The lung clearance index (LCI) as an estimate of ventilation inequalities in patients with cystic fibrosis.

Assessment of respiratory function is indispensable for provision and control of respiratory care in infants and children with lung disease. Based on plethysmographic measurements and the multibreath nitrogen washout (MBNW) distinction of patients with cystic fibrosis (CF) into different functional groups revealed that the mixed type (TGV > 130 % pred. and Raw > 130 % pred.) has to be considered as worst: highest degree of trapped gases (TG) and ventilation inequalities and consequently most impeded gas exchange. Best predictor in patients with abnormal gas exchange are the degree of bronchial obstruction (Raw) and the amount (TG). Vital capacity (VC) as overall estimate of lung function is best predicted by TG, FEV1 and MEF50. The major merit of the MBNW technique is the possibility to have the amount of TG estimated. Based on the present the calculation of the LCI adds no further information of sufficient clinical importance, remaining the question open, whether the assessment of the so called "moment ratios" from the entire washout curve would feature a better estimate of disturbed lung physiology.