Is Forced Expiratory Volume in 1 second (FEV1) abnormally low in Vocal Cord Dysfunction (VCD)?

FEV1 in Vocal Cord Dysfunction

FEV1 is typically normal in patients with Vocal Cord Dysfunction (VCD), as VCD primarily affects the inspiratory phase of breathing rather than the expiratory phase measured by FEV1. 1

Spirometric Findings in VCD

Vocal Cord Dysfunction is characterized by paradoxical adduction of the vocal cords, particularly during inspiration, which leads to airflow obstruction and dyspnea. However, this condition has distinct spirometric patterns compared to obstructive airway diseases like asthma:

• Normal FEV1: Unlike asthma, VCD typically presents with normal FEV1 values when patients are asymptomatic 2
• Inspiratory flow limitation: The hallmark spirometric finding in VCD is limitation of inspiratory flow, visible as a flattening or plateau on the inspiratory portion of the flow-volume loop 1, 3
• Expiratory curves: While less common, up to 81% of VCD patients may also show plateaus in the expiratory curve 3

Diagnostic Considerations

When VCD is suspected, several important diagnostic considerations should be kept in mind:

• Full spirometric maneuvers: The American Thoracic Society guidelines recommend performing full inspiratory and expiratory flow-volume loops when VCD is suspected 1
• Intermittent nature: Physical examination and spirometry may be normal between episodes, making diagnosis challenging 2
• Gold standard diagnosis: Flexible fiberoptic rhinolaryngoscopy remains the definitive diagnostic test for VCD, as spirometric findings alone are insufficient 2

Limitations of Spirometry in VCD Diagnosis

Several studies highlight the limitations of using spirometry alone for VCD diagnosis:

• Poor predictive value: Flow-volume loop patterns have poor diagnostic performance for predicting VCD (area under ROC curve of only 0.68) 4
• Ratio limitations: The MEF50%/MIF50% ratio (ratio between maximum expiratory and inspiratory flows at 50% of forced vital capacity) >2.2 was traditionally thought to suggest VCD, but is present in only a minority of confirmed VCD cases 3
• Inter-observer variability: While pulmonologists may agree on which flow-volume loops suggest VCD, these assessments often don't correlate with laryngoscopic findings 4

Clinical Implications

The normal FEV1 in VCD has important clinical implications:

• Misdiagnosis risk: VCD is often misdiagnosed as asthma, leading to inappropriate treatment with corticosteroids and bronchodilators 2
• Treatment approach: Unlike asthma, VCD management focuses on speech therapy, treatment of underlying conditions (postnasal drip, reflux), and psychological support rather than bronchodilators 2
• Monitoring response: Tools like the VCDQ (Vocal Cord Dysfunction Questionnaire) may be more useful than spirometry for monitoring treatment response 5

Key Takeaways

• VCD typically presents with normal FEV1 values, especially between symptomatic episodes
• The characteristic spirometric finding is flattening of the inspiratory limb of the flow-volume loop
• Spirometry alone has limited diagnostic value for VCD; laryngoscopy remains the gold standard
• The normal FEV1 in VCD contrasts with the reduced FEV1 typically seen in asthma, helping to differentiate these conditions

When evaluating patients with unexplained dyspnea and normal FEV1, VCD should be considered in the differential diagnosis, particularly in females and those with obesity, which are independent predictors of VCD 4.