Hemoglobin levels should be considered. Medical staff may wish to obtain a blood sample for lab measurement. If very low the medical staff may wish to prescribe blood to restore oxygen-carrying capacity as in the case of anemia. Pulse oximetry should be avoided where significant amounts of carbon monoxide have been inhaled until levels have fallen. Significant carboxyhemoglobin levels usually occur in patients admitted from a fire.
Cigarette smoking can cause over-readings up to four hours after smoking a cigarette.
Hypercapnia As well as supplying the body with oxygen, breathing oxygen removes carbon dioxide, a waste product of metabolism. Oximetry measures the saturation of hemoglobin by oxygen, but does not indicate carbon dioxide carriage. Carbon dioxide is used in the production of carbonic acid, the main intravascular acid. Hypercapnia contributes significantly to respiratory acidosis. Nurses should observe patients breathing pattern rate and depth.