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Implications of different degrees of arytenoid cartilage abduction on equine upper airway characteristics
Author(s) -
RAKESH V.,
DUCHARME N. G.,
CHEETHAM J.,
DATTA A.K.,
PEASE A. P.
Publication year - 2008
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/042516408x330329
Subject(s) - glottis , airway , medicine , cricoid cartilage , larynx , airflow , breathing , anatomy , anesthesia , physics , thermodynamics
Summary Reason for performing study : The necessary degree of arytenoid cartilage abduction (ACA) to restore airway patency at maximal exercise has not been determined. Objectives : Use computational fluid dynamics modelling to measure the effects of different degrees of ACA on upper airway characteristics of horses during exercise. Hypothesis : Maximal ACA by laryngoplasty is necessary to restore normal peak airflow and pressure in Thoroughbred racehorses with laryngeal hemiplegia. Methods : The upper airway was modeled with the left arytenoid in 3 different positions: maximal abduction; 88% cross‐sectional area of the rima glottis; and 75% cross‐sectional area of the rima glottis. The right arytenoid cartilage was maximally abducted. Two models were assumed: Model 1 : no compensation of airway pressures; and Model 2 : airway pressure compensation occurs to maintain peak airflow. The cross‐sectional pressure and velocity distributions for turbulent flow were studied at peak flow and at different positions along the airway. Results: Model 1 : In the absence of a change in driving pressure, 12 and 25% reductions in cross‐sectional area of the larynx resulted in 4.11 and 5.65% reductions in peak airflow and 3.68 and 5.64% in tidal volume, respectively, with mild changes in wall pressure. Model 2 : To maintain peak flow, a 6.27% increase in driving tracheal pressure was required to compensate for a cross‐sectional reduction of 12% and a 13.63% increase in driving tracheal pressure was needed for a cross‐sectional area reduction of 25%. This increase in negative driving pressure resulted in regions with low intraluminal and wall pressures, depending on the degree of airway diameter reduction. Conclusion : Assuming no increase in driving pressure, the decrease in left ACA reduced airflow and tidal volume. With increasing driving pressure, a decrease in left ACA changed the wall pressure profile, subjecting the submaximally abducted arytenoid cartilage and adjacent areas to airway collapse. Clinical relevance : The surgical target of ACA resulting in 88% of maximal cross‐sectional area seems to be appropriate.