Functional Residual Capacity (FRC)
Overview
The functional residual capacity, also called resting lung volume is determined by the relationship between lung volume changes and pulmonary vascular components (PVR). The extra-alveolar and the alveolar components are separated.The pulmonary vascular resistance is minimal at functional residual capacity (FRC) and increases, if the lung volume decreases to the residual volume or increases to the total lung capacity.
see [Tobin2013] p.824, [Rimensberger2015] p.550 and [Lucking2012] p.53
Details
The FRC Changes represent in the RIP app volume changes at the end of expiration (amount of gas remaining at the end of normal quiet respiration). They are calculated individually for each signal.To relate FRC Changes, a reference value is needed to compare the changes. This reference value is termed FRC Level. The algorithm is designed to set a reference FRC level for the user. This value is derived from the first inspirational moment for both thorax and abdomen individually.
FRC is calculated based on QDC calibrated AB+RC signals ("Qualitative diagnostic calibration (QDC)").
The FRC level changes are detected with the first inspiratory moment as reference. The FRC value is the first value after an inspiratory trigger, which is larger or equal to the FRC reference level. If no value is greater than the reference level, the FRC value is set to zero.
The FRC reference levels can be set manually or calculated automatically before processing the RIP signals ("Process the source file and calculate RIP based parameters").