CPAP stands for continuous positive airway pressure, one of the problem with SARS(Severe acute respitory syndrom) or Wuhan Fever is it stiffens the lungs making it hard to exhale. This in turn allows the lungs to fill up with fluid, a sort of viral pneumonia. I believe a ventilator uses a negative pressure or vacuum to assist with exhalation and air exchange.
Actually exhalation is passive, not active, in modern day ICU ventilation.
Interesting. How does that work? Does the pressure drop to let air out or something?
I've been looking over the designs being put forward in the various places now, and I cannot understand why people aren't just planning to copy the Manley ventilator. This was the standard ventilator in Europe for decades. It is simple to design, does not even require electricity (mechanical solution driven by air from central compressed air system) so all parts can be sourced locally, and the design has a clinically…
Actually exhalation is passive, not active, in modern day ICU ventilation.
Interesting. How does that work? Does the pressure drop to let air out or something?
To keep it simple you have a device that increases pressure through a closed circuit to push air into the lungs, when its time to exhale it drops pressure (although is still positive pressure i.e PEEP) that is weaker than the natural recoil/elasticity of the chest wall combined with gravity in a supine patient and allows exhalation.
I've been looking over the designs being put forward in the various places now, and I cannot understand why people aren't just planning to copy the Manley ventilator. This was the standard ventilator in Europe for decades. It is simple to design, does not even require electricity (mechanical solution driven by air from central compressed air system) so all parts can be sourced locally, and the design has a clinically…
The issue is that with the kind of ventilation required you need to sedate the patient with gasses and you need to recycle those gasses and unused oxygen. With the length of time patients have to be on this you don't want to lose those gasses and also pump it out into the atmosphere. The Manley design could be a good starting point I suppose, you just have to replace the weight system with controllers and add a carbon scrubbing stage to feed back the gasses. The carbon scrubbing stage is the tricky one, it's something that requires good chemistry and not mechanics and electronics.
I've been looking over the designs being put forward in the various places now, and I cannot understand why people aren't just planning to copy the Manley ventilator. This was the standard ventilator in Europe for decades. It is simple to design, does not even require electricity (mechanical solution driven by air from central compressed air system) so all parts can be sourced locally, and the design has a clinically…
The issue is that with the kind of ventilation required you need to sedate the patient with gasses and you need to recycle those gasses and unused oxygen. With the length of time patients have to be on this you don't want to lose those gasses and also pump it out into the atmosphere. The Manley design could be a good starting point I suppose, you just have to replace the weight system with controllers and add a carbo…
I am ignorant as far as the use of inhalable medications is concerned. However, I find it weird that you'd want to recycle oxygen: carbon dioxide removal is either hard or requires consumables, while oxygen can be concentrates from air using a simple process that consumers only energy (by adsorbing nitrogen on surfaces of particular minerals).
Interesting. How does that work? Does the pressure drop to let air out or something?
To keep it simple you have a device that increases pressure through a closed circuit to push air into the lungs, when its time to exhale it drops pressure (although is still positive pressure i.e PEEP) that is weaker than the natural recoil/elasticity of the chest wall combined with gravity in a supine patient and allows exhalation.
Agree. I'd add that my comment above about exhalation being passive is true in adult ICU practice. In high frequency oscillatory ventilation (HFOV) exhalation is active (a piston actively creates a negative pressure in the breathing circuit). I understand this is still used quite a bit in neonates (though I don't do NICU, so not an expert) but has gone out of favour in adults in a big way due to the results of trials like OSCILLATE (https://www.nejm.org/doi/full/10.1056/NEJMoa1215554). Probably still used in some centres as a rescue therapy, but I haven't used it in years (we'd use VV ECMO for that purpose).
Any thoughts about using a regular sleep apnea CPAP device for this type of situation, where one has access to the pressure settings?
Someone dear to me needs a ventilator per tracheostomy (Trilogy 100). Her Consultant Aenesthesist who was in Italy four weeks ago and works on an Intensive Care Unit told me that 6 out 10 Covid-19 affected ITU patients require an ECMO (https://en.m.wikipedia.org/wiki/Extracorporeal_membrane_oxyg...). This is very bad. I could sense his unease, these are machines you don't come by easily. His ITU is preparing for war, Brexit and the conservative's austerity program has put the NHS to breaking point.