14 Monitoring Airway Flow, Volume and Pressure
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• Periodically check the flow sensor and tubing for excessive moisture or secretion build up.
Perform a purge cycle if droplets are visible within the sensor or tubing. Repeat if necessary. If
purging does not remove the droplets, replace the sensor.
• For routine performance of airway care, separate the system between the endotracheal tube and
the airway adapter (neonatal circuit), or between the endotracheal tube and elbow (pediatric/adult
circuit). Lavage and suctioning of the airway can then be performed without fluids and mucous
accumulating on the airway adapter windows.
• Measurement values provided by a ventilator may differ significantly from the values provided by
the spirometry module, due to different locations of the flow sensor.
• Incorrect entry of gas compensation parameters (i.e. temperature, gas composition) may reduce
the accuracy of the measured values.
• An abnormal volume waveform as displayed below may be an indicator of an air leak:
In general, if
MVexp or TVexp are significantly smaller than MVin or TVin, the tubing should be
checked for leaks.
Zero Calibration
The zero calibration maintains the accuracy of the spirometry waves and numerics by regularly
compensating for drifts within the measurement section. It is performed automatically without user
interaction and takes about 2 seconds to complete. The automatic zero calibration is normally carried
out every ten minutes. During warm-up or when the ambient pressure changes, this interval may be
reduced to two minutes.
During the zero calibration the waveform is flat but the numerics remain on the screen. Typically, a
zero calibration is started at the beginning of a respiration cycle, therefore a waveform may begin
normally and then immediately become flat for the time of the zero calibration.
1 Zero Calibration
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