The Value of Spirometry in Subglottic Stenosis

Abstract

The diagnosis of subglottic stenosis (SGS) is usually made by clinical assessment and definitively by a direct endoscopic examination. This study aimed to evaluate different spirometric values in relation to anatomical grading and severity of subglottic stenosis cases of upper airway obstruction. Cases of SGS that underwent dilatational procedures endoscopically at the otolaryngology department of the King Saud University Medical City, Riyadh, Saudi Arabia, from June 2015 to October 2017 were collected. Pulmonary function test (PFT) pre- and postoperative parameters and the grades of subglottic stenosis were extracted. We compared different spirometric values to the severity of SGS and compared the pre- and postoperative results for each patient. There were 19 cases with a valid PFT study within 7 days preoperatively in addition to a documented intraoperative grading according to the Myer-Cotton grading system; 7 (36.8%) were grade 1, 8 (42.1%) were grade 2, and 4 (21.1%) were grade 3. The actual preoperative ratio of forced expiratory volume (FEV1) in 1 second to peak expiratory flow (PEF) for all 19 patients ranged from 7.34 to 21.40 mL/L/min. We found a significant improvement in all spirometric parameters postdilatation including PEF ( P < .001), FEV1 ( P < .001), FEV1/PEF ( P = .001), forced expiratory flow (FEF) from 25%, 50%, and 75% of vital capacity, respectively, FEF25 ( P < .001), FEF50 ( P = .001), FEF75 ( P = .048), and maximum mid-expiratory flow ( P = .002). We did not find any correlation between the severity of stenosis and spirometric values. This study revealed that spirometry is a useful marker in following up patients with subglottic stenosis and is also a good indicator to determine postairway surgery outcomes. However, these markers do not correlate with anatomical grading and the severity of subglottic stenosis.