Impedance cardiography accurately measures cardiac output during exercise in children with cystic fibrosis

Objectives: After validation of impedance cardiography (ICG) in healthy children, this same device was tested in children with cystic fibrosis (CF) to validate its capability of measuring cardiac output (Q) in this population. Design: Comparative study of ICG vs the indirect Fick (CO₂) method. Setting: Tertiary care children's teaching hospital. Patients: Twenty-one CF children with mean FEV₁ of 77±21% predicted. Measurements: ICG results were compared with CO₂ rebreathing (RB) measurements of Q with sampling of capillary blood gases at two levels of exercise (0.5 and 1.5 W/kg). ICG measurements were made each minute, and duplicate RB measurements from 6 to 8 min at each workload. Q was regressed against oxygen uptake and results by each method were compared. Results: Mean bias (QRB-QICG) was - 0.09±0.94 L/min. The largest deviation of QICC from QRB was +33%, and 83% of corresponding QICG values were within ±20% of QRB result. Conclusions: This device gives rapid, accurate, noninvasive Q measurements in children with CE.