Paradoxical vocal fold motion (PVFM) disorder, often referred to as vocal cord dysfunction (VCD), interferes with breathing because the vocal folds adduct during inspiration making it difficult to inhale. When PVFM is triggered by exercise, it can impact competitive play. Athletes with PVFM are often misdiagnosed as having exercise-induced asthma, but do not respond to asthma treatment. Directly visualizing the larynx (laryngoscopy) when symptoms are present is the current "gold standard" for diagnosing PVFM. However, laryngoscopy is invasive and expensive. Standardized noninvasive alternative methodologies are needed for clinically feasible assessment of PVFM by the speech-language pathologist. Respiratory resistance (Rr), measured with the Airflow Perturbation Device (APD), may be useful for assessing PVFM because vocal fold adduction can increase Rr markedly.

This research comprises three studies with an overarching goal to validate an objective, non-invasive measure of Rr for identifying abnormal constriction of the laryngeal airway associated with PVFM disorder. Study 1 compared APD-measured Rr to glottal area (GA) assessed through laryngoscopy in a healthy subject feigning PVFM-type breathing. Study 2 assessed intra- and intersession test-retest reliability of APD-determined Rr for a control group of 12 healthy female teenage athletes during resting tidal breathing (RTB) and post-exercise breathing (PEB). Study 3 examined differences between the same 12 healthy athletes with 12 athletes diagnosed with PVFM matched for sex, age, and activity level, for Rr, exercise duration, and dyspnea ratings for RTB and PEB.

The results revealed: 1) a strong negative correlation (r = -0.824) between Rr and GA suggesting that the APD can indirectly measure changes in the laryngeal airway; 2) strong test-retest reliability for APD-measured inspiratory (Ri) and expiratory (Re) resistance during RTB (ICC > .95), and PEB (ICC >.85); and 3) in control athletes, Ri and Re decreased during PEB as compared with RTB, whereas in athletes with PVFM, both Ri and Re increased during PEB with statistical significance reached for Ri (p <.001). During exercise, athletes with PVFM reported severe dyspnea and exercised for shorter durations. This research demonstrates that a diagnostic protocol for PVFM should include measures of Rr, exercise duration, and perceived dyspnea.