After physicians diagnose VCD through carefully interpreting screens and airway challenge tests, a multidisciplinary approach in treating patients may include pulmonary, speech therapy, and psychological expertise

Vocal cord dysfunction (VCD) is a dyspneic syndrome that is caused by paradoxic adduction or inappropriate closure of the true vocal cords during the respiratory cycle. This atypical vocal cord motion has usually been recognized during the inspiratory phase^1-3 but has also been reported to occur during expiration.⁴  VCD can be a confusing clinical syndrome because it is often misdiagnosed as severe asthma. In 1983, Christopher et al1 described a small group of patients who presented to National Jewish Medical Center, Denver, with poorly controlled asthma. Since initial reports^1-3 described only a small number of patients, it was suspected that VCD was a relatively rare clinical syndrome. However, increased awareness of the clinical presentation and improved diagnostic sensitivity have led to the recognition of a much larger and varied clinical population. The severity of this disorder is highly variable and may range from intractable respiratory distress with desaturation and eventual intubation⁵ to dyspnea in conditioned athletes only at high levels of exercise.⁶ These patients are often misdiagnosed with symptoms attributed to poorly controlled asthmatic flares, exercise-induced bronchospasm, or exacerbations of chronic obstructive lung disease. They are frequently treated with inappropriate and potentially dangerous therapies including multiple metered dose inhalers and chronic use of high-dose oral steroids. Since RTs play such a critical role in the identification and treatment of VCD, a more heightened awareness of this diagnostic dilemma and better appreciation of available therapeutic options will facilitate proper medical management of this complex group of patients.

Typical Presentation
Patients with VCD often present as poorly controlled, steroid-dependent asthmatics. Several studies^3,7,8 have reported that some patients may in fact have a real obstructive component, in addition to VCD. Patients routinely complain of air hunger, chest or throat tightness, chronic cough, and occasionally voice changes. Poly-pharmacy is extremely common. Newman et al⁷ demonstrated that, in their clinical experience, there is no difference in the use of beta agonists, theophyllines, steroids (inhaled and oral), H2 blockers, or anxiolytics when comparing recognized asthmatics with patients found to have VCD. Many patients admit to a history of trauma, either real or perceived. Histories of near drowning, physical or psychological abuse, and sexual abuse are often reported when questioned directly. Common triggers include exposure to noxious fumes such as cleaning fluid or cigarette smoke, exercise, repetitive deep inspirations, and claustrophobic facial covering. Irritation of the epiglottic area secondary to post-nasal drip or gastroesophageal reflux disease has been reported in numerous symptomatic patients. In the military, mandatory physical fitness training and testing have been associated with an increased incidence of VCD,⁹ particularly in cold or humid weather.

Vocal cord dysfunction patients should be evaluated with an organized approach and high index of suspicion or they will remain a diagnostic dilemma. Medical histories need to concentrate on potential inciting factors. Physical examination should be directed, with attention to evidence of concurrent post-nasal drip or gastst roentgenograms are often completely normal and fail to demonstrate any pulmonary infiltrates, acute air trapping, flattened hemi-diaphragms, or hyperinflation, even during severe symptomatic episodes.roesophageal reflux disease. Inspiratory stridor and expiratory wheezing may be localized to the upper airway instead of more diffusely throughout the thorax. Che

One key to the diagnosis of this syndrome is attention to subtle spirometric changes that have been overlooked by even the more experienced clinician. A flattened inspiratory loop is the most frequently reported abnormality in these patients. A typical loop was from an asymptomatic 42-year-old male VCD patient who had complained of exertional dyspnea and cough over a 3-week period. He had been treated with antibiotics, oral steroids, and an albuterol metered dose inhaler for suspected bronchitis and reactive airways disease. His spirometric volumes are listed in Table 1. Notice that the expiratory volumes and ratios were normal. However, his inspiratory loop was markedly flattened and variable on repeated maneuvers. Typically, the loops are inconsistent and may be either truncated or stair-stepped on successive maneuvers. Although these findings are not specific for the diagnosis of VCD, they should be considered significant in association with the appropriate clinical picture.

Pulmonary function screens may also be completely normal during asymptomatic periods. When abnormalities are noted, there is often considerable variation between maneuvers. One patient’s normal flow volume loops during an asymptomatic period were compared to a later dyspneic exacerbation. She had marked reduction in peak flows, reduction in forced vital capacity, and considerable variation noted between each forced maneuver. The fact that follow-up spirometry returned to a normal baseline demonstrates the intermittent nature of this syndrome.

Bronchoprovocation testing can become a double-edged sword for the RT when evaluating this patient population. Multiple challenges including methacholine, eucapneic hyperventilation, cold air, and exercise testing are frequently utilized to rule out or support the diagnosis of reactive airways disease. Unfortunately, each of these airway challenges has been reported to stimulate the epiglottic area in the VCD patient. Results of these studies may prove difficult to interpret. The flow volume loops from a 23-year-old woman who was being evaluated for exercise-induced asthma had a baseline spirometry that was normal, but there was a significant reduction in the forced expiratory volume (FEV1) after the 4.0 mg/mL methacholine challenge. Expiratory volumes and ratios before and after the methacholine challenge are listed in Table 2. In accordance with the standards of the American Thoracic Society (ATS),¹⁰ the provocational concentration of methacholine that resulted in a 20% fall in FEV1 (PC20) was interpolated to be between 1.0 and 4.0 mg/mL. This study was interpreted as a positive response and considered indicative of mild bronchial hyperreactivity. However, notice that there is a comparable decrease in the forced vital capacity (FVC), no change in the FEV1/FVC ratio, and no evidence of scooping of the expiratory loop of the postchallenge maneuver. These findings speak against a deteriorating obstructive process and most likely represent reduction in vital capacity rather than a true obstructive defect. The ATS has recognized that VCD may limit forced inspiratory flow in bronchoprovocational studies, but has not addressed the interpretation of proportional changes in the FEV1/FVC ratio. This type of result can easily be misinterpreted and may have influenced the number of patients diagnosed with combined VCD and asthma in previous studies.^3,7,8 A portion of the patients reported to have a mixed etiology (VCD plus asthma) may have pure VCD. This is an area that needs further investigation.

The gold standard for diagnosing VCD is documentation of paradoxic vocal cord adduction by laryngoscopy. The true vocal cords usually maintain a neutral position during expiration and further abduct during the inspiratory phase. VCD is diagnosed when the cords inappropriately adduct during either the inspiratory or expiratory phase. Caution must be used in interpreting normal protective maneuvers of the vocal cords. Epiglottic stimulation with the endoscope can be associated with adduction and a false positive reaction. At the same time, the haphazard use of topical anesthesia in the epiglottic area may desensitize the vocal cords, reduce the stimulatory effect of the inciting trigger, and generate a false negative response.

Therapeutic Approach
Therapeutic strategies should be divided into acute and chronic management issues. Initial therapy must be directed at termination of the crisis, while chronic therapy should define and ameliorate the inciting conditions. The severely dyspneic patient who presents with respiratory distress of unclear etiology should be treated initially with standard bronchodilator regiments. If standard protocols prove ineffective, the patient should be carefully reevaluated. Reassurance and relaxation with more attention to expiratory efforts rather than inspiration may prove helpful.

Heliox, a mixture of helium and oxygen, may be considered in the acute management of suspected VCD patients.^5,11 Helium is a biologically inert gas that is 3.5 times less dense than nitrogen. The decreased density of helium compared to nitrogen-oxygen mixtures promotes laminar rather than turbulent flow conditions at higher flow rates. An increased bulk gas flow is often associated with decreased work of breathing and patients often stop struggling, relax, and the dyspneic episode resolves.¹² Heliox blends can be set up in the emergency department or on the wards. Mixtures may be regulated between 60% and 80% helium combined with proportional concentrations of oxygen. A compressed tank with an 80/20 helium/oxygen mixture can be used as the baseline source. Supplemental oxygen may be added to the supply line by a three-way adaptor. An oxygen analyzer should be placed proximal to the patient, in order to monitor delivered oxygen. The heliox mixture should be delivered through a non-rebreathing mask that eliminates any entrained nitrogen. Heliox should be used only as an acute therapy modality and should not be offered to VCD patients for intermittent home use.

Chronic therapy should be directed at the modification of stimulating insult, such as chronic post-nasal drip or gastro-esophageal reflux. Once that is accomplished, speech therapy becomes the mainstay of chronic management. The therapist teaches relaxation techniques with emphasis on the expiratory maneuvers. Patients become more cognizant of initial symptoms and are taught to utilize the learned relaxation techniques to attenuate subsequent attacks. They may eventually be exposed to known stimuli, such as irritating odors or exercise in a controlled setting, and should be able to control their vocal cord response.

There is often a psychological component to this disorder. Careful and sensitive questioning often reveals the history of a previous traumatic event. These have included strangulations, near drownings, and physical or sexual abuse. Each issue must be addressed in order to successfully modify this syndrome complex. Stress may also plan a significant role in clinical exacerbations. Many patients report exacerbations following situational stress or an intense argument. Military health care systems have noticed a higher incidence of this syndrome compared to the civilian sector. This may be associated with inherent stresses and demands associated with that military service. For instance, there was a markedly increased incidence of VCD reported during the Desert Storm conflict.¹³ In addition, there are established demands in meeting physical fitness standards.⁹ If soldiers have difficulty completing a standard 2-mile run within an age-specific prescribed time, they will be at risk of being passed over for promotions or separated from the service. In the civilian sector, patients who become dyspneic with strenuous exercise will most often merely decrease their target level of activity and avoid the inciting stimulation.

Discussion
VCD has been identified as a more common etiology for dyspnea than had previously been suspected; 10% to 25% of patients presenting with acute obstructive symptoms may actually have vocal cord dysfunction, rather than asthma.⁹ In order to diagnose this disorder, the clinical provider must maintain a high level of suspicion. Pulmonary function tests can be suggestive of VCD, but both screens and airway challenge testing must be interpreted carefully. Treatment should be directed at inciting factors and may require a multidisciplinary approach to include pulmonary, speech therapy, and psychological expertise.

Thomas M. Fitzpatrick, MD, PhD, FACP, FCCP, is chief, Critical Care Medicine Service, Department of Surgery, Walter Reed Army Medical Center, Washington, DC, and assistant professor, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md.

Note
The opinions expressed herein are not to be construed as official or as reflecting the policy of either the Department of the Army or the Department of the Defense.

References
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