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

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• Upper airway disorders like vocal cord dysfunction (VCD) can mimic asthma symptoms.
• Accurate differentiation between asthma and VCD is crucial for effective treatment strategies.

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:

• Prospective, observational study (STAMPEDE III) of active duty military personnel with exertional dyspnea.
• Pulmonary function tests including spirometry, impulse oscillometry (IOS), methacholine challenge, and exercise laryngoscopy.
• Direct comparison of flow volume loop (FVL) and IOS data across diagnostic groups (asthma, AHR, VCD).

Main Results:

• Flow volume loop abnormalities were present in all groups, with no significant differentiation.
• Impulse oscillometry revealed significantly elevated baseline resistance (R5, R20) in the asthma group compared to the VCD group.
• Differences in R5-R20 and reactance at 5 Hz (X5) were observed across all three groups, with asthma showing the highest resistance and lowest reactance.

Conclusions:

• Baseline spirometry and FVL are not sufficient to distinguish between asthma and VCD.
• Impulse oscillometry (IOS) findings suggest significant differences in inspiratory impedance between asthma and VCD.
• IOS should be integrated into the diagnostic workup for patients with suspected VCD.