“…One of the techniques which can be applied in this age group is the determination of functional residual capacity (FRC), which requires only the passive co-operation of the child [7,8]. In previous studies of FRC in preschool children, it has already been demonstrated that FRC measurements can be performed in that age group [7][8][9]. There remains, however, much discrepancy between the few prediction equations available, and further modelling is needed to assess the potential influence of gender, weight, posture and age [10].…”