Impulse oscillometry system as a new diagnostic tool in patients with chronic obstructive pulmonary disease

Background
Both diagnosis and assessment of chronic obstructive pulmonary disease (COPD) are based mainly on pulmonary-function tests that are of very important significance in COPD. Impulse oscillometry is a noneffort-dependent method to assess the mechanical structure of the respiratory system.


Objectives
The study aims to evaluate impulse oscillometry system (IOS) as a diagnosis tool of COPD, in a trial to clarify the sensitivity and correlations of IOS parameters with COPD severity.


Patients and methods
The study included 30 healthy volunteers, group I (control group): 15 smokers, 15 nonsmokers, and 60 patients with COPD, group II: 30 patients with mild-to-moderate COPD, and group III: 30 patients with severe COPD. All participants were sequentially assessed by IOS to detect impedance, after this, spirometry was done, and both were repeated 15–45 min after the first dose of inhalation therapy (salbutamol). IOS is more sensitive in detecting small-airway affection in mild-to-moderate COPD than spirometry.


Results
In COPD, a significant increase in IOS-resistant parameters (R5, R5–20), reactance parameter (AX), and a decrease in reactance (X5) parameter was observed in two groups of COPD (groups II and III) if compared with control group I. IOS parameters significantly correlated with spirometric parameters, particularly large-airway parameters (R5 correlated with forced expiratory volume in the first second postbronchodilator in group II and group III), small-airway parameters (R5–20, X5, and AX correlated with maximal mid-expiratory flow postbronchodilator in group III).


Conclusions
IOS is very useful in detecting small-airway affection in mild and moderate COPD and could be done as an alternative to spirometric tests in severe COPD patients with more accurate grading.