By breathing in through the In-Check, a cursor moves along the scale to indicate the inspiratory flow. The flow rate achieved can be noted by checking the position of the cursor against the calibrated scale.
The In-Check may be used to measure either peak or sub-maximal inspiratory flows. The transparent body allows a qualitative view of the inspiratory manoeuvre.
For the measurement of nasal inspiratory flows it is necessary to attach a facemask.
For oral inspiratory flows, a clean mouthpiece (standard or filter type) should be used for each patient. The In-Check should be cleaned in accordance with instructions.