<unk>  is a noninvasive method for monitoring a person's oxygen saturation. Peripheral oxygen saturation <unk>  readings are typically within 2% accuracy (within 4% accuracy in 95% of cases) of the more accurate (and invasive) reading of arterial oxygen saturation <unk>  from arterial blood gas analysis. But the two are correlated well enough that the safe, convenient, noninvasive, inexpensive<unk>  method is valuable for measuring oxygen saturation in clinical use. The most common approach is transmissive<unk> . In this approach, a sensor device is placed on a thin part of the patient's body, usually a fingertip or earlobe, or an infant's foot. Fingertips and earlobes have higher blood flow rates than other tissues, which facilitates heat transfer. The device passes two wavelengths of light through the body part to a photodetector. It measures the changing absorbance at each of the wavelengths, allowing it to determine the absorbances due to the<unk> ng arterial blood alone, excluding venous blood, skin, bone, muscle, fat, and (in most cases) nail<unk> lish. Reflectance<unk>  is a less common alternative to transmissive<unk> . This method does not require a thin section of the person's body and is therefore well suited to a universal application such as the feet, forehead, and chest, but it also has some limitations. Vasodilation and<unk> oling of venous blood in the head due to compromised venous return to the heart can cause a combination of arterial and venous<unk> tions in the forehead region and lead to spurious<unk>  results. Such conditions occur while undergoing anaesthesia with endotracheal intubation and mechanical ventilation or in patients in the Trendelenburg<unk> sition.
Pulse oximetry
Plethysmograph
Oxygenation index
Hyperoxia test
Oxygen saturation 
Oxygen saturation
Fraction of inspired oxygen
Respiratory pressure meter