In vitro evaluation of the effect of a prototype dynamic laryngoplasty system on arytenoid abduction

Abstract

These results support further evaluation of the DLPS to determine the effect of changes in DLPS on airway resistance.

Evaluation of a prototype dynamic laryngoplasty system in vitro with an equine vacuum airflow system

“…Larynges and a segment of attached trachea from 10 standardbred and thoroughbred horses aged 3‐11 years were collected from a commercial abattoir and frozen at −20 °C. The larynges were then thawed at room temperature for 24 hours immediately prior to testing . After the larynges were confirmed to have grossly normal anatomy, the thyroid, cricoid, epiglottic, arytenoid cartilages, 2 tracheal rings, and all intrinsic muscles were retained for testing, with all other soft tissue removed.…”

“…For phase 1 testing, the ends of the suture at the middle of the lateral aspect of the cricoid cartilage were attached to the arms of a Vernier caliper to allow progressively controlled construct shortening at 3‐mm increments by opening the caliper arms, as previously reported . Airflow testing was completed sequentially: 0 mm (suture loop tight and secured but no change in arytenoid position from resting) and then successive 3‐mm shortening to a maximum of 30 mm of shortening (a total of 11 steps per larynx).…”

“…The suture was then tied routinely with a surgeon's knot and 4 single throws to fix the left arytenoid at an approximate before LRQ of 0.5 (ie, left arytenoid at approximately half of the right sided maximal abduction). This starting LRQ was selected on the basis of previous in vitro analysis that demonstrated that maximal activation of the DLPS was able to cause an increase in LRQ from 0.7 to 0.97 (an effective range of 0.27) . As a result, because the target LRQ at maximal abduction to reduce TLI significantly was to be approximately 0.75, the starting LRQ was estimated to be approximately 0.48.…”

“…An inactivated baseline position (approximate LRQ of 0.5) and then 2 levels of activation were achieved by variably injecting saline into the catheter port. The level of activation was selected on the basis of previous mechanical testing results: inactivated (0 psi), moderate activation (25 psi), and a target of 50 psi but if not achieved then the psi that resulted in no further change was recorded as the maximal psi . The injection pressure was measured by using a pressure syringe (Blue Diamond; Merit Medical, South Jordan, Utah) .…”

“…This loss of abduction can be quite variable and presents a challenge to surgeons who are aiming for the target degree of arytenoid abduction that equates to 88% of the cross‐sectional area (CSA) of the rima glottidis on the basis of computational modeling of airflow . According to previous in vitro testing by our group, 88% CSA equates to a left‐to‐right quotient angle (LRQ) of approximately 0.7‐0.75 . Because of the common loss of abduction after surgery, surgeons may be tempted to over abduct the arytenoid at surgery and then rely on this postsurgical loss of abduction to achieve the desired arytenoid position.…”