Physiology-based minimum clinically important difference thresholds in adult laryngotracheal stenosis.

OBJECTIVES/HYPOTHESIS: Delivering evidence-based patient care is predicated on the availability of objective and validated outcome measures. We aimed to calculate physiology-based minimum clinically important difference (MCID) values for adult laryngotracheal stenosis (LTS). STUDY DESIGN: Prospective observational study. METHODS: Patient demographics, morbidities, and stenosis severity were assessed preoperatively. Flow-volume loops and Medical Research Council (MRC) dyspnea grades were measured in 21 males and 44 females before and 6 to 8 weeks after airway surgery, and before treating recurrent disease in 10 patients. Anchor and distribution-based methodologies were used to calculate MCIDs for treatment efficacy and disease recurrence respectively. RESULTS: The mean age at treatment was 46 ± 16 years. The most common etiology was idiopathic subglottic stenosis (38%). Most lesions (66%) obstructed >70% of the lumen. There were strong correlations between treatment-related changes in total peak flow (TPF) (ΔTPF) (peak expiratory flow + |peak inspiratory flow|) and the ratio of area under the flow-volume loop (AUC) to forced vital capacity (FVC) (ΔAUCTotal /FVC), and treatment-related changes in the MRC grade (ΔMRC) (r = -0.76 and r = -0.82, respectively). Both TPF and AUCTotal /FVC discriminated between effective (ΔMRC <0) and ineffective (ΔMRC ≥0) interventions, yielding MCID values of 4.2 L/s for TPF and 2.1 L(2) /s for AUCTotal /FVC, respectively. Ten patients required airway treatment for recurrent disease, and TPF and AUCTotal /FVC levels had distribution-based MCID values of 0.9 and 0.6, respectively. CONCLUSIONS: Flow-volume loops provide a quantitative method of objectively assessing outcomes in LTS. TPF is the most convenient index for this purpose, but AUCTotal /FVC provides marginally greater sensitivity and specificity.

Use of pressure-volume loops for physiological assessment of adult laryngotracheal stenosis.

OBJECTIVES/HYPOTHESIS: To assess the utility of intraoperative pressure-volume curves as an objective method of physiological disease stratification and outcomes assessment in adult laryngotracheal stenosis. STUDY DESIGN: Prospective observational study. METHODS: We prospectively studied 42 tracheotomy-free patients undergoing endoscopic laryngotracheoplasty over 18 months. Patient and lesion characteristics were obtained. Dyspnea severity was assessed using the Medical Research Council scale. Preoperative spirometry and intraoperative pulmonary compliance were recorded. RESULTS: There were 19 male and 23 female patients, and the mean age at treatment was 44 ± 16 years. There were 14 Myer-Cotton 1 lesions and 14 and 13 patients had grade 2 or 3 stenoses, respectively. Pulmonary compliance was strongly correlated with anatomical stenosis severity (r = 0.8, P < .0001) and perceptual dyspnea severity (r = 0.73, P < .0001). The strengths of correlation between pulmonary compliance and anatomical stenosis severity was significantly greater than those between forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and peak expiratory flow. The strength of correlation between pulmonary compliance and perceptual dyspnea severity was significantly greater than those between FEV1 and FVC with perceptual dyspnea severity. The two independent determinants of pulmonary compliance were Myer-Cotton stenosis severity (P < .0001) and patient age (P = .013). CONCLUSIONS: Pulmonary compliance provides an objective measure of physiological airway impairment. It correlates well with anatomical disease severity and perceptual dyspnea severity. Its more widespread use in adult patients and research into its utility in pediatric airway stenosis is recommended.