[Differences in airway resistances in children measured by plethysmography with and without closure of the occluder]

Abstract

Background: There have been several studies that have measured airway resistances using plethysmography without closing the occluder.

Objective: To investigate the differences between the total resistances (sRaw(TOT)) and the specific resistances (sRaw) with the same technique (plethysmography) but different methodology (with and without closure of the occluder) in child subjects.

Material and methods: An observational and cross-sectional study of a consecutive sample of children between 6 and 14 years old who were seen at the Childhood Pneumology clinics from 15th January to 15th February 2009. Determination of sRaw(TOT), sRaw and specific conductance (sGaw) using plethysmography (MasterLab V5.1, Viasys, Wuerzburg, Germany) without closing the occluder. The same determinations were then performed with the occluder closed. The qualitative variables were: sex, diagnosis and treatment, and the quantitative variables: age, weight, height, sRaw(TOT), sRaw, sGaw and respiratory rate with and without closing the occluder. The results were analysed for association and concordance between sRaw(TOT), sRaw and sGaw with and without closure of the occluder using paired Student t test, Bland-Altman method and a scatter plot.

Results: Thirty-six cases were included and all (100%) the tests were performed successfully. The mean age was 9.91+/-2.37 years. There were no differences between sRawTOT, sRaw or sGaw with and without closure of the occluder. Neither were there any differences between the regression of the means obtained for sRaw(TOT), sRaw and sGaw with and without closure of the occluder.

Conclusions: There is good agreement between the sRaw(TOT) y sRaw obtained by plethysmography with and without closure of the occluder.