Transendoscopic neodymium:yttrium aluminum garnet laser irradiation in horses.

The research investigates the impact of transendoscopic neodymium:yttrium aluminum garnet (Nd:YAG) laser application on the corniculate process of the arytenoid cartilage in horses. It studies the penetration depth, the healing process and its effect on respiratory functionality post-treatment.

Experiment Methodology

• The researchers used a neodymium:yttrium aluminum garnet (Nd:YAG) laser to apply laser irradiation to the corniculate process of the arytenoid cartilage in horses. The effects of this treatment were studied.
• The first phase of the research involved in vitro experimentation on 10 corniculate cartilages. These cartilages were subjected to laser irradiation and examined histologically to establish the correct dosimetry, i.e., to identify the penetration depths at various power settings.
• In the second phase, the procedure was applied to living subjects – eleven horses. These horses were sedated and the left ventricle and corniculate process were laser-treated.
• Of the eleven horses, six had left laryngeal hemiplegia. Post-laser application, these horses were euthanatized after 14 weeks and necropsied for assessment of any upper airway stridor.
• The remaining five healthy horses underwent endoscopy, and were also euthanatized and necropsied at determined intervals to monitor the healing process.

Findings

• The healing process was complete at 14 weeks. This healing followed the ‘second intention’ healing process, where the wound heals by granulation formation, contraction, and epithelialization without wound closure.
• In two horses, there were formations of granulation tissue buds along the laser treatment site. These growths resolved after a subsequent laser treatment.
• Scar tissue formation was observed, causing a leftward displacement of the dorsal portion of the right corniculate process.
• The left ventricle area healed without complications, and was entirely ablated after treatment.
• All horses in the study demonstrated inspiratory stridor when exercised 14 weeks post-laser irradiation, which signals potential respiratory complications post-treatment.

Implications

• This research indicates that using neodymium:yttrium aluminum garnet laser treatment on horses has certain potential complications. It affects respiratory functionality in some horses, showing as inspiratory stridor during exercise.
• The identified healing process and the scar tissue formation might have implications in the horses’ airway function, requiring further study to fully understand the long-term impact of the Nd:YAG laser treatment.