Respiratory Inductive Plethysmography (RIP)
OverviewRespiratory Inductive Plethysmography is a technique to measure and analyse volume changes.
DetailsRespiratory inductance plethysmography (RIP) is a technique used to measure volume changes, see [Rimensberger2015] p.327, 988. Therefore elastic bands are placed around the rib cage and abdomen of the patient. Passing a current through the embedded wire in the bands generates a magnetic field. Alterations of the magnetic field resulting from ventilation and breathing are measured as inductive plethysmographic signals in an arbitrary unit (AU).
A calibration of the RIP voltage changes to a known volume is possible but not accurate.
There are three main RIP signals, two signals resulting from the measurements (RC and AB) and a third signal derived from the other two signals (Sum AB+RC). The two measured signals are input signals of the Start app ("Pulmochart default input signals").
Inductive plethysmographiy rib cage band (RC (AU)) signal
The inductive plethysmographic signal from the rib cage band is called RC. Although the band measures are an indication of volume changes, the values use the unit AU (arbitrary unit), because the bands only output an arbitrary count value.
Inductive plethysmographiy abdomen band (AB (AU)) signal
The inductive plethysmographic signal from the abdomen band is called AB (also in an arbitrary unit).
SUM AB+RC (AU) signal
This signal is the un calibrated sum of the RC and AB signal
These three signals are volume indicators. This means a volume increase of either compartment occurs when RIP signals increase. A decrease of either RIP signal represents a volume decrease.
Generally the signals from the abdomen are smoother than the signals from the thorax. The variations on the thorax signal are explained by the physiological processes causing movements of the ribcage. The parts that contribute to volume changes of the thorax are lungs, heart and blood vessels.
RIP analyses are performed based on all three signals, e.g.,
-breath detection (insp and exp triggers)
-functional residual capacity changes
-tidal volume changes