This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
Pulse oximetry monitors 
Select and explain. 
A. Oxygen saturation of hemoglobin, B. Oxygen content of blood, C. Pulse pressure, D. Oxygen paial pressure
A: Oxygen saturation of hemoglobin
Answer: A: Oxygen saturation of hemoglobin 
Explanation: Pulse oxymetry monitors hea rate, oxygen saturation of hemoglobin and gives aerial waveform. It works on the principle of transmission spectrophotometry and optical plethysmography. It has 2light emitting diodes.one is red with the wavelength of 660nm and other one is infrared with the wavelength of 940nm.