Sudden onset dyspnoea and recurrent stridor

VCD, also known as paradoxical vocal cord motion disorder, is a syndrome that describes inappropriate and unintentional vocal cord adduction during the respiratory cycle. This disorder can lead to episodic dyspnoea, wheezing, stridor and apparent upper-airway obstruction — symptoms that may be mistaken for anaphylaxis or asthma. Failure to recognise VCD has been associated with unnecessary treatments and hospitalisation.1

The estimated prevalence of this condition varies, ranging from 2.5% of patients presenting to asthma clinics to 22% of patients with recurrent emergency department presentation for dyspnoea.2,3 The literature suggests that VCD has a female preponderance, although it has also been seen in males,4 and it has been reported in both paediatric and adult populations.

The patient generally reports sudden onset dyspnoea; throat tightness; difficulty breathing in, rather than out; and cough. Stridor can be heard during inspiration, expiration or both, and it is generally heard loudest over the anterior neck. This episode may last minutes to days; in contrast to laryngospasm, which usually subsides over seconds to minutes. Occasionally, the patient can be left with dysphonia after the episode. In contrast to patients with asthma, there is a lack of symptomatic response to asthma therapy, and symptoms can sometimes be abated by distractions. Patients will usually have a normal SpO₂ rate, although the presence of oxygen desaturations does not rule out VCD.

The pathophysiology of VCD is unclear, but autonomic imbalance, laryngeal sensory neuropathy and laryngeal hyper-responsiveness have been postulated as possible mechanisms.3 VCD is commonly precipitated by exercise, airborne irritants, gastroesophageal reflux disease or postnasal drip, and is associated with psychological conditions. Given the lack of prospective evaluation, the relationship between VCD and asthma is unclear, but the two conditions are known to coexist. A study by Newman and colleagues5 showed that 53 of the 95 patients fulfilling laryngoscopic criteria for VCD also had coexistent asthma. The medical literature records numerous cases in which VCD was misdiagnosed as asthma. Moreover, the diagnosis is further complicated by the fact that patients with VCD can have a positive methacholine challenge test, which should not be used to distinguish VCD from asthma.

Pulmonary function test with flow–volume curves and flexible laryngoscopy are the two most useful investigations to diagnose this condition. Typically, spirometry can look normal when the patient is asymptomatic (Box 1, A); however during symptoms the flow–volume curves may show variable flattening of the inspiratory curve but no airflow obstruction (Box 1, B). Flexible laryngoscopy during symptomatic periods is considered the gold standard for diagnosis —paradoxical complete adduction of the vocal cords during inspiration and occasionally during expiration is characteristic (Box 2). A novel imaging technique using dynamic volume CT scans has been used in research settings to diagnose VCD, but this technique is not yet standardised and is not currently widely adopted.6

The management of VCD in acute settings is centred on reassurance and supportive care until the episode resolves spontaneously. Breathing techniques such as forced sniffing, panting or pursed-lip breathing may sometimes help abort the symptoms. These techniques aim to relax the adducted vocal cords by activating the posterior cricoarytenoid muscle and widening the glottic aperture. Continuous positive airway pressure and inhalation of a helium–oxygen mixture have been reported to be useful in acute settings.3 Intralaryngeal botulinum toxin injection has been trialled with varying success.3 The mainstay of treatment for VCD is behavioural and speech therapy in addition to strategies that minimise the precipitating factors (eg, treatment of gastroesophageal reflux disease).