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Polysomnography (PSG) is a multi-parameter type of sleep study [1] and a diagnostic tool in sleep medicine.The test result is called a polysomnogram, also abbreviated PSG.The name is derived from Greek and Latin roots: the Greek πολύς (polus for "many, much", indicating many channels), the Latin somnus ("sleep"), and the Greek γράφειν (graphein, "to write").
The respiratory disturbance index (RDI)—or respiratory distress Index—is a formula used in reporting polysomnography (sleep study) findings. Like the apnea-hypopnea index (AHI), it reports on respiratory distress events during sleep, but unlike the AHI, it also includes respiratory-effort related arousals (RERAs). [1]
Central sleep apnea. During sleep, the breathing centers of the brain can pause their activity, leading to prolonged periods of apnea with potentially serious consequences. Hyperventilation followed by prolonged breath-holding. This hyperventilation, attempted by some swimmers, reduces the amount of carbon dioxide in the lungs.
Pulse oximetry is a method used to estimate the percentage of oxygen bound to hemoglobin in the blood. [10] This approximation to SaO 2 is designated SpO 2 (peripheral oxygen saturation). The pulse oximeter is a small device that clips to the body (typically a finger, an earlobe or an infant's foot) and displays its reading, or transfers it to ...
Hypopnea is overly shallow breathing or an abnormally low respiratory rate. Hypopnea is typically defined by a decreased amount of air movement into the lungs and can cause hypoxemia (low levels of oxygen in the blood.) It commonly is due to partial obstruction of the upper airway, but can also have neurological origins in central sleep apnea.
A pulse oximeter probe applied to a person's finger. A 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. [4]
Sleep apnea – Disorder involving pauses in breathing during sleep; Solid stress – one of the physical hallmarks of cancer; Time of useful consciousness – Duration of effective performance in a hypoxic environment; Tumor hypoxia – Situation where tumor cells have been deprived of oxygen; Vasculogenic Mimicry
The values of SpO2 above 89% are not considered in the calculation of HTi, as such saturation levels do not contribute to the treatment. SpO2 values below 75% count as 75%. HTi is calculated as an integral value of SpO2 readings made with 1 s sampling frequency and divided by 60 in order to produce a “per minute” value.