purpleDx

Issue 8 - Updated 23rd June, 2025

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1.0 User Manual / Instructions for Use

These Instructions for Use are supplied electronically. A paper format is available on request. To receive a hard copy of the Instructions for Use please email admin@electronrx.com with the designated address.

Please read these Instructions carefully before using the application.

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2.0 Intended Use

purpleDx The device is intended to obtain readings of the vital physiological signals heart rate and respiratory rate, for self-monitoring at home.

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3.0 Indications for Use

The device is intended to be used by consumers in the home environment.

It is suitable for use by adults.

Heart rate measuring is intended to only be used by individuals with skin tones I to IV on the Fitzpatrick Scale.​

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4.0  Environment

The application is intended to be used by the patient in a non-specialised environment.

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5.0 Limitations

The following limitations apply to measurements given by the application:

•   Heart rate can only be measured in the range of 50 to 120 beats per minute;

•   Heart rate measurements are accurate to ±5 beats per minute or ±15%, whichever is highest;

•   Respiratory rate can only be measured in the range of 6 to 20 breaths per minute;

•   Respiratory rate measurements are accurate to ±10% or ±2 breaths per minute, whichever is highest.

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6.0 Contraindications

There are no known contraindications.

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7.0 Warnings

•You must not use this app to make any medical decision, including altering your medication or treatment.

• You must seek professional medical advice before making any medical decision.

• purpleDx cannot detect any event or conditions, including but not limited to heart attacks, ischemic conditions, and respiratory conditions. If you experience any symptoms, seek professional medical advice. If you experience symptoms of heart attack (including chest pain, pressure, or tightness), call emergency services.

• purpleDx is not intended to detect, diagnose or measure the progress of any specific condition.

• Do not use purpleDx in a critical care situation.

• Do not use the application while driving.

• The application is not to be used by patients under 16 years old.

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8.0 Precautions

• Ensure the phone used is fully functional. Any errors resulting from using an unsuitable phone or device are the user’s responsibility.

• purpleDx is only intended to be used on the following devices:

◦ iPhone 15, iPhone 15 Plus, iPhone 15 Pro, iPhone 15 Pro Max

◦ iPhone 14, iPhone 14 Plus, iPhone 14 Pro, iPhone 14 Pro Max

◦iPhone 13 mini, iPhone 13 pro max, iPhone 13 pro, IPhone 13

◦ iPhone 12 pro max, iPhone 12 pro, iPhone 12"

• purpleDx is only intended to be used on iOS versions 17 and 18.

 

The following factors may affect the accuracy of measurements made using purpleDx:

• Not to be used by people with skin tones V or VI on the Fitzpatrick Scale.

• Not to be used by patients with facial tattoos.

• Not to be used if the face is obstructed e.g. by hats, glasses, beard etc.

• Not to be used whilst wearing makeup that could obscure the skin.

• not to be used whilst wearing clothes that obstruct the view of chest movement.

• Not to be used by patients with a disability that prevents them performing measurements according to the Instructions for Use.

• Do not perform measurements if the camera lens is unclean or broken.

• Not to be used by patients with reduced blood flow to the face.

• Not to be used after exercising

• Not to be used in light levels outside of the range 250 – 1500 lux. Here are some examples of these light levels in practice:

◦ 250 lux – well-lit indoor spaces with artificial ceiling lighting and low external light through windows

◦ 1500 lux – well-lit indoor spaces with direct white LED illumination with some indirect sunlight through windows

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9.0 Serious Incident Reporting

Any serious incident that occurs in relation to purpleDx should be reported to electronRx and the Medicines & Healthcare Products Regulatory Agency (MHRA).

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10.0 Instruction Manual

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10.1 Login Screen

The Login Screen is allows users to access their account securely. To log in:

•  Open the App – Launch purpleDx on your device.

•  Enter Email – Type your registered email address in the Email field. Ensure that the email is correctly formatted (e.g., user@example.com).

•  Enter Password – Input your secure password in the Password field. Passwords are case-sensitive.

•  Login – Tap the Login button to access your account.

•  Forgot Password? – If you cannot remember your password, tap "Forgot Password?" and follow the instructions to reset it.

•  New Users – If you do not have an account, tap "Sign Up"  to register for a new account.

For security reasons, repeated failed login attempts may result in temporary account lockout. Ensure your credentials are entered correctly.

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10.2 Create an Account

The Sign-Up Screen allows new users to create an account. To create a new account:

•  Open the App – Launch purpleDx on your device.

•  Enter Email – Provide a valid email address in the Email field. The email must be correctly formatted (e.g., user@example.com) and not already associated with an existing account.

•  Create a Password – Enter a secure password in the Password field. Passwords must meet security requirements (at least 8 characters long, at least one upper case and one lower case, a number and a special character).

•  Agree to Terms & Policies – Read and accept the Terms & Conditions and Privacy Policy by checking the provided box. You can read Terms & Conditions and Privacy Policy by clicking on the hyperlink links. You must agree to proceed with account creation.

•  Sign Up – Tap the Sign Up button to create your account.

•  Once registered, you can log in using your email and password.

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10.3 Main Screen

The Main Screen serves as the main navigation screeen to access key features and information quickly.

From the bar menu, users can:

•   Access Instructions for Use – Tap the "Instruction" button to view the Instruction for Use (IFU) document, which provides guidance on using the app’s features.

•   Manage Profile & App Information – Tap the "Profile" button to access your user profile and app-related details an information. And account settings and preferences.

•   Return to Main Screen – Tap the "Main" button at any time to navigate back to the Main Screen

From the Main Screen, users can also start a new measurement by tapping the "Measurement" button.

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10.4 Instructions For Use Screen

The Instructions For Use Screen shows all the instructions on how to use the app to take a recording.

Use the back arrow button to navigate back to the Main Screen.

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10.5 Profile Screen

The Profile Screen allows users to manage their account settings, access important legal information, and perform account-related actions.

•   Access Terms & Conditions – Tap the "Terms & Conditions" link to review the app’s usage policies.

•   View Privacy Policy – Tap the "Privacy Policy" link to understand how your data is collected, stored, and used.

•   View Label – Tap the "About" section to view app label.

•   Log Out – Tap the "Log Out" button to securely sign out of your account.

•   Delete Account – Tap the "Delete Account" option to permanently remove your account and associated data. A confirmation will be required to proceed.

Note: Once an account is deleted, all associated data will be permanently erased and cannot be recovered. Ensure you have backed up any important information before proceeding.

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10.6 Terms and Conditions

The Terms and Conditions Screen contains information about the app usage policies that will need to be agreed to use the app.

Use the “Done” button at the top left corner to navigate back to the app. The full content can be read by scrolling down to the bottom.

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10.7 Privacy Policy

The Privacy Policy Screen contains information about how data is collected, stored, and used. Privacy policy will need to be agreed with the Terms and Conditions to use the app.

Use the “Done” button at the top left corner to navigate back to the app. The full content can be read by scrolling down to the bottom.

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10.8 Guide Screen

The Guide Screen display an instructional guide for taking a good recording, each with an image demonstrating the correct procedure.

The top left of the screen has a back arrow button that navigates back to the Main Screen. Use the “Start” button to progress to the Recording Screen and take a recording.

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10.9 Recording Screen

The Recording Screen displays when a recording is being taken. The screens display the camera output with user feedback indicators overlaid. See Section 11.0 for recording tips.

The recording screen is overlaid with an oval window to guide the user for optimal face location. Use the back button in the top left corner to stop the recording and navigate back to the Guide Screen. Text may appear on the screen to help with taking the recording. "The text may be one of the following: “Starting”, "Measurement is about to start", “Face too far away”, “Face too close”, “Please position your face in the oval”, “Face in correct position Measurement in progress” or “Camera waiting for your face”. The countdown timer shows how much time is left until the recording finishes."

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A completed recording will automatically take the user to the Results Screen.

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Important Note: If the app is being used for the first time, a dialog box will appear requesting camera permissions. Users must accept camera access to enable measurement recording. If permission is denied, the measurement feature will not function.

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10.10 Results Screen

The Results Screen displays the recorded measurement results, including:

·   Average Heart Rate (HR): Measured in beats per minute.

·   Average Respiratory Rate (RR): Measured in breaths per minute.

 

Out-of-Range Measurements

For accuracy and reliability, the app provides exact values only within a validated range:

·   Heart Rate: 50 to 120 beats per minute

·   Respiratory Rate: 6 to 20 breaths per minute

If the calculated measurement falls outside these ranges, the app will display one of the following messages instead of an exact value:

·   "Calculated heart rate is 50 beats per minute or lower."

·   "Calculated heart rate is 120 beats per minute or higher."

·   "Calculated respiratory rate is 6 breaths per minute or lower."

·   "Calculated respiratory rate is 20 breaths per minute or higher."

 

Why Out-of-Range Values Are Displayed as Ranges

The app is designed to provide reliable measurements within the validated range of 50–120 beast per minute for heart rate and 6–20 breaths per minute for respiratory rate. Measurements outside these limits may be less accurate due to technical limitations, such as:

·   Variability in camera-based measurements when detecting extreme values.

·   Motion artifacts affecting signal quality.

·   Individual physiological differences that may require medical-grade equipment for precise readings.

To ensure user safety and prevent misinterpretation, extreme values are grouped into predefined ranges instead of displaying potentially inaccurate numbers. If a measurement appears significantly abnormal or unexpected, users should consult a healthcare provider.

Low Signal Quality Warning

If the recording quality is insufficient, the app will display a message indicating that the signal quality was low. The measurement should be repeated for accurate results.

Use the "Finish" button at the bottom of the screen to navigate back to the Main screen.

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11.0 Tips for Taking A Good Recording​

This section describes the steps required to increase the likelihood of taking a good recording and reduce unnecessary complications regarding receiving an accurate and reliable result.

•   Take recordings in a well-lit room.

•   Remove any hats, sunglasses or any other items of clothing that could prevent the camera from seeing your face.

•   Wear minimal or no makeup, or anything else on your face that could prevent the camera from taking an accurate recording.

•   Make sure the front camera lens is clean and unobstructed for the clearest possible image.

•   Place your face within the oval on the screen at the start of the recording and keep it in the same location for the entirety of the recording.

•   Do not speak or make any facial movements.

•   Stay focused on the recording and remove local distractions to reduce the risk of unexpected movement.

•   Stay as still as possible. The best way to do this is by taking the recording in a seated position with your elbows and back resting against the seat.

•   Keep the camera still during the recording. This is best done by using a phone stand or supporting it with an object on a table.

•   Retake the recording and start again if, at any point in the 60 second recording window, you think that the quality of the recording has been affected.

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12..0 General Information

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12.1 Explanation of Symbols

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