Why avoid high-flow oxygen in COPD with hypercapnia?

Question

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 0.7 to 1 gallon 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 levels. 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.

Answer 1

Hello,

Welcome to icliniq.com.

Patients with long-standing COPD (chronic obstructive pulmonary disease) who require controlled oxygen therapy should be given it to avoid suppression of hypoxic respiratory drive. So, unless they are on BIPAP (bilevel positive airway pressure) or invasive ventilatory support, oxygen should not be given with FiO2 (fraction of inspired oxygen) above 28%. If given above that, the hypoxic respiratory drive in these patients will be abolished without ventilatory support. They will further hypoventilate, leading to the worsening of hypercarbia and carbon dioxide narcosis.

I hope this helps.

Regards.