We describe a method for routine calibration of a pneumotachograph integrator system used for the measurement of maximum expiratory flow-volume (MEFV) curves. This calibration permits the sequential measurement of MEFV curves with the patient breathing air and subsequently a helium-oxygen (80%-20%) mixture (He-O2). An Emerson 3-PV adult volume ventilator is used to deliver a constant volume and reproducible flow pattern with either air or He-O2. Tracings are recorded on an X-Y recorder, and two sets of variable gains on the integrator system permit superimposition of curves of equal volume and flow pattern. Loss of correspondence between curves measured on successive days without recalibration is less than 5%. This method offers a simple, reproducible way of adapting a pneumotachograph integrator system to the measurement of helium flow-volume curves.
Get full access to this article
View all access options for this article.
References
1.
DespasPJ, LerouxM, MacklemPT: Site of airway obstruction in asthma as determined by measuring maximal expiratory flow breathing air and a helium-oxygen mixture. J Clin Invest51:3235, 1972.
2.
DosmanJ, BodeF, UrbanettiJ, MartinR, MacklemPT: The use of a helium-oxygen mixture during maximum expiratory flow to demonstrate obstruction in small airways in smokers. J Clin Invest55:1090, 1975.
3.
SchilderPD, RobertsA, FryDL: Effects of gas density on the maximal expiratory flow-volume relationship. J Clin Invest42:1705, 1963.
4.
VirgultoJ, BouhuysA: Electronic circuits for recording of maximum expiratory flow-volume (MEFV) curves. J Appl Physiol35:145, 1973.
5.
GulesianPJ: An instrument for the accurate measurement of MEFV parameters. IEEE Transactions on Bio-Medical Engineering18:378, 1971.
6.
HutcheonM, GriffinP, LevisonH, ZamelN: Volume of isoflow. Am Rev Respir Dis110:458, 1974.
7.
GelbAF, KleinE: Clinical significance of pulmonary function tests. Chest71:396, 1977.
