How does Respiratory Inductance Plethysmography work?
Inductance Plethysmography employs sensors that are able to measure changes in a cross-sectional area of the patient, specifically the thorax and abdomen during a respiratory cycle. The RIP sensor consists of a belt with a wire woven or sewn in a sine wave or zig-zag pattern along its length, and a driver module with a circuit board, oscillator and battery that passes a weak current through the wire in the band creating a small magnetic field. As the band is stretched and relaxed by the patient’s breathing the cross-section enclosed by the band changes slightly. This change in cross-section produces a slight change in the magnetic field that results in a change in the frequency of the current. This change can be measured and converted to a voltage output that creates the waveform on the PSG recorder. The science behind this phenomenon has to do with currents induced by changing magnetic fields. The key concept is that the stretching and relaxing of the band can be measured accurately a
