Respiratory System MCAT Practice Question
A 45-year-old man presents with progressive hoarseness over 2 weeks. He denies dysphagia or dyspnea at rest. Physical examination reveals a left vocal cord in the paramedian position that does not abduct or adduct with phonation or respiration. Laryngoscopy confirms left recurrent laryngeal nerve (RLN) paralysis. Pulmonary function tests show FVC 92% predicted and FEV1 88% predicted, but the flow-volume loop demonstrates reduced peak expiratory flow with a characteristic flattened appearance during forced expiration. Which of the following best explains the expiratory flow limitation in this patient?
Answer choices
- AThe immobile vocal cord in the paramedian position acts as a fixed obstruction, limiting expiratory airflow through the glottisCorrect answer
- BRLN denervation of the cricothyroid muscle reduces vocal cord tension, preventing adequate glottic opening during expiration
- CLoss of posterior cricoarytenoid innervation impairs abduction of the contralateral vocal cord during forced expiration
- DParalysis of the internal intercostal muscles secondary to RLN injury reduces expiratory muscle force
- EDamage to vagal fibers in the RLN impairs pulmonary stretch receptor signaling, reducing expiratory effort
- FThe vocal cord paralysis causes reflex laryngospasm during forced expiration, narrowing the airway
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