A 25-year-old Caucasian man with a history of spherocytosis, splenectomy, recurrent blood transfusion, and no cardiopulmonary disease presented for an emergent laparoscopic cholecystectomy with a baseline pulse oximetric saturation (SpO2) of 88% while breathing room air. The SpO2 increased to only 89% during preoxygenation with an FIO2 1.0. Multiple arterial blood samples revealed SaO2 as high as 100% with PaO2 averaging 390 mm Hg. He was subsequently diagnosed with a dyshemoglobin, hemoglobin Köln. The simultaneous presentation of a stable patient from a cardiopulmonary perspective with normal arterial oxygen tension and saturation in the blood gas analyses despite a low SpO2 measurement outlines the importance of integrating the history of present illness and both the importance and the limitation of the pulse oximetry.