RIP- Respiratorische Induktive Plethysmographie

What is respiratory inductive plethysmography - RIP?

Respiratory inductive plethysmography (RIP) is a (non-invasive) method of monitoring respiration during sleep studies in the sleep laboratory.

Elastic bands are placed around the thorax and abdomen, and an induction loop incorporated into these bands serves as a sensor that senses the respiratory movements of the thorax and abdomen.
These induction bands are very sensitive transducers for detecting volume changes in the parts of the body enclosed by the belts (thorax and abdomen).
In sleep medicine, this method is used to measure respiratory volume, respiratory rate, and monitor apnea, hypo- and hyperventilation.
With inductive plethysmography, it is possible to derive the relative volume changes within the respiratory system from the body surface movements necessary for breathing. Here, the elastic straps as a whole serve as a sensor (induction loop incorporated into the straps).  
The induction belts placed around the thorax and abdomen register the circumferential changes of the two compartments, i.e. thorax and abdomen.
During inspiration, inhalation, the circumference increases due to the lifting of the thorax and the expansion of the abdominal wall, while during expiration, exhalation, the circumference decreases.
Measurement of circumference change is achieved by recording small changes in coil induction, in the RIP bands.
Technically, this is accomplished by varying the inductance of the (RIP) bands relative to the circumference of the body part they surround. The changes in inductance are then converted to an analog signal in the interface.
The sum signal (SUM) of the two individual compartments (thorax and abdomen) reflects the relative change in air volume in the airways. 
This ensures that a correct signal is delivered regardless of the patient's body position, which may result in strain relief of part of the belt.
When using piezo-based sensors, as they are still used in many laboratories, a strain relief of the belt leads to a failure of the signal.
In respiratory inductive plethysmography, the sum signal of abdomen and thorax is approximately equal to the respiratory volume measured with a pneumotachograph. 

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