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HTM ComDoc 15

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Contents

"The Heart of the PM Debate"

(This document was last revised on 7-27-16)


15.0 The four basic questions about PM (Planned Maintenance)

(This section was last revised on 3-26-15)

  1. How, and to what extent, does performing PM on medical equipment improve patient safety?
  2. Which devices can be made safer by performing periodic PM?
  3. Why do we need to standardize the format of our maintenance reports?
  4. Is there a simple metric that can be used to provide an indication of a device’s documented level of reliability and PM-related safety?

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15.1 How, and to what extent, does performing PM on medical equipment improve patient safety?

(This section was last revised on 10-29-15)

Some medical devices have one or more non-durable parts. These are components of the device that are subject to progressive wear or deterioration. They typically include moving parts,such as bearings, drive belts, pulleys, mechanical fasteners and cables, which require periodic cleaning and lubrication as well as certain non-moving parts such as gaskets, various kinds of filters, flexible tubing and electrical batteries which may need to be restored (cleaned, adjusted, refurbished or replaced) sometime during the useful lifetime of the device. Which parts the manufacturer considers to be non-durable parts are usually identified in the manufacturer's recommended PM procedure. Performing traditional PM on these devices prevents them from failing prematurely and so improves the reliability. If the device is device restoration-critical, it also improves the level of safety of the device. To be considered device restoration-critical the device must have the potential to cause a patient injury if it stops working while in use, as well as a component that the manufacturer has stated needs some kind of periodic restoration. Unless the device is device restoration-critical, traditional preventive maintenance cannot and will not improve the device's level of safety. (See HTM ComDoc 3) Only about 10% of the more than 750 different types of medical devices are potentially device restoration-critical. Of these only about eleven device types are considered to be potentially life-threatening if they fail. (See Table 2)

  • Traditionally PM has been considered to be important primarily because of its potential to reduce operating costs. Preventive maintenance was originally considered to be important because when the earliest machines were developed during the the industrial revolution and the subsequent pre-electronic era, it was widely believed that restoring the device's non-durable parts before the end of the device's anticipated lifetime would be beneficial by reducing the number of machine breakdowns. In return for these scheduled PM interventions to restore the device's non-durable parts, the device users expected a lower level of disruption and loss of productivity from in-use breakdowns as well as some reduction in overall maintenance costs.
  • There is still very little hard data proving that traditional PM has a significant impact on device reliability. Belief in this traditional parts restoration approach to improving machine reliability continues to this day, particularly in certain relatively small industry sectors, even though the findings that started the revolutionary RCM approach to maintenance in the 1970s (see HTM ComDoc 14) have caused a considerable rethinking about whether or not intrusive maintenance interventions really do improve the device's overall reliability by a significant amount. Certainly there are still quite a number of medical devices such as ventilators, traction machines and spirometers that are more mechanical than electronic, where the manufacturers still recommend that certain parts be given some kind of periodic rejuvenation (cleaning, restoration or replacement). However, in reality, we don’t yet have good, independent evidence as to whether or not these manufacturer-recommended PMs, particularly those involving the more intrusive overhauls, are truly beneficial or cost-effective. We have not yet gathered good data on the impact of these recommended interventions on the reliability of these more mechanical devices. (See HTM ComRef 18)

In the special case of medical equipment maintenance, there is a second very important reason, besides restoring the device's non-durable parts (if any), for making periodic safety checks. And that is to detect any significant deterioration in the functional performance of the device or in its condition with respect to relevant safety specifications. These deteriorations can be quite subtle, and in RCM terminology they are called hidden failures. The term is appropriate because these subtle changes do not completely disable the device's primary functions and so these hidden failures usually go completely unnoticed by the device users.

However, it is important to detect these subtle deteriorations (hidden failures) because some types of devices can cause a patient injury if their performance becomes significantly substandard or their level of safety falls below the relevant requirements. Elsewhere (see HTM ComDoc 3) we characterize the types of devices that have a theoretical potential to injure a patient if they deteriorate in this way as safety verification-critical devices and they need to be subjected to periodic safety verification testing (SVT) which is designed to detect any hidden failures that are present. (For more on this see Section 1.6 of HTM ComDoc 1). Appropriate protocols for checking out each particular type of device are usually included as a part of the device manufacturer's recommended PM procedure. However, if the device is not a safety verification-critical device performing this testing (as a part of the PM) cannot and will not improve the device's level of safety. Only about 10% of the more than 750 different types of medical devices are considered to be potentially safety verification-critical. Of these only about sixteen device types are considered to be potentially life-threatening if they develop a hidden failure. (See Table 3)

Reasons other than safety for performing PM

  • Economics. … We may perform PM on some devices because we believe that this will reduce the net cost of maintaining them. However, there is very little data available on economic justifications for doing PM. (See HTM ComDoc 9)
  • Regulatory compliance. … There may be some devices on which we do PM (simply) because some regulatory authority says that we should. However, there is very little justification or technical rationale for any of these regulatory requirements. (See HTM ComDoc 11)
  • Customer courtesy and/ or customer reassurance. … We may perform PM on some other devices because a user has asked us to do so, or because we believe that periodically inspecting and cleaning equipment used for patient care creates a reassuring "cared for" appearance that the user staff appreciates. While this is a qualitative rather than a quantitative benefit it should not be underestimated. Occasionally this also leads to the discovery of unreported broken equipment.

In summary


  • Performing PM can improve patient safety only if the device is PM-critical, i.e. either device restoration-critical (where the device has the theoretical potential to cause a patient injury if it fails completely because a non-durable part was not restored in time) or safety verification-critical where the device has a theoretical potential to injure a patient if it undergoes a significant deterioration in its functional performance or compliance with any relevant safety specifications.
  • Only about ten percent of the device types used in healthcare (about 75 of the approximately 750 different device types) are potentially PM-critical. And, although there is virtually no hard data to prove it at the moment, there is a strong belief that most of those PM-critical devices are extremely reliable and therefore adequately safe. Collecting the data needed to prove this should be a #1 priority.
  • There should be no more "magical thinking" about the "power" of PM. It is extremely important to recognize what PM cannot, and does not, do with respect to patient safety. PM performed on non-critical equipment has absolutely no impact on patient safety. And, even in the case of the PM-critical devices, performing periodic PM has absolutely no impact on >95% of the failures of those devices. The leading causes of failure are (1) unpredictable, random component failures (40-50%) and (2) process-related failures such as user problems, battery management shortcomings, physical damage due to dropping, accessory problems, environmental issues, etc. These are failures that are completely unaffected by PM. (See HTM ComDoc 1 and HTM ComDoc 8)


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15.2 Which devices can be made safer by performing periodic PM?

(This section was last revised on 10-29-15)

As stated in paragraph 15.1 above, only devices that are PM-critical (i.e. either device restoration-critical or safety testing-critical) can be made safer by performing periodic PM. So the question is reduced to - which types of devices are either device restoration-critical or safety testing-critical?

a) The process for determining which device types are device restoration-critical

Although there is a well established and quite rigorous process for making determinations such as this embodied in the widely recognized RCM methodology, it is - for our purpose here - unnecessarily complicated. (See Section 3.3 in HTM ComDoc 3 and Section 14.13 in HTM ComDoc 14) We do not need to document all of each device's failure modes. We can reduce the process to addressing two relatively simple questions.

  1. Could the complete failure of the device while it is in use possibly cause a patient injury or similarly serious adverse consequence?
  2. Does the device, according to the manufacturer's PM recommendations, also have components that need periodic restoration (traditional preventive maintenance) to prevent the device's premature failure?

We have summarized in Table 2 the results of this 2-question process. The table has been separated into three tiers according to the severity of the anticipated outcome of the device failure, with Level 3 (Life-threatening) being the most severe. The statement in the third column of the table summarizes the nature of the anticipated outcome of the device failing while in use.

b) The process for determining which device types are safety testing-critical

In this case the process can be reduced to one simple question.

  1. Could some kind of significant deterioration in the device's functional performance or lack of compliance with any of the relevant safety specifications, that will not be obvious to the device users, cause a patient injury or similarly serious adverse consequence?

The preliminary results of asking this question about each of the device types listed in Table 1 are shown in Table 3 Again the table is separated into three tiers according to the severity of the anticipated outcome of the hidden failure, with Level 3 (Life-threatening) being the most severe. The statement in the third column of the table summarizes the nature of the anticipated outcome of the hidden failure developing while the device is in use.

c) Combining the two sets of findings into a single determination of which devices are PM-critical

The results of these two processes are combined in Table 4 This table is ranked into six tiers (A-F) according to the combined severity of the two sets of results. The top tier lists (in alphabetical order) seven different device types, each of which is considered to have the most severe possible outcome (Level 3) in both analyses. In this sense it could be said that these seven device types should be considered the most PM-critical, and each of the lower tiers could be considered successively less critical with respect to needing regular PM. These are all of the PM-critical device types can be made safer (to some degree) by performing periodic PM.

How to prove that a device that is (theoretically) PM-critical is, in fact, safe

The next important question is - To what extent these devices can actually be made safer by performing regular PM? In order to answer this question it is important to recognize that it is the likelihood (probability) that the critical failures presumed to occur in the critical scenarios will actually occur that determines the actual level of safety of the device.

For example; during the early 1970s much was made of the potential for leakage current to electrocute a patient who had a catheter with an open conductive pathway to the heart, and this failure scenario was used to try to justify mandating the installation of isolated power centers in all special care areas. However, a strong and successful rebuttal was mounted using the argument that this particular failure scenario rarely, if ever, occurred in the real world. (See HTM ComDoc 12). In this case, the rebuttal team was fortunate in being able to prevail without having to produce well-documented evidence that the actual occurrence of excessive levels of leakage current was indeed very rare.

The proper way to make the case that the presumed failure (of either the part that has been designated by the manufacturer as needing periodic restoration, or from the specified hidden deterioration) is highly improbable, is to document the extent to which these presumed events actually do (or do not) appear in real world testing of medical equipment over a reasonably long period. Elsewhere there are suggested thresholds for both of these parameters. (See Section 7.7 in HTM ComDoc 7) There are also some recommendations on how the data should be standardized and how it could be accumulated in a community database. (See HTM ComDoc 7)

Elsewhere, also, is a recommended process for creating a credible community Task Force to periodically review the data accumulated for each manufacturer-model combination of device types designated to be PM-critical and to declare when it should be considered adequately safe. It is suggested that this group maintain a list of manufacturer-model combinations that they (the Task Force) has determined to be "PM-safe".

What about devices that are non-critical?

All non-critical device types (i.e. those that have no PM-critical failure modes) are, by definition, low-risk devices. Whereas, PM-critical device types are high-risk (hazardous) devices unless certain manufacturer-model versions of those device types can be shown to have good reliability (i.e. a low probability of failing) with respect to PM-preventable failures, in which case they can be categorized as low-risk devices. For more on this see Section 14.12 in HTM ComDoc 14


With good reliability With poor reliability
Critical device types Low-risk (safe) devices High-risk (hazardous) devices
Non-critical device types Low-risk (safe) devicesLow-risk (safe) devices

In summary


  • There is a rigorous, but relatively simple, risk-based process for performing the risk analysis required to determine which device types need, for safety reasons, to be subjected to periodic PM.
  • There is no logical reason for each individual healthcare facility to have to perform this same analysis independently.
  • The analysis results in a list of device types that is ranked into six tiers reflecting different levels of PM-criticality.
  • At the moment there is no body of data that can be used to determine whether or not some of the device types are already adequately safe and which will not therefore benefit from periodic PM.
  • There is a huge opportunity to begin accumulating the results of current PM programs to create a body of documented data which would probably prove that there are many device types that are theoretically PM-critical but which already have acceptable levels of intrinsic safety.
  • Addressing this opportunity will require an unprecedented level of leadership and community-wide collaboration.



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15.3 Why we need to standardize the format of our maintenance reports

(This section was last revised on 10-7-16)

There are three key benefits that can be realized if a significant number of the community's maintenance programs could be persuaded to standardize on a common format for their maintenance reports.

  1. Maintenance data could be aggregated in a single, community-wide database which would then produce very helpful safety statistics on at least the more popular medical devices very, very quickly
  2. A comprehensive coding system for characterizing the way devices fail would provide the data we need to optimize the effectiveness of the facility's maintenance and non-maintenance equipment safety strategies.
  3. By documenting the findings of the PMs we perform on critical equipment we could select the right intervals to use for critical PMs.

1) Using aggregated data from a community-wide database to support evidence-based maintenance strategies

As was noted in section 4.4 of HTM ComDoc 4, collecting the amount of data needed for an evidence-based approach to an equipment maintenance strategy will be problematical for most individual healthcare facilities. In many cases they will be unable to collect sufficient data in a reasonable period of time to make their failure rate statistics credible. However, data collected in a consistent, common format can be aggregated into a single database.

This statistical complication arises from three factors.

  • First, because they are designed and constructed differently, different manufacturer-model versions of a given device type, such as defibrillators, can be expected to show different levels of reliability. So each different manufacturer-model combination has to be analyzed and characterized separately.
  • Second, most individual healthcare facilities will probably have only a small number of the individual device types that are PM-critical at the higher acuity levels. (See Table 4).
  • The third factor has to do with the likelihood that devices that are potentially PM-critical are likely to be designed and constructed to have a relatively high level of reliability, i.e. a low failure rate.

The result of these complicating factors is that individual facilities may not generate enough data to get a good indication of each device’s true reliability and level of safety. To get accurate estimates of the reliability of high reliability devices it will be necessary to pool maintenance statistics for each manufacturer-model version of each device from a number of institutions.

For example, suppose a facility has only three similar (same manufacturer – same model) heart-lung units and only three years of maintenance history for each unit. Since the facility has a total of only 9 device-years of experience, it is unlikely – if the actual MTBF of the units is, say, 50 years or more – that the facility will have experienced even one single failure during the 3-year testing period. In this case they would have to report their finding with respect to the devices’ indicated reliability (zero failures over 9 device-years) as undetermined. If, however, they did experience one or more failures of one of these devices during this relatively short period, then the indicated MTBF will appear to be unacceptably short for a critical device. In this situation it would be prudent for the facility to consult the findings on the reliability of these specific types of device in the national database to see whether or not their particular experience was indeed typical (and this type of device is, in fact, not sufficiently reliable) or if their experience was atypical.

For more on this see "Metrics for equipment-related patient safety" (HTM ComRef 16).

2) Failure cause codes for repair calls

A set offailure cause codes for repair calls was developed some time ago (see HTM ComRef 8). It has since been modified to the system shown below (and in Section 4.5 of HTM ComDoc 4). This system has proved to be very effective in providing useful statistics on which of the non-maintenance sources of device failures would be a good target for failure reduction programs. (See HTM ComDoc 8 "Maximizing equipment safety")

(The material immediately following is copied here from HTM ComDoc 1 paragraph 1.4)

There are a number of reasons (causes) why equipment systems fail and it is particularly important to recognize that not all of these failures can be pre-empted by some kind of preventive maintenance. Consider, for example, the following list of possible causes of device failure:

  • The first set of causes can be classified as inherent reliability-related failures (IRFs) that are attributable to the design and construction of the device itself, including the inherent reliability of the components used in the device. They typically represent 45 - 55% of the repair calls. This type of failure can be reduced (but not to zero) only by redesigning the device or changing the way it was constructed.

Category IR1. A device failure caused by the random failure or malfunction of a component part of the device. (Random failure). A result of the device’s inherent unreliability. IR1 calls typically represent between 46-52% of all repair calls.

Category IR2. A device failure attributable to poor fabrication or assembly of the device itself. (Poor construction).

Category IR3. A device failure attributable to poor design of the hardware or processes required to operate the device. (Poor design).


  • The second set of causes can be classified as process-related failures (PRFs). They typically represent 40 - 50% of the repair calls. Reducing or eliminating these types of failure typically requires some kind of redesign of the system’s processes - for example, by using better methods to train the equipment users to operate the equipment (as intended by the manufacturer) or to train them to treat the equipment more carefully. They are not failures that can prevented by any kind of maintenance activities.

Category PR1. A device failure attributable to incorrect set-up or operation of the device by the user. (Use error). User has not set the device up correctly or does not know how to operate it. Typically PR1 calls represent between 13-20% of all repair calls. (Note that although this type of “failure” does not represent a complete loss of function, it can have the same effect. For example, an incorrectly set defibrillator can result in a failure to resuscitate the patient).

Category PR2. A device failure caused by subjecting the device to physical stress outside its design tolerances.(Physical damage). PR2 calls typically represent between 6-25% of all repair calls.

Category PR3. A device failure attributable to a failure to recharge a rechargeable battery. (Battery failure). PR3 calls typically represent between 7-8% of all repair calls.

Category PR4. A device failure caused by the use of a wrong or defective accessory. (Accessory problem). PR4 calls typically represent between 3-9% of all repair calls.

Category PR5. A device failure caused by exposing the device to environmental stress outside its design tolerances. (Environmental stress). PR5 calls typically represent between 1-7% of all repair calls.

Category PR6. A device failure caused by human interference with an internal control. (Tampering). PR6 calls typically represent <1% of all calls.

Category PR7. A device system failure caused by an issue within a data network connected to the device’s output. (Network problem).


  • The third set of causes can be classified as maintenance-related failures (MRFs). They typically represent 2 - 4% of the repair calls. These types of failure can be prevented through some kind of maintenance strategy incorporated into the facility’s maintenance program.

Category MR1. A device failure that could have been prevented by more timely restoration or replacement of a manufacturer-designated non-durable part (PM-preventable failure). E.g. a battery failure, a clogged filter, or build up of dust. Failures due to trapped cables should not be coded this way. MR1 calls typically represent between 1-3% of all repair calls.

Category MR2. A device failure caused by poor or incomplete initial installation or set-up of the device. (Poor set up). MR2 calls typically represent between 1-3% of all repair calls.

Category MR3. A device failure attributable to improper periodic calibration (Recalibration). MR3 calls typically represent <1% of all repair calls.

Category MR4. A device failure attributable to a poor quality previous repair of the device. (Re-repair). MR4 calls typically represent <1% of all repair calls.

Category MR5. A device failure attributable to earlier intrusive maintenance. (Intrusive PM). MR5 calls typically represent much <1% of all repair calls.


While the device’s overall reliability, which corresponds directly to the total number of the repair calls - irrespective of what caused them – determines the device's effective reliability, it is the numbers of maintenance-related failures (MRFs) and inherent reliability-related failures (IRFs) that are of greatest interest to us, as maintainers, at this time. The level of MRFs provides a good measure of the effectiveness of the facility’s maintenance program, and the level of IRFs provides an equally good measure of the basic or inherent reliability of the devices in question.


Acting on this kind of information creates an important opportunity for in-house clinical engineering programs to accept a greater level of responsibility for medical equipment safety by assisting with, or managing, some, or all, of a number of non-maintenance preventive measures.

3) Coding PM Findings

There are a number of benefits that can be realized by standardizing on a set of generic PM procedures for all potentially PM-critical devices. (These will be outlined in sub-section #4) below). One of the most helpful innovations is a reporting section added at the end of each PM procedure asking the service person to indicate, by circling one of three letters (A, B or F), whether or not the performance and safety testing of the device revealed any significant degradations or hidden failures.

A = nominal. The letter A should be circled when the results of all of the PVST tests were in compliance with the relevant specifications, and any other functions tested were within expectations.
B = minor OOS condition(s) found. The letter B should be circled when one or more conditions were found that were slightly out-of-spec (OOS) or slightly outside expectations. The purpose of this B rating is to create a watch list to monitor for future adverse trends in particular performance or safety features, even though the discrepancy is not considered to be significant at this time. An example of this would be an electrical leakage reading of 310 microamps which is within 5% of the 300 microamp limit. A B rating should be considered a passing grade.
F = serious OOS condition(s) found. The letter F should be circled when one or more performance or safety features is found to be significantly out-of-spec. (OOS). This is a failing grade and, if it is a high-risk device, it should be removed from service immediately.

Documenting the discovery of potentially serious hidden failures in this concise manner is clearly helpful in determining the device's vulnerability to developing hidden failures; an important parameter that has not been well reported in the past. The service person is also asked to indicate, by circling one of four numbers/ characters (1, 5, 9 or 0), the physical condition in which the device parts that were restored by the traditional PM tasks were found. The numerical ratings should be circled to indicate one of the following findings.

1 = better than expected. There was very little or no deterioration; i.e. the original physical condition of the now restored part was found to be "still good".
5 = nominal. There was some minor deterioration but no apparent adverse effect on the device’s function; i.e. the physical condition of the now restored part was found to be about "as expected".
9 = serious physical deterioration. The now restored part was already worn out and probably having an adverse effect on device function; i.e. the physical condition was found to be "considerably worse than expected".
0 = no restoration required. The device has no parts needing any kind of physical restoration.

(The material above has been taken from Section 14.15 "Proposed format for documenting the PM Findings data on every PM Report" in HTM ComDoc 14).

There are at the moment no systematic methods for exploring whether or not the length of the PM interval is close to the optimum. What better way to do this than to document at each PM whether or not there is any evidence of premature deterioration of the parts expected to need some kind of restoration. When aggregated, the physical condition indicator provides unique documented evidence as to whether the PM interval is too long, too short, or just right.

  • If the interval is too long for one particular kind of device (at the manufacturer-model level), there will be a higher rate of PM findings that the rejuvenated part(s) were found to be in worse physical condition than was expected (PM Finding Code 9)
  • If the interval is too short, there will be a higher rate of PM findings that the rejuvenated part(s) were found to be in better physical condition than expected (PM Finding Code 1)
  • If the interval is about right, there will be a predominance of PM findings that the rejuvenated part(s) were found to be about as expected (PM Finding Code 5)

4) Some thoughts on optimizing PM intervals

  • For all potential PM-critical devices that are considered "high-risk". To be safe, the manufacturer’s recommendations for the PM (parts restoration) interval for all devices that are considered “high risk” should be respected. It is virtually impossible to judge how conservative the manufacturers’ recommendations for the parts restoration intervals might be for each device. It is also unlikely that there will be any consistency in this safety factor from device to device and from manufacturer to manufacturer.
  • For all non-critical devices. By definition there is no safety downside to these devices failing, and - according to the RCM methodology - unless there is a convincing case that periodic PM can be cost-justified, all “non-critical” device types are excellent candidates for the very cost-efficient Run-to-Failure strategy. In the civil aviation business it was by adopting this RTF strategy that they were able to reduce the industry’s maintenance costs by 50% - which also (amazingly) increased their reliability and safety statistics by a factor of 200 times! (see HTM ComDoc 14)
  • For potential PM-critical devices with non-durable parts that are considered "low-risk". The logical rule here should be to explore extending the interval until there is evidence that it has become too long, at which time it should be reduced to the last interval where there is evidence that it is acceptable. As a practical matter, there is very little disadvantage in testing for hidden failures at the same interval as is used for any parts restoration tasks. If the device has no non-durable parts then it is acceptable to use whatever interval is convenient for any other reason.
  • For devices that have no non-durable parts. For devices that do not have any parts that need restoration and the only “maintenance” that the manufacturer recommends is for periodic performance checking and safety testing, there are logical relationships between the maintenance interval and the MTBFs of the failures that can be explored. In the case of PVST tasks there is no optimum interval (shorter is always better) but it has been shown elsewhere (HTM ComDoc 6“Choosing appropriate PM intervals” ) that using reasonable estimates of the MTBFs of random device failures (between 50 and 250 years) and typical maintenance/ inspection intervals (between 6 months and 5 years) the increase in the time that the patient would be exposed to the potentially-hazardous hidden failure if the maintenance interval is extended is extremely small.

For a more in-depth discussion on how to use the PM Findings on the physical condition of the non-durable parts see Section 6.2 "Interval exploration " in HTM ComDoc 6 and Section 14.14 "Determining the relationship between the length of the maintenance interval and the threat to the health and safety of patients and staff" in HTM ComDoc 14.

5) Other benefits from developing a set of standard, generic PM procedures

You can view a sample of the generic procedures that have been developed so far by clicking on the 6-character code in the 5th column of Table 1, or the 6th column of Table 4, or the 1st column of Table 10.

The HTMC PM Procedure format has the following important features (see HTM ComDoc 5):

  1. It uses the same simple, consistent terminology used in all of the HTM Community documents
  2. The concise, 6-character procedure code ties the procedure to a device at the manufacturer-model level. This code is specifically customized to this particular manufacturer-model version of the device type; however, it may not be unique to this particular version. The same version of the Code may be appropriate for a number of different manufacturer-model versions of the same type of device.
  3. The format of the procedure is that of a simple list of concise, easy-to-perform task statements.
  4. There are separate lists of TPM tasks (to address the restoration of any non-durable parts) and PVST tasks (to detect any hidden performance or safety degradations)
  5. The scope of the list of TPM rejuvenation tasks is made consistent with the scope of the manufacturer-provided PM procedure.
  6. The scope of the list of PVST tasks is also made consistent with the scope of the manufacturer-provided PM procedure and with any other known critical failure modes that are not included in the manufacturer-provided procedure.
  7. Each of the tasks that are judged to be potentially critical are annotated with a statement in red indicating a judgement on the worst-case severity of the potential adverse effect (Life-threatening/ possible patient injury/ or possible disruption of care) if the device should require either an unusual level of restoration, or should fail the performance or safety test.
  8. A specially-formatted reporting section at the end of the procedure (as described in Section #5) above) that prompts the technician to capture all of the findings from the restoration and testing tasks using a simple, intuitive form of coding.

In summary


  • Developing the hard evidence needed for a convincing evidence-based approach to the regulating agencies, the accrediting organizations and our clinical colleagues requires a commitment to (a) a standardized format for our maintenance reports, and (b) establishment of a community-wide database for aggregating the maintenance data.
  • A standardized format for coding equipment repair calls and PM Findings offers several significant strategic benefits to the HTM community.
  • There appears to be a solid, logical case that can be made for diverting some, if not all, of the manpower and other resources that are currently being wasted on low-value or worthless PM activities to other technical activities such as CEIT and improving patient alarms that would really improve patient safety.

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15.4 Is there a simple metric that can be used to provide an indication of a device’s documented level of reliability and PM-related safety?

(This section was last revised on 10-29-15)

Only one simple metric has been proposed to date. It is the mean time between failures (MTBF) of any devices that are considered to be PM-critical. This is described in an article titled "Final Word: Doing it by the Numbers" by Malcolm Ridgway and Alan Lipshultz - published in BI&T; 48:72; Jan/ Feb 2014 - (HTM ComRef 15)

Please note that these articles use some terminology that has since been updated. Instead of the terms "reliability-critical" and "maintenance-critical", we now use the term "life-support-critical". And instead of the term "performance-critical" we now use the term "hidden-failure-critical".

The use of this particular metric was also discussed in an article titled "Metrics for equipment-related patient safety" by Malcolm Ridgway and Larry Fennigkoh - published in BI&T; 48:199-202; May/ June 2014 - (HTM ComRef 16)

In summary


  • There isn't much competition so far; only one candidate metric has been proposed. (See above.) However, it does seem to be more relevant and more valid than the only other parameter that has been used to date - which is the facility's current overall PM completion rate.
  • There is still only a small amount of data available on typical MTBFs of potentially PM-critical devices available (see Table 5), so there is still a reasonable question about whether or not this is a practical solution.



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