Below are insights written by James C. Roberts, P.E., chief engineer at IS International Services LLC. He provides an overview of adding machine safety barriers and E-Stops on a variety of medical device manufacturing machines, optimized for operator usability and accessibility. 

1. Why Retrofit Machines for Safety – Short History

   The medical device industry is constantly developing new products and processes.  This frequently leads to the development and deployment of new machinery to meet these needs.  New machines are manufactured to current standards and are either supplied with modern machine safeguarding already in place or at least designed for it to be easily added. 

   But what about cases where legacy machines have been in use for decades? Often these were built and installed before the wide-spread adoption of NEMA and ISO safeguarding standards and are not designed for the currently required levels of risk isolation. Retrofitting these machines to bring them into compliance while still maintaining their functionality and maintainability requires careful engineering and plenty of communications.

2. Regulatory Standards to Comply With

   When it comes to machine safeguarding, the risks are identified and ranked through a series of steps including Risk and Hazard Assessments and Layers of Protection Analysis (LOPA), designed to determine what needs to be protected and how reliable and secure the protection should be.  A couple of the key outcomes from this process are the identification of items that can be passively protected with techniques such as barriers, non-slip surfaces and keylocks and items that require active protection using safety circuits or similar interlocking. 

   These outcomes are the starting point for designing the safeguarding requirements for the machine. It is likely that protection needs were identified and mitigation methods were prescribed during the analysis phase. 

3. Distance, Energy, Procedures

   While the particulars will vary on a case-by-case basis, the primary tools typically boil down to these three concepts:

   • Guard the machinery in a manner that provides enough distance between personnel and hazards to allow additional safeguarding measures to take effect, preventing the personnel from being exposed to the hazard
   • Remove all energy that may constitute or enable the hazard (most typically electrical and pneumatic energy sources in the Medical Device Industry)
   • Develop and enforce of access limitation policies to prevent people from bypassing the first two concepts

     Policies are usually the domain of Operations, but frequently the Controls Engineer is required to implement the first two out.

     Many older machines are designed for direct operator interaction.  When retrofitting these machines, the original functionality needs to be understood, and when possible, fully enabled within a safer, better-guarded environment.

     Proper solutions must adequately address operability and maintainability because implementing the above three concepts without considering how the machine is used will often result in designs which interfere with day-to-day operations to an impractical degree, resulting in unnecessarily lost run time.

4. Guarding

   A fundamental principle of machine protection is that it takes time for an operator to move from a safe location to a point exposed to risk (time-of-flight.)  A design is considered safe if the machine can be stopped and made safe during the time-of-flight and before an operator can reach the hazard. Fixed barriers, such as mechanical guards, cages and fences create permanent blockages that completely prevent operators from reaching hazards while in place.

   The downside is these barriers are often inflexible making it extremely difficult for the operators and maintenance staff to access protected areas, even when their duties require them this ability as a part of their job function.  Often, materials will need to pass through these boundaries while the machine is in operation. In both cases, openings in the barriers are required. 

   

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   The standard tool for determining how large these openings is based on human anatomy, typically for fingers and arms, that allow larger gaps if the danger points are further from the barrier.  A good example of this is the OSHA Guard Opening Scale.  Only smaller holes are allowed if the distance is less than finger length and larger holes are allowed if a hazard is further than arm length away.

   Non-fixed barriers, such as light curtains and scanners provide more flexibility in both physical design and in the ability to modify the boundaries based on current conditions.  These are typically more expensive and the larger access windows these provide means that the proper consideration of time-of-flight is critical.  A combination of fixed and non-fixed guards typically provides the best solution.

   With either type of guarding, it is important to consider not only how the operators work on the machine, but also how maintenance technicians will access it.  Disassembly of bolt-in-place guard panels may be permissible for major maintenance, but areas of frequent maintenance need guards and protective panels that can be quickly removed or frequently adjusted equipment and instruments need to be relocated to hazard free locations.  When used, quick release panels will need to have proof that they are properly reinstalled prior to being able to reset the protective circuits. 

   A sound strategy to use when adding machine guarding is to work with operations and maintenance to develop potential approaches and then conduct a Management of Change (MOC) meeting with Safety, Operations and Maintenance team members to select the approach that meets the needs of all parties. These meetings are most successful when all concerned departments are present at the same time.  3D renderings showing the guards on the machine are often key to helping all team members visualize the restrictions and access paths being proposed.

5. Energy Removal

   Once the access protection methods are established, energy removal can be addressed.

   It wasn’t long ago that local motor disconnects and simple standard relay latching circuits were considered best practice. This is no longer the case with the introduction of concepts such as Safety Categories and Performance Levels. Now, it is common to find requirements such as “CAT3/PLd” for machine protection. 

   “CAT3” refers to the ISO 13849-1 Category 3 fault reaction performance level, in which a single fault in the safety system will create a trip, but not all faults will be detected. Essentially this means simple redundancy at every level of the safety circuit.

   As defined in ISO 13849-1, the Performance Level or PL is a measure of the reliability of the overall safety system to function correctly and trip when it is required to. A PL of “d” would be expected to not function correctly in the range of once every 100,000 to 1,000,000 hours and is equivalent to SIL2 in the process industry.

   Designing safety circuits of this class requires special logic solvers (safety monitoring relays or safety logic solvers), redundant-contact detection devices (position switches and pushbuttons), use of redundant pairs of contactors specially designed with cage-guided proof contacts, and similar specialty devices.  Single-contact switches and standard relays cannot provide the level of protection this requires.

   Fortunately, vendors are developing new and unique standards-compliant detection and actuation devices that continually add to the arsenal of the controls engineer.  Now there are safety-rated area scanners, compressed air supply/dump valves, access gate locks and similar devices that provide flexibility and space saving solutions often necessary in retrofitting process machinery.

6. Policy Development

   All of the guarding design and interlocking designs won’t help a bit unless they are accompanied by proper procedures that require the operating and maintenance personnel to respect the inherent dangers associated with the machines and to not tamper with the guards. Inflexible protection designs or loose policy application will inevitably lead to bypasses of the systems, resulting in exposure to the hazards and potentially loss of life or limb.

7. Summary

Machine safety systems are often viewed as necessary evils, but with careful planning and execution, the protection can often be added in ways that both protect the people that need to work on the equipment and still perform their jobs correctly, efficiently and safely. It is up to the Controls Engineer to work with all the people and tools available to make sure the systems they deliver are safe and functional so that they are appreciated and respected.

About the company:

IS International Services, LLC (IS) is a global services and engineering company focused on clients with an emphasis on providing quick and quality deliverables. They are a member of Control System Integrators Association (CSIA). 

Manufacturing and supply chain expert, Lisa Anderson, MBA, CSCP, CLTD, president of LMA Consulting Group Inc. has released, Emerging Above & Beyond: 21 Insights for 2021 from Manufacturing, Supply Chain and Technology Executives. This special report, available for free download, provides insights into the challenges that manufacturers and their extended supply chains faced during the pandemic, how they adapted successfully, and what opportunities exist for the future. LMA Consulting Group works with manufacturers and distributors on strategy and end-to-end supply chain transformation to maximize the customer experience and enable profitable, scalable, dramatic business growth.

Did you miss our Future-Proofing Manufacturing & the Supply Chain webinar featuring Lisa Anderson, view it now on demand. 

"The 2020 COVID-19 pandemic consumed manufacturers, distributors, and product-related organizations like healthcare. Early on, it became apparent that understanding, anticipating, and responding to changing customer needs would be the game-changers. Staffing, supply, process flows, and critical supply chain elements were stretched, re-assessed, and improved to address evolving customer demand. Providing a superior customer experience has separated the weak from the strong," Anderson comments.

The changing market dynamics impacted all aspects of organizations. From evaluating and upgrading e-commerce platforms and reskilling the workforce to reconfiguring relationships with supplier partners, manufacturers seized opportunities to improve their position for growth.

"Smart manufacturers took time to look for opportunities and innovate. Sometimes it required massive steps into uncharted territory. Other times, it required reworking and repurposing for improvement. No matter the changes required, they looked at it as a way to accelerate growth and learn from the process. There were key learnings in so many areas that I decided to call on other manufacturing, supply chain and technology experts to provide their insights and experiences. Emerging from 2020 intact is a good place to start. Yet, the best have the opportunity to pull significantly ahead of the competition at a rate only achieved since the Great Depression. Those who learn from the experience, adapt, build resiliency, and innovate with the customer in mind will emerge above and beyond," Anderson says.

Emerging Above & Beyond: 21 Insights for 2021 from Manufacturing, Supply Chain & Technology Executives provides critical elements to the roadmap for success. Reflective and predictive, the special report features leaders from all aspects of manufacturing, supply chain, and technology. Manufacturing and distribution leaders, along with experts in technology, finance, sales and marketing, and human capital, contributed their views on 2020 and insights into best practices for 2021.

"The experts cover a lot of ground and provide thought-provoking ideas. It’s meant to provide takeaways for everyone," she concludes.

Smart speakers, such as Amazon Echo and Google Home, have proven adept at monitoring certain healthcare issues at home. For example, researchers at the University of Washington have shown that these devices can detect cardiac arrests or monitor babies breathing.

But what about tracking something even smaller: the minute motion of individual heartbeats in a person sitting in front of a smart speaker?

UW researchers have developed a new skill for a smart speaker that monitors regular and irregular heartbeats without physical contact. The system sends inaudible sounds from the speaker out into a room and, based on the way the sounds are reflected back to the speaker, it can identify and monitor individual heartbeats. Because the heartbeat is such a tiny motion on the chest surface, the team's system uses machine learning to help the smart speaker locate signals from regular and irregular heartbeats.

When the researchers tested this system on healthy participants and hospitalized cardiac patients, the smart speaker detected heartbeats that closely matched the beats detected by standard heartbeat monitors. The team published these findings in Communications Biology.

© Mark Stone/University of Washington | https://www.washington.edu

"Regular heartbeats are easy enough to detect even if the signal is small, because you can look for a periodic pattern in the data," says co-senior author Shyam Gollakota, a UW associate professor in the Paul G. Allen School of Computer Science & Engineering. "But irregular heartbeats are really challenging because there is no such pattern. I wasn't sure that it would be possible to detect them, so I was pleasantly surprised that our algorithms could identify irregular heartbeats during tests with cardiac patients."

While many people are familiar with the concept of a heart rate, doctors are more interested in the assessment of heart rhythm. Heart rate is the average of heartbeats over time, whereas a heart rhythm describes the pattern of heartbeats.

For example, if a person has a heart rate of 60 beats per minute, they could have a regular heart rhythm – one beat every second, or an irregular heart rhythm – beats are randomly scattered across that minute but average out to 60 beats per minute.

"Heart rhythm disorders are actually more common than some other well-known heart conditions. Cardiac arrhythmias can cause major morbidities such as strokes, but can be highly unpredictable in occurrence, and thus difficult to diagnose," says co-senior author Dr. Arun Sridhar, assistant professor of cardiology at the UW School of Medicine. "Availability of a low-cost test that can be performed frequently and at the convenience of home can be a game-changer for certain patients in terms of early diagnosis and management."

© Mark Stone/University of Washington | https://www.washington.edu

The key to assessing heart rhythm lies in identifying the individual heartbeats. For this system, the search for heartbeats begins when a person sits within 1ft to 2ft in front of the smart speaker. Then the system plays an inaudible continuous sound, which bounces off the person and returns to the speaker. Based on how the returned sound has changed, the system can isolate movements on the person – including the rise and fall of their chest as they breathe.

"The motion from someone's breathing is orders of magnitude larger on the chest wall than the motion from heartbeats, so that poses a pretty big challenge," says lead author Anran Wang, a doctoral student in the Allen School. "And the breathing signal is not regular so it's hard to simply filter it out. Using the fact that smart speakers have multiple microphones, we designed a new beam-forming algorithm to help the speakers find heartbeats."

The team designed what's called a self-supervised machine learning algorithm, which learns on the fly instead of from a training set. This algorithm combines signals from the smart speaker's multiple microphones to identify the elusive heartbeat signal.

"This is similar to how Alexa can always find my voice even if I'm playing a video or if there are multiple people talking in the room," Gollakota explains. "When I say, 'Hey, Alexa,' the microphones are working together to find me in the room and listen to what I say next. That's basically what's happening here but with the heartbeat."

The heartbeat signals that the smart speaker detects don't look like the typical peaks that are commonly associated with traditional heartbeat monitors. The researchers used a second algorithm to segment the signal into individual heartbeats so that the system could extract what is known as the inter-beat interval, or the amount of time between two heartbeats.

"With this method, we are not getting the electric signal of the heart contracting. Instead, we're seeing the vibrations on the skin when the heart beats," Wang says.

The researchers tested a prototype smart speaker running this system on two groups: 26 healthy participants and 24 hospitalized patients with a diversity of cardiac conditions, including atrial fibrillation and heart failure. The team compared the smart speaker's inter-beat interval with one from a standard heartbeat monitor. Of the nearly 12,300 heartbeats measured for the healthy participants, the smart speaker's median inter-beat interval was within 28 milliseconds of the standard monitor. The smart speaker performed almost as well with cardiac patients: of the more than 5,600 heartbeats measured, the median inter-beat interval was within 30 milliseconds of the standard.

Currently this system is set up for spot checks: If a person is concerned about their heart rhythm, they can sit in front of a smart speaker to get a reading. But the research team hopes that future versions could continuously monitor heartbeats while people are asleep, something that could help doctors diagnose conditions such as sleep apnea.

"If you have a device like this, you can monitor a patient on an extended basis and define patterns that are individualized for the patient. For example, we can figure out when arrhythmias are happening for each specific patient and then develop corresponding care plans that are tailored for when the patients actually need them," Sridhar says. "This is the future of cardiology. And the beauty of using these kinds of devices is that they are already in people's homes."

Dr. Dan Nguyen, a clinical instructor at the UW School of Medicine, is a co-author on the paper. This research was funded by the National Science Foundation.

Being able to make blind people see again sounds like the stuff of miracles or even science fiction. And it has always been one of the biggest challenges for scientists. Diego Ghezzi, who holds the Medtronic Chair in Neuroengineering (LNE) at EPFL's School of Engineering, has made this issue a research focus. Since 2015, he and his team have been developing a retinal implant that works with camera-equipped smart glasses and a microcomputer.

"Our system is designed to give blind people a form of artificial vision by using electrodes to stimulate their retinal cells," Ghezzi says.

Star-spangled sky
The camera embedded in the smart glasses captures images in the wearer's field of vision, and sends the data to a microcomputer placed in one of the eyeglasses' end-pieces. The microcomputer turns the data into light signals which are transmitted to electrodes in the retinal implant. The electrodes then stimulate the retina in such a way that the wearer sees a simplified, black-and-white version of the image. This simplified version is made up of dots of light that appear when the retinal cells are stimulated. However, wearers must learn to interpret the many dots of light in order to make out shapes and objects.

"It's like when you look at stars in the night sky - you can learn to recognize specific constellations. Blind patients would see something similar with our system," Ghezzi says.

Running simulations, for now
The only catch is that the system has not yet been tested on humans. The research team first needs to be certain of their results. "We aren't yet authorized to implant our device in human patients, since obtaining the medical approval takes a long time. But we came up with a process for testing it virtually - a type of work-around," Ghezzi says.

More specifically, the engineers developed a virtual reality program that can simulate what patients would see with the implants. Their findings have just been published in Communication Materials.

Field of vision and resolution
Two parameters are used to measure vision: field of vision and resolution. The engineers therefore used these same two parameters to evaluate their system. The retinal implants they developed contain 10,500 electrodes, with each one serving to generate a dot of light.

"We weren't sure if this would be too many electrodes or not enough. We had to find just the right number so that the reproduced image doesn't become too hard to make out. The dots have to be far enough apart that patients can distinguish two of them close to each other, but there has to be enough of them to provide sufficient image resolution," Ghezzi says.

The engineers also had to make sure that each electrode could reliably produce a dot of light.

Ghezzi explains: "We wanted to make sure that two electrodes don't stimulate the same part of the retina. So we carried out electrophysiological tests that involved recording the activity of retinal ganglion cells. And the results confirmed that each electrode does indeed activate a different part of the retina."

The next step was to check whether 10,500 light dots provide good enough resolution – and that's where the virtual reality program came in.

"Our simulations showed that the chosen number of dots, and therefore of electrodes, works well. Using any more wouldn't deliver any real benefits to patients in terms of definition," Ghezzi says.

The engineers also performed tests at constant resolution but different field-of-vision angles.

"We started at five degrees and opened up the field all the way to 45 degrees. We found that the saturation point is 35 degrees - the object remains stable beyond that point," Ghezzi says.

All these experiments demonstrated that the system's capacity doesn't need to be improved any further, and that it's ready for clinical trials. But the team will have to wait a little longer before their technology can be implanted in actual patients. For now, restoring vision remains in the realm of science fiction.