Forced inspiratory volume in 1 second (FIV1)

FIV1 is the volume that can be forcefully inhaled in the first second during a forced inspiratory maneuver started from residual volume. The measurement is performed during an FIVC maneuver. Most people find the inspiratory maneuver difficult to perform.

There are no official guidelines (ECCS, ATS, ERS) with regard to the measurement of this index. Analogous to requirements for the FEV1 the following is recommended:

• Report the largest of 3 satisfactory maneuvers.
• Obtain the start of the forced inspiration by extrapolating the steep initial portion of the volume-time recording.

FIV1 is useful in quantifying extrathoracic airway obstruction, and when combined with the FEV1 to assess whether loss of lung elastic recoil contributes to expiratory flow limitation. Normally FIV1 is > 80% IVC (ref. 1).

Ref. 1 - Reference values for FIV1

1. Tammeling GJ. Standard values for lung volumes and ventilatory capacity of sanatorium patients. Selected Papers. Royal Neth Tuberc Ass 1961; 1: 65-89.