Introduction

Impulse oscillometry (IOS) is an effort-independent tool to assess the physiological properties of the lung. Th aim was to evaluate the correlation between IOS and forced spirometry parameters in adults with pulmonary obstructive diseases.

Methods

Adult subjects with an obstructive pattern confirmed by spirometry, following Spanish recommendations, and IOS measures with coherence at 5Hz (0.6-0.9) and at 20Hz (0.8-1.0) were included in this cross-sectional study. Sociodemographic data and IOS and spirometry parameters were registered. Obstruction was defined in spirometry as FEV1%/FVC<0.70 and in IOS as R5Hz above the upper limit of normal (ULN) or >150% of the predicted value and delta R5-R20 >20%.

Results

Table 1 describes the sociodemographic and the IOS and spirometry parameters obtained from the 56 patients recruited, 70% of whom were men, with a mean age of 68 ± 10. Mean FEV1% was 58.9 ± 23.8. The resonance frequency, the delta R5-R20 and the reactance area showed a negative and moderate correlation with FEV1/FVC (r=0.442, p= 0.001; r= 0.432, p= 0.001; r= 0.427, p=0.001) and with FEV1 (r=0.468, p= 0.001; r=0.358, p=0.007; r=0.365, p=0.006). R5 Hz > 150% presented a sensitivity of 65%, while for delta R5-R20 95%.

Conclusions

The delta resistance had an acceptable correlation and sensitivity with obstructive spirometry values, which suggests that the distal airways are the main determinant of increased pulmonary resistance.