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Quantifying the Physiology of Laryngotracheal Stenosis: Changes in Pulmonary Dynamics in Response to Graded Extrathoracic Resistive Loading
Author(s) -
Nouraei S A. Reza,
Winterborn Claire,
Nouraei S Mahmoud,
Giussani Dino A.,
Murphy Kevin,
Howard David J.,
Sandhu Guri S.
Publication year - 2007
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1097/mlg.0b013e3180310574
Subject(s) - spirometer , medicine , airway , airway resistance , airway obstruction , cardiology , receiver operating characteristic , stenosis , laryngotracheal stenosis , anesthesia , nuclear medicine , bronchoconstriction , tracheal stenosis , exhaled nitric oxide
Objectives/Hypothesis : A model of airway obstruction was developed to study the impact of changes in airway resistance on ventilatory mechanics. This was used to derive quantitative indices of airway obstruction to aid in the objective diagnosis and physiological monitoring of adult patients with laryngotracheal stenosis (LTS). Methods : Six airway resistors, the characteristics of which mirrored the selective impediment to inspiratory airflow that occurs in patients with LTS, were created and calibrated. Maximum‐effort flow‐volume loops were obtained from 15 volunteers with resistors placed in series with the spirometer. Diagnostic and monitoring performances of various flow‐volume indices were assessed with receiver‐operating characteristics (ROC) and analysis of variance (ANOVA), respectively. Promising indices were further evaluated in patients with LTS. Results : Experimentally, the ratio of expiratory and inspiratory flows at midvital capacity (MEF 50 /MIF 50 ) and peak expiratory to inspiratory flow ratio (PEF/PIF) had diagnostic sensitivities of 87% and 89%, respectively. The best index, both experimentally and clinically, was the ratio of area under the expiratory and inspiratory curves (ratio of integrals), with experimental and clinical sensitivities of 97% and 100%, respectively. A clinical specificity of 95%, and area under the curve of 0.965 were achieved for this index. Both PEF/PIF and the ratio of integrals could identify step changes in airway resistance greater than 10 cmH 2 O · sec · L −1 ( P < .05; ANOVA). Conclusions : Flow‐volume testing is simple and noninvasive and can be used to quantify the diagnosis and physiological monitoring of patients with LTS. The ratio of areas under the expiratory and inspiratory curves appears to be the optimal index for this purpose.