This test is based on a vital capacity
manoeuvre with an added element of speed; a subject expires as
fast and as forcibly as he or she can.
- Turn the spirometer on, choosing a
chart speed of 20 mm/second, and move the piston
so the pen is at the center of the chart paper.
- The subject should put on the noseclip
and place the mouthpiece attached to the hose in the mouth.
- Press the handswitch to start
recording. After recording a few normal breaths, the subject
should be instructed to inhale maximally then exhale
forcefully and quickly, without holding lung volume at
the maximal inspiratory level. The subject should then return to
normal breathing for a few breaths. Press the handswitch to stop
recording. This is the Forced Vital Capacity
Manoeuvre.
The figure below represents a sample
tracing you might obtain in the lab. Determine values for FVC and
FEV1.
Check your answer by clicking on the image. |