CO-Oximetry Interference in a Patient with Dyspnea Refractory to Oxygen Therapy.

Abstract

A 37-year-old female with a past medical history of renal transplant secondary to nephropathic cystinosis, chronic kidney disease, and Pneumocystis jirovecii pneumonia 7 months prior presented to the emergency department with exertional dyspnea 5 days after initiating dapsone for Pneumocystis jirovecii pneumonia prophylaxis. Vitals and physical exam were significant for tachycardia, peripheral cyanosis, and peripheral functional oxygen saturation via pulse oximetry of 89% with no increase following initiation of 40 L/min of oxygen therapy. Respiratory exam findings were normal, and the patient was afebrile. Initial lab values were significant for anemia with no leukocytosis noted. Portable chest radiograph and chest computed tomography revealed no acute thoracic pathology, and ventilation/perfusion scan revealed a low probability of pulmonary embolism. In-house testing for presumed methemoglobinemia was pursued, and the patient was admitted. Fractional methemoglobin [(F)metHb] was tested with a Radiometer ABL835 FLEX but was unable to be obtained due to an...