Defining the appropriate waiting time between multiple-breath nitrogen washout measurements.

Static lung volume measurements allow objective assessment of total lung capacity (TLC), functional residual capacity (FRC) and residual volume, and assist in the diagnosis and management of lung disease [1, 2]. The use of gas dilution techniques, such as multiple-breath nitrogen washout (MBNW), require minimal patient cooperation and allow FRC to be determined in those individuals unable to complete plethysmographic measurements. The MBNW technique is used clinically and for research, and provides accurate and repeatable measures in both children and adults [3, 4].