An Intensive Push to Make Ventilators for the COVID-19 Pandemic
Creating a New Design in 47 Days for the UK Ventilator Challenge
On March 13, 2020,剑桥顾问, a technology consultancy in England, received a call from the UK government. COVID-19 was sweeping through the country, and while the National Health Service had 8,000 ventilators on hand, they were expecting to need 30,000 in worst-case scenarios. Even if established ventilator manufacturers worked full steam ahead, they wouldn’t be able to meet the demand. What’s more, travel restrictions were creating a shortage of parts in global supply chains.
In just 47 days, Cambridge Consultants designed a simple new ventilator that provided several settings for clinicians, eight alarms, and a custom mix of air and oxygen.
因此，政府发布了呼吸机挑战，要求几家英国公司从地上设计新设备，可以用当地零件迅速制作。该公司有几个星期的时间来做。
“Day one, we had a call from the cabinet office saying, ‘Do this please,’” says Sean Thompson, a senior mechatronics engineer at Cambridge Consultants. “That came Friday. A team of senior consultants and technical leads in the med tech division worked the entire weekend.
“I showed up Monday, and I had a whole bunch of missed calls. I logged into my email, and I’ve been invited to two days solid of workshops. I wondered, ‘Oh no, what’s going on?’ And so, a team of 30 or 40 of us from all around the business sat for two days and just smashed through a whole bunch of different concepts.”
What they landed on was a relatively simple design with only two sensors—airway pressure and inspiratory flow rate—but a lot of features. Clinicians would be able to set the inspiratory pressure, the oxygen level, the respiratory rate, and the ratio of inspiratory and expiratory time. In addition, it would have eight alarms for things like patient disconnection, airway obstruction, tidal volume out of bounds, and overpressure. It would also have a custom blender for mixing pure oxygen and regular air.
剑桥顾问accelerated the design of the ventilator using simulation, including hardware-in-the-loop simulations. Image credit: Cambridge Consultants
From Virtual to Reality
The project timing would not have been possible if they’d had to design and test everything starting with physical parts. Building and rebuilding the machine would have been too slow. Instead, they first built it in software, running simulations that they could tweak endlessly.
Much of that work was done with MATLAB®and Simulink®. The team used graphical programming by connecting blocks that represented mathematical functions. Libraries of physical components in Simscape™, such as springs and valves, enabled the team to create models of the lung and ventilator. Simulations let them test the system-level operation each time one of the blocks in the design was tweaked.
即使是最简单的呼吸机也是棘手的。“在MathWorks的高级产品经理Kirthi Devleker说：”它必须做好地向肺部提供空气，以便为肺部实际播出。““你不能只是打开一个粉丝然后思考，”好的，这将是我的呼吸器。“
气动系统模型在simscape。图片信用：剑桥顾问
“There wasn’t enough time to identify a component, order it, test it in the lab, then make a decision. We could go at the speed of simulation. That was really cool.”
Sean Thompson, senior mechatronics engineer at Cambridge Consultants
Basic ventilator and lung models were supplied by MathWorks, but Thompson expanded on them. The lung model was basically a gas-driven piston with springs and dampeners, “and that actually models the human lung really well,” he says.
Building the ventilator model, and writing the algorithms for controlling it, involved pair programing, with Thompson sitting at a computer while on a video call with others on the team. His collaborators, each responsible for an aspect of the system, would give high-level instructions, and he would implement them in the model. Both the visual nature of the coding and the tools for visualizing results allowed nonprogrammers to understand what was happening. “We could just leave it running there, watching it step through the program, a whole bunch of charts going by—that’s that event, that’s that event, that’s that event,” he says.
“The accessible nature of graphical programming in Simulink made it easy for us to tap into the expertise of many of our colleagues,” Thompson says. “That meant we could get all of these really useful insights into the system. Due to the accelerated schedule, there wasn’t enough time to identify a component, order it, test it in the lab, then make a decision. We could go at the speed of simulation. That was really cool.”
一旦设计开始塑造，大约三分之一的过程，团队建造了物理原型并将其挂钩到了ASL 5000Breathing Simulator, which acted as a physical lung model. The ventilator was still controlled by the algorithms on the computer (thanks to Simulink Desktop Real-Time™), though, in a setup akin to a hardware-in-the-loop rig.
尽管模拟的力量，但硬件的测试很重要。硬件测试还帮助团队校准了软件模型。在软件中，该团队可以更快地迭代设计并测试呼吸机的限制，而无需担心对硬件造成损坏。
A Change of Plans
剑桥顾问中途通过该项目获得曲线球。呼吸机要求改变了。最初，这个想法是将肺部视为呼吸中的被动伙伴，惰性袋膨胀和放气。但是在计时器上的机械通风会在几天后引起肺部损伤。如果患者从镇静中出现并且计时器没有用自然呼吸对齐，那么不适可能是极端的。在回应中，药物和医疗保健产品监管机构（MHRA）要求自发呼吸模式，其中呼吸机将从患者下载188bet金宝搏的肺部提示。
汤普森得到了他的肺模型积极呼吸，然后在下午看看他是否可以让呼吸机算法检测呼吸，尽管机器缺乏这种任务的理想传感器。“我们在被要求这样做的两天内与测试肺一起工作，”他说。“这是我曾经工作过的最神奇的事情之一。通过我们所有人在这个大型综合环境中工作，试图解决所有这些不同的技术问题，我们建立了这一基础设施，让我们令人难以置信地发展这种复杂的功能。“
Max Curzi, senior software engineer at Cambridge Consultants, took the control panel design and implemented it in Simulink to look just like it would on the device, using Simulink Dashboard blocks to make an interactive interface. This proved critical when the MHRA wanted to check on their response to the new requirement.
A Simulink model of dashboard panel based on the actual UI of the device. Image credit: Cambridge Consultants
When requirements changed to include a spontaneous breathing mode, in which the ventilator would take its cues from the patient’s lungs, the team adapted their model and had a working test lung in just two days.
“Within a week,” Curzi says, “we were able to demonstrate the full working system to the MHRA panel of experts in a video call. The Simulink model had all the knobs, gauges, and buttons of the real system and could control the ventilator in real time. During the call, they asked to interact with the ventilator in a variety of scenarios, saying ‘Okay, what if you do this? What if you do that?’ They were trying to stress it to break it. But it didn’t. It worked well, and they were pleased with the results.”
把事情简单化
球队面临着许多挑战。首先，有时间压力。该范围的项目需要各种工程专业知识，也需要人类因素，采购，项目管理和临床专家。所有这些团队（约200人在山顶上）在七周内并行流行，许多工作加班，以及在办公室的一些睡觉。任务的某些方面并没有很好地定义。基本组件，如压力调节器和气体混合器，在晚期重新设计或更换，但通过具有不同的机械特性，它们显着改变了系统动态：这需要团队重新设计，实施和测试一些警报算法这个项目的一个很晚的阶段。
设计团队在挂接到呼吸机的传感器和电磁阀（中间）的P金宝appC上运行Simulink Model（右侧）。使用人工肺，ASL-5000（左）模拟现实患者行为。图片信用：剑桥顾问
The final design worked, cost a fraction of what commercial ventilators cost, and was simple.
But the final design worked, cost a fraction of what commercial ventilators cost, and was simple. “You can count on two hands the number of components,” Curzi says. Regarding his own contributions, “I was really proud of making something that was simple and robust,” he says. “As an engineer, it’s tempting to develop sophisticated systems, but the complexity makes it harder to prove safety and robustness under all scenarios. Using a few fundamental blocks allowed the development of alarms and assisted breathing algorithms that would be robust and require a few lines of code to implement and test. Simple systems fail in predictable ways, so it’s easier to prove that the ventilator would be safe to use once the failure modes are accounted for.”
Ready Should the Need Reemerge
在呼吸机送达前一天，剑桥顾问得知它不再需要。英国的需求愉快地与预测的最坏情况模型一样大。Curzi说，这与医疗设备经常发生。“我们开发了希望不需要的呼吸机。”
The engineers learned a lot and found the experience hugely rewarding. “These things typically take years to develop,” Curzi says. “Being able to see the full development, from a blank canvas to the physical thing that will go into clinical trials, in 40 days was fantastic.”
“Being able to see the full development, from a blank canvas to the physical thing that will go into clinical trials, in 40 days was fantastic.”
Max Curzi, senior software engineer at Cambridge Consultants
“From a personal point of view,” Thompson says, “this project was an unbelievable experience, and it’s something I’m unlikely to repeat in my professional career. It was an amazing view of what is possible to achieve if you want it hard enough. I’m grateful to have been a part of something this unique.”
虽然英国暂停了呼吸机挑战，但该设计应该准备好。
ROBOTICS / AUTONOMOUS SYSTEMS
A 10-Day Dash to Build Robots That Fight COVID-19
Mobile Robots Help Disinfect High-Touch Surfaces
