Trouble breathing without a CPAP machine

I have a question, because the doctors aren't telling us anything and they seem just as clueless as we are about what's actually going on.

Here’s the situation.
A person in their 70s is currently in the ICU. They had spinal surgery a few months back due to fused discs, which triggered a massive bout of depression. They've been relying on half a Praxiten every single night just to sleep. They lost a significant amount of weight, too. About four months ago, they even sat their son down and said goodbye, telling him this was the end and it would be the last time they saw each other.
They've lived with liver cirrhosis for 20 years, but recent tests from a couple of days ago showed the liver looks like a baby's—completely regenerated.

During a hospital visit for some tests, they started choking and coughing up fluid. They suffered two cardiac arrests and had to be resuscitated. Their skin has taken on this greenish tint.
It's been two days on life support. As soon as they try to take them off the ventilator, they stop breathing.
The doctors are stumped. They ran tests just two days ago—CT scan was clear, lungs look fine, heart seems okay (they initially suspected an esophageal vein issue or an enlarged aorta, but ruled those out). Basically, everything looks perfect on paper.
They might run some additional tests today.
We just don't get it. If everything is "fine," why can't they breathe without the machine?

Does anyone have any ideas? We really need help here. The doctors aren't giving us straight answers because, if they're being honest, they don't know what's happening either.

Thanks in advance.

Fine, feel free to lock this thread or just delete it entirely.
The doctors finally figured it out—it's myasthenia gravis.

First off, you really need to double-check if we’re actually talking about myasthenia gravis here and how they landed on that diagnosis. Like, did a neurologist sign off on an official chart, or was it just some quick note from an ER doctor on duty, or maybe just a passing mention of myasthenic syndrome?

When it comes to ventilators and weaning someone off them, things get pretty complicated in these situations.
For one thing, the patient is older, and when someone is already dealing with a bunch of different diagnoses, getting them off the machine isn't always a smooth ride.
Plus, an acute myasthenic crisis can drag on for quite a while. Since this whole thing happens at the neurotransmitter level and it's autoimmune, the person basically loses their muscle strength—some people might struggle to lift an arm or a leg, or even hold their head up... but for others, the clinical picture is so bad they don't even have the strength to breathe.

With those acute attacks that lead to respiratory failure, doctors often use plasma exchange several times alongside bedside care—it’s a type of dialysis technique where they try to clear out those autoimmune antibodies from the bloodstream.
If a patient has been on a ventilator for more than ten days or looks like they'll be stuck on it for much longer, they’ll definitely perform a tracheotomy—basically opening the windpipe in the neck and placing a tracheal cannula so the ventilator works through that tube instead.
It is super important during mechanical ventilation to regularly clean the airways using sterile techniques—you know, suctioning the secretions out of the lungs. If you aren't keeping the lungs clear, ventilation gets much harder and the risk of developing pneumonia shoots way up.
While they're ventilating, if the machine allows for it, you want to use advanced modes like BIPAP, CPAP+PSV, or PCV+PSV... the ones that support the patient even when they make tiny attempts to breathe, rather than sticking to old-school volume modes like IPPV or CMV.
You'll also need to feed the patient via a nasogastric tube with the right nutritional formulas, especially since they usually won't be able to eat on their own.
And don't forget regular physical therapy to keep the joints moving and prevent contractures, plus you've got to keep turning the patient in bed constantly so they don't end up with pressure sores.

Thanks for the detailed breakdown.
He can move around, use his hands, and turn his head. But they had to restrain his arms because he keeps pulling at the breathing tube. He was heavily sedated for two days, but things started looking up yesterday.
Just a heads-up, three fingers on each hand—starting from the middle one—have been curled inward for years now. It’s a real struggle for him to straighten them out.

The doctors are about 90% certain it's Myasthenia Gravis, though they’re running more tests. They also brought up the possibility of plasmapheresis.