Attach a fresh mouthpiece to the
spirometer hose. Turn the spirometer on, choosing a chart speed of 5
mm/sec, and move the piston so the pen is at the center of the chart
paper.
The subject should put on the noseclip, place the mouthpiece attached to
the hose in the mouth, and breathe in and out of the spirometer at a
normal rate and depth.
When the subject is used to the new
situation, press the handswitch to start recording. The subject should
breathe a few normal breaths, and then inspire maximally and exhale
maximally. Press the handswitch to stop recording. This is the
Vital Capacity Manoeuvre.
The figure below represents
a sample tracing you might obtain in the lab. Determine values for VC
and its subdivisions. Remember that you inspired first (inspiratory
trace down).
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