So in my WIP one of my MC's is stabbed in a fight and passes out, the where, whats and hows are not a necessity to this question; lets just say if he was unconcious and had a knife sticking out of him and was bleeding would they think he was dead? Did they check for pulses during the early renaissance(1500s)?
Until the past century or so they more likely would have checked for breathing, such as fogging a glass, to see if a person was dead.
And also how long would he stay unconcious?
I knife wound doesn't make you unconscious until you're nearly dead from blood loss. If you want him unconscious, hit him on the head.
Would someone die from having a untreated collasped lung?
Maybe, maybe not. A collapsed lung (pneumothorax) can be total, and compress the heart besides, leading to death without treatment (and they had no treatment then), or it could be partial, leading to shortness of breath and difficulty breathing. You could easily make it less than life-threatening if you liked. For example, tuberculosis was very common then, and TB often causes enough scarring of the surface of the lung (the pleura), that the lung doesn't collapse completely because part of it is plastered to the inside of the chest wall. There are some fairly big blood vessels in the area, so you'd need to have your knife miss them.
