Preventive Maintenance (Scheduled Maintenance)

Purpose and Methodology. Scheduled maintenance ensures that equipment previously acquired continues to function

Figure 10. Preventive maintenance cell saver. Depending on the medical instrument, preventive maintenance can be more involved than just a functional and safety test. Problems that are uncovered must be rectified, and some instrumentation requires that compo­nents be replaced due to wear or number of hours of use. This, as well as observed spills, may necessitate opening the unit. The cell saver shown is used to salvage blood shed during an operation allowing its return to the same patient.

properly, has not deteriorated (due to usage and aging), and is safe for use. An attempt is made to uncover and correct problems that have not been reported or of which the user is unaware. Problem correction at an early stage can prevent incidents from occurring.

Testing done during PM tends to be more functionally ori­ented and is not as inclusive as that done during acceptance testing. Equipment that is mechanical in nature is tested to ensure that moving parts are structurally sound. If electri­cally operated, ac safety tests are performed (Fig. 10).

Some equipment requires replacement of parts normally expected to deteriorate with use, such as O-rings, gaskets, and brushes. In fact, some PM (i. e., for dialysis machines and some ventilators) is scheduled not by period (yearly, etc.), but by number of hours of equipment operation. PM kits are ob­tainable from the manufacturer. Other sensitive medical equipment (audiometer) requires extensive calibration dur­ing PM.

PM procedures specifically geared toward each instrument are used, except when the instrument is simple enough that a generic PM procedure can be used. Procedures can either be written in-house or purchased commercially. A PM worksheet keyed to the instrument’s unique identification number is filled out and filed in the equipment’s history folder.

Most equipment is maintained on-site in the user facility or clinical area, while others must be done in the clinical engi­neering laboratories. Precautions should be taken to ensure that the equipment has been properly cleaned and/or steri­lized before work on it is attempted. The infection control de­partment has guidelines on cleaning prior to repair. Notation must be made in the computerized maintenance management system (CMMS) of equipment that is temporarily taken out of service, its storage location, and whether PM must be done while it is stored. The unit should be tagged indicating that clinical engineering staff must inspect it prior to its being put back into service. Clinical engineering’s test equipment used to maintain and calibrate the medical instrumentation must also be periodically checked and calibrated. Certification against standards traceable to the National Bureau of Stan­dards may be required.

A recent trend is to use laptop computers to collect test data on-site which are then imported into the CMMS. Com­puter-compatible test equipment can also be used to some­what automate the test process. Such systems are available from Bio-Tek and DNI Nevada Inc.

PM Risk Management. Risk factors are used to determine if equipment requires scheduled PM, and if so, how often. This allows health-care organizations to concentrate their re­sources on equipment presenting the greatest risk. All pa — tient-care equipment is evaluated, independent of the manner in which the institution acquired it.

During risk analysis, consideration is given to equipment function, physical risk associated with clinical application, and equipment maintenance requirements. A weighted num­bering system is used and an appropriate threshold is set. Clinical engineering experience (incident history and fre­quency of use) is used to modify the initial assessment as re­quired (22). Some low-risk devices with no PM requirements only require acceptance testing when first acquired, and a zero PM frequency assigned. The following is one example of assigning risk levels.

Equipment Function. This assessment considers how a de­vice and its data are used and the possible consequences of its failure. It is important whether a device is used for life support, routine treatment, diagnosis, monitoring, or for mi­nor functions.

Patient related and other

A device malfunction could result in—

Patient death 5

Patient or operator injury 4

Inappropriate therapy or misdiagnosis 3

Patient’s discomfort 2

No significant risk 1

Maintenance Requirements.

This assessment considers whether the device requires periodic parts replacement, recal­ibration, lubrication, and clinical engineering tasks necessary to supplement user maintenance.

Maintenance is weighted as follows:



Above average




Below average




Cannot Locate. Equipment that cannot be located (CNL) is an ongoing problem that most clinical engineering depart­ments face when attempting to do PM. Movable equipment often winds up in locations other than those indicated in the inventory records. The equipment may even have left the in­stitution with the patient upon transport. This requires ex­tensive search time, entails hospital sweeps, and if unsuccess­ful, notification to the user and the Safety Committee. Should the device not turn up in a reasonable time period set by the institution (i. e., within three PM periods, two years), the clini­cal owner and property control personnel should be notified and the device removed from the active equipment inventory list.

Reduction of PM Requirements. From 1974, when the JCAHO first required that all electrically powered equipment be tested four times a year, through 1988, when the JCAHO introduced risk-based equipment management, which encour­aged health-care facilities to develop more realistic equipment management programs, there has been a decline in the re­quirement to do PM (39).

Today (1998), as competition between health-care institu­tions intensifies and resources dwindle, further PM reduction is being discussed. At issue is the extent that PM contributes to patient care, patient and user safety or quality. PM is la­bor-intensive and uses personnel resources that are in short supply. Advances in the manufacture of medical devices (in­cluding the use of solid-state integrated circuits) produce in­struments with longer mean times to failure rates and better electrical isolation. It is questioned if PM further improves these failure rates and whether clinical engineering resources would be better spent in providing additional training to equipment operators to improve their skills, thus reducing patient incidents and enhancing patient care (39). It remains to be seen if this approach will be adopted. For now, time spent on PM should be limited to what is required by law or as determined by prudent practice (17).