Impulse Oscillometry vs Spirometry for Measuring COPD Airway Obstruction

In a recent study published in Multidisciplinary Respiratory Medicine, impulse oscillometry demonstrated greater sensitivity than spirometry for monitoring airway obstruction outcome measures and the effect of long-term therapy with indacaterol/glycopyrronium compared with tiotropium on moderate to severe chronic obstructive pulmonary disease (COPD).

Using impulse oscillometry, researchers found that the long-acting beta-2 agonist/long-acting muscarinic antagonist combination significantly reduced bronchial obstruction in small airways compared with tiotropium (control).

A total of 40 patients were randomly assigned to 2 groups and received either fixed-dose once-daily indacaterol/glycopyrronium or single-agent tiotropium. IOS was used to measure airway resistance at 5 Hz (R5) and 20 Hz (R20), and lung reactance (X). The investigators also evaluated inspiratory capacity, forced expiratory volume in 1 second, forced vital capacity, exacerbation rate, and quality of life.

The investigators reported a significant difference between predosing R5 Hz value at V₁ and at follow-up visits in patients who received dual bronchodilation (P =.0122), but not in the control group (P =.4111). Similar changes were noted for R20 Hz (P =.0318) and for reactance (X; P =.0017). Spirometry was also performed before and after inhaled therapy. Investigators found that predosing inspiratory capacity values in patients who received dual bronchodilation had a statistically significant variation (P <.05). Other lung parameters did not change for either the dual bronchodilation group or the monobronchodilation group. Patients who received dual bronchodilation had a 66% reduction in exacerbations (P =.0017), although the hospitalization rates did not differ between the groups. In contrast, patients who received tiotropium had more frequent exacerbators.

The authors concluded that oscillometry is a better monitor of airway obstruction outcome measures and the effect of long-term therapy in COPD than spirometry because it evaluates small airway obstruction, which is more relevant to the disease than large airway obstruction measured by spirometry. Furthermore, the results of the study showed that dual bronchodilator therapy improves airway caliber and decreases hyperinflation in patients with COPD.

Reference

Molino A, Simioli F, Stanziola AA, Mormile M, Martino M, D’Amato M. Effects of combination therapy indacaterol/glycopyrronium versus tiotropium on moderate to severe COPD: evaluation of impulse oscillometry and exacerbation rate [published online September 27, 2017]. Multidiscip Respir Med. doi:10.1186/s40248-017-0105-4