The bias flow nitrogen washout technique for measuring the functional residual capacity in infants

The functional residual capacity (FRC) is the most commonly measured static lung volume in infants. It is important for interpreting volume-dependent pulmonary mechanics, e.g. airway resistance, and defining normal lung growt h. The bias flow nitrogen washout technique is widely used for measuring FR C because the dead space and circuit resistance are low, making it suitable for small or sick infants. Moreover, data acquisition and calculation are easily programmed for a personal computer. The aim of this paper is to provide recommendations pertaining to equipment requirements, study procedures and reporting of data for functional residu al capacity measurements. While measuring the functional residual capacity is regarded as physiologically and clinically important, the accuracy of th e measurement is undoubtedly equally important. Hence, the paper also empha sizes factors influencing the accuracy of functional residual capacity meas urements independent of equipment requirements. These recommendations repre sent the "State of the Art" in 2000.