4 ms·

These comments appear to conflate the surgical bypass and VAD literature. Also, the timeframe for valvular calcification and thrombosis are not similar. Thromb

These comments appear to conflate the surgical bypass and VAD literature. Also, the timeframe for valvular calcification and thrombosis are not similar. Thrombosis is the killer when it comes to devices.

iancmceachern 3y ago
There is no way to conflate them. They are the same, they both have to do with the human body and its needs. It doesn't matter if you have one article about weed wacking that says some things about grass, and another article about mowing that also says things about grass. If one wanted to know about grass, it's reasonable to assume you would aggregate the knowledge from both weed wacking and mowing sources so as to have the most complete picture of grass. Same here, we don't have a lot of studies on this whole cutting a head off and keeping it alive. The closest two things we have are artificial hearts/lvads, and CPB pumps. It's reasonable for us to take those knowledge bases and like with the grass, learn the most from what we have. You are right, those processes are different and as such have different time frames and clinical implications. Another interesting point of note. Every artificial heart that is still implanted (Syncardia, Carmet), is about to start to ve implanted (Swedish realheart, bivacor) or has been implanted (abiocor, jarvik 7 which is now the syncardia, etc) were/are all fully pulsatile. There is one case where Cohn and Frazier implanted a truly hand made bubble gum and duct tape pump made from 2 heartmate ii lvads fiberglassed together, that wasn't pulsatile but the patient was never expected to live long and it was really something they shouldn't have done.
- carbocation 3y ago
  I cannot stress how different routine cardiopulmonary bypass is versus VAD implantation. From patient selection to procedural considerations, no clinician would treat them as if they were the same thing. I'm saying this for the benefit of other HN readers.
  - iancmceachern 3y ago
    100%. I'm speaking from a design perspective. When we design a pump, any pump, we need to design it to certain design inputs. Say we're designing a well pump. We need the pump to pump a certain amount of water, a certain height, with a certain input power. It's the same when we design LVADs or CBP pumps, peristaltic blood pumps for dialysis machines, etc. One example. I lead the team that designed the peristaltic blood pump (and most of the whole system really) for the Outset medical Tablo kidney dialysis machine. I also have designed several other peristaltic pumps that pump other fluids. Pragmatically, the designs are almost identical. It's because pumps are pumps. The renal technician is going to say that the pump on their Gambro Dialysis machine is completely different than the pump in the Wendy's frosty machine down thr street, but the design engineer that designed them both knows better. Back to this topic. When we design a blood pump, it needs to meet certain design requirements. To test our design we need to model the body, it's response to inputs, etc. When we do this, we use the exact same models, exact same tools, exact same design principles, exact same process, amd exact same requirement s in many cases. Indeed, no clinician would ever treat these things the same just like no mechanic would treat a Ford the same as a Toyota. But at the design level, they're the sake. They're both designed using the same CAD software, share many of the same suppliers and middle ware suppliers, etc. I cannot stress how similar so many things are in medicine, in medical device design. So many people try to put up walls like this. It's not helpful to highlight differences, it's helpful to identify similarities, because that's where the economy of scale lieslies, that's where we can come together and solve problems.
    - carbocation 3y ago
      Actually, it's important to distinguish things that are not clinically similar. The physical principle being the same, in this case, has little to no bearing on the clinical context or consequence.
      - iancmceachern 3y ago
        Not at all. Physics is physics, it doesn't magically stop just because it's in the body. Just because we put two identical things into use doing 2 different things, doesn't mean they're not the same. A person with a back ache could be prescribed aspirin. Another person with blood clots could also be prescribed aspirin. Clinically these are very different things. The aspirin, and the factory that makes it, and the biochemistry by which it works, is the same. Blood pumps are blood pumps, aspirin is aspirin. What you do with them clinically, and how, can vary widely. Agreed. But that doesn't mean the chemistry, physics, engineering behind them does too.

iancmceachern 3y ago

There is no way to conflate them. They are the same, they both have to do with the human body and its needs. It doesn't matter if you have one article about weed wacking that says some things about grass, and another article about mowing that also says things about grass. If one wanted to know about grass, it's reasonable to assume you would aggregate the knowledge from both weed wacking and mowing sources so as to have the most complete picture of grass. Same here, we don't have a lot of studies on this whole cutting a head off and keeping it alive. The closest two things we have are artificial hearts/lvads, and CPB pumps. It's reasonable for us to take those knowledge bases and like with the grass, learn the most from what we have. You are right, those processes are different and as such have different time frames and clinical implications. Another interesting point of note. Every artificial heart that is still implanted (Syncardia, Carmet), is about to start to ve implanted (Swedish realheart, bivacor) or has been implanted (abiocor, jarvik 7 which is now the syncardia, etc) were/are all fully pulsatile. There is one case where Cohn and Frazier implanted a truly hand made bubble gum and duct tape pump made from 2 heartmate ii lvads fiberglassed together, that wasn't pulsatile but the patient was never expected to live long and it was really something they shouldn't have done.

carbocation 3y ago
I cannot stress how different routine cardiopulmonary bypass is versus VAD implantation. From patient selection to procedural considerations, no clinician would treat them as if they were the same thing. I'm saying this for the benefit of other HN readers.
- iancmceachern 3y ago
  100%. I'm speaking from a design perspective. When we design a pump, any pump, we need to design it to certain design inputs. Say we're designing a well pump. We need the pump to pump a certain amount of water, a certain height, with a certain input power. It's the same when we design LVADs or CBP pumps, peristaltic blood pumps for dialysis machines, etc. One example. I lead the team that designed the peristaltic blood pump (and most of the whole system really) for the Outset medical Tablo kidney dialysis machine. I also have designed several other peristaltic pumps that pump other fluids. Pragmatically, the designs are almost identical. It's because pumps are pumps. The renal technician is going to say that the pump on their Gambro Dialysis machine is completely different than the pump in the Wendy's frosty machine down thr street, but the design engineer that designed them both knows better. Back to this topic. When we design a blood pump, it needs to meet certain design requirements. To test our design we need to model the body, it's response to inputs, etc. When we do this, we use the exact same models, exact same tools, exact same design principles, exact same process, amd exact same requirement s in many cases. Indeed, no clinician would ever treat these things the same just like no mechanic would treat a Ford the same as a Toyota. But at the design level, they're the sake. They're both designed using the same CAD software, share many of the same suppliers and middle ware suppliers, etc. I cannot stress how similar so many things are in medicine, in medical device design. So many people try to put up walls like this. It's not helpful to highlight differences, it's helpful to identify similarities, because that's where the economy of scale lieslies, that's where we can come together and solve problems.
  - carbocation 3y ago
    Actually, it's important to distinguish things that are not clinically similar. The physical principle being the same, in this case, has little to no bearing on the clinical context or consequence.
    - iancmceachern 3y ago
      Not at all. Physics is physics, it doesn't magically stop just because it's in the body. Just because we put two identical things into use doing 2 different things, doesn't mean they're not the same. A person with a back ache could be prescribed aspirin. Another person with blood clots could also be prescribed aspirin. Clinically these are very different things. The aspirin, and the factory that makes it, and the biochemistry by which it works, is the same. Blood pumps are blood pumps, aspirin is aspirin. What you do with them clinically, and how, can vary widely. Agreed. But that doesn't mean the chemistry, physics, engineering behind them does too.