Pulmonary Function Testing and Upper Airway Disorders: Analysis From the STAMPEDE III Database

Area of Science:

• Pulmonology
• Respiratory Medicine
• Diagnostic Imaging

Background:

• Vocal cord dysfunction (VCD) and asthma share similar symptoms, complicating diagnosis and treatment.
• Accurate differentiation is crucial for effective management of respiratory conditions.

Purpose of the Study:

• To reanalyze pulmonary function data from the STAMPEDE III study.
• To compare findings in patients diagnosed with asthma, airway hyperreactivity (AHR), and VCD.
• To identify objective measures for differentiating these conditions.

Main Methods:

• Utilized data from the STAMPEDE III prospective, observational study.
• Included spirometry with bronchodilator response, impulse oscillometry (IOS), methacholine challenge testing, and exercise laryngoscopy.
• Compared pulmonary function testing, flow volume loop (FVL), and IOS results across diagnostic groups.

Main Results:

• Flow volume loop abnormalities were present in all groups, with no significant differentiation.
• Impulse oscillometry (IOS) revealed significant differences: elevated resistance (R5, R20) and lower reactance (X5) in the asthma group compared to VCD and AHR.
• R5-R20 values were highest in asthma, followed by VCD, then AHR, indicating distinct impedance patterns.

Conclusions:

• Baseline spirometry and FVL are inadequate for distinguishing asthma from VCD.
• Impulse oscillometry (IOS) provides valuable data, particularly inspiratory impedance measurements, for differentiating between asthma and VCD.
• IOS should be integrated into the diagnostic workup for patients with suspected VCD.