Early Small Airway Mechanics and Functional Correlates in Asymptomatic Smokers: An Impulse Oscillometry-Based Study

Area of Science:

• Respiratory Medicine
• Pulmonary Physiology
• Cardiopulmonary Exercise Testing

Background:

• Asymptomatic smokers may have early small airway mechanical changes.
• Standard spirometry might not detect these subtle alterations.
• Impulse oscillometry (IOS) offers a potential method for early detection.

Purpose of the Study:

• Evaluate respiratory system mechanics using IOS in asymptomatic smokers.
• Investigate the relationship between IOS parameters, exercise capacity, and muscle oxygenation in smokers.
• Determine if IOS can identify early smoking-related airway dysfunction.

Main Methods:

• Cross-sectional study comparing university student smokers and non-smokers.
• Spirometry and IOS measurements before and after a six-minute walk test (6MWT).
• Assessment of respiratory muscle strength and vastus lateralis muscle oxygen saturation (SmO₂).

Main Results:

• Smokers showed significantly higher resistance (R5, R5-R20) and altered reactance (AX, Fres, X5, X5VIN) compared to non-smokers, despite normal spirometry.
• Smoking exposure correlated with increased resistance and decreased reactance.
• Smokers had reduced 6MWT distance and lower SmO₂ levels; lower R5 and higher X5VIN correlated with better exercise capacity.

Conclusions:

• IOS effectively identifies early small airway mechanical changes in asymptomatic smokers, undetectable by spirometry alone.
• These IOS-detected changes are functionally relevant, correlating with impaired exercise capacity and muscle oxygenation.
• IOS is a valuable complementary tool for assessing multidimensional smoking-related airway effects.