Plain English Summary
Background and study aims
It has been assumed that the differences between manual and automated blood pressure recordings are due to the way the automated machine works. However, it is possible that these differences depend on precisely how the manual blood pressure is detected and on differences in the group of people in whom the machines are being tested. The aim of this study is to to see if understanding some of these factors may improve the accuracy of blood pressure machine validation. This includes looking at whether a microphone would be better than using humans to listen to blood pressure sounds, and whether the intervals between readings or the cuff used in the comparison makes a difference. The researchers will also look at whether the squeezability of a person's arm and the speed of the pulse flowing down the arm could also affect the readings.
Who can participate?
Healthy volunteers aged between 18 and 85
What does the study involve?
The researchers measure specific physical characteristics which may influence blood pressure measurement such as weight, height, arm size and pulse velocity. They then assess blood pressure derived from the monitor and by manual readings using two trained independent observers using a double-headed stethoscope. Sounds from the stethoscopes are also measured as well as the point at which the arterial pulse returns below the cuff as the cuff is deflated. Nine alternating manual and automated readings are made at either 30- or 60-second intervals before a 10-minute rest. A second set of nine alternating manual and automated readings are made at the alternative time interval (30 or 60 seconds) and then the arm size and blood flow measurements are repeated before a further 10-minute rest. The researchers then measure nine alternating manual and automated blood pressure readings with either an automated cuff or a cuff of similar design made with the same materials as the cuff used for manual readings in the first part of the validation, and repeat using the alternative cuff for a further nine readings followed by arm size and blood flow measurements at the end of the experiment. Differences in automated and manual readings are analysed with respect to the way in which the manual readings were detected and the physical characteristics of the participants.
What are the possible benefits and risks of participating?
Potential benefits of participating include the possibility of having an unexpected high or low blood pressure or an irregular pulse recognised. Whilst this means that the person cannot continue in the study it may lead to earlier awareness of a possible health problem. Taking part in a study which may help others in the future can be satisfying. A pleasant experience in this study may encourage people to take part in other research and to volunteer in other ways in the health community. For some volunteers who are working within healthcare, experiencing first-hand what research is like can arouse a possible interest in asking research questions of their own. People who have taken part in similar studies have found it a positive experience and have found hospitals and research less frightening than anticipated. Potential risks include some mild discomfort and slight bruising after repeated blood pressure measurements, although there have been no significant complaints from over 300 people who have taken part in similar studies. Breach of confidentiality is very unlikely to be significant since all individual data is de-identified at the time of recording. No personal facts of any potentially embarrassing nature are sought and no personal details are recorded apart from age, sex, ethnicity, height, weight, arm dimensions and blood pressure.
Where is the study run from?
Stepping Hill Hospital (UK)
When is the study starting and how long is it expected to run for?
January 2016 to March 2019
Who is funding the study?
Omron Healthcare UK
Who is the main contact?
Dr Philip Lewis
Analysis of physical and human factors affecting blood pressure measurement with especial relevance to validations of blood pressure monitors in man
Using a standard international protocol for comparing machine blood pressures with those obtained manually, an unpublished UK study in 2015 showed less favourable comparability than a study using the same machine in France published in the previous year. Based on their previous and current research, the researchers believe that a variety of factors might lead to such a disparity including differences in 1) the accuracy of the observers' assessment of the blood pressure sounds, 2) physical characteristics of the subjects used, 3) the effect of exchanging the cuffs between readings and 4) differences in the recovery of blood flow in the arm dependent on variations in the time between readings allowed within the protocol. The researchers wish to investigate whether such variations can be circumvented in order to produce a better validation protocol.
1. Do differences between manual and automated blood pressures result from differences in the intervals between readings and do changes of cuffs between each reading increase the variability of blood pressure measurements?
2. Are sequential changes in blood pressure related to the number of measurements made, to changes in arm circumference or skinfold thickness, changes in pulse wave velocity or other factors related to the subject of the measurement or the cuff used in measurement? If there are local factors affecting blood pressure changes related to the cuff-inflation-deflation cycles, does the contralateral blood pressure measured without cuff compression remain relatively unaltered or mirror the pressure changes in the arm in which cuff measurements are taken?
3. Can automated detection of blood pressure by acoustic or Doppler wave analysis be used instead of auscultation (listening to the blood pressure sounds) thus making blood pressure measurement standards more objective and reproducible?
Approved 14/08/2017, North of Scotland REC 1 (North of Scotland Research Ethics Service, Summerfield House, 2 Eday Road, Aberdeen, AB15 6RE, UK; Tel: +44 (0)1224 558458; Email: email@example.com), ref: 17/NS/0075
Within-subject cross over randomized observational single centre study
Primary study design
Secondary study design
Case crossover study
Patient information sheet
Not available in web format. Please use contact details to request a participant information sheet
Blood pressure measurement
The researchers will recruit 80 volunteers and measure specific physical characteristics which may influence blood pressure measurement e.g. weight, height, arm size and pulse velocity. Then they will assess blood pressure derived from the monitor and by manual readings using two trained independent observers using a double-headed stethoscope. Sounds from the stethoscopes will also be measured as well as measuring the point at which the arterial pulse returns below the cuff as the cuff is deflated. Nine alternating manual and automated readings will be made at either 30- or 60-second intervals prior to a 10-minute rest. A second set of nine alternating manual and automated readings will be made at the alternative time interval (30 or 60 seconds) and then the arm size and blood flow measurements will be repeated prior to a further 10-minute rest. The researchers will then measure nine alternating manual and automated blood pressure readings with either an automated cuff or a cuff of similar design made with the same materials as the cuff used for manual readings in the first part of the validation, and repeat using the alternative cuff for a further nine readings followed by arm size and blood flow measurements at the end of the experiment. Differences in automated and manual readings will be analysed with respect to the way in which the manual readings were detected and physical characteristics of the participants.
Primary outcome measure
Systolic and diastolic blood pressure measured manually by two observers using standard auscultation and a mercury-containing sphygmomanometer, by an automated blood pressure recorder (Omron M6), by microphone, Doppler waveform and continuous sphygmomanometer cuff pressure waveform and video-recording of the mercury column in two sequences of nine blood pressure readings made alternately manually (with an appropriately sized Accoson cuff) or by the Omron M6 (using an Omron cuff) at 30 or 60 second intervals
Secondary outcome measures
1. Systolic and diastolic blood pressure measured manually by two observers using standard auscultation and a mercury-containing sphygmomanometer, by an automated blood pressure recorder (Omron M6), by microphone, Doppler waveform and continuous sphygmomanometer cuff pressure waveform and video-recording of the mercury column made alternately manually or by the Omron M6 in two sequences of nine blood pressure readings at 60-second intervals. One sequence will use the Omron cuff and the other will use a specially constructed cuff which resembles the Omron cuff in size and shape but differs in using the same materials as the previously-used Accoson cuffs.
2. Continuous finger blood pressure measured using a Portapres recorder on the contralateral side during all four sequences
3. Upper arm circumference measured with a spring-loaded tape measure and triceps skin-fold thickness measured using callipers before and after each sequence of nine blood pressure measurements
4. Bilateral pulse wave velocity (carotid-radial) measured using a Complior device before and after each sequence of nine blood pressure measurements
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Healthy volunteers aged between 18 and 85 years of age
2. Willing to have repeated blood pressure measured whilst sitting silently in four sequences of 9 readings in any one sequence
3. Resting heart rate between 50-110 bpm
4. Upper arm circumference ≥ 22 cm and ≤ 42 cm
5. Resting systolic blood pressure ≥ 90 and ≤ 180 mm Hg
Target number of participants
Participant exclusion criteria
1. Take anticoagulants
2. Bruise easily
3. Have circulatory problems (e.g. have an arterial shunt or arterial narrowing)
4. Have a pacemaker
5. Have atrial fibrillation
6. Have any other marked pulse irregularity
7. Have a resting heart rate < 50 or > 110 bpm
8. Have systolic and/or diastolic blood pressure sounds in either arm which are not easily heard by the observers
9. Have initial systolic and/or diastolic blood pressures in either arm which differ by > 4 mmHg
10. Have systolic blood pressure at rest < 90 or > 180 mmHg
11. Have blood pressure differences between arms at rest of ≥ 20 mmHg systolic and/or ≥ 10 mmHg diastolic
12. Have disorders of upper arm anatomy, muscle tone, tremor or power
13. Take medications or substances likely to cause short term changes in blood flow or pressure
14. Those who have had caffeine-containing drinks, alcohol or nicotine within 4 hours of the beginning of the study
15. Those lacking capacity to provide informed consent
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Stepping Hill Hospital
Research & Innovation Centre Stepping Hill Hospital
Omron Healthcare UK
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
After analysis of the results the researchers will present the findings at specialist conferences and in peer-reviewed journals concerned with blood pressure measurement.
IPD sharing statement
Individual de-identified participant datasets generated and/or analysed during the current study during this study will be included in the subsequent results publication.
Intention to publish date
Participant level data
Basic results (scientific)