Tightlacing

You know this... *sigh*
The above image (far left and far right - see the original in the linked wikipedia article) is from 1880s.
I have taken the image, measured about where the ladies are the same (red lines in the third body), and then squeezed with paintshop UNDER the line, leaving the ribcage untouched, to show that when one wears a corset, the ribcage isn't effected much. It doesn't get squeezed together like in the horror image.
You can also experiment with your own ribcage. How hard to you need to push, squeeze, press, to get it to move at all? One can stand on one's ribcage without it giving much in. Do you think a corset could put that much pressure on it?

Then I dressed the ladies, to show how off the proportions are. It's easy to miss, when they are presented like that, and you are told what to see, but just look at the first lady. I had to make the t-shirt image a lot smaller over her shoulders and upper arms to get it fit even that well, and it's still too big. Her lower body is too big compared to the upper body. Her waist is very long. Because of this, the actual 1850s corsets on the body sit very badly. I had to take it in on the hips of the second lady, and as you can see, I would have needed to make it a bit larger at the waist for the horror lady. There is no 1880s corset with that tight waist.

So... what does this mean? They have exaggerated the proportions to enhance the "difference" - the uncorseted body is bigger than normal uncorseted body, the corseted smaller than normal corseted body. A corset would not have much effect at all on the ribcage and therefore on anything covered with the ribcage, that is lungs, heart, etc. Also, the effect is only on less than 4 inches.

This is an 1880 corset, in Fashion Institute of Technology's museum. No, it's not for pregnant women. That's what all corsets look seen from side. A lot of people just look at the full frontal, and focus on the hourglass figure, forgetting that women were supposed to look like hourglasses all around. They didn't have any "flat belly" ideas.

ALSO, the 16-inch, 13-inch waist, that was extreme body modification that wasn't the norm. If you look at the antique dresses, there's in average just 10 inches between waist and chest size. Like Gal Gadot. I suppose that means she's dead because of her impossibly cinched waist. She must have removed some ribs to get those measurements. Or Kendall Jenner. Same proportions. Would fit in a antique Victorian dress without a corset. So horrible.

I mean, seriously!

People have claimed that wearing a corset damages your heart. There is no evidence of this.
People have claimed that wearing a corset damages your lungs or makes it harder to breathe. Your lungs are encased in the ribcage, and the corset doesn't do anything about the ribcage, so how could it? Not one woman wearing a well-fitted corset complains about difficulties breathing. It's mostly psychological.
People have claimed that a corset will misshape your ribcage. Funnily, there are no skeletons to prove this theory, even though women have been wearing corsets and stays for some 500 years.
People have claimed wearing a corset damages your liver. No evidence of this either.
I mean... people just claim things, and there is no evidence of any of this. On the contrary, people who actually wear corsets say this:

"I myself have never felt any ill effects from nearly 30 years of the most severe tight lacing, nor have I yet found any authentic case of real harm being done by stays, even when laced to the utmost degree of tightness, both day and night.

People who write against the practice of tight lacing are either those who have never been laced and have never take the trouble to inquire into the pros and cons of the subject, or those who have, perhaps been once lace up very tightly in badly made, ill-fitting stays with the settled determination of finding them most awful instruments of torture."

- a corset wearing lady, 1893

But, no, one rather believes one's own prejudices and preconceived notions than educate oneself and listen to people who actually know what they are talking about.