The relationship of impulse oscillometry results with respiratory muscle strength and exercise capacity in patients with emphysema.

OBJECTIVE: Assessment of small airway function, respiratory mechanics, respiratory muscle strength, and exercise capacity plays a crucial role in both pharmacological and non-pharmacological treatment planning, as well as in evaluating treatment efficacy in patients with emphysema. Impulse oscillometry (IOS) allows for the evaluation of the physiological properties of both large and small airways, along with lung parenchyma involvement. This study aimed to in*vestigate small airway function and respiratory mechanics related to lung parenchyma using IOS and to examine their relationship with respiratory muscle strength and exercise capacity in emphysema patients.

METHODS: Thirty patients diagnosed with emphysema by high-resolution computed tomography (HRCT) and airway obstruction based on GOLD (Global Initiative for Chronic Obstructive Lung Diseases) spirometric criteria were included in this study. Demographic characteristics, IOS parameters, respiratory muscle strength (MIP, MEP), and exercise capacity (Endurance Shuttle Walk Test [ESWT], VO2 peak) were analyzed. The study was approved by the Ankara Kecioren Training and Research Hospital Ethics Committee (approval number: 2012-KAEK-15/2210) and conducted in accordance with the Declaration of Helsinki.

RESULTS: There was a statistically significant positive correlation between GOLD spirometric stages and IOS parameters, particularly the resistance difference at 5 and 20 Hz (R5-R20) and reactance area (AX). A significant negative correlation was observed between GOLD stages and reactance at 5 Hz (X5), maximal inspiratory pressure (MIP), ESWT, and VO2 peak. Additionally, MIP was negatively correlated with R5, R5-R20, and AX, but positively correlated with X5. VO2 peak was negatively correlated with R5, R20, R5-R20, and AX, while it was positively correlated with X5, MIP, and maximal expiratory pressure (MEP). ESWT was negatively correlated with R5, R5-R20, and AX, and positively correlated with X5.

CONCLUSION: This study demonstrated that emphysema involves impairment of small airways and lung parenchyma, which can be effectively assessed using IOS. The impaired respiratory mechanics significantly decrease exercise capacity. Prioritizing therapies that target small airways may enhance pharmacological outcomes, and the observed correlation between IOS parameters and respiratory muscle strength may provide guidance for inhaler selection in clinical practice.