Comparison of IOS and Body Plethysmography Findings in Patients with Interstitial Lung Disease

In patients with ILD, the static expiratory pressure-volume curve of the lung is generally shifted downward and to the right, and spirometry results reveal reduced vital capacity. However, decreased vital capacity may occur even in patients with obstructive lung diseases and in other situations, such as chest wall restriction, lung resection, inspiratory muscle weakness, or poor cooperation with spirometry. In addition, spirometry is sometimes difficult to perform with elderly, cognitively impaired patients or with severe respiratory distress. IOS is a simple, non-invasiv e method requiring only passive patient cooperation that allows for the evaluation of lung function through the measurement of both airway resistance and airway reactance. This study aims to assess the role of IOS in the evaluation of cases of interstitial lung diseases.

This study included 53 patients with interstitial lung diseases of different causes. Pulmonary function test by spirometry was done to measure FEV1, FVC, FEV1/FVC, MEF25-75, and pulmonary function test by impulse oscillometry (IOS). We measured R5, R20, X5, RF.

Examining the indicators evaluated based on IOS shows that the numerical values of R5 have not increased significantly. Regarding R20 and R5-R20, exhalation values are more than two, and as a result, the interval (expinsp) is a positive number. The values of X5, AX, and Fres increased as expected (213%).

X5 was lower in patients with ILD, indicating a restrictive pattern. Conversely, there is a negative correlation between X5 and FVC. Based on the numerical values of R5 and R20, it can be inferred that patients experience small airway obstruction.