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Performance Criteria

Performance Criteria

Assemble the spirometer and verify to see if calibration is within acceptable limits. Check it is clean and the vane spinning and wash hands regularly throughout. Perform spirometry at room temperature between 20 – 25 degrees centigrade.

Explain the purpose and nature of the test to the patient and ensure they are fit and well for the procedure (if not re-book).

Measure the patient’s height, without shoes, accurately. For patients with deformities of the thoracic cage the arm span from finger tip to finger tip can be used instead.

The patient should by sitting in a chair with arms with their feet flat on the floor. Dentures should be left in place unless they are loose.

Enter age, sex height and ethnicity into the spirometer for calculation of predicted values. The date and time are already set on the spirometer.

Three relaxed vital capacities are performed first. Instruct the patient to take a deep breath then place teeth and lips over the mouthpiece and blow out as far as possible in their own time until no further air can be exhaled. At least two of these readings should be within 5% of each other.

Then three forced vital capacities are performed as for the relaxed blows except the patient is instructed to blow out as hard and fast as they can until no further air can be exhaled.


3 technically acceptable VC’s the best 2 within 5% or 100mls, whichever is the greatest.
A minimum of three forced blows with the best 2 within 5% or 100mls, whichever is the greatest.
Recording continues long enough for a plateau to be reached on the volume time curve for 2 seconds
A rapid rise at the start of the flow volume trace until a peak is reached. The trace should rise almost vertically.
Maximum effort throughout the blow with no sudden cessation of flow.
Traces should be smooth and free from any irregularities