• Resistance is elevated across all measured frequencies, not only R5 and R20:
  • R5 0.88, 203% predicted, z-score +3.44
  • R20 0.65, 173% predicted, z-score +2.50
• There is marked frequency dependence of resistance: R5-R20 is 0.76 pre-bronchodilator, falling to 0.37 post-bronchodilator. This supports a peripheral/small-airway component, but R20 elevation also indicates increased resistance in more central conducting airways. So it is not purely small-airway disease.
• Reactance at 5 Hz (X5) is within the reference range pre-bronchodilator (z-score about -0.08), so saying “reactance is normal” is reasonable. However, AX is substantially elevated (4.43) and Fres is high (40.19 Hz), both supporting abnormal peripheral airway mechanics.
• The study shows a very large bronchodilator response:
  • R5 decreases 56%: 0.88 to 0.39
  • R20 decreases 46%: 0.65 to 0.35
  • R5-R20 decreases 52%
  • Fres decreases 53%: 40.19 to 18.88 Hz
  • AX decreases 88%: 4.43 to 0.55

Abnormal impulse oscillometry with increased respiratory resistance at 5-20 Hz and marked frequency dependence of resistance (elevated R5-R20), consistent with airflow obstruction involving both central and peripheral airways, with a prominent small-airway component. X5 is within normal limits; however, Fres and AX are elevated, further supporting peripheral airway dysfunction. Following bronchodilator, there is a marked response, with reductions in R5 (56%), R20 (46%), R5-R20 (52%), Fres (53%), and AX (88%). Findings demonstrate significant reversible airway obstruction. Clinical correlation with spirometry and the overall clinical setting is advised.