Medic30,
Vent and I see eye to eye on a lot things. This is no different. I can understand why they nasally intubated. When you don't have RSI/DAI capabilities, you have to go nasal in order to better secure the airway sometimes. However, "Airway" and "Breathing" are not the same. In the same way "Oxygenation" (measured by SpO2%), "Respiration" (respiratory rate), and "Ventilation" (measured by EtCO2) are three completely different entities.
You can be breathing normally and oxygenating like a champ, but if you're not ventilating worth a damn, you're still gonna die. You've seen this happen. We've all seen this happen. If the CO2 gets too high, the pH will drop too low. Nothing will work in an acidic medium; up to and including pulses.
Did any adverse conditions actually happen? Probably not. But here's the thing. Luck counts, but don't count on luck.
Bag 'em. If they're still breathing, bag with them, but still bag 'em.