Dose-related tissue effects of the CO2 and noncontact Nd:YAG lasers in the canine glottis

Minimizing Thermal Damage During Thulium Laser-Assisted Partial Arytenoidectomy: Pulsed Versus Continuous Cutting in an Ex-Vivo Calf Model

OBJECTIVES

The 2 µm-wavelength thulium laser is an effective cutter during partial arytenoidectomy, but thermal trauma can damage adjacent laryngeal tissue. Pulsing laser energy may reduce trauma when compared to continuous-wave cutting. This study measured temperature changes, thermal trauma, and time to complete partial arytenoidectomy, with and without pulsing, in an ex-vivo calf model.

METHODS

Tissue temperature and time to complete a trans-cartilaginous cut were measured during partial arytenoidectomy on ex-vivo calf vocal folds (N = 24) using a thulium laser in continuous-wave (CW, N = 12) and pulsed-wave (PW, N = 12) modes. Energy was 5 W for CW and PW cuts; pulse-widths were 250, 500, and 750 ms. Thermal damage was analyzed histologically by measuring the depth of lactate dehydrogenase (LDH) inactivation perpendicular to the laser-cut edge at the vocal process. Paired t-tests compared CW and PW modes.

RESULTS

Change in temperature was lower using CW (6.5°C) compared to PW modes (250 ms = 18°; 500 ms = 16°; 750 = 19°; P < .05). Trans-cartilaginous cuts were completed faster using CW (37 seconds) compared to PW (250 ms = 136 seconds; 500 ms = 61 seconds; 750 = 44 seconds; P < .05), and both modes delivered the same total Joules. The average depth of LDH depletion (thermal damage) was similar for all cuts.

CONCLUSIONS

1. Thulium laser cuts in continuous-mode unexpectedly produced less tissue heating yet created similar thermal damage than pulsed-mode cuts during simulated partial arytenoidectomy. 2. Trans-cartilaginous cuts were completed significantly faster in continuous-mode as compared to pulsed-mode cutting. 3. Pulsing the thulium laser does not minimize thermal damage compared to continuous wave cutting during thulium laser-assisted partial arytenoidectomy.

Cooling the "oven": a temperature study of air and glottal tissue during laser surgery in an ex vivo calf larynx model

OBJECTIVES

Endoscopic microlaryngeal laser surgery performed with general anesthesia through a laryngoscope speculum generates heat that accumulates at the distal lumen, creating an "oven" effect and potentially causing bystander thermal damage to nontarget tissue such as the contralateral vocal fold. We report the effects of cooling on air and tissue temperatures that occurred during simulated laryngeal laser surgery with KTP and thulium lasers in an ex vivo calf model.

METHODS

Ten fresh excised calf larynges were studied at room temperature. Laser energy was applied to one vocal fold for 2 minutes, with or without cooling, while temperatures were monitored with sensors placed within the glottal lumen or inserted superficially into the contralateral vocal fold. A pulsed KTP laser (525 mJ) was used for 5 larynges, and a thulium laser (7 W, continuous) was used for the other 5 larynges.

RESULTS

Heating was slightly greater for the KTP laser than for the thulium laser with use of these parameters. The lumen temperatures for both lasers increased an average of 13.2 degrees C without cooling, but only 6.7 degrees C with cooling (p < 0.05). The contralateral vocal fold (subepithelial space) temperature increased an average of 6.8 degrees C without cooling, but only 4.2 degrees C with cooling (p > 0.05).

CONCLUSIONS

Cooling with room-temperature air during laryngeal laser surgery reduces luminal air and contralateral vocal fold temperatures. This effect is believed to be due to elimination of the plume of steam and smoke that significantly heats surrounding structures.

Voice Outcomes Following Repeated Surgical Resection of Laryngeal Papillomata in Children

OBJECTIVES: 1) To apply perceptual and acoustic voice assessments to children treated for juvenile-onset recurrent respiratory papillomatosis (JORRP); 2) to compare voice outcomes following treatment for JORRP using microdebrider versus carbon dioxide (CO2) laser.

STUDY DESIGN: Prospective cohort study.

SETTING: This study was conducted at a tertiary pediatric academic center (March 2008-March 2009).

SUBJECTS AND METHODS: Children with active JORRP were assessed using perceptual and acoustic voice analysis following treatment with either CO2 laser or microdebrider. Outcome measures included overall severity rating, jitter, shimmer, and noise-to-harmonic ratio (NHR). The unpaired Student t test and Pearson correlation tests were used to explore the statistical significance of hypothesis tests.

RESULTS: Eleven patients (8 male, 3 female) aged three to 17 years were enrolled. There were six children in the CO2 laser cohort and five children in the microdebrider cohort. The immediate postoperative scores were significantly lower in the microdebrider cohort (vs the CO2 cohort) for jitter, shimmer, NHR, and perceptual scores ( P < 0.05), indicating a better voice quality in the microdebrider group. Jitter, shimmer, and NHR showed a significant positive correlation with the proportion of CO2 laser procedures ( P < 0.05).

CONCLUSION: This is the first study to use perceptual and objective acoustic evaluations to compare voice outcomes following microdebrider or CO2 laser treatment of JORRP. The results of this study suggest that treatment with the microdebrider results in a better immediate and early postoperative voice outcome. Moreover, the data demonstrate a correlation of worsening voice quality with increased exposure to the CO2 laser.