Instructions for inspiratory and expiratory maneuvers
If both inspiratory and expiratory flow-volume curves are required, the inspiratory effort is commonly performed after the expiratory one. It is preferable, however, that the inspiratory effort is performed immediately prior to the expiratory one, as one then obtains the IVC: an IVC that is clearly larger than the FVC is a sign of expiratory airway obstruction. Many subjects find the inspiratory maneuver difficult to perform.
- the patient may be seated or standing (makes no difference to test results (ref. 1). See to it that the patient is comfortable, have the patient loosen or remove all restricting clothing
- apply the noseclip with a tissue, hand a tissue out to the patient for use when removing the mouthpiece. Ask the patient to gently press against the noseclip to test for leaks.
- hand the measuring device to the patient,
- ask the patient to place the mouthpiece in the mouth, chin slightly elevated, the neck stretched, and
- allow the patient to get accustomed to breathing into the apparatus;
- when the patient reaches the end of
a normal inspiration, quickly tell him or her to
‘Now slowly blow out …. as deep as you can ….. out …. out …. get it all out.’
Do avoid a protracted expiratory effort near or at RV.
- when the expiratory effort is completed,
quickly tell the patient to
‘take a slow deep breath …. as deep as you can ….. deep …. deep.’
- do not make the patient pause at the
level of the total lung capacity but say
‘Now blow as hard and as fast as you can’,
and while the patient blows out encourage to blow longer by saying
‘blow …. blow … keep it coming … a little longer …. get it all out’.
Particularly in patients with obstructive lung disease an effort should be made to extend the expiratory effort to 6 s or more . The trunk and head should remain upright throughout the maneuver.
- take the mouthpiece out of the patient’s mouth with a piece of tissue, but leave the noseclip attached
- allow the patient to rest for a short time (15-30 s) and explain in what respect the maneuver needs to be improved, or reassure if it was properly performed
- after a sufficiently long break repeat the maneuver; if the test maneuvers are repeated too rapidly the patient will not be able to perform maximally and may develop symptoms of hyperventilation
- check each FVC maneuver for satisfactory performance, instruct the patient how to improve on it, and assess whether 3 satisfactory maneuvers meeting criteria for the reproducibility of FVC and FEV1 have been obtained. Do not press for more than 8 maneuvers; in a naïve subject you might regard the first 2 as practice attempts.
- let the patient remove the mouthpiece from the mouth using the tissue to collect any saliva, remove the noseclip.
In the case of a declining trend in FVC and FEV1 do consider the fact that the respiratory maneuvers may induce airway obstruction in this patient.
Ref. 1 - Standing or sitting position does not make a difference
- Pierson DJ, Nick NP, Petty TL. A comparison of spirometric values with subjects in standing and sitting positions. Chest 1976; 70: 17-20.
- Townsend MC. Spirometric forced expiratory volumes measured in standing versus the sitting posture. Am Rev Respir Dis 1984; 30-123-124. (According to this author in middle-aged subjects the VC is about 70 mL smaller in the sitting than in the standing posture).
- Lalloo UG, Becklake MR, Goldsmith CM. Effect of standing versus sitting position on spirometric indices in healthy subjects. Respiration 1991; 58: 122-125.