Medical device safety testing is the process of proving that a device can work as intended without creating unacceptable risk for patients, users, or clinicians. Devices such as infusion pumps, wearable heart monitors, surgical tools, and implantable sensors must be checked before they are used in clinical care. Testing looks for hazards such as electrical shock, overheating, software errors, material failure, inaccurate readings, and mechanical breakage.
This matters because even a small device failure can affect diagnosis, treatment, or patient safety.
Key Facts
- Risk = probability of harm x severity of harm.
- Electrical safety testing checks leakage current, grounding, insulation, and protection from shock.
- Durability testing often uses repeated stress cycles, such as 10,000 button presses or bend tests, to simulate long-term use.
- Reliability can be estimated with failure rate, λ = number of failures / total operating time.
- Accuracy is often measured by percent error, percent error = |measured value - true value| / true value x 100%.
- A device is approved for clinical use only after evidence shows that safety, performance, labeling, and risk controls meet required standards.
Vocabulary
- Safety testing
- Safety testing is the evaluation of a device to identify hazards and confirm that risks are controlled to an acceptable level.
- Reliability
- Reliability is the ability of a device to perform correctly over time without failing.
- Durability
- Durability is the ability of a device to withstand physical wear, repeated use, cleaning, transport, and environmental stress.
- Leakage current
- Leakage current is a small unwanted electric current that can flow from a powered device to a patient or user.
- Calibration
- Calibration is the process of comparing and adjusting a device measurement against a known standard.
Common Mistakes to Avoid
- Assuming a device is safe because it turns on, which is wrong because startup does not prove accuracy, electrical safety, software reliability, or performance under stress.
- Testing only one device sample, which is wrong because manufacturing variation can cause different units to behave differently.
- Ignoring real-use conditions, which is wrong because heat, moisture, drops, cleaning chemicals, battery drain, and user handling can reveal failures not seen in ideal lab conditions.
- Confusing accuracy with reliability, which is wrong because a device can give the same reading repeatedly but still be consistently incorrect.
Practice Questions
- 1 An infusion pump is tested for 2,000 hours and has 4 failures. Calculate the failure rate in failures per hour using λ = number of failures / total operating time.
- 2 A heart monitor reads a heart rate of 76 beats per minute when the reference standard is 80 beats per minute. Calculate the percent error.
- 3 A wearable medical sensor passes accuracy tests in the lab but fails after repeated exposure to sweat and cleaning wipes. Explain which type of safety testing was missing and why it matters before clinical use.