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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.

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

  1. Pierson DJ, Nick NP, Petty TL. A comparison of spirometric values with subjects in standing and sitting positions. Chest 1976; 70: 17-20.
  2. 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).
  3. Lalloo UG, Becklake MR, Goldsmith CM. Effect of standing versus sitting position on spirometric indices in healthy subjects. Respiration 1991; 58: 122-125.
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