Respiratory shock test according to tiffeneau

Determination of the amount of air that can be exhaled again in a shock after slow, deepest possible inhalation.

FEV1 (respiratory impulse value or Tiffeneau value) is defined as the volume of air exhaled in 1 second by a maximum expiratory impulse (= maximum volume of air breathed out in 1 second, capacity of seconds).

In addition to the absolute value FEV1, the relative seconds capacity, also known as Tiffeneau index, is evaluated.

With the Tiffeneau-Index the respiratory impulse value FEV1 is set in relation to the current vital capacity: VEF1%VC (normal 75-85%), or - modified - to the target value of the vital capacity.

The Tiffeneau index is important for differentiating between obstruction and restriction.