In terms of respiratory drive and need for oxygenation, the only difference between a COPD patient and a non-COPD patient, is their biochemical trigger of respiration. Regardless of what the patients underlying condition is, the cells still require a sufficient level of oxygen to function... which is why we NEVER withhold oxygen.
What they won't teach you in your EMT program and expands on your question:
NORMAL, NON-COPD PATIENT
A non-COPD patient (you and I) breathe based on the level of CO2 or more specifically the hydrogen level sensed within the cerebral spinal fluid. When our bodies sense a rising CO2 level, our receptors sense this rise and our breathing center kicks in to make us breathe faster or just to breathe period to keep the CO2 level normal and maintain homeostasis.
COPD PATIENT
A COPD patient has chronically elevated levels of CO2 (or more specifically hydrogen) and as a result, the receptors become desensitized to these high levels of CO2 which forces the body to disregard this increase since this newly aquired high CO2 level is now the bodies norm. Since the receptors are desensitized and ignore the CO2 level, a new drive (or biochemical trigger) needs to come into play... which becomes the patients oxygen level (or PaO2).
So now, when the oxygen level gets low (hypoxic), the body triggers respiration. And if the body senses too much oxygen, the body basicly says... "hold up, too much oxygen, lets slow down breathing"... this is the hypoxic drive. Sometimes when the body gets flooded by a NRB, the body shuts down breathing all together to try to maintain what it thinks should be normal.