Medical Device Reliability Test and Standards

Why Medical Devices Need Reliability Test?

As a product of modern science and technology, medical devices have been widely used in the prevention, diagnosis, treatment, health care and rehabilitation of diseases with the rapid development of medical diagnosis and treatment technology. From thermometers, disposable infusion sets to monitors, ventilators, from cardiac pacemakers, artificial blood vessels to intravascular stents, artificial joints, most of the medical work in hospitals requires the assistance of medical equipment. Not only that, many medical devices will be implanted into the human body temporarily or for a long time. For medical staff, the reliability of medical devices is inevitable. The low reliability of medical devices will not only cause economic losses, reduce the reputation of manufacturers, but also directly endanger the lives of patients. So considering all of these, we should improve the reliability of the medical devices as much as possible.

Test Standards for Medical Devices

With the development of medical industry and the upgrading of some hospital equipment, the market demand for medical equipment has increased rapidly, which has objectively promoted the development of medical equipment industry. The selection of medical devices will become more and more advanced, its product structure will be continuously adjusted, its functions will be more diversified, and its market capacity will continue to expand.

For some companies, the research and design of their products did not take into account the electromagnetic compatibility and other information at the beginning, and it was impossible to pass the medical equipment record or apply for a medical registration certificate at one time.

IEC 60601 is a series of technical standards for the safety and essential performance of medical electrical equipment, published by the International Electrotechnical Commission. First published in 1977 and regularly updated and restructured, as of 2011 it consists of a general standard, about 10 collateral standards, and about 80 particular standards.

1.General standard

The general standard IEC 60601-1 – Medical electrical equipment

Part 1: General requirements for basic safety and essential performance – gives general requirements of the series of standards. 60601 is a widely accepted benchmark for medical electrical equipment and compliance with IEC60601-1 has become a requirement for the commercialisation of electrical medical equipment in many countries. Many companies view compliance with IEC 60601-1 as a requirement for most markets. This standard does not assure effectiveness of a medical device.

In the US, evidence of effectiveness is required by the FDA and confirmed through either a Premarket Approval (PMA) or similarity to a predicate device via a 510(k) Premarket Notification.

National deviations of this series of standards exist which include country specific requirements.

The European EN and Canadian CSA versions of the standard are identical to the IEC standard.v2.Revisions

In 2005, the third edition of IEC 60601-1 was published. It was the result of a comprehensive review of the second edition (dating from 1988). Some key changes are: the outline and the numbering scheme of the clauses and subclauses were changed, risk management was made much more relevant and the concept of essential performance was added.

Currently (2012), the applicability of the second and third edition is somewhat overlapping depending on the products under consideration and the country/area of application. IEC 60601-1-11 (2010) must now be incorporated into the design and verification of a wide range of home use and point of care medical devices along with other applicable standards in the IEC 60601 3rd edition series. IEC 60601-1 merged to medical device directive 93/42/EEC which covers all IEC standard of electromedical & electrical safety so it is clear that EC cover all Previous IEC standard to medical device directive 93/42/EEC

The mandatory date for implementation of the EN European version of the standard is June 1, 2012. The US FDA requires the use of the standard on June 30, 2013, while Health Canada recently extended the required date from June 2012 to April 2013. The North American agencies will only require these standards for new device submissions, while the EU will take the more severe approach of requiring all applicable devices being placed on the market to consider the home healthcare standard.

3.Collateral and particular standards

Requirements of 60601-1 may be overridden or bypassed by specific language in the standards for a particular product. Collateral standards (numbered 60601-1-X) define the requirements for certain aspects of safety and performance, e.g. Electromagnetic Disturbances (IEC 60601-1-2) or Protection for diagnostic use of X-rays (IEC 60601-1-3). Particular standards (numbered 60601-2-X) define the requirements for specific products or specific measurements built into products, e.g. MR scanners (IEC 60601-2-33) or Electroencephalograms (IEC 60601-2-26).

Collaterals and Particulars may have their own revisions which are different from the General Standard.

Environmental Tests Required for Medical Devices

Under normal circumstances, because the future use, transportation and storage process of the product is very complex, it is often impossible to carry out in the determined order, and often repeatedly in these three states, which makes the environmental order it will encounter in the future cannot be fixed. Therefore, in most cases, it is impossible to arrange the reliability test items in the order of actual use, but to start from the purpose of the test, according to the principles described above, and further consider the characteristics of each test item and its possible impact on each other, and other factors to select the order of reliability test items. The following is a brief analysis of the characteristics and effects of each reliability test item, and suggestions for sequencing as much as possible.

1.Altitude test

Under normal circumstances, the Altitude Test should be performed before other environmental tests, that is, the environmental test starts with low pressure. The reason is that low air pressure is less destructive to the test sample, and once there is damage, it usually occurs early in the life cycle. However, when other environmental tests of the test sample will have a great impact on its low pressure test effect, the low pressure test should be carried out after these tests. These tests and effects are: high and low temperature tests affect the sealing effect, kinetic tests affect the structural integrity of the test sample, and solar radiation tests reduce the strength of non-metallic parts by aging. If a low pressure test is performed after these tests, its harmful effects will be further increased.

LIB altitude test chamber, a necessary equipment for low pressure test. Low pressure test is mainly used in aviation, aerospace, information, electronics and other fields, to determine instruments, electrical products, materials, parts, equipment in low pressure, high temperature, low temperature single or simultaneous environmental adaptability and reliability test. It can be applied at the same time as the test piece energized for electrical performance parameters measurement.

In the natural environment, the air pressure gradually decreases with increasing altitude. At altitudes approaching 5,000 m, the atmospheric pressure drops to about half of sea level standard atmosphere, at altitudes approaching 16,000 M to about 1/10 of sea level standard atmosphere, and at altitudes approaching 31,000 m to about 1/100 of sea level standard atmosphere.

Altitude test chamber offers strict testing conditions which can provide assurance for the quality testing of the above industry product.

2.High temperature storage and low temperature storage test

The influence of low temperature test on the product is mainly manifested in making the material hard and brittle, broken and cracked, the strength is reduced, the viscosity of the lubricant is increased, the lubrication effect is reduced, and the performance of electronic components is changed. Low temperature tests generally do not cause permanent damage to the sample, so they are often scheduled early in the test sequence. Low temperature test will greatly change the performance of seals during low pressure test, the impact of high temperature test on the product is mainly manifested in changing the physical properties and size of the material, the lubrication viscosity is reduced, the lubricant outflow causes the loss of lubrication capacity at the connection, the transformer and electromechanical components are overheated and damaged, the inconsistency of different materials makes the parts bonded, and the stability of electronic circuits changes. The high temperature test is generally scheduled early in the test, immediately after the initial power transport test. The high temperature test will greatly help to enhance the low pressure test effect of the seal. If you want to take advantage of the superposition effect between the various test effects as much as possible, the high and low temperature tests should be carried out after mechanical tests such as vibration and shock, and before the low pressure test, in order to achieve the best combined exposure effect.

3. High temperature work and low temperature work test

The temperature severity of high-temperature work and low-temperature work tests is generally lower than the storage temperature by 10°C. For some electrical products with high current and high heat generation, the high-temperature work test can replace the high-temperature storage test, because the working temperature has exceeded its storage temperature. Therefore, it is only necessary to conduct a high temperature working test (for example: front combination lamp).

4.Thermal shock test

The impact of the thermal shock test on the product is mainly manifested in material fragmentation, separation of components, bonding or slowing down of moving parts, electronic or mechanical failures caused by rapid condensation and frosting, cracking of surface coatings, leakage of sealing parts, etc. . The upper and lower limits of the thermal shock test often use the upper and lower limits of the high and low temperature storage tests, so information such as the temperature response characteristics of the test samples obtained in the high and low temperature storage tests can be used in the thermal shock test. Therefore, the thermal shock test is generally arranged after the high and low temperature storage test.

5.Temperature change test

The upper and lower limits of the temperature change test often use the upper and lower limits of the high and low temperature work test, and the product is in the working state in some cases during the test, so this kind of test can replace the high temperature work test when it is carried out, because it is under high temperature conditions in the test. The product is in working condition, but it cannot replace the low temperature test, so the low temperature working time is too short when the test is carried out, and its low temperature working stability cannot be assessed.

6. Solar radiation test

Solar radiation tests are usually performed at any point in the test sequence. However, it should be noted that high temperature and photochemical effects may affect the strength and size of the material, thereby affecting the results of subsequent dynamic tests (such as vibration tests). When the analysis will have this effect, the solar radiation test should be arranged after the vibration test.

7. Waterproof test

The water resistance tests are generally performed in any order, but are more effectively used to determine the structural integrity of the test specimen enclosure if performed after the dynamic test. Therefore, for products with casings that require a waterproof test, the test should be arranged after the dynamic test such as vibration as much as possible, so as to better determine the impact of the dynamic test on its structural integrity. In order to avoid the dust and other sundries on the product from affecting the filtering effect of the circulating water in the waterproof test box after the dustproof test, the waterproof test should be done first, and then the dustproof test.

8.Dustproof test

The dustproof test shall be carried out after the fungus, salt spray and damp heat test. Because after the dustproof test, a dust coating and severe abrasion will be produced on the test sample: on the other hand, the co-existence of dust with other environmental parameters such as temperature and humidity can cause corrosion and mold growth. Warm and humid environments can cause corrosion in the presence of chemically aggressive dust. Therefore, it will affect the results of damp heat, mold and salt spray tests. In addition, if the temperature parameters in the dustproof test need to be determined according to the results obtained from the high temperature test, the dustproof test should be carried out after the high temperature test. The dustproof test after high temperature can check whether the product is deformed at high temperature, which will eventually affect its sealing performance. Therefore, the dustproof and waterproof tests are generally placed after the high temperature test to check the sealing performance of the product under the influence of temperature.

9.Damp heat test

The damp heat test often causes the metal material of the test sample to be corroded and some materials are deformed due to water absorption. These effects are often irreversible. When the test samples with these effects are left for subsequent tests, the results of the subsequent tests will be false. Therefore, damp heat tests should generally be arranged after these tests. The damp heat test should not be carried out with the same test sample that has been subjected to the salt spray, dust proof and mold tests. In order to evaluate whether the moisture-proof material in the circuit still has a moisture-proof effect after being subjected to extreme temperature and vibration tests, the damp heat test should be carried out after the temperature and vibration tests. For sealed or semi-sealed products, it is mainly because condensation affects the performance of the product or the penetration of water vapor is accelerated by the phenomenon of respiration, so the alternating damp heat test is often used. The choice of constant damp heat and alternating damp heat can be determined according to the type of product. If adsorption and absorption play a major role, the constant damp heat test is used. When there is penetration but no respiration, the constant damp heat or alternating damp heat test can be selected according to the type of product and its application. When the test results obtained by constant damp heat and alternating damp heat are basically the same, the constant damp heat test should be adopted from technical and economical considerations. In order to evaluate whether the moisture-proof material in the circuit loses its protective effect after being subjected to extreme temperature or vibration test, usually the damp heat test cannot be carried out before the temperature, low pressure and vibration test.

10. Salt spray test

If multiple climatic tests are performed using the same test sample, in most cases the salt spray test should be performed after other climatic tests, especially after mold tests and humid heat tests. Because salt deposition has a potentially destructive effect, it can interfere with the effect of other tests. Generally, the same test sample should not be used for salt spray, mold and humid heat tests. If necessary, the salt spray test should be performed after the mold and damp heat test. However, if the same test sample is required for a dust test, the dust test should be carried out after the salt spray test.

11. Vibration test

The impact of the vibration test on the product is mainly manifested in the loosening of fasteners, seal failure, cracks and fractures, contact and short circuit between live components, wire friction, etc. The cumulative result of vibration-induced stress may affect equipment performance in combination with other environmental conditions such as high temperature, altitude, humidity, immersion, or electromagnetic interference/compatibility. Jiayu Testing Network recommends that if the same test sample is to be used to evaluate the cumulative effect of vibration and other environmental factors, the vibration test is generally performed first. If another environmental factor (such as temperature cycling) is expected to cause more severe damage to the equipment than vibration, for example, temperature cycling may cause fatigue cracks that will propagate under vibration, then the vibration test is performed after this test. The EMC electromagnetic compatibility test should be placed after vibration, because the structure of the product and the welding of electronic components are assessed in the vibration test. The test will accelerate the destruction of the welding structure of electronic components, and the components will be shaken off in severe cases. In actual tests, capacitors and other vibrations are often encountered, which will not affect the function of the product, but will affect the EMC of the product.

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