How Do Ventilators Achieve Breathing?

[ToraToraTora]

Ok I know how they work physically but if the lungs are not functioning how does oxygen get into the blood via what would normally be the gaseous exchange? I assume they put pure oxygen into the lungs but if the lungs are not working how does that achieve "breathing", how does the oxygen get into the blood? Thanks.

[Mamyalynne]

This explanation may help.

https://www.nytimes.com/article/ventilator-coronavirus.html

[rowanwitch]

rarely 100% oxygen, a percentage appropriate to the patients needs
Various modes but the key thing is ventilation 'reverses the normal way we breathe in that it is a positive pressure system where air is pumped into the lungs and !leaves passively due to mechanical recoil. Normal breathing is expansion of the thorax creates negative pressure draws air in and expiration is a result of recoil and compression.
1. Full ventilation where the patient is unable to breathe for themself. Usually because they are in an induced coma with a paralyzing agent so they can't 'fight' the machine
2 partial ventilation where they are not paralysed and can breathe a bit, and the ventilator supports the breaths either by topping up the size of the breath of adding supplementary ones
3. Supported self ventilation where the patient initiates each breath but they are supplemented by the positive pressure from the ventilator.

Oxygen exchange occurs in the normal way but the drugs used to sedate and paralyze the patient may reduce blood pressure dramatically so that may need to be supported with drugs like adrenaline usually in tiny doses via a slow infusion.

Been a long time since I had to explain that so hope I got it right and it's simple enough

[ToraToraTora]

thanks, rowan, so the alveoli must still be functioning?

[Togo]

That is where pneumonia strikes TTT. It drastically reduces the efficiency of the alveoli and can cause death when severe even though a patient is being fully ventilated. Great synopsis from Rowan.

[rowanwitch]

Yes, but there is always a risk of high airway pressure causing some damage over extended periods, and in a condition that where pneumonia they can fill with fluid making ventilation very difficult. If the facility is available then extra corporeal oxygenation might be possible but centres that have the equipment and trained staff are very limited