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The pulse oximeter, which is used to evaluate oxygen in the blood of patients in a variety of clinical settings, has become an increasingly common piece of monitoring equipment. It provides a continuous, non-invasive monitoring of the oxygen saturation of hemoglobin in the arterial blood. Your results are updated with each pulse wave.
The pulse oximeters do not provide information about the hemoglobin concentration, the heartbeat, the efficiency of oxygen delivery to tissues, oxygen consumption, the adequacy of oxygenation or adequacy of ventilation. They, however, offer an opportunity for saturation levels to be seen immediately, as a warning signal for clinicians to help prevent the consequences of desaturation and to detect hypoxemia before it produces cyanosis.
Due to the great interest, I would like to briefly comment on the functionality of these devices today.
Pulse oximeters measure arterial oxygen saturation in the finger via light absorption and fluoroscopy of the skin. Radiation of the arterial blood vessels can be performed on all accessible parts of the body, eg on the finger, on the toe or on the earlobe. The pulse oximeters were developed especially for the measurement on the finger.
Within the device is a light source that emits infrared light waves (about 900 nm) and red light waves (660 nm), and a light sensor that measures the absorbed light. During the measurement, the wavelengths are set in proportion and the arterial oxygen saturation is calculated. This value is called the SpO2 value (the pulse oxymetry measured oxygen saturation).
Important in pulse oximetry is the pulsatile absorption. This means that the filling of the arteries with oxygenated blood changes in the pulse rhythm, that is, more or less filled. When the filling is weaker, the hemoglobin loses its reddish color, causing color differences. During a pulse wave, two readings are taken: deoxyhemoglobin (deoxygenated hemoglobin) and total hemoglobin. These are set in relation to one another and thus the oxygen saturation is calculated. The measured value is then shown on the display. Many pulse oximeters are also equipped with an alarm function, which notifies when the oxygen saturation falls below certain preset values.
Oxygen saturation is an important indicator for checking the oxygen supply. The normal value of oxygen saturation is 98%. In children and young adults, the value may also be 100%. In asthmatics, people with sleep apnea or COPD, the values can also vary between 95% and 85%. The limit of oxygen saturation, which is still within the tolerable range, must be set for each self or the doctor.
Faulty measured values or strong deviations from the normal measured values have different causes. For example, already painted fingernails can influence the measured data. Bright ambient light sources, heavy movement, carbon monoxide poisoning or jamming due to jamming can also interfere with the measurement.