Abstract: Methods and systems to determine the lung clearance index (LCI) or other indices of ventilation inhomogeneity of lungs of a paediatric subject are provided. Inert tracer gas is washed-in and the wash-out is conducted by inhaling atmospheric air from the surroundings and exhaling to a confined space until the end-tidal tracer gas concentration has fallen below a predetermined fraction of the starting concentration. The LCI is calculated as the ratio between the cumulative expired volume (VCE) required to clear the inert tracer gas concentration from the lungs below a predetermined fraction of the starting concentration and the functional residual capacity (FRC) determined by dividing the net volume of inert tracer gas exhaled with the difference in end-tidal fractional concentration of the inert tracer gas at the start and end of the wash-out period; where VCE is determined by measuring the total volume in the collection bag after completed wash-out period.

Abstract: Methods and systems to determine the lung clearance index (LCI) or other indices of ventilation inhomogeneity of lungs of a paediatric subject are provided. Inert tracer gas is washed-in and the wash-out is conducted by inhaling atmospheric air from the surroundings and exhaling to a confined space until the end-tidal tracer gas concentration has fallen below a predetermined fraction of the starting concentration. The LCI is calculated as the ratio between the cumulative expired volume (VCE) required to clear the inert tracer gas concentration from the lungs below a predetermined fraction of the starting concentration and the functional residual capacity (FRC) determined by dividing the net volume of inert tracer gas exhaled with the difference in end-tidal fractional concentration of the inert tracer gas at the start and end of the wash-out period; where VCE is determined by measuring the total volume in the collection bag after completed wash-out period.