Not yet investigated
What we have so far
Carboxyhaemoglobin absorbs almost exactly like oxyhaemoglobin at the wavelength the oximeter uses, so the reading is normal or high while the blood carries almost nothing.
This star is on the map because the show intends to take the question apart properly — the trials, how it is actually tested, whether the thing sold is the thing studied. That work is not done yet, and nothing here should be read as a conclusion. When the investigation is published it will appear on this page.