Selected Reports

Diagnosis of Vocal Cord Dysfunction: The Utility of Spirometry and Plethysmography

Most primary medical conditions cause a wide spectrum of complications and sequelae, which may compromise physiologic and psychological function. Comprehensive, integrated care based on key principles includes individualized plan, multidisciplinary teamwork, and recognition of all the elements of the disease. The primary goal is to help the individual with a chronic medical condition enhance the exercise capacity, functional status, and quality of life. For the most part, treatment relies heavily on well assessment and aims to address clinical performance by physiotherapy, exercise training, education, and psychosocial intervention.

Paradoxical vocal fold motion disorder, also commonly termed vocal cord dysfunction, is a poorly understood cause of acute upper airway obstruction. Patients with paradoxical vocal fold motion frequently present to the emergency department (ED) with acute respiratory distress and stridor. Lack of familiarity with this disorder may lead to delayed diagnosis or misdiagnosis and unnecessary intubations or surgical airway procedures. Although long-term management of paradoxical vocal fold motion is well described, there is a paucity of information about acute evaluation and management. This article aims to summarize the ED presentation and management of paradoxical vocal fold motion.

La pletismografía corporal completa permite la medición de volúmenes, capacidades y resistencias pulmonares. Es una técnica bien estandarizada y ampliamente utilizada en neumología pediátrica, aunque requiere equipo específico, personal especializado y cierta colaboración por parte del paciente. La pletismografía utiliza la ley de Boyle para determinar el volumen de gas intratorácico o capacidad residual funcional, y una vez determinada esta, se extrapolan el volumen residual y la capacidad pulmonar total. La medición de la capacidad pulmonar total es necesaria para el diagnóstico de patología restrictiva. La resistencia de la vía aérea es una medida de obstrucción, pudiéndose determinar la resistencia total, que incluye la resistencia de la pared torácica, tejido pulmonar y vía aérea, y la resistencia específica, que es un parámetro más estable que corresponde al producto de la resistencia de la vía aérea por la capacidad residual funcional. La complejidad de esta técnica, las ecuaciones de referencia, las diferencias en el equipamiento, la variabilidad de la misma y las condiciones en las que se realiza han hecho necesaria su estandarización. Se analizan a lo largo del artículo los aspectos prácticos de esta técnica, especificando las recomendaciones para su realización, sistemática de calibración y los cálculos que se deben llevar a cabo, así como la interpretación de los resultados obtenidos. El objetivo de esta publicación es favorecer una mejor comprensión de los principios de la pletismografía completa con el fin de optimizar la interpretación de los resultados favoreciendo un mejor manejo del paciente y un consenso en la especialidad.

Whole body plethysmography is used to measure lung volumes, capacities and resistances. It is a well standardised technique, and although it is widely used in paediatric chest diseases units, it requires specific equipment, specialist staff, and some cooperation by the patient. Plethysmography uses Boyle's law in order to measure the intrathoracic gas volume or functional residual capacity, and once this is determined, the residual volume and total lung capacity is extrapolated. The measurement of total lung capacity is necessary for the diagnosis of restrictive diseases. Airway resistance is a measurement of obstruction, with the total resistance being able to be measured, which includes chest wall, lung tissue and airway resistance, as well as the specific airway resistance, which is a more stable parameter that is determined by multiplying the measured values of airway resistance and functional residual capacity. The complexity of this technique, the reference equations, the differences in the equipment and their variability, and the conditions in which it is performed, has led to the need for its standardisation. Throughout this article, the practical aspects of plethysmography are analysed, specifying recommendations for performing it, its systematic calibration and the calculations that must be made, as well as the interpretation of the results obtained. The aim of this article is to provide a better understanding of the principles of whole body plethysmography with the aim of optimising the interpretation of the results, leading to improved management of the patient, as well as a consensus among the speciality.

La disfunción de cuerdas vocales (DCV) es una enfermedad poco frecuente caracterizada por un cierre paradójico de las cuerdas vocales, habitualmente en la inspiración. Produce una obstrucción de la vía respiratoria que provoca disnea y estridor. La alteración espirométrica más frecuentemente descrita es el aplanamiento de la curva inspiratoria, aunque es posible encontrar también aplanamiento del asa espiratoria. El objetivo de este estudio fue evaluar las características espirométricas más frecuentes de la DCV y, de forma secundaria, describir las características clínicas, demográficas y el tratamiento seguido en los pacientes con un diagnóstico definitivo de DCV.

Estudio retrospectivo de los casos de DCV entre 2000 y 2010. Se consideró definitivo el diagnóstico cuando se evidenció el cierre paradójico de las cuerdas vocales en la laringoscopia. Se realizó una prueba de esfuerzo sobre tapiz rodante para provocar los síntomas. Se recogieron los datos clínicos y demográficos y se estudiaron las curvas de espirometría forzada.

De 36 casos sospechosos, se confirmó la DCV en 11 (30,5%), con una edad media 13,5 años; 10 eran mujeres. Se encontraron posibles desencadenantes en 5 de los pacientes. Seis pacientes presentaban antecedentes de asma. Todos los pacientes presentaron aplanamiento de la curva inspiratoria y 9 de ellos (81%) también de la espiratoria. Solo 4 pacientes presentaron una ratio entre los flujos espiratorio e inspiratorio máximos al 50% de la capacidad vital forzada (MEF_50%/MIF_50%) > 2,2.

Aunque la alteración espirométrica más frecuente en la DCV es el aplanamiento de la curva inspiratoria, un porcentaje importante de pacientes presentan aplanamiento también de la curva espiratoria. Este hecho podría invalidar la ratio MEF_50%/MIF_50% para el diagnóstico de DCV.

Vocal cord dysfunction (VCD) is a rare disease characterized by a paradoxical closure of the vocal cords, usually in inspiration, that causes dyspnea and stridor. The spirometry pattern that is more often described is a plateau in the inspiratory curve, but it can be also found in the expiratory loop The aim of this study was to evaluate the most common spirometry characteristics of patients with VCD and, secondarily, to describe the clinical and demographic characteristics and the treatment of patients with a definitive diagnosis of this disease.

A retrospective study was made of cases of VCD between 2000 and 2010. Diagnosis was considered definitive when a paradoxical closure of the vocal cords became clear on laryngoscopy. Exercise challenge on a treadmill was performed to produce symptoms. Demographic and clinical data were collected, and flow-volume curves were studied.

Of 36 suspected cases, VCD was confirmed in 11 (30.5%). The mean age was 13.5 years, 10 were female. Possible triggers were found in 5 patients. Six patients had a previous history of asthma. All patients had a plateau in the inspiratory curve, and 9 (81%) of them also in the expiratory loop. Only 4 patients had a ratio between maximum inspiratory and expiratory flows at 50% of forced vital capacity (MEF_50%/MIF_50%) > 2.2.

Although the most frequent spirometry pattern in VCD is a plateau in the inspiratory curve, a significant percentage of patients also have a plateau in the expiratory curve. This could invalidate the MEF_50%/MIF_50% ratio for the diagnosis of VCD.