Spirometry Measuring Technology

In its simplest form, spirometry is the measurement of how much air a person can breathe out in one forced breath, known as forced expiratory vital capacity (FVC). Different parameters can be measured from the flows that occur during the FVC maneuver. Healthcare professionals interpret volume and flow data alongside graphs showing volume/time and flow/volume to assess lung health.

Vitalograph has investigated many different precision technologies for measuring flows and volumes. Today, the preferred technology used in Vitalograph diagnostic spirometers for flow measurement is the Fleisch Pneumotachograph, and for volume measurement is the Rolling Seal. We use Lilly-type screen pneumotachographs in our lab spirometers and stator-rotor flow measuring technology in our monitoring and screening devices.


Fleisch Pneumotachograph

Vitalograph flow-measuring spirometers feature a Fleisch Pneumotachograph which is an established technology, developed by Professor Alfred Fleisch in Lausanne in 1953. 


Vitalograph monitoring and screening devices use stator-rotor flow measuring technology. These lightweight handheld devices have a limited lifespan compared to spirometers and are ideally suited to home monitoring or for respiratory screening.

Rolling Seal

Vitalograph volume-measuring spirometers feature rolling seal technology, measuring up to 12L. Rolling seal technology measures true volume displacement, thereby providing the highest level of accuracy for volume measurements.

Screen Pneumotachograph (Lilly-type)

Heated Lilly-type screen pneumotachographs are used in lab spirometers where additional test types need to be integrated into the flowhead and the requirement for easy cleaning, servicing and stability through extended periods of testing are of paramount consideration.


Ultrasonic technology is used in flow measuring office spirometry systems. Small and lightweight, ultrasonic spirometers measure flow by determining the Doppler effect in both expired and inspired air, using ultrasound. The variation in ultrasonic waves caused by a change in gas velocity is used to give a measure of the average gas velocity between 2 transducers as an analog signal.

Hot Wire Anemometer

In spirometers using hot wire anemometer flow measuring technology, the measuring principle is based on the change of resistance in a heated wire as heat is transferred to gas flowing past it.

Legacy and Research Spirometer Technology

Wedge Bellows

Vitalograph is probably best known for its iconic wedge bellows spirometers which were produced from 1962 with the last examples of such devices sold in the early 2000s. Many of these devices are still in use in research and teaching establishments, indicating the robustness and high quality build that Vitalograph devices espouse.

Water Seal

Water seal spirometers are rarely used today as they are large and heavy, difficult to move, provide a potential source of contamination from water spills, and it is difficult to keep the device clean. However they are still sometimes used in teaching and research as, like wedge bellows technology, they provide high accuracy volumes and the direct determination of volumes is clear and simple for demonstration purposes.