There is a lot more to the ABG then just a few numbers. What was the PaO2 and A-a gradient? What was the base deficit? Lactate? Anion gap? Those will give a clue about the events leading up to the present situation.
Most patients that fall into the category of "COPD" are not retainers. Either way, you treat hypoxia especially when a patient is this symptomatic. The hypoxic drive has been disputed for over 30 years and it is now thought to be the pulmonary vasoconstriction response to high FiO2 that causes the rise in PaCO2. If it is significant enough to cause an immediate need for intubation, then the patient was heading that way already. Long term use of a higher FiO2 can influence the patient's PaCO2 retention but in the ED, this will probably not be an issue.
BiPAP splints the airways and also promotes fluid redistribution for patient who may have a CHF component or for cor pulmonale. Cor Pulmonale itself is an interesting factor.
Now I don't know a NRB would be the way to go. Honestly, we have special flow meters at our facility where we can use what's called a "high flow" mask and I've found it works MUCH better than a NRB.
The reasoning behind this is that the NRB is not a high flow device. It is actually a low flow device because it limits the amount of flow a patient can receive. To be clasisified as a high flow device it must be able to meet both the patient's inspiratory flow demand and total minute volume. Patients in respiratory distress can require a minute volume of over 20 liters. The NRB mask is a device that is limiting with a set flow. A venturi device which is probably what the high flow system you are descibing is based, will enable a total flow of over 40 liters/minute and probably more. You may have seen some RTs rig up two aerosol flow devices in attempt to gain more flow and a consistent FiO2. If the patient can acheive and adequate flow for a stable FiO2, the FiO2 might be lowered.
Fluid overload due to heart failure? Pneumonia? The hypoxia is the symptom, if possible you wanted to try to find the cause of the problem. On our telemetery floor, we can't initiate Bipap..per RT protocol, they have to go to ICU if no documented sleep study.
BiPAP for sleep apnea and that for an acute situation are two different things. Even if the patient has a documented sleep study, when something acute arises, this patient needs more monitoring. The setting for their home sleep machine was designed for a normal night's sleep and not treating unknown situations. It is lucky your RTs have specifically spelled out their protocols because some places don't and then the RNs end up with a very hgh acuity patient.