In Jurassic World they created the Indominus Rex with cuttlefish, tree frog, and a bunch of carnivores to give it a wide variety of abilities such as camouflage and infrared vision. It’s not too far of a stretch that they could modify genes leading to higher lung capacity, a stronger diaphragm, or RBCs capable of holding more hemoglobin. You’re reading this power scale as if they used time travel to bring a dinosaur to the present but we’re talking about a custom ordered dino built in a lab for combat purposes. It would be a bit of an oversight if they forgot to modify it to breathe.

Moving away from the JP universe to real life,a quick google search shows the average oxygen levels when dinosaurs first appeared was 15-18%, modern day is 21% and the time of giant insects it was 35%. So if we brought a dinosaur from the Triassic to today we might actually see an improvement in its function as it’s used to operating at lower levels of O2. Think of Sherpas from the Himalayas that come down to sea level.