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Explore This IssueMarch 2021
Subglottic stenosis is a clinically heterogenous disorder that can be attributed to intubation, trauma, granulomatosis with polyangiitis, relapsing polychondritis, and an idiopathic etiology. Symptoms vary and include dyspnea, stridor, dysphonia, and cough. The diagnostic workup can include videolaryngoscopy, laboratory tests (e.g., antineutrophil cytoplasmic antibodies), and computed tomography scanning. Although commonly obtained by laryngologists in the workup of subglottic stenosis, controversy remains regarding the role of pulmonary function testing (PFT) in preoperative decision making and follow-up for these patients. Because this controversy exists, it is important to be familiar with the recent literature examining the significance of PFTs.
Endoscopic grading has been used for decades in the evaluation and management of subglottic stenosis. The most widely used grading system is the four-grade Myer-Cotton, which is based on the degree of obstruction. Grade 1 is less than 50% stenosis; grade 2 is between 51% and 70%; grade 3 is between 71% and 99%; and grade 4 is 100% obstruction. Historically, the treatment of subglottic stenosis relied primarily on clinical symptoms and endoscopic assessment. Often, patients would be observed until their dyspnea became severe enough to warrant treatment. Recent literature describes using PFT as a noninvasive tool to assess disease progression and treatment effectiveness in idiopathic subglottic stenosis, especially given its tendency for recurrence.
Lately, the treatment of idiopathic subglottic stenosis employs a multimodality approach utilizing conservative measures for early disease (e.g., serial intralesional steroid injections, balloon dilation, endoscopic resection), while reserving open surgical resection and reconstruction for more advanced or refractory cases. We can use PFT values to define the patient’s breathing when dyspneic, measure the effectiveness of the various procedures used to improve the breathing, and allow us to noninvasively track these patients over time so we can offer an intervention before they become limited by their breathing.
PFT is useful in the evaluation and management of subglottic stenosis because it provides a precise and objective functional assessment of obstruction compared to subjective endoscopic stenosis grading. Peak expiratory flow percentage is a valuable metric to longitudinally follow disease progression, determine treatment effectiveness, and measure quantifiable differences when changes on endoscopic examination are imperceptible. Because PFTs can detect subclinical changes to the stenosis, clinicians can provide treatment prior to the onset of devastating dyspnea.