Comparison of interrupter resistance with flow/volume method in childREN

Airway resistance measurement with the Interrupter Technique (RINT) has been proposed as a valid method for the evaluation of bronchial obstruction and, being easy to administer, could find its application in the uncooperative child (Ch). In order to evaluate the possible clinical application of RINT (Micro Medical MICROLAB 4000), this technique was compared with the Flow/Volume curve (F/V) (SPIROPRO 2000 Pabysch) in Ch (mean age 109.39±39 months). We studied : A) 54 Ch with normal F/V in baseline conditions; B) 50 asthmatic Ch before and after the exercise test (6' free running); C) 102 asthmatic Ch before and after inhalation of 200 ug salbutamol MDI. RINT was calculated, both with mouthpiece and face mask, as the average of 20 measurements for test A and 10 for tests B and C. Paired t test (significant for p<0.05) and Pearson correlation coefficient (significant for r2 0.50) were calculated. Results : A) RINT vs FEV1, PEF, MEF 25, 50 and 75 were not correlated (r2<0.50) even though r revealed an inverse trend (negative sign). Mean values with mouthpiece were higher than those with face mask (p<0.005). B) The change in mean values of expiratory flows was significant at 6', 12' and 20', while mean RINT change was significant only at 6' whether with mouthpiece or with face mask; r had a negative sign but r2<0.50. C) The bronchodilator test showd significant changes in values (p<0.001) both with RINT and F/V. r had a negative sign but r2 < 0.50. Conclusions : RINT measurements are not generally comparable with F/V curve values. Only the bronchodilator test showed significant changes. The mouthpiece measurements are much lower than those with face mask. The results are extremely non-homogeneous and we conclude that the RINT system used has to be improved before it can be applied in clinical practice. © 1997 Wiley-Liss, Inc.