A ventilator can be set up several ways. With every breath that we control with a ventilator certain levels of pressure are delivered with every breath. The goal is to open wider or hold open longer the alveoli which are the oxygen exchangers for the lungs. In that same process Co2 is exchanged.
Ards (adult respiratory distress syndrome) and covid 19 pts have alveoli that are compromised but the compromise is different.
Best example I can give is a balloon. Blowing an empty collapsed balloon takes an initial force to open up a balloon. That's forced inspiratory pressure. You can blow up a balloon filled with water and still have a high % of surface area available for air exchange. (ARDS). You blow up a balloon that is 3 times thicker with water in it... Covid alveoli.
Letting the air out of the balloon is important too. When you take a balloon and pull on both sides of the top and it makes that screetchy sound... You just added PEEP ( Positive end expiratory pressure). It controls how long and with how much pressure you exhale.
Vent PEEP for any pt is 5-8. ARDS 10-12 and the covid pts I cared for 14. If we tried to reduce their PEEP to 12 their oxygen content in their blood would drop to half of what it was.
The reason this is such a concern Is too little oxygen and the body reacts and becomes acidic which will eventually kill you. Too much pressure can cause barotrauma to the lungs and permanently damage the lungs.
It is what it is. We don't have a comparable template to run this on. We are reducing oxygen slowly then reducing PEEP. We do recruitment measures in which we take their PEEP to 22-24 for x minutes, then slowly reduce it over 10 minutes. It in effect " blows them open" and we see oxygenation get much better and the pt then expends much less energy to breath. Mind you this procedure drops their BP dramatically so Im in the room controlling the BP with IV meds. It can take up to an hour to get them stabilized again.
I've left out several other factors that we consider when ventilating a pt.