Concise Software Operator's Guide Rev1.0.

ENGLISH

COPYRIGHT ®

SphygmoCor Pulse Wave Analysis System Model SCOR-Px ®

SphygmoCor Pulse Wave Velocity System Model SCOR-Vx Copyright © 2006 AtCor Medical Pty. Ltd., Sydney Australia. All rights reserved. Under the copyright laws, this manual cannot be reproduced in any form without prior written permission of AtCor Medical Pty. Ltd. Printed in Australia. Rev: 1.0/0-CSOG (ENGLISH) DCN: 100599 P/N: 1-00561 ®

SphygmoCor Software Version: 8 Head Office: AtCor Medical Pty Ltd West Ryde Corporate Centre Suite 11 1059-1063 Victoria Rd. West Ryde NSW 2114 (Sydney) Australia Telephone:

+(61 2) 9874 8761

Facsimile:

+(61 2) 9874 9022

Email:

inquiry@atcormedical.com

Web:

http://www.atcormedical.com

European Authorised Representative: AtCor Medical (UK) Ltd Draycott Business Centre Draycott Moreton-in-Marsh, Gloucestershire GL56 OJQ, United Kingdom Telephone:

+(44) 1386 701 700

Facsimile:

+(44) 1386 701 800

DISCLAIMER This manual has been validated and reviewed for accuracy. The instructions and descriptions it contains are accurate for the AtCor Medical product models at the time of this manual’s production. However, succeeding models and manuals are subject to change without notice. AtCor Medical assumes no liability for damages incurred directly or indirectly from errors, omissions or discrepancies between the product and the manual. This Manual is produced on the assumption that the operator is an experienced user of the Windows 98SE/ME/2000/XP operating Systems. If the operator is not familiar with Windows operations, please refer to the On-line Help of Windows or the Windows User Manual.

TRADEMARKS ®

“SphygmoCor ” is a registered trademark of AtCor Medical Pty Ltd. Millar, IBM, IBM PC, Microsoft, Windows, Excel, SPSS, Cidex, PCMCIA and Alconox are the registered trademarks of their respective holders.

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REGULATORY APPROVALS The SphygmoCor System is designed, tested and approved to the following standards:

EC Declaration of Conformity AtCor Medical Pty Ltd, West Ryde (Sydney), Australia Herewith declares that the product SphygmoCor Px Pulse Wave Analysis System Model SCOR-Px SphygmoCor Vx Pulse Wave Velocity System Model SCOR-Vx Described hereafter has been classified as Class IIa (Annex IX Rule 10) and is in conformity with the Annex I essential requirements and provisions of Council Directive 93/42/EEC Annex II.

0120 Signature:

Date:

16/7/01

Place: Sydney, Australia

•

IEC60601-1 (EN60601-1)

Medical electrical equipment with Amendments 1 & 2

Part 1: General requirements for safety (the International Electro-Medical Safety Standard for medical equipment)

•

IEC60601-1 -2 (EN60601-1-2)

Medical electrical equipment

Part 1: General requirements for safety Collateral Standard: Electromagnetic compatibility - Requirements and tests that also requires approval to:

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WARNINGS Before use, operators should ensure that there are no conditions present that would impair accuracy of blood pressure measurement in the radial artery. The radial pulse should be identical in both arms, within the perception of the examining physician, and arterial pressure by cuff sphygmomanometry should be within 10 mmHg systolic prior to use. Since peripheral vasodilatation as in reaction hyperaemia, caused by arterial obstruction, alters brachial wave transmission, at least two minutes should elapse after use of the cuff sphygmomanometer before radial pressure waveform recordings are taken. The system is not applicable in generalised constriction or localised spasm of muscular conduit arteries such as seen immediately after hypothermic cardiopulmonary bypass surgery or accompanying Raynaud's phenomena or intense cold. •

The SphygmoCor process should not be used in persons with significant aortic valve stenosis (gradient >60mmHg)

•

Values of parameters determined from ejection duration when ejection duration values are outside the range 200-400 msec should be disregarded.

•

Values of parameters determined from P1 and T1 should be viewed with caution when T1 is outside the range 80-133 msec.

CAUTION U.S. Federal law limits sale of this device by or on the order of a physician

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Contents Copyright ...3 Disclaimer...3 Trademarks ...3 Regulatory Approvals...4 Warnings ...5

1.

INTRODUCTION ...7 1.1

Px - Pulse Wave Analysis (PWA) ...7

1.2

Vx - Pulse Wave Velocity (PWV) ...7

2.

PWA PROCEDURES...8 2.1

Patient Entry - Select or Enter a New Patient ...8

2.2

entering study details...8

2.3

performing the data capture...9

2.4

examine the report for quality control...10

2.5

Working with the report screens ...12

3.

PWV PROCEDURES...14 3.1

Patient Entry - Select or Enter a New Patient ...14

3.2

perform the study (take a pwv measurement)...14

3.3

examine the report for quality control...17

3.4

working with the report screen...19

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1. INTRODUCTION 1.1

Px - PULSE WAVE ANALYSIS (PWA)

The following is a brief overview of the SphygmoCor® Px Pulse Wave Analysis (PWA) System and a guide to taking pulse wave analysis (PWA) measurements from the radial artery. The SphygmoCor® Px is a non-invasive tool used for assessing and managing cardiovascular risk. The SphygmoCor® Px provides central blood pressures and key heart function parameters for the assessment and management of cardiovascular risk and disease. The SphygmoCor® Px derives a calibrated blood pressure waveform at the ascending aorta from a peripheral pressure waveform, recorded non-invasively at the radial artery. By analysing the shape of the aortic pressure waveform, SphygmoCor can assess arterial stiffness, the degree of systolic afterload, and central systolic and pulse pressures, along with other key parameters important in assessing myocardial perfusion and ventricular function. The SphygmoCor® Px System uses a high-fidelity pressure transducer to non-invasively record the pressure wave at the radial artery. This is achieved by partially flattening the radial artery against the underlying bone in the wrist (applanation tonometry). A validated generalised transfer function is applied to the peripheral pressure waveform to derive the ascending aortic pressure waveform. Key measurements of cardiovascular risk and heart function are calculated from this aortic pressure waveform. The following is a brief step-by-step guide to taking a PWA measurement. For more detailed information, please refer to the Pulse Wave Analysis Software Manual.

1.2

Vx - PULSE WAVE VELOCITY (PWV)

Pulse wave velocity is a well established technique for measuring large artery stiffness. Pulse wave velocity refers to the speed the pressure wave is travelling between two arterial locations, which is directly affected by the stiffness of that arterial segment. Most commonly pulse wave velocity is recorded between the carotid and femoral artery sites to provide a measure of aortic stiffness. However, the SphygmoCor® Vx Pulse Wave Velocity (PWV) System allows pulse wave velocity to be measured between any two superficial arterial locations. For example, recordings can be taken between the carotid and radial arteries, or the femoral and dorsalis pedis arteries to provide measures of the stiffness of the large vessels in the upper and lower limbs respectively. The SphygmoCor® Vx system uses applanation tonometry in conjunction with a 3-lead ECG to take sequential measurements at two arterial sites. The timing of the onset of systole of the pressure waves are compared with the timing of the corresponding R waves on the ECG recording, with the time delay calculated by the software. Pulse wave velocity is calculated as the ratio of the distance travelled (calculated as distance in mm of distal minus proximal, where measures are taken from the suprasternal notch to the sampling site) and the foot-tofoot time delay between the pulse waves and expressed in meters per second (m/s). The following information is a brief step-by-step guide to taking a PWV measurement and assessing the report for quality. For more detailed information, please refer to the Pulse Wave Velocity Software Manual. Page 7

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2. PWA PROCEDURES 2.1

PATIENT ENTRY - SELECT OR ENTER A NEW PATIENT

Open the ‘Patient’ screen by clicking on the ‘Patient’ button, or pressing F2 on your keyboard function keys. This screen will allow you to create a new patient entry or select a patient that is already present in the database. To create a new patient entry, select the ‘Create New’ button and enter the patient details. You can move between the fields by using the Tab key on your keyboard or placing the curser inside the field into which you wish to enter details, and clicking the left mouse button. The following fields are mandatory: ‘Last name’, ‘First name’, ‘Date of birth’, and ‘Sex’. Once you have finished entering the patient details, click on the ‘Update’ button to add the details of the patient to the database. To select an existing patient from the database, you may choose the patient by one of the following means: • Scroll down the list of patients and click on the row to select that patient. If you click on the heading ‘Family name’ at the top of the browser this will place the patients in alphabetical order. When the patient is selected the patient name is highlighted. OR • Place the curser in the ‘Patient Search’ field and enter the patient’s family name. Click the ‘Search’ button or press ‘Enter’’ and the system will select the patient whose family name is the closest match. Ensure the patient you wish to select has been highlighted. Note: Before creating a new patient entry, please check that the patient does not already exist in the database, as separate patient entries cannot be merged.

2.2

ENTERING STUDY DETAILS

While still in the ‘Patient Screen’; select ‘PWA’ mode by clicking on the ‘PWA’ button on the left-hand side of the screen. Open the Study Screen by clicking on the “Study” button or pressing the F3 button on your keyboard. This screen will allow you to enter the study details and to proceed to ‘Capture data’. For measurements taken at the radial artery: • Click the ‘radial’ check box. • Enter the diastolic and systolic blood pressure values that have been obtained from the cuff sphygmomanometer or automatic blood pressure device. • The Medication, Notes, Operator and Anthropometric fields are optional. Note: The patient should be seated comfortably beside a table with their arm resting on the table and their palm facing upward. Allow the patient to rest for approximately 5 minutes before taking the blood pressure. At least 2 minutes should elapse between taking the blood pressure and performing the tonometry reading.

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2.3

PERFORMING THE DATA CAPTURE

To proceed to the capture data screen, click on the ‘Capture Data’ button or press ‘Enter’ on your keyboard. Placement of the tonometer: • Feel for the location of the strongest pulse at the radial artery of the patient’s wrist, and place the tonometer on the skin at this point. The best results are obtained if the patient’s wrist is bent slightly downwards, in the ‘dorsiflex’ position. You may wish to support the patient’s wrist in your hand or place a small pillow or rolled towel under the patient’s wrist for support. • Gently press the tonometer into the skin until a waveform signal appears on the screen. If the trace is off the screen, a straight line will be drawn across the horizontal axis of either the top or bottom of the signal screen, indicating that either too much or not enough pressure is being applied, respectively. • The tonometer should be perpendicular to the wrist and adjustments to the position should be made until a strong, accurate and reproducible waveform is displayed in the ‘Signal detail’ window. This signal will be automatically re-scaled and zoomed to fit the waveform within the signal detail window every 5 seconds. Capturing the waveforms: • Once you have achieved a consistent pressure waveform, hold steady for at least 12 seconds (equal to approximately 3 screen sweeps of waveforms) press the ‘Space Bar’ on your keyboard or click the ‘OK’ button. The ‘Signal for Processing Area’ immediately below the ‘Signal Detail’ window shows the 12 seconds of waveforms that will be captured if you press the Space Bar, allowing you to ensure that the waveforms are consistent. Signal Detail

Signal for Processing

Signal Statistics Page 9

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• You must have a minimum of 12 seconds of signal for the data to be captured. The last 2 seconds of waveforms will be deleted, allowing sufficient time to remove the tonometer from the wrist and activate the capture of data. The software then analyses the remaining 10 seconds of waveforms. Note: For measurements taken at the carotid artery, please refer to Carotid Measurement Technical Datasheet for more information

2.4

EXAMINE THE REPORT FOR QUALITY CONTROL Patient/Study Data

Report Browser

Averaged Aortic Waveform

Report tool-bar

Study Data

Key Parameters Operator Index

Parameter Graphs

After you have completed the data capture, the ‘Report Screen’ will be automatically displayed. This can also be recalled at any time by selecting the patient in the ‘Patient Screen’ and pressing the ‘Report’ button. Three types of report screens are available: Clinical Screen, Reference Range Screen and Detailed Screen. These screens may be selected by clicking on the ‘Clinical’, ‘Reference Range’ or ‘Detailed’ tabs directly above the patient data section. Page 10

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Before proceeding with the interpretation of results it is important to check the quality of the recorded waveforms to ensure data quality. The Clinical and Detailed report provides a number of indices that give information on the quality and reproducibility of the pulse waves captured. Measurements that are not considered to be of sufficient quality should be repeated. For further information on assuring quality of Pulse Wave Analysis Measurements refer to Technical Note No: 14. Quality Control Operator Index The main quality control parameter is the Operator Index. This is displayed on both the Clinical and Detailed Screen. The Operator Index is a number that is calculated from a weighting equation using the four quality indices listed below. The Operator Index range is 0-100. As a general guide, if the Operator Index is ≥ 80 it is considered acceptable. If the Operator Index is between 75-79 it is of borderline quality, and analysis of the Quality Control Indices should be undertaken to determine if the recording is acceptable. If the Operator Index is ≤ 74 the recording is unacceptable and should be repeated. Waveform Overlay and Quality Indices For detailed assessment of the quality of the measurement, the pulse overlay and quality indices should be examined. These are located on the ‘Detailed Screen’. The graph displaying the overlay of captured individual waveforms should be examined to ensure there is as little variability as possible between each waveform. The Quality Indices are presented in green or red, based on limits set using the Configuration Settings in the software (refer to Operators Manual for detailed information on this). The figures will appear in green if they are within the limits and red if they are outside the limits. The Quality Indices are: •

Average Pulse Height – average height of the pulses measured.

•

Pulse Height Variation – amount of variation present in the height of the pulses measured.

•

Shape Deviation – amount of variation present in the shape of the systolic portion of the waveforms.

•

Diastolic Variation – amount of variation present in the diastolic point of the pulse waves and indicates how constant the baseline pressure was during the measurement.

As a general guide the following values for quality indices would be considered acceptable: • • • •

Average Pulse Height ≥ 80 Pulse Height Variation ≤ 5 Diastolic Variation ≤5 Shape Deviation ≤ 2 Page 11

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“Note:” Message The software identifies certain waveforms and labels the report with ‘Note:’ in the top right of the report screen, in the patient and study section of the report. This may occur because the Operator Index is well below the acceptable range or the time of the first peak (T1) is outside the physiological range. Refer to Technical Note 18 for further information on understanding reports with this label. If you have performed more than one reading on a patient, the studies are listed chronologically in the ‘Study Time’ window. The most recent report will be at the bottom of the list. Each of the reports may be viewed by clicking on the study you wish to view. The report being displayed will correspond to the highlighted study in the ‘Study Time’ window

2.5

WORKING WITH THE REPORT SCREENS

The following section provides a brief description of the three report screens available in the software. Note that in all report screens the following functions are available: ƒ Print – prints the report related to the current report screen ƒ Delete – will delete the current study for that patient ƒ Modify – allows the following fields to be edited or details entered: site of tonometry measurement, cuff blood pressure, medication, notes, operator, height, weight, and interpretation. ƒ Export – allows the current report screen to be exported ‘As graphic’ or the current study to be exported ‘As text’. Clinical Screen The Clinical Screen shows the patient and study data that was entered in the Patient Screen and Study Screen. The Average Aortic Pulse, Operator Index and Central Clinical Parameters are all based on the derived ascending aortic pressure waveforms. The Central Clinical Parameters has two sections: •

The first shows the values for Aortic Pressures [systolic/diastolic (mean)], AP, AIx, and HR.

•

The second section shows values, numerical reference ranges and a graphical representation of the patient’s value compared to the reference range for Aortic SP, Aortic PP, AP, AIx@HR75, Ejection Duration and SEVR. o

The reference ranges for Aortic SP, Aortic PP, AP and AIx@HR75 are age related and ranges shown are specific to gender, whilst the SEVR and ED are heart rate related and not gender specific.

o

For the age related graphs (Aortic SP, Aortic PP, AP, AIx@HR75), the bar will change from yellow to green to red depending on the location in the reference range: ƒ Yellow - below the 90% confidence interval (ie lower 5%) ƒ Green - within the 90% confidence interval but below the mean ƒ Yellow - within the 90% confidence interval but above the mean ƒ Red - above the 90% confidence interval (ie. upper 5%). Page 12

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o

For the ED graph the bar will change from yellow to green to red depending on the location in the reference range: ƒ Yellow - below the 90% confidence interval (ie. lower 5%) ƒ Green - within the 90% confidence interval ƒ Red - above the 90% confidence interval (ie. upper 5%)

o

For the SEVR graph the bar will change from red to yellow to green depending on the location in the reference range: ƒ Red - below the 90% confidence interval (lower 5%) and for ALL values of SEVR below 120% ƒ Yellow - within the 90% confidence interval but below the mean ƒ Green - within the 90% confidence interval but above the mean ƒ Green - above the 90% confidence interval (ie. upper 5%).

Detailed Screen The detailed screen also shows the patient and study data that was entered in the Patient Screen and Study Screen. All Quality Control parameters are shown with the waveform overlay. Along with the display of the 10 seconds of captured radial waveforms and derived aortic waveforms, the average peripheral (radial) and aortic waveforms are displayed. Reference Range Screen The Reference Range Screen displays the population statistical comparison graphs for aortic systolic pressure, pulse pressure, AP, AIx, Ejection Duration and SEVR, with each parameter indicating the patient’s position. The AIx graph will indicate the position for both the AIx and AIx@HR75 values of the patient. Clicking on a small graph will change the display so that the selected graph is displayed as the large graph on the screen.

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3. PWV PROCEDURES 3.1

PATIENT ENTRY - SELECT OR ENTER A NEW PATIENT

Open the ‘Patient’ screen by clicking on the ‘Patient’ Button, or pressing F2 on your keyboard. This screen will allow you to create a new patient entry or select a patient that is already present in the database. To create a new patient entry, select the ‘Create New’ button and enter the patient details. You can move between the fields by using the Tab key on your keyboard or placing the curser inside the field into which you wish to enter details, and clicking the left mouse button. The following fields are mandatory: ‘Last name’, ‘First name’, ‘Date of birth’, and ‘Sex’. Once you have finished entering the patient details, click on the ‘Update’ button to add the details of the patient to the database. To select an existing patient from the database, you may choose the patient by one of the following means: • Scroll down the list of patients and click on the row to select that patient. If you click on the heading ‘Family name’ at the top of the browser this will place the patients in alphabetical order. When the patient is selected the patient name is highlighted. OR • Place the curser in the ‘Patient Search’ field and enter the patient’s family name. Click the ‘Search’ button or press ‘Enter’ and the system will select the patient whose family name is the closest match. Ensure the patient you wish to select has been highlighted. Note: Before creating a new patient entry, please check that the patient does not already exist in the database, as separate patient entries cannot be merged.

3.2

PERFORM THE STUDY (TAKE A PWV MEASUREMENT)

While still in the ‘Patient Screen’; select PWV mode by clicking on the ‘PWV’ button on the left-hand side of the screen. Open the Study Screen by clicking on the ‘Study’ button or pressing F3 on your keyboard. This screen will allow you to enter the study details and to proceed to ‘Capture data’. Mandatory fields to be selected or entered: • Click in the box corresponding to the site from where the measurement is to be taken. This is to be done for both Site A and Site B. Site A is the site at which the first measurement is to be taken and Site B refers to the site at which the second measurement will be taken. • Enter the blood pressure (systolic and diastolic, or mean and diastolic) that has been obtained from the cuff sphygmomanometer or automatic blood pressure device. • The Capture Time is set to a default of 10 seconds for both the Site A and Site B measurements. Alternative capture times can be selected for either or both sites if required. Page 14

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• The Distance should be measured and entered as follows: for carotid – femoral and carotid – radial, the distance in millimetres directly between each artery location and the supra-sternal notch are entered in the distal and proximal boxes. In the instance of femoral – dorsalis pedis (Distal Box) the actual measurement between the sites can be entered directly into the PWV box. • The default setting for the PWV algorithm is Intersecting Tangents. For further information on this, please refer to the Pulse Wave Velocity Software Manual and the PWV Algorithm Technical Information Sheet (Technical Note 3). To select a different algorithm, click in the circle next to the corresponding algorithm of choice. • The Medication, Notes, Operator and Anthropometric fields are optional. Note: At present, there is no definitive way to measure the distance between the aorta and the femoral artery non-invasively. As a result there are a number of methods that are used to measure the distance. If there is no existing methodology already in place, it is recommended that the measurement be taken in a direct line between the supra-sternal notch and the femoral artery. Placement of ECG leads: To ensure a stable, artifact free ECG, the skin should be properly prepared (hair removed at electrode site and skin cleaned with an alcohol wipe), and the electrodes positioned correctly. The ECG leads should be positioned as shown in the diagram below. This is a Lead II configuration. The leads can be placed either on the limbs or on the chest area if required for stronger QRS levels). To proceed to the capture data screen, click on the ‘Capture Data’ button or press ‘Enter’ on your keyboard. Once the ECG trace is visible on the screen and is steady, proceed as follows: • Check that the R wave on the ECG trace is the tallest part of each ECG waveform, noting that this may require adjustment of the ECG cables or ECG electrodes. • The tonometer should be placed at the artery defined for Site A and adjustments to the position of the tonometer made until a strong, accurate and reproducible waveform is displayed in the ‘Signal Detail’ window. This signal will be automatically re-scaled and zoomed to fit the waveform within the signal detail window every 5 seconds. • When you are satisfied that you have a good reading, press the ‘Space Bar’ on your keyboard or click the ‘OK’ button at the top of the screen. • You must have a minimum of 12 seconds of signal for the data to be captured (minimum of 22 seconds or 32 seconds if you have selected a capture time of 20 or 30 sec in the Study Screen). The last 2 seconds of waveforms will be deleted, allowing sufficient time to remove the tonometer from the artery and activate the capture of data. Page 15

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• A prompt window will appear confirming that the signals have been captured successfully. When you are ready to proceed to take the reading at Site B, click the OK button or press ‘Enter’ on your keyboard. If you wish to take the reading again, click No and repeat the reading at Site A. • Repeat the process by placing the tonometer on the artery defined for Site B and proceed with the capture when you have obtained a signal of satisfactory quality. A prompt box will appear to confirm that the signal was captured successfully. If you are satisfied with the reading at Site B and wish to proceed to the report, click OK. If you wish to repeat the reading at Site B, click No and repeat the reading at Site B. Note: Remember that the signal representing the tonometer waveform for Sites A & B should be the arteries selected in the ‘Study Screen’. Signal Detail Area

Signal Statistics

Signal for Processing

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3.3

EXAMINE THE REPORT FOR QUALITY CONTROL

After you have completed the data capture, the Report Screen will automatically be displayed. This can also be recalled at any time by selecting the patient in the Patient Screen and pressing the ‘Report’ button. Check that information was entered correctly on the Study Screen. If the patient data is incorrect, click the patient tool-bar button to return to the Patient Screen and update patient details. If the study data is incorrect, click the ‘Recalculate’ tool-bar button to open the SphygmoCor Recalculate Report window. This window allows you to change any of the details that you entered in the Study Screen before you performed the data capture. Before proceeding with the interpretation of results it is important to check the quality control to ensure that your measurement has been recorded with sufficient quality. Therefore the Quality Control parameters suggested here are to provide a guide to the quality of the reading rather than provide a cut-off value to accept or reject data. Measurements that are of an unacceptable quality should be repeated. Quality Control checks: • The tonometry waveforms should be clear and smooth and it is important that the foot of the waveform is easily identified. The quality control parameters used in PWA may assist in assessing the quality of the tonometry waveform and are displayed to the right of the waveforms. The green dots on the waveforms indicate the marker for calculating timing from the waveform to the ECG (onset points) and it is important that these are in a similar location on each waveform. • The R wave on the ECG should be the tallest part of the ECG trace and the green dots should be located at the top of the R wave and not on any other part of the ECG trace. • The software requires a minimum of 3 pairs of data (ie. time recorded between the corresponding waveform and ECG trace) to calculate the result, if there are less than 3 pairs of data accepted, the software will not calculate a PWV reading. • The SD(ms) in the statistical table should be below 6% of the mean time. If the SD is above 6% it will appear in red. • It is recommended that PWV value should have a SD ≤ 10%. A SD between 10% and 15%, is borderline and waveforms should be carefully examined before making a decision as to whether to repeat the reading. For a SD above 20% a repeat reading is recommended. The SD of the PWV and mean time provide an indication of how consistent the data is and may include some biological variation that is inherent in the reading. Note: If you have performed more than one reading on a patient, the studies are listed chronologically in the ‘Study Time’ window. The most recent report will be at the bottom of the list. Each of the reports may be viewed by clicking on the study you wish to view. The report being displayed will correspond to the highlighted study in the ‘Study Time’ window.

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Patient/Study Data

Report Browser

Graph of ΔΤs

Report tool-bar

Site B Waveform Site A Waveform Statistical Table & ECG & ECG

Quality Control

Carotid – Femoral Reference Range

Additional comments on performing carotid and femoral measurements: Carotid Measurement: The patient should be lying on a bed with their head tilted slightly to the back and to one side (either left or right). This is best achieved in the absence of a pillow. The operator should feel for the position for the strongest pulse and place the tonometer directly on the top of the skin at this point. The operator can be standing or seated behind the patient’s head or standing to one side. A pillow may be placed across the shoulder of the patient to allow the operator to rest their forearm to ensure that the tonometer and wrist remain steady during the measurement. Femoral Measurement: The patient should be lying on a bed. The femoral pulse is best felt by pressing directly backward at a point that is midway between the anterior superior iliac spine and the front of the pubic bone, with the thigh flexed at the hip joint, moved away from the midline of the body and rotated away from the body.

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3.4

WORKING WITH THE REPORT SCREEN

The following section provides a brief description of the report screen, with the following functions available on this screen: ƒ Print – prints the report related to the current report screen ƒ Delete – will delete the current study for that patient ƒ Recalculate – allows the following fields to be edited or details entered: site of tonometry measurement, cuff blood pressure, PWV path distance, medication, notes, operator, height, weight, and interpretation. ƒ Calculate a PWA Report – allows you to create a PWA report from a carotid or radial recording. Once calculated, the report can be viewed in PWA mode on the Report Screen for the patient. ƒ Export – allows the current report screen to be exported ‘As graphic’ or the current study to be exported ‘As text’. The raw waveform and ECG data from Site A and Site B are shown. The location of onset points used in calculating time differences between the ECG and tonometry waveforms are shown for each site. To the right side of each the waveforms are the corresponding quality control parameters similar to the information provided in PWA mode. A graphical representation of the ∆Ts (time difference) for each site for the pressure-ECG waveform pair over the complete capture period is shown at the bottom left of the screen. The dots provide a visual indication of how variable the individual time differences are over the complete capture period. The statistical table provides the following measures: • • • •

MeanT (ms) - mean ∆T over the capture period for each pressure-ECG waveform pair. SD (ms) – Standard Deviation of ∆Ts. N – the number of onset pairs used to derive the MeanT, SD and PWV values. HR (bpm) – heart rate.

The Pulse Wave Velocity for the study is shown immediately below the statistical table and uses the MeanT and PWV distance for the final calculation (the standard error of the mean (SEM) is also shown. A graphical illustration of the patient’s PWV compared to normal PWV values plotted by age for the carotid-femoral arterial pathway is shown on the bottom-right of the screen.

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