Pressure cooking vacuum sealed meat

This probably isn't safe, and there's no reason to do it in the first place

The purpose of sous vide cooking is to get your food to a very specific and even temperature throughout, in order to guarantee a certain degree of doneness and minimise the possibility of overcooking. It achieves this by holding the food in a water bath at that appropriate temperature until the food has equalised with the water in temperature.

Pressure cookers, on the other hand, work by preventing steam from escaping from a boiling liquid, thereby raising the pressure in the vessel and hence raising the boiling temperature, which will allow certain reactions in the food to proceed more quickly than they would at a regular boil. This means that a pressure cooker is held at a much, much higher temperature than a sous vide water bath - indeed, if i wanted to overcook food without burning it, an extended stay in a pressure cooker is the most effective method I can think of.

If your sous vide bags can handle the elevated temperatures of a pressure cooker (and I don't think that's true for you; a quick Google suggests that pressure cookers are generally capable of hitting 250 degrees Fahrenheit, which is the number you provided for your specific bags) there may still be a danger in putting them in your pressure cooker; when you release the pressure, the liquid inside your pressure cooker boils rapidly to come back down to a temperature that makes sense at its new pressure; the liquid sealed inside your sous vide bags, however, can't vent to the atmosphere, meaning that your sous vide bags are suddenly themselves tiny pressure cookers, except they're not built to withstand internal pressure like that and will likely burst, spraying boiling liquid out of the pot.

In summary, cooking food sous vide inside a pressure cooker will generally drastically overcook it, and then, if you're not careful, spray boiling liquid around your kitchen. Personally, I wouldn't try it.

As long as your bag can handle the temperature you should be fine. The bag exploding is not an issue because there is no way for it to expand under the pressure. Once you release the pressure, the liquid starts to boil, reducing the temperature to a maximum of the boiling point of water (212?). Since there is no air in the bag, only liquid, and because it's under vaccum, it will not over expand. Also do a natural release as to prevent a potential problem just to be sure. (important). I have found it to be completely safe. Simple thermodynamics.

For example, Sous Vide pork ribs @ 145? can take as much as 36 hours. On the other hand, pressure-cooked ribs take less than an hour but the seasonings and juices end up in the bottom of the pot due to the steam created from the water in the bottom which is needed to generate pressure. Would I pressure cook a filet? No. but there is an application for other meats.

Instead, by pressure cooking in a vaccum sealed bag you infuse the meat with seasoning and retain moisture while dramatically reducing cooking time. Finish in the oven or smoker/grill.

If you think it through, there is no fuss/muss, drastic reduction of time and the meat turns out brilliantly. A 2 day job is cut down to a few hours. It's a winner for me!

Sous Vide bags are NOT little pressure cookers. They are under internal vaccum and external pressure and liquids don't expand like air. To close the point, if you do a natural release, the pressure in the pressure cooker will prevent the liquid in the bag from expanding. A natural release reduces temperature and presure in a controlled manner at the same time. QED.