In vitro and in vivo determination of the thermal effect of middle ear endoscopy.

During middle ear endoscopy, patients frequently experience vertigo. We theorized that this effect is secondary to heat produced by the scope. We evaluated two Hopkins rods and two fiberoptic scopes to assess the temperature elevation at the lateral semicircular canal (LSCC) of temporal bones and in a live canine model. These results were compared to the results of a standard 44 degrees C water caloric. We demonstrated in both models that the temperature rise at the LSCC increased relative to the scope diameter and that the Hopkins rods produced the same or greater heating effect than a warm caloric. Direct exposure of the thermocouple to the light produced a greater temperature elevation. We conclude that endoscopes produce sufficient heat to induce caloric stimulation of the LSCC. Care should be exercised to prevent the possibility of thermal injury.

A combined endoscopic Co2 laser and external approach for treatment of glottic cancer involving the anterior commissure: an animal study.

Endoscopic laser resection usually has been discouraged for anterior commissure (AC) carcinoma because of inadequate exposure and close proximity to underlying cartilage. A new technique combining endoscopic CO2 laser incision and an external approach, creating a window in the thyroid cartilage, was tested in this in vivo study of six dogs. An en bloc specimen including adjacent cartilage was excised while preserving the thyroid framework. The glottic reconstruction was accomplished with external placement of a sternohyoid muscle flap, by either using a bipedicled muscle flap with overlying skin or a unipedicled muscle flap with a graft of free mucosa. The results showed a satisfactory anatomic reconstruction and acceptable functions. The bipedicled muscle flap was superior to the unipedicled muscle flap due to a better AC reconstruction. It is believed that this new combined technique may overcome limited access with endoscopic technique and excessive cartilage resection with the external partial laryngectomy.

Endoscopic diode laser welding of mucosal grafts on the larynx: a new technique.

Epithelial coverage of a laryngotracheal wound is an important factor in preventing stenosis, and endoscopic transplantation of a free mucosal graft without stents or sutures would be a significant therapeutic advance. In vitro and in vivo canine studies were performed to explore the feasibility of transplantation with a low-power diode laser (400 mW) enhanced by indocyanine green dye-doped albumin. The tensile strength of graft adherence in 10 cadaver larynges was strong (35.25 +/- 10.39 g). Survival studies in live canine models with a specially designed endoscopic instrument set showed excellent healing at 6, 14, and 28 days. Healing was documented with photography and by histologic examination. Successful endoscopic transplantation of a free mucosal graft should improve results of treatment for laryngotracheal stenosis and laryngeal reconstructive surgery.

Erbium laser in middle ear surgery: in vitro and in vivo animal study.

Cadaveric human temporal bones, cadaveric rabbits, and live rats were used to demonstrate the utility and safety of the erbium:yttrium-scandium-gallium-garnet (Er:YSGG) laser for otologic applications. The shallow penetration in water of this wave-length and its ability to ablate bony tissue with minimal collateral thermal effects spare underlying and adjacent structures and make it appealing for stapedotomy. The authors were able to satisfactorily perform small fenestra stapedotomy, atticotomy facial nerve decompression, and mastoidectomy. Temperature measurements from the round window area during Er:YSGG stapedotomy recorded an elevation of less than 2 degrees C, which is well within acceptable limits. An acoustic shock produced at the impact site is the major disadvantage and requires further in vivo investigation of the transient and sustained deleterious effects away from the application site. This work supports further investigation into potential applications of the Er:YSGG laser in otology.

Early diagnosis of upper aerodigestive tract cancer by autofluorescence.

OBJECTIVE: To explore the potential of autofluorescence spectroscopy as a tool for early detection of upper aerodigestive tract cancer. DESIGN: Autofluorescence spectral characteristics of 19 untreated oral and oropharyngeal lesions in 13 patients were studied with excitation wavelengths of 370 and 410 nm generated by a nitrogen pumped dye laser. Ten healthy volunteers were recruited to characterize the fluorescence spectra of normal mucosa at different oral sites and to study individual variations. Fluorescence intensity and line shape of the spectra from lesions were compared with the same parameters from the contralateral control site in the same individual. SETTING: Otolaryngology Research Center, Department of Otolaryngology-Head and Neck Surgery, New England Medical Center, Boston, Mass. RESULTS: The ratio of peak fluorescence intensities of the neoplastic lesions to contralateral normal control mucosa were consistently different compared with these ratios in benign lesions or normal mucosa. These differences were seen in 2 distinct regions of the fluorescence spectrum with both of the excitation wavelengths, but were more obvious with the excitation wavelength of 410 nm. Using these differences, we were able to correctly diagnose 17 of the 19 lesions studied, with 2 false-positive results. CONCLUSIONS: Neoplastic oral mucosa shows consistent differences in autofluorescence spectral intensity and line shape when compared with the normal mucosa in the same individual. These early results show that fluorescence spectroscopy may represent a useful technique for noninvasive early diagnosis of cancer of the upper aerodigestive tract.

Mucosal intact laser tonsillar ablation.

BACKGROUND: A laser technique has been developed in the laboratory using a noncontact 810-nm diode laser. RESULTS: Mucosal intact laser tonsillar ablation (MILTA) coagulates tonsillar lymphoid tissue while preserving the overlying mucosa. A canine model was used to evaluate this new method. The canine tonsils were exposed to laser energy for 5 to 6 minutes each at 8 to 10 W of power. This technique was compared with standard "cold" knife tonsillectomy. The dogs were observed carefully during the postoperative period. When comparing parameters such as onset of eating solid food, amount of food ingested per day, onset of normal activity, and degree of weight loss, MILTA showed significant benefit over the standard technique. The operative sites were evaluated and compared at 1.5 hours and at 7, 21, and 45 days after treatment. CONCLUSIONS: None of the tonsils treated by MILTA showed mucosal ulceration. At the end of 45 days, histopathological examination showed complete absence of tonsillar tissue with normal mucosa in both the MILTA and standard groups. Traditional tonsillectomy techniques are associated with moderate morbidity and the potential for serious hemorrhage. With the preservation of the overlying mucosa, the possible clinical advantages of this approach to tonsillectomy are the absence of bleeding, avoidance of general anesthesia in older patients, less operating time, and decreased postoperative morbidity. The potential for office treatment exists. Additional laboratory studies, as well as careful clinical trials, are indicated based on these encouraging results.

Biomechanics of combined arytenoid adduction and medialization laryngoplasty in an ex vivo canine model.

Arytenoid adduction (AA) and medialization laryngoplasty (ML) are being performed concurrently in patients with unilateral vocal fold paralysis with a large posterior glottal gap. The biomechanical effects of this combined procedure on the larynx have not been studied. An excised canine larynx model was used to study the effects of AA, ML, and combined AA and ML (AA-ML) on vocal fold configuration (length and degree of medialization) and tension. AA-ML lengthens the affected vocal fold relative to the opposite vocal fold, although both were slightly shortened compared with the control state (nonsignificant trends). AA-ML medializes the entire length of the vocal fold more effectively than AA or ML alone. Midmembranous vocal fold tension did not increase with AA-ML. With AA-ML, the vocal process resisted significantly greater lateralizing forces than with the control state or ML. We conclude that in an excised canine model, AA-ML combines the biomechanical properties of AA and ML. The larynx appears to be divided into 2 biomechanical subunits: membranous vocal fold (anterior) and arytenoid cartilage (posterior). When surgical rehabilitation of both laryngeal subunits is required, AA-ML appears to be a better choice than AA or ML alone.

Biomechanics of arytenoid adduction surgery in an ex vivo canine model.

The biomechanics of arytenoid adduction surgery are not well understood. An excised canine larynx model was used to study the effects of variable suture tension on glottal configuration and on vocal fold tension (at the midfold and the vocal process). Arytenoid adduction both medializes the vocal fold and closes a posterior glottal chink. Vocal fold tension at the midfold did not vary significantly with suture tension. As suture tension increased to approximately 100 g, vocal fold tension at the vocal process also increased. Beyond 100 g of suture tension, vocal fold tension at the vocal process did not increase. We conclude that the effects of suture tension on the resistance to lateral movement are different at the midfold compared to the vocal process. Procedures for surgical rehabilitation of vocal fold paralysis should address the biomechanical subunits of the larynx individually in order to achieve optimum results.

Endoscopic laser-assisted reshaping of collapsed tracheal cartilage: a laboratory study.

Repair of anterior tracheal wall collapse is a common and troublesome problem encountered by the head and neck surgeon. The standard treatment calls for an open procedure with or without stenting, depending on the extent of the damage. To avoid the morbidity of the open procedure, a new concept of endoscopic cartilage reshaping was investigated in a laboratory animal study. It involved the application of 1.44-micron pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) laser at relatively low power to restructure without devitalizing cartilage. An in vivo study was done in six dogs to determine appropriate laser dosimetry in a model of tracheal wall collapse created by a tracheotomy. The deformed cartilage was treated endoscopically with a noncontact 1.44-micron Nd:YAG laser, at 2 to 4 W of power with a repetition rate of 20 Hz, in three animals. As a control, three animals had endoscopic cartilage incisions followed by stent placement. Six weeks postoperatively, both groups had an adequate airway lined by healthy mucosa. In the animals with stenting, however, there was stenosis formation due to scarring at both ends of the stent, with significant inflammatory response in the local area. This study shows that it is possible to use low-power laser energy to reshape cartilage without destroying its viability, and to restore the tracheal wall to a normal contour without ablation or vaporization. The reshaped cartilage will tend to retain its shape with functional elastic force, as seen in in vitro studies. These preliminary results are encouraging, and it seems reasonable to consider using the technique in selected clinical cases as an alternative to conventional open surgery.

"Window" laryngoplasty: a new combined laser endoscopic and open technique for conservation surgery.

Endoscopic laser resection of early laryngeal carcinoma is an increasingly used treatment modality; however, the limited exposure achieved and the alteration of vocal function are still major problems. A new surgical procedure, "window" laryngoplasty, has been devised and tested in an in vivo study in 6 canines with 50 days' survival. The right vocal cord was incised endoscopically with the carbon dioxide laser, and the en bloc specimen with adjacent thyroid cartilage was removed through a window approach made in the thyroid cartilage. A sternohyoid muscle flap based superiorly was inserted into the cartilaginous window to reconstruct a pseudocord with coverage of either mucosa or fascia. A diode laser soldering technique was used to secure the mucosal graft in place. Epithelial transplantation can be accomplished externally with precise endoscopic guidance for reliable placement of the pseudocord. The results show that the new technique, a combination of endoscopic and open approaches, may be a better treatment choice than standard vertical partial laryngectomy in selected patients. Advantages of this technique include adequate en bloc resection, including adjacent cartilage for pathologic evaluation, preservation of the integrity of most of the laryngeal framework, avoidance of tracheotomy, and better functional results.

Resurfacing of a large laryngeal wound with mucosa grafting: a combined technique using endoscopic suture and laser soldering.

Resurfacing of a large laryngeal wound has traditionally been accomplished via an open approach--transplanting free mucosa either onto the wound directly or upon a stent. This study proposes a new approach for wound resurfacing that combines endoscopic suturing with a laser welding technique. By means of a carbon dioxide (CO2) laser, a large (20 x 25 mm) defect in laryngeal mucosa involving the glottic and subglottic area was created in five dogs. Two of the animals served as controls and received no further treatment. In the remaining three animals the wound was resurfaced with buccal mucosal grafts fixed in place by standard suture placement and a technique of CO2 laser-assisted tissue soldering. The accessible edges of the graft were soldered endoscopically with human albumin-based tissue adhesive "activated" by low power (0.8 to 1.0 W) of a CO2 laser. All animals were examined endoscopically 1 week after surgery and sacrificed painlessly 4 weeks after surgery. The treated animals showed a viable mucosal graft with improved wound healing and voice function compared to that of the control animals. This new approach combines suture fixation of the inferior aspect of the mucosal graft, an area not well exposed endoscopically, and endoscopic laser soldering techniques for the repair of large laryngeal wounds.

The biomechanics of the medialization laryngoplasty (thyroplasty type 1) in an ex vivo canine model.

The biomechanics of medialization laryngoplasty are not well understood. An excised canine larynx model was used to test the effects of various sized silicon implants. The vocal fold length, position, and tension were measured. Medialization laryngoplasty did not affect vocal fold length. At the mid-membranous vocal fold, larger shims resulted in greater medialization and tension. Medialization laryngoplasty neither medialized nor stiffened the vocal process to resist lateralizing forces. We conclude that medialization laryngoplasty provides bulk and support for defects of the membranous region of the vocal fold, but does not appear to close a posterior glottal gap. The selection of a surgical procedure to treat glottal incompetence should take into account the unique biomechanical properties of the anterior (membranous vocal folds) and posterior (cartilaginous portion) glottis.

Jet ventilation in upper airway obstruction: description and model lung testing of a new jetting device.

UNLABELLED: Patients with critical upper airway stenosis require a tracheotomy for corrective surgery. We describe a new transtracheal device that permits safe ventilation of these patients without tracheotomy. It is based on a coaxial bicannular design that allows "push-pull" ventilation by jetting gas through the inner cannula and applying suction through the outer cannula. It further allows monitoring of airway pressure, tidal volume, and end-tidal CO2. The device was placed in the "trachea" of an artificial lung, and the preparation was made airtight by sealing the proximal end of the trachea. Tidal volumes and their associated pressures were measured simultaneously at different parts of the airway at several lung compliances and airway resistance settings while varying the jet and suction pressures. A large range of tidal volumes was achieved at safe airway pressures using clinically relevant airway resistance and lung compliance settings. Airway pressures measured through the device correlated well with pressures measured directly in the airways at the same time. Tidal volumes, measured through a Wright respirometer in the suction line, exceeded actual values at high suction settings and decreased below actual values at low suction settings. This new form of jet ventilation allowed efficient ventilation of the artificial lung with a totally occluded upper airway. IMPLICATIONS: Tracheotomy is required for surgery to relieve stridor because gas forced into the trachea at high pressures through a percutaneously placed needle (jetting) cannot be exhaled quickly enough for respiration. We describe a device that allows jetting in the stridorous patient by actively assisting expiration, thereby eliminating the tracheotomy requirement.

Autofluorescence characteristics of oral mucosa.

BACKGROUND: The fluorescence characteristics of tissues depend upon their biochemical composition and histomorphological architecture, both of which undergo a change during malignant transformation. These changes are detectable as an alteration in the fluorescence spectral profile of the tissues. METHODS: Biopsy specimens from clinically suspicious lesions and normal-appearing oral mucosa were obtained from patients. Fluorescence spectroscopic measurements were obtained to study the differences between normal and dysplastic tissues and to determine the most appropriate excitation wavelength(s) for exploiting these differences. RESULTS: Fluorescence spectra from a total of 12 histologically normal (healthy mucosa or benign lesions) and ten abnormal (dysplastic or malignant) tissue samples were compared. Significant spectral differences were seen between the two groups. These differences were most marked at the excitation wavelength of 410 nm. Using this wavelength, fluorescence correctly diagnosed 20 of 22 samples studied. CONCLUSIONS: This technique accurately differentiates normal from abnormal tissues in vitro and has the potential applications for in vivo use as a noninvasive diagnostic tool.