


Individual accuracy can be more important in special patient groups such as early stages of CKD, diabetic nephropathy or patients having extraosseus/vascular calcifications.

The nephrology clinics have a great role and responsibility to encourage optimal circumstances for SMBP at home for their patients and they can be organized for training programs and check of individual accuracy.


Active guidance of nephrologists to all steps of SMBP at home will improve control of BP and increase quality of patient care in CKD.

References http://www.dableducational.org. http://www.bhsoc.org/blood_pressure_list.stm J Hypertens 2008; 26: 1505-26. J Cardiovasc Nurs 2008; 23: 299-323. J Hypertens 1993; 11 (suppl 2): S43–S63. Blood Press Monit 2009; 14: 208-215. Blood Press Monit 2002; 7: 313-8. Blood Press Monit 2002; 7: 3-17. Hypertens Res 2003; 26: 771-82.

http://www.dableducational.org/

http://www.dableducational.org/

http://www.bhsoc.org/blood_pressure_list.stm

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Home sphygmomanometers