Mechanical ventilation appears (to me, a naive observer) to help only push air into the lungs if a person cannot breathe well— that is to say, having difficulty inhaling and exhaling. It makes sense to me that a person who is perhaps paralyzed would need a machine to force the lungs the work, mechanically speaking.
But how does this help someone suffering from injury or disease in the lungs themselves? Is a ventilator better at delivering oxygen than our own normal breathing process?
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A ventilator isn’t needed if the respiratory system is working normally. It’s there to help when you *can’t* breath normally. That doesn’t necessarily have to be something wrong with the diaphragm itself, it could be something else wrong that prevents you from getting oxygen properly. The ventilator doesn’t just take over for the diaphragm, it can also adjust oxygen percentage, humidity, etc.
If there is a problem in your lungs you may need to breathe more deeply just to get enough air while sitting still or lying down. This deep, labored breathing can be exhausting, and in fact if you have to keep this up for long enough your breathing muscles can give out. So in these cases it can be beneficial to let a ventilator do the heavy lifting instead.
Not sure if this will help. I haven’t been intubated but I was on assisted breathing for a while. I was struggling to breathe, my heart rate and blood pressure were up and I was exhausted. The stuck these prongs up my nose and I had straps going over and around my head to hold it in place. The prongs were attached to a big flexible tube that had come through a machine that mixed oxygen with warmth and humidity. I think it was blowing 30L a minute in to my lungs at the start. Imagine sitting in front of a very strong fan, opening your mouth and letting the air push in. The moment they put in on me, I my muscles relaxed. I wasn’t sucking in air or trying to push it out. I didn’t realise it but my diaphragm, back, shoulder and neck muscles were all sore from the effort.
Your body seems to realise it is getting the oxygen it needs so it stops putting in as much strenuous effort and you get a bit of a physical break.
>Mechanical ventilation appears (to me, a naive observer) to help only push air into the lungs
You are correct. Normal lung use is sucking air in. This is the active part of normal breathing and requires energy. Energy requires oxygen. Keep this in mind.
Air coming out is passive. Our system returns to normal or relaxes.
Pressure likes to be equal. So when the lungs expand it creates negative pressure inside the body and outside air goes in to equalize.
The ventilator is a positive pressure system. Your body requires no extra energy to move the respiratory muscles around.
>But how does this help someone suffering from injury or disease in the lungs themselves?
Many ways. One in particular is shock. The most basic definition is low oxygen to the cells, the reasons are many. So if you’re in shock and need more oxygen a simple way for us to reduce consumption is to stop the muscles from burning it or more of it. Regardless of how well the diaphragm works seeing as we can’t stop say.. The heart.
Say the body needs exactly 100 oxygens to function.
Those 100 are split up by all the different systems with some left over. Let’s say suddenly the body is no longer able to deliver those 100 oxygen because it lost half of your blood. Now you only have 50 oxygens but the rest of your body is fine and still needs its reserved number. If we remove (paralyze) the respiratory system (diaphragm too) the required oxygens is now less. All the other systems get more available oxygens.
>Is a ventilator better at delivering oxygen than our own normal breathing process?
In a normal healthy person, no.
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