Multiple breath washout with a sidestream ultrasonic flow sensor and mass spectrometry: A comparative study

Abstract

Over recent years, there has been renewed interest in the multiple breath wash-out (MBW) technique for assessing ventilation inhomogeneity (VI) as a measure of early lung disease in children. While currently considered the gold standard, use of mass spectrometry (MS) to measure MBW is not commercially available, thereby limiting widespread application of this technique. A mainstream ultrasonic flow sensor was marketed for MBW a few years ago, but its use was limited to infants. We have recently undertaken intensive modifications of both hardware and software for the ultrasonic system to extend its use for older children. The aim of the current in vivo study was to compare simultaneous measurements of end-tidal tracer gas concentrations and lung clearance index (LCI) from this modified ultrasonic device with those from a mass spectrometer. Paired measurements of three MBW, using 4% sulfur hexafluoride (SF(6)) as the tracer gas and the two systems in series, were obtained in nine healthy adult volunteers. End-tidal tracer gas concentrations (n = 675 paired values) demonstrated close agreement (95% CI of difference -0.23; -0.17%, r(2) = 1). FRC was slightly higher from the MS (95%CI 0.08;0.17 L), but there was no difference in LCI (95%CI -0.10; 0.3). We conclude, that this ultrasonic prototype system measures end-tidal tracer gas concentration accurately and may therefore be a valid tool for MBW beyond early childhood. This prototype system could be the basis for a commercial device allowing more widespread application of MBW in the near future.

Consensus statement for inert gas washout measurement using multiple- and single- breath tests

“…MM based measurement of SF 6 or He are also feasible [44][45][46]. Mainstream MM SF 6 washout has been validated in infants [46,47]; however, lack of validated correction algorithms for detrimental temperature and humidity fluctuations limit utility beyond infancy [48].…”

Agreement between multiple-breath nitrogen washout systems in children and adults

“…Comparison of indices estimating ventilation inhomogeneity currently lack a gold standard comparator [25,36,37]. Computed tomography scans may over-or underestimate lung disease in children [37].…”

CTLA4 polymorphisms and COPD: Table 1—

“…428 unrelated Caucasian PiZZ subjects were fully characterised regarding COPD phenotypes, as described previously [3], and genotyped for rs231775 and rs3087243 using TaqMan1 (Applied Biosystems, Foster City, CA, USA) genotyping technologies. Association with chronic bronchitis and forced expiratory volume in 1 s (FEV1) were sought using logistic and linear regression, respectively, adjusting for age, sex and pack-yrs smoked.…”