Abstract
Multi-center studies in specific airway resistance have shown significant inter laboratory variability. Comparison of plethysmographic equipment using a lung model easily transportable from one site to another should be of help to international normative studies. A resistor made of parallel capillary tubes – insuring adequate linearity within 1 L/sec – was connected to a glass bottle. Thermal time constants were measured while the bottle was empty and while stuffed with steel wool. In the latter, isothermal condition was estimated to occur only at very low frequency (around 0.01 Hz) and gas compression was polytropic up to 0.6 Hz. With the empty analog, adiabatic gas compression was estimated to occur at frequencies ≥0.2 Hz, and more accurate volume estimation was obtained. The empty analog volume and specific resistance measured in a body plethysmograph on different days indicated within 5% accuracy as well as intersession repeatability. It is concluded that a physical analog built out of simple material provides accurate measurements of specific resistance. The apparatus should be of help to compare plethysmographic equipments from different laboratories.
Highlights
International collaborative studies are important to better understand, assess and manage pediatric respiratory diseases such as asthma, chronic lung disease of prematurity or cystic fibrosis
The plethysmographic measurement of specific airway resistance has gained popularity in preschool children during the last few years as it is achievable with minimal subject cooperation
Because the protocol for plethysmographic assessment depended on determination of analog characteristics, method and result sections were pooled for each part of the study
Summary
International collaborative studies are important to better understand, assess and manage pediatric respiratory diseases such as asthma, chronic lung disease of prematurity or cystic fibrosis. It is of primary importance that standardized procedures are used and equipment measures among and across centers. Procedures may be formulated and standardized at international workshop conferences, and it is a matter of discussion and communication to delineate recommendations and guidelines based on experience sharing and literature review (Stocks and Quanjer, 1995; Miller et al, 2005; Beydon et al, 2007). Equipment type and/or specifications often differ among laboratories and between-center agreement has to be tested for optimal interpretation. The plethysmographic measurement of specific airway resistance (sRaw) has gained popularity in preschool children during the last few years as it is achievable with minimal subject cooperation
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