Can 100 % oxygen be given to a COPD patient?

Hello doctor,

I need help with a question. I was working as a hospitalist. A 67-year-old man had been admitted over the weekend for confusion and a high ammonia level. He had also fallen down five to six times before admission. He had a history of chronic obstructive pulmonary disease (COPD) with permissive hypercapnia and was on three to four liters of oxygen through a nasal cannula. In the afternoon, he became more confused and delirious. I suspected hypoxia, intracranial bleeding, and a combination of hypercarbia and elevated ammonia level. I asked the respiratory therapist to check the pulse oximeter and, if hypoxic, give 100 % oxygen. At the same time, I wrote orders to check arterial blood gas analysis (ABGs) and bilevel positive airway pressure (BIPAP) and called emergency medical services (EMS) to transfer the patient to a higher-level hospital. While waiting for the ambulance, I got a quick head computed tomography (CT) since there was no change in the patient's condition. When the patient got to the higher-level hospital, he was also placed on 100 % oxygen with BIPAP and later weaned down. The respiratory therapist complained to the chief that I was wrong to use 100 % oxygen to get a CT. Please advise.

Thank you.