3 ms·

Setting up a ventilator for treating ARDS (caused by the viral infection and inflammatory response) is at the much harder end of respiratory therapy unfortunate

Setting up a ventilator for treating ARDS (caused by the viral infection and inflammatory response) is at the much harder end of respiratory therapy unfortunately. This is also one reason why just building the simplest possible ventilator simply isn't possible / useful here. Yes you could basically build a 1960s design en-masse but at the moment 50% of people on modern vents are surviving so this is no panacea. The trick will be to find a minimal feature set design, that doesn't use a lot of specialist long lead time components, can be used by people who are less experienced, and is suitable for treating ARDS. That is a much harder problem than the basic one of getting some kind of ventilator mass produced on an emergency basis.

thu2111 7y ago
That minimal feature set is a CPAP machine + maybe an oxygen valve of the 3D printable variety. Modern CPAP machines can generate phenomenal pressures and can be adjusted with simple touch screens. They support automatic pressure reduction on exhalation, and Bluetooth/cloud access to the data in them for remote monitoring via mobile apps. BTW it's not quite as simple as 'hospital ventilators are hard to use'. Firstly, modern ventilators are much easier because the manufacturers realised that high training costs were limiting their market, so they've got a lot easier to use. Secondly, the US did a previous disaster response training exercise where they trained a bunch of non-specialist medical staff like nurses and even vetinarians how to use the machines. After 2 days of training there was an exam: the vets did best.
- Mvandenbergh 7y ago
  CPAP machines generate continuous positive pressures though, they assist breathing. I know they have slow ramp capabilities for comfort reasons (start off at low positive pressure when you fall asleep and then increase) but I don't think they can swing pressure fast enough to enable inhalation and exhalation. You need: -Gas blending (relatively trivial) -A source of pressure (CPAP has this) -A way of modifying pressure up and down quickly and precisely enough to stimulate breathing (Don't think CPAP has this) -A way of measuring flow and pressure (Does CPAP have this with good time resolution? I doubt it as not required for CPAP) -A controller which uses the flow and pressure data to vary the system pressure (CPAP doesn't have the right software but presumably this is less time constrained than the others) So I'm really not sure that you can do this with a modified CPAP machine. BTW I'm not sure that you can print oxygen valves, maybe air valves or patient valves. High pressure inlet oxygen parts need to be oxygen compatible and many 3d printed materials may combust under those conditions.
  - thu2111 7y ago
    CPAP machines technically can't but CPAP has become a generic term that also encompasses bi-level/APAP machines that can swing pressure fast enough to track inhalation/exhalation. Both mine do. They're not that old but they're not top-end either. I don't know how many active machines are pre-APAP/BiPAP/A-Flex (there are different names for it). A comment below says 90% but this seems very high to me. I wonder if it's possible some doctors don't realise the machines have this feature or it's importance? When I first was prescribed CPAP the machine did not come with bi-level flex enabled, it made it very hard to tolerate. I pushed through it for months but when I "cracked" the doctor-only DRM (i.e. looked up the cheat code on Google) and enabled A-Flex it instantly became way easier to handle the machine and my AHI scores were super low; big success. Doctor was quite happy with my altered configuration. I was just surprised such a basic thing hadn't been explained to me. I suspect a lot of CPAP machines support bi-flex but it either isn't activated or could be added via a software update. I don't think you need extra components. Oxygen valves come from here: https://learningenglish.voanews.com/a/volunteers-produce-3d-printed-valves-for-italian-coronavirus-patients/5334261.html https://learningenglish.voanews.com/a/volunteers-produce-3d-...
    - Mvandenbergh 7y ago
      Very interesting, thanks. If that is the case then it may indeed simply be a software thing. Specifically for treating ARDS you need: -High PEEP (obviously any CPAP machine can do this) -Low plateau pressure (probably possible, that's just software) -Low tidal volume and high breathing rate. Breathing rate is just a cycling variable so should be software only issue. Managing low tidal volume will require the machines to have a flow sensor. Do you know if any of your machines do? If so, then this is likely fixable with only software. My interpretation of that article is it must refer to the patient valve as those are one-time use (as they in contact with contaminated patient exhalations) rather than O2 inlet valves which are not disposable. Patients are breathing high-ish O2 but obviously not HP pure O2 so 3d printed is fine for that. 3D printing is useful for cases like that where due to logistics there is a temporary shortfall in local supply. I suspect that 3 months from now we are unlikely to be using those measures as global production and distribution of ventilator consumables ramp up.
- tomatotomato37 7y ago
  A CPAP is fixed pressure, what your thinking of is a APAP or the bilevel type of positive air-pressure machines. And there lies the problem with you're miniumum feature set; not all *PAPs are fully-featured machines. Maybe only 10% or so are suitable for ventilator duty, which means they too are supply-limited
  - thu2111 7y ago
    I own two CPAP machines and yes they both implement bi-level/APAP features. CPAP is a bit of an ambiguous term these days; whilst there are technical differences between them, most people call all such devices CPAP machines. For instance, https://www.usa.philips.com/healthcare/product/HCNOCTN447/dreamstation-cpap-bi-level-therapy-systems https://www.usa.philips.com/healthcare/product/HCNOCTN447/dr... It's advertised as "CPAP & Bi-Level therapy". To be clear, I'm talking about the ones that implement bi-level pressure. The difference is (as far as I know) primarily a matter of software; perhaps older machines can be upgraded if pricing/selling upgrades is taken out of the equation? I've had my machines for I think a couple of years now and they were all bi-level from the start. I'm not sure when that started becoming standard or where you got that 10% figure from, you may well be right. But there are 300,000+ sleep apnea patients being treated in the UK alone. If even only 10% of them use modern machines (seems low given how much better bi-level makes it), that's still 30,000 portable ventilators available to be requisitioned at short notice. Sleep apnea patients don't have a critical need for them.

thu2111 7y ago

That minimal feature set is a CPAP machine + maybe an oxygen valve of the 3D printable variety. Modern CPAP machines can generate phenomenal pressures and can be adjusted with simple touch screens. They support automatic pressure reduction on exhalation, and Bluetooth/cloud access to the data in them for remote monitoring via mobile apps. BTW it's not quite as simple as 'hospital ventilators are hard to use'. Firstly, modern ventilators are much easier because the manufacturers realised that high training costs were limiting their market, so they've got a lot easier to use. Secondly, the US did a previous disaster response training exercise where they trained a bunch of non-specialist medical staff like nurses and even vetinarians how to use the machines. After 2 days of training there was an exam: the vets did best.

Mvandenbergh 7y ago
CPAP machines generate continuous positive pressures though, they assist breathing. I know they have slow ramp capabilities for comfort reasons (start off at low positive pressure when you fall asleep and then increase) but I don't think they can swing pressure fast enough to enable inhalation and exhalation. You need: -Gas blending (relatively trivial) -A source of pressure (CPAP has this) -A way of modifying pressure up and down quickly and precisely enough to stimulate breathing (Don't think CPAP has this) -A way of measuring flow and pressure (Does CPAP have this with good time resolution? I doubt it as not required for CPAP) -A controller which uses the flow and pressure data to vary the system pressure (CPAP doesn't have the right software but presumably this is less time constrained than the others) So I'm really not sure that you can do this with a modified CPAP machine. BTW I'm not sure that you can print oxygen valves, maybe air valves or patient valves. High pressure inlet oxygen parts need to be oxygen compatible and many 3d printed materials may combust under those conditions.
- thu2111 7y ago
  CPAP machines technically can't but CPAP has become a generic term that also encompasses bi-level/APAP machines that can swing pressure fast enough to track inhalation/exhalation. Both mine do. They're not that old but they're not top-end either. I don't know how many active machines are pre-APAP/BiPAP/A-Flex (there are different names for it). A comment below says 90% but this seems very high to me. I wonder if it's possible some doctors don't realise the machines have this feature or it's importance? When I first was prescribed CPAP the machine did not come with bi-level flex enabled, it made it very hard to tolerate. I pushed through it for months but when I "cracked" the doctor-only DRM (i.e. looked up the cheat code on Google) and enabled A-Flex it instantly became way easier to handle the machine and my AHI scores were super low; big success. Doctor was quite happy with my altered configuration. I was just surprised such a basic thing hadn't been explained to me. I suspect a lot of CPAP machines support bi-flex but it either isn't activated or could be added via a software update. I don't think you need extra components. Oxygen valves come from here: https://learningenglish.voanews.com/a/volunteers-produce-3d-printed-valves-for-italian-coronavirus-patients/5334261.html https://learningenglish.voanews.com/a/volunteers-produce-3d-...
  - Mvandenbergh 7y ago
    Very interesting, thanks. If that is the case then it may indeed simply be a software thing. Specifically for treating ARDS you need: -High PEEP (obviously any CPAP machine can do this) -Low plateau pressure (probably possible, that's just software) -Low tidal volume and high breathing rate. Breathing rate is just a cycling variable so should be software only issue. Managing low tidal volume will require the machines to have a flow sensor. Do you know if any of your machines do? If so, then this is likely fixable with only software. My interpretation of that article is it must refer to the patient valve as those are one-time use (as they in contact with contaminated patient exhalations) rather than O2 inlet valves which are not disposable. Patients are breathing high-ish O2 but obviously not HP pure O2 so 3d printed is fine for that. 3D printing is useful for cases like that where due to logistics there is a temporary shortfall in local supply. I suspect that 3 months from now we are unlikely to be using those measures as global production and distribution of ventilator consumables ramp up.
tomatotomato37 7y ago
A CPAP is fixed pressure, what your thinking of is a APAP or the bilevel type of positive air-pressure machines. And there lies the problem with you're miniumum feature set; not all *PAPs are fully-featured machines. Maybe only 10% or so are suitable for ventilator duty, which means they too are supply-limited
- thu2111 7y ago
  I own two CPAP machines and yes they both implement bi-level/APAP features. CPAP is a bit of an ambiguous term these days; whilst there are technical differences between them, most people call all such devices CPAP machines. For instance, https://www.usa.philips.com/healthcare/product/HCNOCTN447/dreamstation-cpap-bi-level-therapy-systems https://www.usa.philips.com/healthcare/product/HCNOCTN447/dr... It's advertised as "CPAP & Bi-Level therapy". To be clear, I'm talking about the ones that implement bi-level pressure. The difference is (as far as I know) primarily a matter of software; perhaps older machines can be upgraded if pricing/selling upgrades is taken out of the equation? I've had my machines for I think a couple of years now and they were all bi-level from the start. I'm not sure when that started becoming standard or where you got that 10% figure from, you may well be right. But there are 300,000+ sleep apnea patients being treated in the UK alone. If even only 10% of them use modern machines (seems low given how much better bi-level makes it), that's still 30,000 portable ventilators available to be requisitioned at short notice. Sleep apnea patients don't have a critical need for them.