Pulse oximeter, the fifth vital sign: a safety belt or a prison of the mind?

A 48-year-old woman hospitalized in the hematologic clinic because of chronic myeloid leukemia, during the night required the attention of the on-call physician for dyspnea associated with tachycardia. General physical examination revealed pallor and rhythmic tachycardia (145 beats/min). Her temperature was 98.6F (37C), respiratory rate was 32 breaths/min, blood pressure was 104/54 mmHg, and oxygen saturation was 95%. A complete blood count performed in the afternoon demonstrated an Hb of 9 g/dL, but the patient reported she had hematemesis in the late evening. ‘‘Did you give oxygen?’’, asked the physician to the nurse. ‘‘No doctor, oxygen saturation is 95%. She called me for tachycardia, should I ask for the cardiologist?’’ Blood withdrawn was performed again, showing a further decrease in the Hb level (6 g/dL). Blood was requested and in the meantime colloid infusion started. The reluctance of the nurse was finally overcome and oxygen was added at 10 L/min. Tachycardia and dyspnea gradually relapsed.