Can PFTS Differentiate PVFMD From Subglottic Stenosis?

OBJECTIVE: To determine if the results of routine spirometry and flow volume loops (Pulmonary Function Tests (PFTs)) can be used to distinguish Paradoxic Vocal Fold Movement Disorder (PVFMD) from Subglottic Stenosis (SGS).

METHODS: PFT records and medical history of 49 patients with diagnosis of PVFMD and 39 patients with SGS were compared. Groups were then subdivided to compare PFTs in patients with and without smoking history or lung disease.

RESULTS: Peak expiratory flow rate (PEFR) and Expiratory Disproportion Index (ratio of forced expiratory volume in 1 second (FEV1) over PEFR (FEV1/PEFR)) were both significantly different between patients with SGS and those with PVFMD (p<0.02). FEV1 was also significantly different, but only in the patients with no smoking history or lung disease (p<0.02).

CONCLUSIONS: The findings suggest that spirometry can be a valuable tool in distinguishing SGS from PVFMD. Previous studies have shown the utility of PFTs for distinguishing SGS from pulmonary pathology, but this is the first study to exploit PFTs for distinction of SGS from PVFMD. Given that the flexible laryngoscopic exam used to diagnose PVFMD does not always visualize the subglottis completely, PFTs can be used to increase suspicion of SGS and direct further work-up.