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A man undergoing whole body plethysmography. A modern body plethysmograph using ultrasound. A plethysmograph is an instrument for measuring changes in volume within an organ or whole body (usually resulting from fluctuations in the amount of blood or air it contains).
A photoplethysmogram (PPG) is an optically obtained plethysmogram that can be used to detect blood volume changes in the microvascular bed of tissue. [1] [2] A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption. [3]
Respiratory inductance plethysmography (RIP) is a method of evaluating pulmonary ventilation by measuring the movement of the chest and abdominal wall. Accurate measurement of pulmonary ventilation or breathing often requires the use of devices such as masks or mouthpieces coupled to the airway opening.
With air-displacement plethysmography, the volume of an object is measured indirectly by determining the volume of air it displaces inside an enclosed chamber (plethysmograph).
Pleth variability index (PVI) is a measure of the variability of the perfusion index, which occurs during breathing cycles. Mathematically it is calculated as (Pi max − Pi min )/Pi max × 100% , where the maximum and minimum Pi values are from one or many breathing cycles. [ 42 ]
For example, if a rule establishes a threshold at the value 6.5, it needs to be clear about whether a district with a value of exactly 6.5 will be classified into the lower or upper class (i.e., whether the definition of the lower class is <6.5 or ≤6.5 and whether the upper class is >6.5 or ≥6.5).
Lung volumes. Functional residual capacity (FRC) is the volume of air present in the lungs at the end of passive expiration. [1] At FRC, the opposing elastic recoil forces of the lungs and chest wall are in equilibrium and there is no exertion by the diaphragm or other respiratory muscles.
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").