Reference equations for respiratory system resistance and reactance in adults☆
Introduction
The forced oscillation technique (FOT) is assuming an increasingly important role as a clinical tool in lung function laboratories. Furthermore, ongoing refinement of hardware and software is likely to increase the use of FOT in the general practice setting. Other potential applications of FOT include the assessment of small airway function and self-monitoring of lung function at home.
With the widespread use of FOT the need for appropriate reference values has become increasingly important. Reference values or equations for forced oscillatory impedance parameters have previously been reported for adults (Jiemsripong et al., 1976, Landser et al., 1982, Clement et al., 1983, Gimeno et al., 1992, Pasker et al., 1994, Pasker et al., 1996, Peslin et al., 1994, Guo et al., 2005, Shiota et al., 2005, Newbury et al., 2008). The limitations of these studies include small sample sizes (Jiemsripong et al., 1976, Landser et al., 1982, Gimeno et al., 1992, Pasker et al., 1994, Pasker et al., 1996, Guo et al., 2005, Shiota et al., 2005, Newbury et al., 2008), samples recruited from selective rather than general populations (Landser et al., 1982, Gimeno et al., 1992, Pasker et al., 1996, Guo et al., 2005, Shiota et al., 2005), an unspecified source of subjects (Jiemsripong et al., 1976, Clement et al., 1983, Pasker et al., 1994), single sex samples (Landser et al., 1982, Clement et al., 1983, Gimeno et al., 1992), the inclusion of current smokers (Clement et al., 1983, Gimeno et al., 1992, Pasker et al., 1996, Shiota et al., 2005), or a restricted age range (Guo et al., 2005). A European Respiratory Society Task Force on FOT expressed the need for further large scale studies in adults to validate existing reference equations (Oostveen et al., 2003).
The Busselton Health Study is a series of large representative cross-sectional surveys and longitudinal studies, which have been conducted in Busselton, a regional center in the south-west of Western Australia, over more than 40 years. The aim of the present study was to generate reference equations for respiratory system resistance and reactance in adults by obtaining forced oscillatory impedance measurements, using the method of pseudorandom noise, in a large representative sample of the general population of Busselton. Some preliminary results of this study have been previously reported in the form of an abstract (Brown et al., 2009).
Section snippets
Methods
The study was approved by the University of Western Australia Human Ethics Committee (Protocol Number RA4/1/0841). All subjects gave written informed consent.
Results
A total of 2391 subjects completed all the tests. Application of the exclusion criteria resulted in a total of 904 adults (341 males) aged 18–92 who were included in the analysis (see Table 1). Anthropometric characteristics and spirometric results are shown in Table 2. Mean Rrs and Xrs for the group are shown in Table 3.
Discussion
In this study we developed reference equations for Rrs and Xrs at 6, 11 and 19 Hz for adults, using a large, well-characterized, randomly selected sample from a general population. There is a clinical need for equations that are relevant to our local population, which almost certainly differs significantly from populations on which existing reference values are based. Oscillatory mechanics may differ between populations due to differences in the distributions of BMI or age, or the types of
Conflicts of interest
None of the authors have conflicts of interest related to the subject matter to disclose. The Woolcock Institute of Medical Research (NJB, WX, CMS, NB, GGK) receives unrestricted grants from Boehringer Ingelheim, AstraZeneca and GlaxoSmithKline, which form a general source of funds for research purposes across all research groups at The Woolcock. The Woolcock Institute of Medical Research also has current and past consultancy agreements with Pfizer, Boehringer Ingelheim, AstraZeneca and
Acknowledgements
NJB analyzed and interpreted the data, and drafted the article. WX analyzed and interpreted the data. MLH contributed to study design and acquisition of the data. CMS, NB, AWM, ALJ, GGK conceived of and designed the study. All authors critically revised the article and approved the final version for publication.
The authors wish to thank Dr Gunnar Unger and Mr Tom Li from the Woolcock Institute of Medical Research for providing valuable biomedical engineering expertise, Professor Matthew Knuiman
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This work was supported by the Co-operative Research Centre for Asthma and Airways, and National Health and Medical Research Council of Australia [ID# 353532].