PURPOSE: Existing techniques to measure airway lumen before and after therapeutic interventions for central airway obstruction are either subjective or labor intensive. In this paper we describe the use of digital image analysis software to quantify degree of airway narrowing in patients with various forms of central airway obstruction.
METHODS: Using “Image J”, a public domain image analysis program developed by National Institutes of Health (http://rsb.info.nih.gov/ij/) and previously validated in pediatrics, the degree of airway narrowing was calculated in pixels from still photos obtained during videobronchoscopy. This number was then used to calculate a Stenosis Index (SI) for patients with fixed central airway obstruction (i.e. tracheal stenosis, extrinsic compression, intraluminal tumor) and a Collapsibility Index (CI) for patients with expiratory central airway collapse [i.e. tracheobronchomalacia, excessive dynamic airway collapse (EDAC)]. SI was defined as (CSA normal- CSA stenosis) × 100%/ CSA normal, where CSA normal= Cross Sectional Area of the normal airway lumen proximal or distal to the stenotic lesion and CSA stenosis= Cross Sectional Area at the level of airway stenosis). CI was defined as (CSAi- CSAe) × 100%/ CSAi, where CSAe =Cross Sectional Area at end-expiration and CSAi = Cross Sectional Area at end-inspiration.
RESULTS: The SI and CI results for five patterns of central airway obstruction are demonstrated in Figure 1. Videobronchoscopic imaging and computer based analysis are illustrated using a case of fixed CAO (i.e. subglottic stenosis) and expiratory central airway collapse (i.e. EDAC) (Figure 2).
CONCLUSION: Morphometric bronchoscopy using calculated indices provides objective measurement of degree of airway narrowing for various forms of central airway obstruction.
CLINICAL IMPLICATIONS: The use of calculated indices potentially makes the labor intensive measurement of absolute cross sectional area unnecessary. Objective measurements of airway lumen before and after therapeutic interventions will allow studies to determine correlations between degree of airway narrowing, degree of ventilatory impairment and patient symptoms.
DISCLOSURE: Septimiu Murgu, No Financial Disclosure Information; No Product/Research Disclosure Information