This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Monitoring in Anesthesia, Subject name: Anaesthesia
[{'content': 'Which is false regarding pulse oximetry? \nSelect and explain. \nA. Hemoglobin saturation can be monitored in real time, B. In heavy smokers it may show a false high value, C. False value in anaemia, D. Probe can be attached to ear lobe in children', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Anaemia does not affect the reading of pulse oximetry. Factors affecting its accuracy- 1. Dyshemoglobins For example Met Hb absorb red and infrared wavelengths of light in a 1:1 ratio corresponding to an SpO2 of approximately 85%. Therefore, increases in Met Hb produce an underestimation when SpO2> 70% and an overestimation when SpO2 <70%. 2. Dyes (Methylene blue, indocyamine green) 3. Nail polish 4. Ambient light 5. Hypotension 6. Hypothermia 7. electrocautery', 'role': 'assistant'}]