Basics | spirometry | quantitative assessment
The following parameters can be obtained during spirometry (spirometry | qualitative assessment).
- inspiratory vital capacity (IVC or VCIN)
- forced vital capazität (FVC)
- forced expiratory volume in one second during Tiffeneau test (FEV1)
- Tiffeneau index (FEV1 / VC max)
- peak expiratory flow (PEF)
- mean expiratory flow at 75% (MEF 75), 50% (MEF 50) and 25% (MEF 25) of the vital capacity
PEF is measured at the beginning of expiration followed by MEF 75, 50 and 25.
FEV1 is reduced in any ventilatoin disorder. In restriction, a normal Tiffeneau-index can be found in combination with a reduced vital capacity which also serves for graduation. On the contrary, the Tiffeneau-index is reduced in obstruction combined with a normal vital capacity before bronchodilation (exception: emphysema with increased residual volume and consecutive reduction of the vital capacity). All flow parameters (PEF and MEF) are reduced. For graduation of obstructive disorders post bronchodilator values of FEV1 or airway resistance (only body plethysmography) are used.
For those who want to learn more…
Dyspnea, suspected obstructive oder restrictive ventilation disorder
Normal findings and normal values
Normal values are calculated as a function of age, gender and height resulting in the percentage value of predicted used for severity graduation (normal between 80-120% of predicted).
Obstructive disorders are classified using post bronchodilator FEV1 or post bronchodilator airway resistance sRaw (only body plethysmography), restrictive disorders using VC.
Finding: normal ventilaton
71-year-old male patient. Normal Tiffeneau index 93%, FEV1 decreased to 53%.
Finding: Moderately severe restriction with a reduced VC (here: FVC) to 58%.
67-year-old female patient. Tiffeneau index 38% of predicted before bronchodilation (obstruktion, left). FEV1 25% post bronchodilation (right).
Finding: Very severe obstruction with negative bronchodilation. VC slightly reduced before bronchodilation (left) normalizing afterwards ⇒ suspected air trapping and emphysema (residual volume).