Tidal breath analysis for infant pulmonary function testing

The aim of this position paper is to provide recommendations pertaining to software and equipment requirements when analysing tidal breathing measurements in infants. These guidelines cover numerous aspects including terminology and definitions, equipment, data acquisition and analysis, and reporting of results, and highlight areas in which further research is needed before consensus can be reached. When collecting tidal breathing data in infants and children, equipment dead space and resistance must be minimized, all sources of leak eliminated, and a flowmeter with appropriate frequency response and linearity employed. Inspired gases should be corrected to body temperature, barometric pressure and saturated with water vapour conditions and efforts made to eliminate the various sources of drift in volume that can occur. In addition, the analogue-to-digital converter used to sample data must be capable of adequately resolving the highest and lowest flows required by the study. An adequate sampling rate must be used; 50-100 Hz may be sufficient for the determination of timing and volume parameters, especially in older infants, but rates of 200 Hz are recommended for analysis of the tidal breathing flow/volume loop and other sensitive parameters such as time to peak tidal expiratory flow/expiratory time. The potentially most troublesome aspect of tidal breath analysis from the computational point of view is the identification of the beginning and end of inspiration and expiration. Once methods and equipment for the measurement and analysis of tidal breathing in infants have been standardized, there is an urgent need to establish appropriate reference ranges for various key parameters so that they may be used more effectively in the clinical setting. Implementation of these recommendations should help to ensure that such measurements are as accurate as possible and that more meaningful comparisons can be made between data collected in different centres or with different equipment.