Month: November 2020

1) Severity table used for risk assessment – with score definitions 

Severity Table

Rating	Severity of Effect	Future consequences	Treatment
10	Death	–	–
9	Cardiac Arrest	Cardiac Tissue Damage	Use a Defibrillator
8	Arthymea	Unstable Heart Rate	Reset heart rhythm
7	Pulmonary Embolism	Lung cell death	Lung surgery
6	Severe Skin Burns	Permanent tissue damage, scarring	Burn treatment, and surgeries
5	DVT Formation	Vessel Damage	Anticoagulant medication
4	Mild Skin Burns	Tissue Damage, Scarring	Burn treatment,
3	Skin Burns from electric shocks	Tissue damage	Heals over time.
2	Severe Skin Irritation	Long Lasting Discomfort	Remove Irritant, Cortical Lotion
1	Mild Skin Irritation	Mild Discomfort	Remove Irritant

2) Occurrence table used for risk assessment – with score definitions 

Rating	Probability of Occurrence
10	Happening every use
9	Happening every other user
8	1 in 5
7	1 in 10
6	1 in 50
5	1 in 100
4	1 in 500
3	1 in 1000
2	1 in 5000
1	Inconceivable

3) RPN table used for risk classification 

4) Hazard and risk assessment spreadsheet – with score justifications 

Hazard	Chain of Events	Hazardous situation	Potential Harms	Severity	Probability	Risk
Battery Explosion	Overtaxed power supply, Overheated Battery, failure of battery controller. Batteries get wet	Battery incineration	Skin burns	Serious  (6)	Improbable(1)	R2
Electric shock	Circuit malfunction, Circuits get wet, Physical damage to device creates open circuit.	Electric shock	Skin burns	Minor(3)	Improbable(1)	R1
Skin irritation	LED lights react to skin, camera reacts to skin, rough material to the skin	Reaction between the skin and some parts of the device	Reddening and inflammation, which Skew the results	Negligible (1)	Occasional (6)	R2
Wrong data collection – O2 levels	Device disconnects from Oximiter.	Low O2 stats present without detection	DVT Formation, Pulmonary Embolism, Vessel Damage	Critical (7)	Improbable(1)	R2
Wrong data collection – inflammation levels	Device Dysfunction inflammation	Inflammation without detection	DVT Formation, Pulmonary Embolism, Vessel Damage	Critical(7)	Improbable (1)	R2
LED Burns	Arduino malfunctions increase the time of LED light exposure	High temperature	Damages skin	Negligible (1)	Improbable (1)	R1
Cut blood circulation	Device is too tight, device is too small for the user to use	Reduction in blood circulating to lower extremities	Increase vessel damage and clotting	Critical (7)	Remote(3)	R2

5) Mitigation, as needed

Hazard	Mitigation technique
Battery Explosion	Microcontroller that checks voltage overshoot and shuts off power.
Electric shock	Ground the device, Protect the device circuits from water
Skin irritation	Instruct medical practitioners to check with patients for any discomfort regularly.
LED Burns	The frequency of what we measure will depend on the time the LED takes to cool down to room temperature.
Cut blood circulation	Instruct medical practitioners on proper technique to tighten and secure device fittings.

Safety Survey form completed and signed off by advisor.

wiring		1	N/A	$5.00
Sony Spresense 5MP Camera Board	Adafruit/ Sony	1	4417	$35.00
3d printed brace		1	N/A	$10.00
adjustable component(We did not on how to best do this.)		1	N/A	$10.00
HiLetgo HC-05	HiLetgo	1	8541554474	$7.99
fabric for comfortability (We did not on how to best do this.)		1	N/A	$5.00
Battey Pack (Lithium Polymer 16000mAh) (for testing)	REV	1	REV16000	$0.00
OpenMV Cam H7 – MicroPython Embedded Vision + Machine Learning (Maybe)	Adafruit	1	PRODUCT ID: 4478	$65.00
Switch from TCNJ Labs		1	N/A	$1.00
White LED Backlight Module – Large 45mm x 86mm	Adafruit	1	1621	$2.95
Arduino(Prob esp8266 feather weather huzzah)	Adafruit	1	2821	$16.95
OxySmart™ Fingertip Pulse Oximeter (for testing)	Wellue	1		$49.00
Light Blocker		1		$5.00
Battery pack()
Total for Project				$212.89

1. Electrical Safety & Testing UNE-EN 60601-1-12:2015

Link: https://drive.google.com/file/d/1hZYfmD98XaBcHyK2A0W9vxkIC-0Y50SJ/view?usp=sharing

The device will likely use a battery of low voltage for power. The power itself is not harmful. However, this standard also addresses the safety of using rechargeable batteries in medical devices as they could ignite if certain conditions are met. The standard also puts guidelines for storing and in the case of continuous usage of electrical devices

Relevant parts are:

4.2.1 (environmental considerations during transport and storage for electrical devices)

4.2.2.1 (operating period is less than 20 minutes)

6.2 (Protection of hardware from damage)

6.3.1 (Indications of use on the device)

6.3.2 (battery life must be calculated)

6.3.3 (Device startup procedure)

8.3 (Continuous indication of the state of power)

2. Oximetry standards(ISO 80601-2-61 Second edition 2017-12 (Corrected version 2018-02) Medical electrical equipment – Part 2-61: Particular requirements for basic safety and essential performance of pulse oximeter equipment)

Link: https://drive.google.com/file/d/1L-cJqoC-HMEVvTGFa5ww03OIujjUbQ6O/view?usp=sharing

This standard covers basic safety and essential performance of pulse oximeters. We are mostly interested in testing the accuracy and safety of pulse oximeters that we want to use. Relevant parts are: 

201.7.4.3 (Units of measurement)

201.10.4 Lasers

201.11 Protection against excessive temperatures and other HAZARDS

201.11.6.5.101 Additional requirements for ingress of water or particulate matter into

ME EQUIPMENT or ME SYSTEM

201.11.8.101.1 TECHNICAL ALARM CONDITION for power supply failure

201.12.1.101  SpO2 ACCURACY of PULSE OXIMETER EQUIPMENT

201.12.1.101.1   Specification

201.12.1.101.2   Data collection for determination of SpO2 ACCURACY

201.12.1.101.3   Data analysis for determination of SpO2 ACCURACY

201.12.4.101   DATA UPDATE PERIOD

201.12.4.102   Signal inadequacy

201.103.2   Connection to electronic health record

EE.3 (Non invasive accuracy testing of pulse oximeters)

Annex GG (informative) Concepts of ME EQUIPMENT response time

Annex HH (normative) Data interface requirements

3. Re-sterilizability (ISO 17664:2004)

Link: https://drive.google.com/file/d/1VCxNX5wsAhe4FguwHZtTCq4Z9qQiB8ei/view?usp=sharing 

Cleaning, disinfecting and sterilizing is important so that when the medical device is being reused that risk of infections are minimized. This document lists requirements for the medical device manufacturer to use to ensure their device is clean and reusable. 

1 Scope (Lists the requirements to be checked by the manufacturer) 

4.1 – 4.3 Validation of the processes for each of the requirements

6.2 Processing Instructions 

6.6 Cleaning (Automated and Manual)

6.7 Disinfecting (Automated and Manual) 

6.8 Drying

6.9 Inspection and Maintenance

6.10 Packaging

6.11 Sterilization 

6.12 Storage

6.13 Transportation 

Annex A – Commonly used processing methods 

Annex B – Example of processing instructions for reusable medical devices

Annex C – Classification of medical devices 

Using these, we will take into account that the device will be easily maintainable in cleanliness and maintenance. These standards will be useful for our requirement of having little to no skin irritation as well as allow the device to be reusable after every use. 

4. Integrating/Interoperability medical devices standards : ASTM F2761-09 (2013) Medical Devices and Medical Systems – Essential safety requirements for equipment comprising the patient-centric integrated clinical environment (ICE) – Part 1: General requirements and conceptual model

Link: https://drive.google.com/file/d/1khRMujI0EgfChK1KXbB05JiIWJf2EjlY/view?usp=sharing 

This document is to layout the interface of the medical device with the patient to the physician/nurse. It represents the inputs and outputs of integrating the readings that the device will measure from the patient to the user. 

4 Conceptual Functional Model

4.2 Network Controller (Interfaces)

4.3 Supervisor 

4.4 Equipment Interface

5.1 Risk Management Process

5.2 Equipment Interface qualification test

5.3 Software

5.4 Communication management 

5.5 Alarm system 

These standards will be used to fulfill several of our requirements, measuring systemic oxygen saturation levels, detection of inflammation on the skin surface, as well as notify the user if any of these parameters are outside their thresholds. In addition, using these standards will be used for ensuring the readings are able to be interpreted with a quality interface for the user to read when monitoring the patient. 

5. Standard: Health informatics Digital imaging and communication in medicine(DICOM) including workflow and data management (ISO 12052:2017)

Source: ISO

Link:https://drive.google.com/file/d/1q2jTtMMB8Hck-9bF8CrrJ9zYGO12avo_/view?usp=sharing 

This device will likely use a form of imaging technology to acquire medical images. Since this device will be possibly storing or transmitting medical images of human patients it falls under the guidelines of this standard that address how sensitive medical images should be encoded and stored in data structures as well as proper protocols for sending images electronically.

6.5 PS3.5 (Address the specific data compression techniques and protocols to loosely compress medical images so they can be stored)

6.8 PS3.8: (Address the services and protocols that can be used to transmit sensitive medical images over through a network such as the internet connection found in hospitals)

6.10 PS3.10: (Address the proper formatting of files when being stored on removable media such as an SD card)

6.12 PS3.12: (Address specifically the properties of hardware that can be used to safely and securely store medical images so they aren’t corrupted or stolen)

This standard will be used to create a new requirement addressing the data security of the medical device. This requirement will have two specifications one addressing the security of any kind of data transfer of medical images from the device to external systems, and a specification dealing with the security of hardware used in the device to store medical images safely. 

6. Medical device software Software life-cycle processes (IEC 62304:2006)

Source: IEC

Link:https://drive.google.com/file/d/1ERiiIgBgGyBUGlLqMGK-BqWpUfRjKPp_/view?usp=sharing 

This device will have to perform some form of signal or image analysis to assess DVT risk. Since the risk assessment component of this device may contain software that analyzes medical images it falls under the guidelines of this standard which addresses the overall process of verifying that medical software was designed and maintained properly. 

5.1.3 (Address testing procedures to valid that any kind of development plan for medical software)

5.1.6 ( Address procedures for verification testing of medical software)

5.2.6 (Address procedures for verification testing of medical software with host system)

5.6.2 (Address procedures for verification testing of software security)

This standard will be used to design the verification testing procedures for the medical software in the device. This verification testing will need to meet the requirements of this standard addressing the security and integrity of the software. It will also address the requirements for ensuring that the software is compatible with the hardware and host system software that the device runs. It will also create verification procedures for whether or not the software accomplishes the results needed to fulfill the requirement dealing with erythema detection. 

Type	Constraint	Justification	Requirement/Specification
Global and ethical	The device must work with skin tones from all over the world. This is also an ethical constraint.	Skin tone ranges can vary between countries this device must work just as well for all ranges to be used anywhere.	Add specification, which states that the device can perform just as well (within 5% deviation) on all skin tones from around the world.
Global	The device must present the information using different measurement systems from all over the world.	Not doing so might lead to conversion errors and a harm to the patient.	Add Specification the device must have a UI that allows users to adjust the measuring system.(Metric and Imperial systems are enough).
Economic	The device must be affordable.	Current DVT treatments can be expensive and can exclude individuals from getting the care they need.	The ability to diagnose early should be cheaper than the current treatments.
Environmental	The device must be rechargeable.	One time usage battery manufacturing produces way more green gases than rechargeable ones.	Add Specification for the device’s battery must be able to function for at least 500 recharge cycles.
Social	The device does not have any social constraints.	Intended use in the hospital only, doesn’t affect the patient’s quality of life.	Does not Exist.
Political	The device can be manufactured using common parts that are widely available around the world.	This is in order to surpass sanctions that can be imposed on other countries.	Add Specification parts used for imaging and compatible oximeters must be available to all major countries.
Safety	The device is electrically secure.	Electrical surges might be lethal or harm the patient.	Has to comply with the relevant parts of IEC 60601-1-11:2015. This is a specification for a new requirement for electrical safety.
Manufacturability	The design has to be valid for mass manufacturing.	Mass manufacturing is essential to benefit as many people as possible.	Easily repeatable parts that do not require very specific machinery to make. This is a new requirement.
Sustainability	Can be used with multiple patients.	The device shouldn’t be one time use as that can cause a large waste in materials and manufacturing efforts.	Add Requirement the device electrical components should be built protected so the device can be sterilized and reused.

1. The device must be able to detect inflammation presented on the skin surface for all different skin tones

Justification:-

Skin discoloration is a symptom of reduced blood flow, which is a correlate for DVT. 

Specifications:-

1.1) The device correctly identifies  presentation of erythema from digital images regardless of skin tone over 85% of the time.³

Verifications:-

1.1) Test the algorithm using a new dataset of skin images and verify that 85% of true positives are identified.

2. The device must be able to obtain the patient’s Hemoglobin bound Oxygen Levels.

Justification:- 

Systemic O₂ levels are related to blood clot formation.

Hemoglobin bound Oxygen accounts for 97% of Systemic Oxygen.

Specifications:-

2.1) Obtains measurement at 1Hz from hospital oximeter.⁵

Verifications:-

2.1) Find the frequency at which the oximeter is taking measurements to ensure it’s no less than 1Hz.

3. The device must accommodate a wide range of sizes to match the user.

Justification:- 

A wide range of sizes will allow the device to be worn comfortably as well as prevent the device interfering with DVT assessment.

Specifications:-

3.1) Ankle (Mean ± SD)

Male: 23.5 cm ± 1.5 cm (19.0 – 28.0 cm) 

Female: 21.9 cm ± 1.3 cm (18.0 – 25.8 cm)

3.2) Must be able to adjust circumference to accommodate the location’s size

Verifications:-

3.1 & 3.2) Verify that the size of the device will be incrementally changeable to accommodate the desired ranges by measuring the device’s length’s. 

4. The device must have sufficient battery life to monitor the patient’s stats for long periods of time.

Justification:- 

A long battery life will allow for continuous monitoring of patients without disruption.

Specifications:-

4.1) More than 12 hours to allow changing of nurse shifts.

Verifications:-

4.1) Measure power consumption of the device and its constituent parts using a LabView model and/or test the physical parts specifications.

5. Device must cause little to no reaction to the skin of the patient.

Justification:- 

Reactions to the skin can cause interferences with monitoring results and can change patient DVT detection.

Specifications:-

5.1) The power delivered to the skin from the LEDs is less than 180 mW/cm² at a rate of 0.2 mJ/cm².⁶

5.2) The material used that contacts skin should be compliant with ISO 10993-10:2010(E)⁷.

Verifications:-

5.1) Measure the power output from the LED’s dedicated device to ensure it remains within desired range. 

5.2) Place material on participant skins and check for discoloration, damage, and inflammation. 

6. The device must be able to alert healthcare workers when DVT risk reaches threshold level set by healthcare workers.

Justification:- 

Alerting healthcare workers will allow for preventive measures to be taken and prevent further clot formation and damage to the blood vessels.

Specifications:-

6.1) Trigger alarm within <1s when the threshold is reached.

6.2) SpO₂ threshold can be set between 95% and 98% with 1% resolution.

6.3) Erythema threshold can be set between 10-25% of the area of the skin displaying inflammation with 1% resolution.

Verifications:-

6.1) Time the delay between the artificial triggering of the device and the triggering of the alarm. 

6.2) Test that the device SpO₂ threshold can be altered by a user within the given ranges and resolution.

6.3) Test that the device erythema threshold can be altered by a user within the given ranges and resolution.

7. The device must remain comfortable to wear.

Justification:- 

User comfortability is important as the user will be wearing the device for long periods of times, at least 12 hours.