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BMC Research Notes

, 4:23

First Online: 28 January 2011Received: 11 October 2010Accepted: 28 January 2011DOI: 10.1186-1756-0500-4-23

Cite this article as: Groepenhoff, H., Terwee, C.B., Jak, P.M. et al. BMC Res Notes 2011 4: 23. doi:10.1186-1756-0500-4-23


BackgroundTo assess a pulmonary function change over time the mass flow sensor and the pneumotachograph are widely used in commercially available instruments. However, the smallest detectable change for both devices has never been compared. Therefore, the aim of this study is to determine the smallest detectable change in vital capacity VC and single-breath diffusion parameters measured by mass flow sensor and or pneumotachograph.

MethodIn 28 healthy pulmonary function technicians VC, transfer factor for carbon monoxide DLCO and alveolar volume VA was repeatedly 10× measured. The smallest detectable change was calculated by 1.96 x Standard Error of Measurement ×√2.

FindingsThe mean range of the smallest detectable change measured by mass flow sensor and pneumotachograph respectively, were for VC in Liter: 0.53 0.46-0.65; 0.25 0.17-0.36 p = 0.04, DLCO in mmol*kPa*min: 1.53 1.26-1.7; 1.18 0.84-1.39 p = 0.07, VA in Liter: 0.66. 0.53-0.82; 0.43 0.34-0.53 p = 0.04 and DLCO-VA in mmol*kPa*min*L: 0.22 0.19-0.28; 0.19 0.14-0.22 p = 0.79.

ConclusionsSmallest detectable significant change in VC and VA as measured by pneumotachograph are smaller than by mass flow sensor. Therefore, the pneumotachograph is the preferred instrument to estimate lung volume change over time in individual patients.

Electronic supplementary materialThe online version of this article doi:10.1186-1756-0500-4-23 contains supplementary material, which is available to authorized users.

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Autor: Herman Groepenhoff - Caroline B Terwee - Patrick MC Jak - Anton Vonk-Noordegraaf


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