Why is a Volume Correction required for Spirometry recordings?

Expired volume is greater than inspired volume under most atmospheric conditions; this increase, due to warming and humidification of the inspired volume in the lungs, is typically 5-10%.  For this reason there will be “breath-dependent drift” of the volume trace, even when the spirometer is correctly zeroed.  This is minimized in LabChart's Spirometry extension by performing a volume correction protocol.  The correction protocol should be performed and the subsequent correction factor applied after the spirometer pod or spirometer amplifier has been warmed up, zeroed, and at the beginning of the each experiment as the correction factor required can vary per person, per day, and per equipment. 

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