A reduced PaO 2 is a non-specific finding. A low PaO 2 should not be used to make any particular diagnosis, including pulmonary embolism. High FIO 2 doesn't affect COPD hypoxic drive. The reason a high FIO 2 may raise PaCO 2 in a patient with COPD is not because the extra oxygen cuts off the hypoxic drive. The actual FIO 2 with nasal oxygen depends on the patient's breathing rate and tidal volume, i.e., the amount of room air inhaled through the mouth and nose that mixes with the supplemental oxygen.
Oxygen masks migrate.
Consult your health professional for advice relating to a medical problem or condition.