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Changes in pulmonary dynamics in response to graded extrathoracic inspiratory resistive loading
Author(s) -
Nouraei S.A.R.,
Winterborn C.,
Howard D.J.,
Sandhu G.S.
Publication year - 2006
Publication title -
clinical otolaryngology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.914
H-Index - 68
eISSN - 1749-4486
pISSN - 1749-4478
DOI - 10.1111/j.1365-2273.2006.01341_1.x
Subject(s) - medicine , spirometer , airway resistance , airway , cardiology , airway obstruction , airflow , spirometry , peak flow meter , anesthesia , bronchoconstriction , asthma , exhaled nitric oxide , mechanical engineering , engineering
Objectives. To investigate the impact of changes in inspiratory airway resistance on pulmonary dynamics as measured with flow‐volume phase plots under controlled conditions, to simulate the variable extrathoracic airway obstruction that commonly manifests in patients with sub‐glottic airway stenosis as a selective impediment to inspiratory airflow, to assess whether flow‐volume loops could provide quantitative physiological indices for the diagnosis and monitoring of this condition. Method. We developed six selective inspiratory airway resistors by modifying Valsalva valves, and determined their airflow resistance characteristics using a flow‐pressure device. Maximum‐effort flow‐volume loops were recorded from fifteen healthy subjects, with the different inspiratory resistors, supplied at a random order, placed in series with the spirometer. The diagnostic and monitoring performances of the different indices derived from flow‐volume loops were assessed with Receiver Operator Characteristic plots, and Analysis of Variance respectively. Results. The ratio between peak expiratory and inspiratory flows (PEF/PIF) had a sensitivity of 89% and a specificity of 70% for diagnosing extrathoracic obstruction, and could identify increases in airway resistance of over 10 cmH 2 O/s/L ( P < 0.05; anova ). The ratio of areas under the expiratory and inspiratory curves (AUCexpir/AUCinspir) of the flow‐volume loop provided the most sensitive index, with a sensitivity of 97.4%, and a specificity of 90.5%. Other previously‐reported indices, like the Empey ratio were significantly less sensitive. Conclusions. Flow‐volume loop studies are non‐invasive and simple to perform, and can be used to add a quantitative physiological dimension to the initial diagnosis, and ongoing monitoring of patients with extrathoracic airway stenosis throughout treatment.