Pulmochart Reference
Signals required by the Pulmochart apps.

Pulmochart default input signals


Especially the start app expects a number of pre-defined signals. The other apps use the output file of the Start app as input signals.


The expected signals are a flow-, a pressure signal, respiratory inductance plethysmography (RIP RC and RIP AB) signals and a capnographic signal (CO2). Depending on the desired analyses not all input signals might be required. Furthermore it is possible to load additional signals. These signals are not included in any calculations, but are copied to the resulting files. The expected pre-defined signals are described in detail in the next paragraphs.

Flow- and Pressure signals

Main air flow (Flow (mL/min))
The main air flow (Flow) is represented by the raw flow signal as was measured by any flow sensor.
The airway gas flow can be laminar or turbulent, depending mainly on the tube diameter and the composition of the air used for ventilation, see [Rimensberger2015] p.300. Important is, that the raw flow signal is used and not a pre-filtered signal, because filtering may supress certain features in the signal that make the outcome of Pulmochart less precise.

Main airway pressure (P (cmH2O))
The airway pressure is defined as the force applied to the respiratory system by the mechanical ventilator. If the ventilated patient is also breathing, the applied force on the respiratory system is included in the measured airway pressure, see [Rimensberger2015] p.302.
The pressure (P) is used as the raw air pressure measured at the mask (Pmask).

Respiratory inductance plethysmography (RIP) signals

Respiratory 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.
A volume increase of either compartment occurs when RIP signals increase. A decrease of either RIP signal represents a volume decrease.
For further information about RIP analysis see "Respiratory Inductive Plethysmography (RIP)".

Inductive plethysmographiy rib cage band (RC (AU))
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))
The inductive plethysmographic signal from the abdomen band is called AB (also in an arbitrary unit).

Capnographic signals:
Capnography or also called capnometry, is a non-invasive method to measure carbon dioxide in the expired gas, see [Rimensberger2015] p.388, [Lucking2012] p.12. The method results in the graphical description of the exhaled CO2 waveform, see [Tobin2013] p.887.

Main capnographic signal (CO2 (mmHg))
The main capnographic signal is a measurement of the exhaled CO2.

Signals background
A signal S is a time series of arbitrary length n.

Ideally a signal is sampled at equidistant time points:

The resulting frequency f is:

Usually signals are recorded with a sample frequency of a few hundred samples per second.

Pulmochart expects different signals in one source file to be timely aligned, i.e. samples in signals from different sensors should roughly have the same time stamp. Pulmochart offers limited options to shift signals in relation to eachother.