Ex vivo modeling of the airflow dynamics and two-and three-dimensional biomechanical effects of suture placements for prosthetic laryngoplasty in horses

Abstract

OBJECTIVE To identify the degree of left arytenoid cartilage (LAC) abduction that allows laryngeal airflow similar to that in galloping horses, assess 2-D and 3-D biomechanical effects of prosthetic laryngoplasty on LAC movement and airflow, and determine the influence of suture position through the muscular process of the arytenoid cartilage (MPA) on these variables. SAMPLE 7 equine cadaver larynges. PROCEDURES With the right arytenoid cartilage maximally abducted and inspiratory airflow simulated by vacuum, laryngeal airflow and translaryngeal pressure and impedance were measured at 12 incremental LAC abduction forces (0% to 100% [maximum abduction]) applied through laryngoplasty sutures passed caudocranially or mediolaterally through the left MPA. Cross-sectional area of the rima glottis and left-to-right angle quotient were determined from photographs at each abduction force; CT images were obtained at alternate forces. Arytenoid and cricoid cartilage markers allowed calculation of LAC roll, pitch, and yaw through use of Euler angles on 3-D reconstructed CT images. RESULTS Translaryngeal pressure and impedance decreased, and airflow increased rapidly at low abduction forces, then slowed until a plateau was reached at approximately 50% of maximum abduction force. The greatest LAC motion was rocking (pitch). Suture position through the left MPA did not significantly affect airflow data. Approximately 50% of maximum abduction force, corresponding to a left arytenoid angle of approximately 30° and left-to-right angle quotient of 0.79 to 0.84, allowed airflow of approximately 61 ± 6.5 L/s. CONCLUSIONS AND CLINICAL RELEVANCE Ex vivo modeling results suggested little benefit to LAC abduction forces > 50%, which allowed airflow similar to that reported elsewhere for galloping horses.

Evaluation of the airway mechanics of modified toggle laryngoplasty constructs using a vacuum chamber airflow model

“…The LP constructs were assessed by subjecting specimens to negative pressure and airflow using the model described by Cheetham 20 and used by others 18,19,21–23 . In our study, the modified toggle LP constructs had similar peak translaryngeal impedance before and after cyclic testing, whereas the standard LP constructs had a slight increase in peak translaryngeal impedance after cyclic testing.…”

“…Cheetham et al developed a flow chamber that produces airflow and inspiratory pressures similar to those recorded in horses during maximal exertion 20 . This experimental model can be used to determine the translaryngeal impedance of different LP techniques under conditions of high airflow rates 19–22 . Moreover, this experimental model exposes LP constructs to intermittent airflow in a controlled fashion, thus reducing experimental variability 19,21–23 .…”

“…This experimental model can be used to determine the translaryngeal impedance of different LP techniques under conditions of high airflow rates 19–22 . Moreover, this experimental model exposes LP constructs to intermittent airflow in a controlled fashion, thus reducing experimental variability 19,21–23 . The objective of this study was to evaluate the airway mechanics of modified toggle LP constructs in an airflow chamber model and compare these to the airway mechanics of standard LP constructs.…”

The effect of repeated freezing and thawing on the suture pull‐out strength in equine arytenoid and cricoid cartilages

“…Most studies have used 1 of 2 methods for storing laryngeal specimens before testing. One method involves preserving specimens in a 2% solution of 2‐phenoxyethanol at 0‐4 °C and then allowing the specimens to reach 20 °C before use 1,7,8 . The second method preserves specimens by wrapping them in gauze soaked with 0.9% sodium chloride and storing them at −20 °C.…”

“…One method involves preserving specimens in a 2% solution of 2-phenoxyethanol at 0-4 C and then allowing the specimens to reach 20 C before use. 1,7,8 The second method preserves specimens by wrapping them in gauze soaked with 0.9% sodium chloride and storing them at À20 C. The specimens are then thawed at room temperature (20 C) for 12 to 24 h before use. 9 This method is widely used, 3,[10][11][12][13][14][15] but it is unknown if freezing and thawing cadaveric larynges multiple times adversely affects the mechanical properties of the cartilages.…”