Assessment of an infant whole-body plethysmograph using an infant lung function model

In order to facilitate international multicentre studies and improve the quality control of infant pulmonary function measurements, the European Respiratory Society-American Thoracic Society Task Force for infant lung function testing has recently developed specifications for standardized infant lung function equipment and software. A mechanical infant lung model analogue has been developed to assess whether infant lung function equipment is able to meet these requirements. However, the practical testing of infant lung function equipment using such models is highly complex because of the need to use very small pressure and flow changes, and the numerous potentially confounding factors associated with both the design of the device and the testing procedure. The aim of this study was to determine whether the infant lung model is capable of assessing the overall function of an whole-body infant- plethysmograph, using the only infant plethysmograph that was commercially available at the time as an example. The mechanical characteristics of the model such as vibrations or noise did not disturb the delicate plethysmographic measurements and thereby allowed a reliable assessment of the system. A series of tests revealed that the plethysmograph was able to measure airway resistance 1-3.5 kPa.L(-1).s with an accuracy of +/-2.5% and lung volumes 75-300 mL with an accuracy of +/-2.5% under in vitro conditions. To conclude, the infant lung model is a useful means of assessing the overall in vitro performance of infant whole-body plethysmographs, but thermal, mechanical and frequency response characteristics of such a device must be taken into account when interpreting the results of such assessments.