Acute exacerbation of COPD. Arterial Bood Gas indicated?

[Admin]

A final year medical student from Malaysia asked me: In a patient with acute exacerbation of COPD and pulse oxymetry shows normal oxygen saturation. If you are the doctor, will you do ABG measurement? Is the invasive procedure indicated?

In my own opinion, I will still do it because pulse oxymetry only tells me the pulse rate and oxygen saturation. In COPD patient, we also need to know the PCO2 and also whether patient is in acidosis. PCO2 of upgoing trend in COPD patient signifies impending Type 2 respiratory failure and the management is different.

So, dear colleagues, what do you think?