Therefore, the routine administration of supplemental oxygen may be unwarranted if the patient is able to maintain adequate oxygenation in room air, since it can result in hypoventilation going undetected. However, the use of a pulse oximeter to detect hypoventilation is impaired with the use of supplemental oxygen, as it is only when patients breathe room air that abnormalities in respiratory function can be detected reliably with its use. It is possible that it can also be used to detect abnormalities in ventilation. For this purpose, it is necessary to also measure carbon dioxide (CO 2) levels. Although a pulse oximeter is used to monitor oxygenation, it cannot determine the metabolism of oxygen, or the amount of oxygen being used by a patient. Pulse oximetry is useful in any setting where a patient's oxygenation is unstable, including intensive care, operating, recovery, emergency and hospital ward settings, pilots in unpressurized aircraft, for assessment of any patient's oxygenation, and determining the effectiveness of or need for supplemental oxygen. In contrast, blood gas levels must otherwise be determined in a laboratory on a drawn blood sample. Pulse oximetry is particularly convenient for noninvasive continuous measurement of blood oxygen saturation. Portable, battery-operated pulse oximeters are also available for transport or home blood-oxygen monitoring. Most monitors also display the pulse rate. The pulse oximeter may be incorporated into a multiparameter patient monitor. Ī pulse oximeter probe applied to a person's fingerĪ pulse oximeter is a medical device that indirectly monitors the oxygen saturation of a patient's blood (as opposed to measuring oxygen saturation directly through a blood sample) and changes in blood volume in the skin, producing a photoplethysmogram that may be further processed into other measurements. Such conditions occur while undergoing anaesthesia with endotracheal intubation and mechanical ventilation or in patients in the Trendelenburg position. Vasodilation and pooling of venous blood in the head due to compromised venous return to the heart can cause a combination of arterial and venous pulsations in the forehead region and lead to spurious Sp O 2 results. 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. Reflectance pulse oximetry is a less common alternative to transmissive pulse oximetry. It measures the changing absorbance at each of the wavelengths, allowing it to determine the absorbances due to the pulsing arterial blood alone, excluding venous blood, skin, bone, muscle, fat, and (in most cases) nail polish.
The device passes two wavelengths of light through the body part to a photodetector. Fingertips and earlobes have higher blood flow rates than other tissues, which facilitates heat transfer. 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. The most common approach is transmissive pulse oximetry. But the two are correlated well enough that the safe, convenient, noninvasive, inexpensive pulse oximetry method is valuable for measuring oxygen saturation in clinical use. Peripheral oxygen saturation (Sp O 2) readings are typically within 2% accuracy (within 4% accuracy in 95% of cases) of the more accurate (and invasive) reading of arterial oxygen saturation (Sa O 2) from arterial blood gas analysis. Pulse oximetry is a noninvasive method for monitoring a person's oxygen saturation.
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