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

Abstract

Objective: To evaluate a prototype dynamic laryngoplasty system (DLPS) in a static airflow model. Study design: Experimental. Sample population: Ten equine larynges. Methods: The right arytenoid was fixed in abduction in all specimens. A left-sided laryngoplasty was performed with No. 2 Fiberwire and a FASTakII anchor. Each larynx was tested in a static airflow model. The system was adjusted to a flow rate of 55 L/s and prelaryngeal pressure of 12 mm Hg prior to testing in maximal arytenoid abduction. In phase 1, the left suture was loosened, shortened, and tested in 3-mm steps from 0 to 30 mm. In phase 2, the suture was tied with the DLPS in position at a target left-to-right quotient angle (LRQ) of 0.5. The DLPS was activated to target psi of 0, 25, and 50 for testing. Translaryngeal impedance (TLI), LRQ, cross-sectional areas (CSA), and resultant change in LRQ and CSA between, before, and during airflow testing were calculated. Results: In phase 1, TLI was reduced by suture shortening up to 6 mm (P = .001) but not by additional shortening (P > .05). In phase 2, activation of the DLPS reduced the TLI from 0 psi (0.43 ± 0.08 mm Hg/L/s) to 25 psi (0.16 ± 0.04 mm Hg/L/s, P < .001), but no further reduction was detected at maximal psi (P = .10). Conclusion: Activation of the DLPS effectively reduced TLI. Clinical significance: These results justify further investigation of the DLPS to assess its clinical applicability.

Influence of unilateral and bilateral vocal cordectomy on airflow across cadaveric equine larynges at different Rakestraw grades of arytenoid abduction

“…A major limitation of ex vivo airflow testing models is that the flow conditions that are used often do not directly correlate with in vivo conditions, which can vary widely. The flow rate of 55 L/s used in this study is similar to that of previous publications that used unidirectional airflow models 21,22 . This is approximately 75% of the VO 2max and greater than 75% but less than 100% HR max in an exercising horse 22,26 .…”

“…Thawed larynges were wrapped again in saline‐soaked gauze to prevent drying of the tissues prior to testing. Soft‐tissue dissection was performed as previously described maintaining the intrinsic laryngeal musculature 21 . The cricoid length of each larynx was measured at the dorsal midline from cranial to caudal using calipers, and subsequently, the left CAD muscle was sharply transected caudal to its insertion on the muscular process of the arytenoid cartilage.…”

“…The procedure was repeated on the left side but, rather than being tied, the suture ends were clamped using a Kelly hemostat to allow repositioning of the arytenoid cartilage following calibration. During calibration, the inlet valve and voltage regulator were adjusted such that a flow rate of 55 L/s and a prelaryngeal pressure of 12 mmHg was achieved, similar to previous studies 21–24 …”

“…Soft-tissue dissection was performed as previously described maintaining the intrinsic laryngeal musculature. 21 The cricoid length of each larynx was measured at the dorsal midline from cranial to caudal using calipers, and subsequently, the left CAD muscle was sharply transected caudal to its insertion on the muscular process of the arytenoid cartilage. Testing was performed on a single day in a temperaturecontrolled laboratory.…”

“…The larynx was mounted in a unidirectional vacuum system as described by Ahern et al (2019) for testing. 21 Two vacuum/blowers (2400 W 230-240 V 50 Hz, Ryobi, Japan), set on vacuum mode, controlled using a variable autotransformer (Powertech SRV-5, Variac, Australia), and attached to an ergospirometer (Quadflow Equine Spirometry, QF, RobacScience Pty Ltd, Australia) were connected via a 50 mm PVC pipe to the testing chamber.…”