Abstract
There is growing interest in the nitrogen washout technique, especially for cystic fibrosis patients. The aim of our study was to compare conventional FRC measurements (body box and He washin) with 2 commercially available nitrogen washout devices.
Methods: 17 healthy subjects (13F/4M, 25-55 years) performed FRC measurements with He washin and body box (Jaeger) which were compared to 2 nitrogen washout devices (NDD easyone Pro lab and Cosmed Quark PFT). All measurements were done twice. If FRC did not reproduce within 10% a third measurement was done. No fixed breathing pattern was imposed. From all measurements we determined TLC, FRC, RV and VC and from washouts also LCI (Lung Clearance Index).
Results: All VC values were in close range. Compared with He washin FRC NDD was significantly lower and for TLC and RV both washout systems showed lower results. LCI values were for both systems higher than predicted, while the smallest difference was for NDD.
Conclusions: FRC measurements using NDD device were significantly lower than other FRC measurements with concomitant decreases in RV and TLC. The lower values for TLC and RV using the Cosmed device may be due to separation of VC and FRC measurements. Both devices use indirect measurement of FN2 which may deviate especially at low FN2 values.
- © 2014 ERS