Vocal Cord Dysfunction Mimicking Exercise-induced Bronchospasm in Adolescents

To the Editor. The discussion of vocal cord dysfunction (VCD) by Landwehr et al1 provides a much-needed contribution to the pediatric literature. VCD is more common than is appreciated; the diagnosis is frequently not considered. Therapy for reactive airway disease (RAD) does not help the VCD aspect even if RAD coexists and improves with therapy. The potential for escalation of therapy to levels of care with significant side effects is detailed by Landwehr, Wood, and Milgrom. A heightened awareness of this condition is critical to the suspicion of the diagnosis—suspicion being a prerequisite to proving the condition. The report makes mention that pulmonary function tests will show a restrictive pattern during an episode, but that the diagnosis requires fiberoptic endoscopic demonstration of abnormal cord activity. The definitive therapy is voice training.To provide further clinical evidence of VCD in these anxious, atypical RAD patients, we have used heliox for acute symptomatic relief and for diagnostic evidence of VCD. Heliox is a mixture of oxygen and helium in ratios of 80:20, 70:30, or 60:40. It is used in hyperbaric injury, for rapid decompression injury, and in upper airway lesions, usually and hopefully temporary and improving. The risk is that the definitive sign of worsening upper airway obstruction, ie, increasing stridor, is not evident until late in the disease process and definitive therapy has thus been delayed. Heliox is not useful in acute asthma or other lower airway disease. Although heliox has little immediate impact on acute RAD, the effect on VCD is profound, dramatic, and immediate. Patients with VCD are exceedingly anxious and that anxiety increases as they fail to respond to routine RAD therapy. As anxiety increases, so does the respiratory noise, although the pulse oximetry reading does not deteriorate. With the introduction of heliox to the suspected VCD patient, turbulence reduction removes respiratory distress and the process is aborted in a dramatic fashion. The parent and the pediatric patient experience relief of anxiety in the success of heliox therapy; evidence for VCD is convincing. We believe that heliox provides a prompt resolution and demonstration that RAD is less significant than VCD. We are looking critically at our experience with heliox as it affects the ultimate outcome. Although it is possible that heliox promotes patient understanding and enhances the definitive role of voice training, it is also possible that the ease of therapy with heliox interferes with the impact of the more protracted, less dramatic effect of speech therapy. The acute effect of heliox has been more persuasive than a video of the endoscopic study. The psychologic elements emphasized in the report are too great to use a therapy that might interfere with the definitive treatment.Drs Weir and Ehl bring up important points in the diagnosis and treatment of vocal cord dysfunction (VCD). Heliox, the mixture of helium and oxygen, is usually highly effective in the treatment of acute symptoms of VCD, although we have encountered attacks that failed to improve with this therapy but resolved after the initiation of breathing exercises (F. B. Blager, unpublished observations). This mixture, less dense than air, more easily traverses areas of high turbulence and reduces dyspnea and the anxiety associated with VCD.1-1 Satisfactory response to treatment with heliox may suggest the diagnosis of VCD in patients who fail to improve with bronchodilators, but heliox also relieves the dyspnea associated with bronchospasm,1-2 and it may be difficult to distinguish the two conditions on the basis of this therapeutic intervention. Patients suffering an acute exacerbation of presumed asthma should be evaluated by spirometry and oxymetry.1-2 These procedures are necessary to diagnose and assess the severity of airway obstruction and to differentiate between asthma and VCD. Accurate diagnosis is necessary to avoid prescribing unwarranted doses of corticosteroids and bronchodilators to patients who will not benefit from them.1-3 The use of spirometry and oxymetry is of particular importance for those individuals who frequently require emergency care.The use of heliox provides short-term relief of dyspnea and associated anxiety for patients suffering an acute episode of VCD, but its benefits are not limited to this disorder. The definitive diagnosis of VCD is best made by direct observation of the vocal cords of a patient who is experiencing symptoms.1-3 Flexible fiberoptic rhinolaryngoscopy, performed by a skilled clinician, causes minimal discomfort and the complications are rare and insignificant.1-4 This procedure also establishes the presence of rare laryngeal disorders such as vocal cord paralysis, laryngospasm, papillomas, and exercise-induced laryngomalacia that produce similar symptoms, cannot be recognized without direct visualization, and require specific therapy based on accurate diagnosis.1-51-6The treatment of both asthma and VCD must be maintained beyond the resolution of acute exacerbation. The success of treatment for both disorders relies on correct diagnosis. For this reason patients suspected of having these conditions should be investigated with both pulmonary function testing and rhinolaryngoscopy. Challenge procedures that reproduce symptoms should be used in asymptomatic patients.1-3