Rise of the electronic spirometer

The transition from water-seal volume displacement spirometers to electronic flow measurement systems began in the 1970’s.  The first instruments were completely analog but as microprocessors became more powerful spirometers eventually became fully digital.  Because this kind of spirometer is relatively inexpensive to develop and manufacture, this era (which continues to today) saw many small companies rise and either fall or get acquired by larger corporations.


Godart Pneumotachograph, 1962.  From the time before electronics became miniaturized.  An amplifier and integrator for a Fleisch pneumotach.  From “Pneumotachography” by W.M. Pols, Acta Anaesthesiologica Scandinavica, 1962, page 178.


Mercury Electronics Computing Spirometer CS1, circa 1970.  From a Mercury Electronics product brochure, found on the Legacy Tobacco Documents website. Undated, but likely from around 1970.


National Cylinder Gas Pulmonary Function Indicator, probably manufactured in the 1970′s. Used a hot-wire transducer to measure flow.  A completely analog spirometer.  Taken from an Ebay listing.

Spirostar S, Feyves & Gut, circa 1970.  From a sales brochure kindly provided by Emanuele Isnardi.  The entire sales brochure can be downloaded here.

“Principle of measurement: the patient breathes room air (or, in special cases, a gas mixture) through a sterilisable, heated pneumotachograph head fitted to a mouthpiece of breathing mask. The resulting pressure different of a few millimetres water gauage picked up the the pneumotachotraph and proportional to the flow V is concerted to the corresponding positive and negative voltages by means of a pressure transducer and registered in an electronic integrator after amplification. The voltage resulting from this operation is proportional to the tidal volume (TV). The factor of the proportional relationship is determined by volumetric calibration, using a calibration pump. One litre of air is pumped through the pneumotachograph head, which is pre-heated to operating temperature. This is the only reasonable method of checking the entire system. A balance control compensates for any lack of symmetry between pneumotachograph heads.

The S basic unit this consists of a slide-in unit for measuring the flow and a linked integrator and calibrating device. Measurements ranges: 1, 2, 5, 10, 20 litres or litres/sec., respectively, on full-scale deflection; time constants: 1000, 20 , 10, 5 seconds. Push-button selectors.  Automatic marking of zero-flow pointes V=0; heating of pneumotachograph head; data output using optional built-in single- or multi-channel compensated direct recordes or X-Y records; repectively.

Determinable parameters at rest and during exercise: tidal volume TV, inspiratory reserve volume IRV, expiratory reserve volume ERV, inspiratory capacity IC, forced inspiratory volume FIV, vital capacity VC, forced vital capacity FVC, forced expiratory volume FEV1, percentage expired %FEV1/VC and %FEV1/FVC, mean inspiratory flow MIFR, mean expiratory flow rate MEFR, mean flow rate MFR, peak inspiratory flow PIFR, peak expiratory flow rate PEFR, peak flow rate PFR, forced inspiratory flow FIF, forced expiratory FEF, forced mid-expiratory flow rate FMF, minute volume MV, maximum breathing capacity MBC, indirect maximum breathing capacity IMBC, maximum voluntary ventilation MVV, excess exercise ventilation EEV, standardised ventilation SV, ventilation in response to exercie VRE, respiratory frequency F, duration of inspiration, and expiration, respectively, flow-volume diagram also with He2 (X-Y recorder necessary).”


National Cylinder Gas (division of Chemtron) Pulmonary Function Indicator, 1974.  Used a hot-wire transducer to measure gas flow, now partly digital.

From: Burton RM, Kozel WM, Penley RP, Ward GH, Chapman RS.  Application and evaluation of portable field instruments for measuring Forced Expiratory Volume of children and adults in environmental health surveys.  Environmental Health Perspectives, 1974; 8: 123-131.  Page 125.


Donti Pulmonary Performance Analyzer.  Manufactured by Cavitron. Advertisement in Chest, vol 65, no 3, March 1974, page 356D.  Although it had a digital display it was primarily analog circuitry.


Marion Labs Spirostat, 1970s: The Marion Labs Spirostat was an odd blend of optical, analog and digital components.  It used a disposable turbine sensor. An optical pickup counted the revolutions and converted them to volume.  A volume-time curve was printed using a packed array of optical fibers onto Polaroid film and the plastic overlay was used to measure FVC and FEV1.  The turbine was small (less than 1/2″ in diameter) and resistance through the sensor was high. Manufactured and sold in the late 1970’s.  Picture found on a Ebay listing.


Monaghan M403, 1974:  Used a hot-wire sensor.  The readout was digital, the rest of its electronic circuitry was likely analog. From: The British Journal of Anesthesia, 1974, Vol 46, No.2, Page 1.


Tracor DS-601 R, 1976.  From Medical Instrumentation for Healthcare, by Cromwell L, Arditti M, Weibell FJ, Pfeiffer EA, Steele B, Labok J.  Published by Prentice-Hall, 1976.  Page 261.  This spirometer was later sold as the LSE Vanguard and was probably the first to use disposable pneumotachs.  Numerical results were displayed one at a time on the digital front panel by pressing a button to step through them.  The optional strip chart recorder is shown on the right.


deVilbiss Surveyor I, late 1970’s.  Photograph courtesy of Richard H. Lord of µPward Concepts.  Developed by Biotrine Inc. for deVilbiss.   It had an embedded 6800 (8-bit) processor and used a ceramic pneumotachograph.  It had a 40 character single-line display.  A small text printer and an HP pen plotter were options.


Vitalograph Spirometer, Model S, 1980.  Probably the first computer-based system from Vitalograph.  From InfoWorld Sep 15, 1980, page 22.


CDX Autospiro from the late 1970′s or early 1980’s.  Used a vortex-shedding mass flow sensor.  Probably completely digital but limited by the digital displays available at that time.  Cheap LCD displays were still a decade or two away.  Found on a Dotmed listing.


Gould 5000 IV, 1983: The Gould 5000 IV was capable of performing spirometry, single-breath DLCO, closing volumes and either helium dilution or nitrogen washout lung volumes.  It came with a “large 9″ CRT for real-time graphics” and used a dry, rolling-seal spirometer.  Photo from a sales brochure courtesy of James Sullivan, BA, RPFT, Supervisor, Pulmonary Laboratories, Memorial Sloan Kettering Cancer Center


Pneumedics Dataloop Spirometer, 1984:  Pneumotach-based.  Photo from a sales brochure courtesy of James Sullivan, BA, RPFT, Supervisor, Pulmonary Laboratories, Memorial Sloan Kettering Cancer Center


Spirometrics 2500, 1980’s.  Spirometers kept getting smaller and lighter.  Pneumotach based.  From a Dotmed Listing.  


Micro Medical turbine spirometer, 1987.  One of the very first hand-held spirometers.  From: Gunawardena KA, Houston K, Smith AP.  Evaluation of the turbine pocket spirometer.  Thorax 1987; 42: 689-693. Page 690.


CDX SpiroComp, 1987.  Used an un-heated Fleish pneumotach.  From Office Spirometry. A practical guide to the selection and use of spirometers.  By PL Enright and RE Hyatt.  Published by Lea and Febiger, 1987.  Page 109.


Medical Equipment Designs MultiSpiro PC, 1987.  Originally manufactured by Biotrine and re-sold by Medical Equipment Designs.  Used a ceramic pneumotach with an integral temperature sensor.  From Office Spirometry. A practical guide to the selection and use of spirometers.  By PL Enright and RE Hyatt.  Published by Lea and Febiger, 1987.  Page 135.

Spirometer_SpiroScreen_Gould_SRL_1987 Originally manufactured by Chest Corporation of Japan and re-sold by SpectraMed, a division or subsidiary of Gould/SRL.  From Office Spirometry. A practical guide to the selection and use of spirometers.  By PL Enright and RE Hyatt.  Published by Lea and Febiger, 1987.  Page 113.


CDX101, 1987.  Manufactured by CDX for Mayo Pulmonary Services as the 3M/Mayo2001.  Included a telephone modem to transmit results. From Office Spirometry. A practical guide to the selection and use of spirometers.  By PL Enright and RE Hyatt.  Published by Lea and Febiger, 1987.  Page 109.


Spirometerics 4000, 1990’s.  One of the first spirometers with a graphics LCD display.  Pneumotach based.  From a Dotmed listing


Creative Biomedics DX Plus spirometer, late 1990’s.  From a Creative Biomedics sales brochure. Many PC-based spirometry systems have a birthday cake with candles displayed on the screen as an incentive during spirometry. This spirometer came with its own birthday cake!


Puritan Bennett PS600, circa 1990’s.  A volume displacement spirometer that included a microprocessor.  Found on an Ebay listing.


Spirometrics CMD/PC-Flow+, 1997.  Page 1 of a brochure kindly provided by Angela Cole, RN.


A Koko Legend Spirometer.  Typical of the electronic spirometers of today, it has a color LCD touch display and is battery powered.

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PFT History by Richard Johnston is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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The diverse, quirky and mostly forgotten history of Pulmonary Function testing