To think this reaction is self absorbed.

A real event where life was actually in danger, completely.

OP’s experience doesn’t quite sound like that. I’ve had a couple of moments where DC sleep awkwardly or look like they’re choking and the fear is real for sure, but it’s still a non issue as it’s my own interpretation of an event rather than what actually happened.

I hope you're ok OP. I'm not going to interrogate you about the duvet and the sheet or whether your child is disabled etc because that would be fucking stupid and seem almost designed to dismiss your feelings and upset you more.

It sounds like your husband couldn't be bothered to go upstairs. Answering 'yes'? like that was a lazy, nasty response and you're not wrong to be upset about it.

Is he generally like that when it comes to his parenting responsibilities?

Witnessing something where you think someone might die, might have died or might be seriously injured is a traumatic event.

Glad you have spoken with your child, I was going to suggest maybe you could check in on your child sooner in the evening, 20 mins or so after bedtime, to check they have settled as it did sound like they were playing a game by the fact your said their slippers were in the covers.

I would also suggest your husband didn't really react as he didn't see the situation or understand your panic. If I was worried my child had strangled themselves I would be trying to shake them away and screaming for help, not just shouting my husbands name. I am not sure whether you did try waking your child or whether you had realised he was fine and you simply untangled the sheets after the initial second or so of panic, in which case there was no issue.
I think I would have gone downstairs differently, and made a comment about myself overreacting and panicking child was strangled when I then realised then must have been playing. I think going down and basically saying 'where were you' is looking for a fight. So I can see why your husband thought you were having a go rather than focusing on your concern over the child. It could have been something you laughed about together 'child gave me such a fright', 'well that's good it wasn't anything serious and they just have been playing. Kids hey'

You would have;

heard your partner shout you and ignored it?
seen they were upset and offered no empathy?
assumed they were being critical and rather than asking, get angry?

He should have gone up to check everything was ok.
He should have offered empathy.
He should have apologised for not coming up.

Sounds like you had a real fright, and that’s completely understandable. But a real fright over a non issue does make you look dramatic and the self absorbed one to others which is why there’s a lack of sympathy from posters and probably your DH too.

It was a non issue that happened last night, best put it behind and move on.

Tbh if you are concerned about strangulation you shouldn't be giving him safety 'advice' you should be sternly giving him RULES.
You don't say 'oh it's not the best idea to do that with your duvet it's not safe' - that's too wishy washy. You say 'you Must NOT undo your duvet cover' and not in a nice sing songy voice in a firm tone that's black and white.
His bed is for sleeping not mucking around this is not the time for creativity

My DS did this when he was younger - I don't think he was quite as tangled up as you describe your DS to be tho. It is deeply upsetting to find your child in a potentially dangerous situation and I am glad it is all ok.
There are 2 issues here - 1 is you being deeply shaken by what your DS did and the other is lack of concern by your DH. Perhaps talk to your DH when everyone is calmer to explain why you were so upset. Hopefully he will understand your point of view.

Excellent advice.

The OP has said clearly she didn’t criticise him. My DH is like this to the extreme. Will think I’m criticising him when I’m not and respond angrily. Her DH is a twat IMHO.

OP I absolutely feel your frustration - I've had very similar fall outs. It doesn't really matter if the danger was real or imaginary (although it could well have been real!). The point is that in that moment you were very worried. But you didn't get the help you need. And instead of actually seeing if his was kid was OK, and then whether you were ok, he chose to focus on his feelings and how it all affected him. This is possibly a lack of emotional intelligence on his part, at worst slightly narcissistic behaviour - but hopefully it was a one-off and just down to misunderstanding.

I think a few posters here have been very unkind. I don't think you're unreasonable to feel this way.

You got a fright and that’s ok, probably a lot of us have had moments like that with our kids. Having said that I would imagine it only took two seconds to realise he is fine. I’d have a deep breath, phew he’s ok and then composed myself. I’d have then gone downstairs and said crikey 4 yr old gave me the fright of my life for a few seconds. I’d probably also have said to dh can you come up in future if I call you as it could be something urgent or worrying otherwise I wouldn’t be calling you in the first place. I probably would decide not to put a duvet cover on for a while just to have peace of mind for a while.

Your dh should have given you a reassuring cuddle though when he saw how upset you were as it costs nothing but can mean a lot.

Honestly OP, I would leave this thread to rumble on with the pile-on. It's a waste of your time to keep reiterating your point. People don't want to understand you, they want to have a go. And those who have already misfired and jumped in with both feet will want to defend their lack of comprehension by doubling down.

Think about starting a thread in relationships instead, talking about your dh's propensity to go on the defensive and adopt the role of victim. You'll get better responses than you have had here.

It’s not naughty. Kids experiment and play. It’s a learning opportunity.

Naughty? FFS.

Also, what PPs (and your DH) appear to have an empathy bypass about is that it’s a terrible shock to check on your child, expect to find them tucked up in bed as usual, then find them wrapped up like a mummy.

Whatever the potential risk, it’s the shock of finding a child like that. And the immediate fear your mind leaps to, i.e. are they breathing.

It’s like witnessing someone nearly being hit by a car or finding someone who’s fallen. They may be fine, but you’ve still had a shock.

My son went through a phase with this as he likened it to a sleeping bag like in camping.

The opening post explains it though.
He didn't come when she called. He's "gone on the defensive" so clearly Op has criticised him.
It's hard to be empathetic when you are being criticised but also when the issue has already been (very) easily resolved.
Pretty sure if Op had just come downstairs shaken her DH would have asked what's wrong or she could explain her fright without blaming DH for not helping.

Like "fck, that was horrible I just found our DS tangled in his sheet...he'd done x,y,z and j really panicked for a minute"
DH "why didn't you shout louder"
Me "He's fine now but I was shouting for you to help. I'm just a bit shaken now but hes OK"
DH "why are you just coming downstairs to have a go at me"
Me "I'm not, I'm just a bit upset I thought for a moment something awful had happened"
DH [Raises voice] "Well it just sounds like you came down to have a go at me"*

It sounds like there's a bigger picture of your DH not really showing care. I don't know if I would have expected my DH to hug me and be overly comforting in this sort of situation. If this is how your conversation with him went, I think it's odd that he shut you down by saying you were having a go at him and blaming you for not shouting louder. I think a caring partner wouldn't have turned the situation around to make it about him and his feelings.

Duvet covers are woven cotton you can breathe through it? It's not a fabric air can't get through??
Kindly OP, this is something my family would have probably laughed at, like Omg look what the little pickle has done?!
Tbh your bigger issue is your child's behaviour - he should have been sleeping/lying sensibly not undoing the duvet cover, removing the duvet etc? That's quite naughty??