Design input requirements typically can be sorted into 3 categories. These requirement categories are: functional, performance, and interface. Functional requirements specify what the device does, which includes its operational characteristics, and input processing and resulting outputs. Performance requirements specify use characteristics, which includes speed, strength, and response times. Interface requirements specify essential compatibility with external systems characteristics. Being able to differentiate between these categories ensures a better understanding of the product as it shifts a person’s mindset from a concept to a design. These requirements are essential to a successful product commercialization because they are the basis of the design verification and validation phases.
Provide at least one example of each requirement category for a medical device of your choosing.
One of the functional requirements for an artificial cervical disc is that it should permit the cervical spine to move in a manner that is comparable to that of a healthy natural disc, including flexion, extension, lateral bending, and rotation.A prime example of a performance criterion is that the prosthetic cervical disc must be able to bear the loads and biomechanical stresses that the cervical spine experiences on a daily basis.In order to meet the conditions for interference, we must demonstrate that the device cannot negatively interact with the patient's immune system or the tissues around it.
The medical device that I will be discussing is the digital blood pressure monitor.
The functional requirement of this device would be that the device should accurately measure systolic and diastolic blood pressure values and accurately output the heart rate of the user. An additional functional requirement of this device is that the device should record the last few readings of the users so that the user has the ability to view their blood pressure and heart rate readings if they choose to view it.
A performance requirement for this device is that the measurements should be outputted almost instantly after recording the values. Additionally, the device should have a decent battery life so that it can be sustained for a longer time. Lastly, the device should be accurate in its readings. Meaning, the margin of error should be 2-5 readings away from the actual value.
An interface requirement for this device is that it should be user-friendly, especially since many users will not have any medical background knowledge. The device should have a clear LCD display with easy-to-use instructions and it should be easily connectable with a smartphone so that the user can have access to history of readings or maybe remote access.
A heart monitor is a device that adheres to a patient's chest for a specified amount of time and records their heartbeat in that duration. A functional requirement is that it must be able to accurately obtain data on the electrical signals from the heart through electrodes. This is it's essential function, so its the most important specification. A performance requirement could be a specified sampling rate. How many samples per second is ideal for the heart monitor. It cannot be so high that there a lot of unnecessary data comes through and takes up storage on the small device, but it cannot be so low that results cannot be interpreted from the data obtained. An interface requirement is that it must have a method to transfer data to another device, like a computer. This could mean that the device has a port for a direct connection or has a method for the data to transfer wirelessly.
A device that has really had my attention for a while and of one I want to discuss in this forum is the Left Ventricular Assist Device also commonly known as the LVAD. The functional requirement of the LVAD is to act as the name suggests, which is to help send oxygenated blood from the bottom left chamber (ventricle) of the heart to the aorta which further carries the blood away from the heart to other parts of the body. The LVAD should be capable of adjusting the pumping speed based on the patient's physiological needs, such as changes in activity level or heart rate. The device should also have a fail-safe mechanism to prevent over-pumping or under-pumping. The performance requirement consists of the amount of blood it should be able to pump or how consistently it should pump without altering or creating other side effects such as large noises. Physiologically it should be compatible with various surgical implantation techniques and be designed to integrate seamlessly with the patient's circulatory system. It should have a user interface for healthcare providers to monitor and adjust pump settings, as well as a patient-friendly interface for self-monitoring and troubleshooting.
Certainly! Let's consider an example of each requirement category for a medical device:
-
Functional Requirement:
- Example: For a medical infusion pump, a functional requirement would be to precisely control the rate of drug delivery. This includes specifying the pump's ability to accurately administer a set volume of medication per unit of time.
-
Performance Requirement:
- Example: In the case of a medical imaging device (such as an MRI machine), a performance requirement could be the spatial resolution. It may specify the level of detail the imaging system needs to achieve in terms of visualizing structures within the human body.
-
Interface Requirement:
- Example: Consider a patient monitoring system used in a hospital. An interface requirement could involve compatibility with Electronic Health Record (EHR) systems. This means that the monitoring system should be able to seamlessly integrate and share patient data with the hospital's electronic record-keeping system.
These examples illustrate how different requirement categories can be applied to various types of medical devices. Functional requirements define what the device does, performance requirements outline how well it does it, and interface requirements ensure compatibility with external systems or processes. Understanding and properly defining these categories are crucial for the successful design, verification, and validation of medical devices.
The device I'll discuss is the LTV 950 ventilator:
Functional - One functional requirement of the device is for it to output oxygen into a patient's lungs when they are physically incapable of doing it themselves, or they have a hard time getting enough oxygen while breathing normally.
Performance - Being able to output the quantity of oxygen that the patient is receiving is crucial to ensure their survival. In this case, on the front of the machine, there are small screens that are able to display this data.
Interface - Returning to the screens on the front of the ventilator, each screen has a button or dial associated with it to allow for the user to see different types of data and adjust accordingly. In this case it would involve the quantity and rate at which oxygen is being delivered to the patient, but these inputs can change depending on the data requested.
