New-generation pulsed carbon dioxide laser: comparative effects on vocal fold wound healing

Carbon dioxide laser versus cold-steel supraglottoplasty: A comparison of post-operative outcomes

OBJECTIVE

Supraglottoplasty is the mainstay of surgical treatment for laryngomalacia, and is commonly performed via two methods: cold steel or carbon dioxide (CO₂) laser. The degree of post-operative monitoring following supraglottoplasty varies, both within and between institutions. The aim of this study was to compare the post-operative monitoring and interventions required by patients undergoing cold-steel versus CO₂ laser supraglottoplasty.

DESIGN

Retrospective cohort of pediatric patients (age < 18 years) undergoing supraglottoplasty at a tertiary care pediatric hospital. The primary exposure was the surgical instrument(s) used during supraglottoplasty. The primary outcome was prolonged intensive care unit (ICU)-stay (defined as >24 h).

RESULTS

155 cases were eligible for inclusion. Fifty-eight (37.4%) patients had a comorbid condition. Common indications for surgery included feeding difficulty (56.1%), severe respiratory distress (33.5%), and obstructive sleep apnea (25.2%). CO₂ laser was employed in 49 cases and cold-steel in 106 cases. Prolonged ICU-stay (>24 h) was observed in 14 CO₂ laser cases (28.6%) and 11 cold-steel cases (10.4%) (adjusted OR 3.42; 95% CI 1.43, 8.33). CO₂ laser cases were more likely to require post-operative intubation, non-invasive positive pressure ventilation, and nebulized racemic epinephrine. Concomitant neurological condition was associated with an increased risk of prolonged ICU-stay, while extent of surgery and age were not.

CONCLUSIONS

CO₂ laser supraglottoplasty is associated with an increased risk of prolonged ICU-stay and need for ICU-level airway intervention, compared to the cold-steel technique. While this association should not be misconstrued as a causal relationship, the current study demonstrates that specific surgical factors may influence the patient monitoring requirements following supraglottoplasty, particularly the choice of instrument and the extent of surgery.

Comparative study of acute tissue damage induced by the CO2 laser versus microelectrodes in cordectomies

OBJECTIVE:

This study compared the acute tissue damage produced by a CO2 laser and microelectrodes in samples of vocal cords from patients undergoing laryngeal endoscopic surgery for stage T1 squamous cell carcinoma.

STUDY DESIGN AND SETTING:

Based on prior surgical experience with the CO2 laser and microelectrodes, the study protocol used hematoxylin-eosin staining of vocal cords treated with a CO2 laser (n = 20) or microelectrode (n = 20).

RESULTS AND CONCLUSION:

The acute tissue damage produced by the CO2 laser was similar to that induced by microelectrodes in cutting mode. The tissue damage resulting from the use of the microelectrode in coagulation mode was comparatively greater.

Relationship between CO2 laser-induced artifact and glottic cancer surgical margins at variable power doses

BACKGROUND

The carbon dioxide laser can induce thermal cytologic artifacts at the margin of early glottic squamous cell carcinoma histologic specimens, which makes assessment of the margin difficult. This study assesses and correlates the depth of laser-induced thermal artifact with laser power rating.

METHODS

The surgical margins of 30 patients with early glottic squamous cell carcinomas who underwent laser resection were reanalyzed retrospectively.

RESULTS

Thermal damage consisted of collagen denaturation within the vocal cord lamina propria and vocalis muscle, and epithelial structural changes. There was a decrease in depth of tissue artifact with increased power rating (p > .05). The average depth of thermal damage was 380.83 ± 178.79 μm.

CONCLUSION

The laser causes less thermal damage at higher power, presumably because of the increased speed of cutting and reduced contact time with surrounding cells. Knowledge of the depth of thermal artifact is important surgically when ensuring the cancer is excised with sufficient oncologic margin. © 2015 Wiley Periodicals, Inc. Head Neck 38: E712-E716, 2016.

CO(2) laser versus cold steel margin analysis following endoscopic excision of glottic cancer

Objective

To compare the suitability of CO₂ laser with steel instruments for margin excision in transoral laser microsurgery.

Methods

Prospective randomized blinded study. Patients with glottic cancer undergoing laser resection were randomized to margin excision by either steel instruments or CO₂ laser. Margins were analyzed for size, interpretability and degree of artifact by a pathologist who was blinded to technique.

Results

45 patients were enrolled in the study with 226 total margins taken. 39 margins taken by laser had marked artifact and 0 were uninterpretable. 20 margins taken by steel instruments had marked artifact, and 2 were uninterpretable. Controlling for margin size, the laser technique was associated with increasing degrees of margin artifact (p = 0.210), but there was no difference in crude rates of uninterpretability (p = 0.24).

Conclusion

Laser margin excision is associated with a greater degree of artifact than steel instrument excision, but was not associated with higher rate of uninterpretability.

Cause of vocal fold scar

PURPOSE OF REVIEW

The prolonged debilitation, loss of income, and decrement in quality of life caused by vocal fold scar is exacerbated by our inability to successfully treat this difficult problem. As technology focuses on developing innovative treatments, we need to fully appreciate and understand the mechanisms giving rise to glottal scar, on both a macroscopic and microscopic level. This review examines recent literature pertaining to the gross and molecular mechanisms which give rise to vocal fold scar.

RECENT FINDINGS

Mechanisms of vocal fold scar production have been examined in both macroscopic and microscopic detail. Trauma and injury involving any aspect of the lamina propria, particularly the deeper layers, may result in epithelial tethering and scar formation. At the molecular level, early inflammatory cytokines activate and recruit fibroblasts which then drive the fibrotic cascade. Transforming growth factor-β enhances fibrosis and is balanced by tissue matrix metalloproteinases and hepatocyte growth factor activity. Molecular signaling offers novel opportunities to intervene in scar formation.

SUMMARY

New work investigating the cause of vocal fold scar identifies complex molecular processes leading to fibrosis in the lamina propria. Improved mechanistic understanding offers insight into prevention strategies and possible targets for antifibrotic therapies that may help prevent or treat this debilitating condition.

Establishing a new animal model for the study of laryngeal biology and disease: an anatomic study of the mouse larynx

PURPOSE

Animal models have contributed greatly to the study of voice, permitting the examination of laryngeal biology and the testing of surgical, medical, and behavioral interventions. Various models have been used. However, until recently, the mouse (Mus musculus) has not been used in laryngeal research, and features of the mouse larynx have not been defined. Therefore, the purpose of this study was to qualitatively describe mouse laryngeal anatomy in relation to known human anatomy.

METHODS

Larynges of 7 C57BL mice were examined and photographed under stereotactic and light microscopy.

RESULTS

The authors found that mouse laryngeal organization was similar to that of humans. The hyoid bone and epiglottal, thyroid, cricoid, and arytenoid cartilages were identified. An additional cartilage was present ventrally. Thyroarytenoid, posterior cricoarytenoid, lateral cricoarytenoid, and cricothyroid muscles were grossly positioned as in humans. Interarytenoid muscles were not present; however, a functional counterpart was identified.

CONCLUSIONS

The authors provide an initial description of mouse laryngeal anatomy. Because of its amenability to genetic engineering, the mouse is the premiere model for the study of disease and the testing of interventions. Introduction of the mouse model for laryngeal study offers a tool for the study of normal laryngeal cell biology and tissue response to disease processes.

Vocal Fold Healing after Laser Cordectomy with Adjuvant Cryotherapy

OBJECTIVES

To understand the effect of adjuvant cryotherapy on glottic wound healing after endoscopic CO2 laser cordectomy.

STUDY DESIGN

Canine acute injury model with videolaryngostroboscopic and histopathologic outcomes analysis.

METHODS

Twelve adult male dogs underwent bilateral endoscopic CO2 laser transmuscular cordectomy followed by randomized unilateral endoscopic glottic cryotherapy. The animals were randomly divided into four groups and underwent videolaryngostroboscopy followed by sacrifice at 0, 2, 6, and 12 weeks postoperatively. Three untreated male dogs served as controls. Histopathologic sections were prepared with Alcian blue, Giemsa, hematoxylin-eosin, movat's, Masson's trichrome, and picrosirius stains.

RESULTS

Videostroboscopy demonstrated an earlier restoration of glottic volume and a return of mucosal waves among vocal folds treated with combined therapy by 6 weeks posttreatment. The mean depth of inflammatory reaction in the vocal cords treated with combined therapy was 1.07 mm versus 1.15 mm in vocal cords treated with CO2 laser therapy alone. At 2 and 6 weeks postoperatively, combined treatment was associated with a decreased volume of collagen. At 12 weeks postoperatively, combined treatment was associated with greater collagen organization, normalized collagen histoarchitecture, and decreased keratinization.

CONCLUSIONS

Adjuvant cryotherapy appears to alter glottis-specific wound healing, leading to decreased and more organized collagen formation and decreased keratinization with a resultant improvement in glottic function, when compared with CO2 laser surgery alone, in an acute canine injury model. Studies in humans are ongoing to further evaluate the clinical potential of cryotherapy on glottic wound healing.