Lung function measurements in children - copsac

Conclusion and future perspectives
Study I
In conclusion, using a biological control we revealed errors in the accuracy of sRaw
measurements at some centers despite normal calibration of the mechanical
components. This study highlights the need for the development of equipment allowing
control of the actual resistance measurements and not only some of its mechanical
components. When software versions are upgraded with possible changes in algorithms,
this could result in an undiscovered difference in sRaw value, unless the company
provides a correction factor. A portable mechanical lung model analogue is needed for
quality control of whole-body plethysmograph in preschool children. In addition,
quality assurance could be optimized by developing the software to determine the best
breath curves from algorithms as flow and respiratory rates or encourage the child (with
animated bio-feedback) to breath with optimal respiratory rates and flow. This could be
a commercial responsibility or be developed in collaboration with a technical
department. Until such equipment becomes available the only option is to use healthy
subjects to assure that the absolute value measured is similar to the normative values
reported in this and a previous report of healthy young children.
If the measured baseline sRaw value is in the normal range and the clinician still
suspects asthma, regardless of equipment type or software version, we recommend to
measure bronchial hyperreactivity (≥25% increase in sRaw) (18) or bronchodilator
responsiveness with a short-acting beta2-agonist (≥25% decrease in sRaw) (38); these
tests can contribute to the asthma diagnose (11). Furthermore, the sRaw method has a
good short and long term repeatability between occasions in stable asthmatics as
previously presented by Klug et al. (1997) (15, 50), which is useful for the clinician in
assessing asthma control for the individual patient.
We have examined the agreement of sRaw values between 6 centers using same
equipment and produced a new set of normative data. It is uncertain if the normative
values can be applied on other commercial whole-body plethysmographs. Our study
showed a variation between the different centers and one can speculate if there exists a
true reference interval when measurement of sRaw values seems to depend on the
equipment. Preliminary results suggest that there are differences in sRaw values
measured between different commercial whole-body plethysmographs. However,
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