Improved canine model for laryngotracheal stenosis

Rapid Establishment of Tracheal Stenosis in Pigs Using Endotracheal Tube Cuff Overpressure and Electrocautery

To apply a new airway treatment to humans, preclinical studies in an appropriate animal model is needed. Canine, porcine and leporine tracheas have been employed as animal airway stenosis models using various methods such as chemical caustic agents, laser, and electrocautery. However, existing models take a long time to develop (3-8 weeks) and the mechanism of stenosis is different from that in humans. The aim of the present study was to establish a new and fast tracheal stenosis model in pigs using a combination of cuff overpressure intubation (COI) and electrocautery. Fourteen pigs were divided into three groups: tracheal cautery (TC) group (n=3), COI group (n=3), and COI-TC combination group (n=8). Cuff overpressure (200/400/500 mmHg) was applied using a 9-mm endotracheal tube. Tracheal cautery (40/60 watts) was performed using a rigid bronchoscopic electrocoagulator. After intervention, the pigs were observed for 3 weeks and bronchoscopy was performed every 7 days. When the cross-sectional area decreased by > 50%, it was confirmed that tracheal stenosis was established. The time for tracheal stenosis was 14 days in the TC group and 7 days in the COI-TC combination group. In the COI group, no stenosis occurred. In the COI-TC group, electrocautery (40 watts) immediately after intubation for >1 h with a cuff pressure of 200 mmHg or more resulted in sufficient tracheal stenosis within 7 days. Moreover, the degree of tracheal stenosis increased in proportion to the cuff pressure and tracheal intubation time. The combined use of cuff overpressure and electrocautery helped to establish tracheal stenosis in pigs rapidly.

Experimental animal model for assessment of tracheal epithelium regeneration

OBJECTIVES/HYPOTHESIS

To develop an experimental model in rabbits for assessment of tracheal epithelium regeneration through application of either natural or artificial polymer scaffolds.

STUDY DESIGN

First, we identified the size of full-thickness mucosal defect, which does not allow self-healing (a "critical defect"), thus representing an adequate experimental model for regenerative therapy of tracheal epithelium damage. Then, two methods of polymer scaffold fixation at the site of the epithelium defect were compared: suturing and fixation with a stent. This was done through: 1) formation of a full-thickness anterolateral mucosal defect by tracheal mucosa excision; and 2) fixation of the scaffold at the site of the tracheal epithelium defect using sutures (through a tracheal wall "window") or a vascular stent (through a small tracheal incision).

RESULTS

The dimension of a critical anterolateral mucosal defect of the trachea for rabbits was found to be 1.5 cm in length and more than 50% of the tracheal circumference. Fixation of the scaffold with a stent proved to be more efficient due to a uniform distribution of the pressure over the entire surface of the scaffold, whereas the suturing of the scaffold provided unsatisfactory results. In addition, fixation of the scaffold by suturing required formation of a large "window" in the tracheal wall. Thus, using the stent appeared to be technically less complicated and much less traumatic as compared to suturing.

CONCLUSION

We present an experimental in vivo animal model of tracheal epithelium injury and recovery. It can be effectively used with certain further modifications as a basis for routine testing of bioengineered constructs.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E213-E219, 2019.

Purulent Chondritis of the Laryngeal Framework Cartilages

This manuscript reports on our experience with purulent chondritis of the laryngeal cartilages (PCLC), an entity that has not yet been described. Three patients had a diagnosis of PCLC. The probable causes were relapsing polychondritis, a previous prolonged intubation, and an idiopathic cause. The patients suffered from hoarseness and inspiratory stridor for 1 to 3 months before diagnosis. None complained of pain in the neck. Laryngoscopy showed supraglottic edema. A computed tomography scan revealed abscess formation between the intact inner and outer perichondria of the thyroid cartilage. The treatment included rigid endoscopy, external incision and drainage, and prolonged medical therapy. The culture results were Staphylococcus aureus in the first 2 cases and Aspergillus fumigatus in the third. The second patient (in whom the cricoid cartilage was also affected) required emergency tracheotomy. The other 2 patients did not require airway intervention. The rarity of PCLC and the relatively mild symptoms require a high index of suspicion for its diagnosis.

Subglottic injury: a clinically relevant animal model

OBJECTIVES/HYPOTHESIS

To develop a clinically aligned, reproducible model for subglottic injury.

STUDY DESIGN

Prospective randomized control pilot study.

METHODS

Juvenile (3-month-old) New Zealand White rabbits underwent intubation with a 3-cm length of an endotracheal tube that was chosen so that there would be no air leak below 20 cm of water. This tube was one or two sizes above the appropriate tube for the animal. It was held in situ with a suture placed at the trachea and secured over a button in the neck for a period of 1 week. Animals were sacrificed 1 week postextubation, and larynges were harvested. A range of histological techniques and gross morphology were utilized to examine the injury caused at the level of the subglottis. Unintubated animals constituted controlled specimens.

RESULTS

Intubated animals demonstrated considerable histopathology including evidence of ulceration, inflammation, granulation tissue, perichondritis, and chondritis when compared with control animals. Morphometric analysis demonstrated a significant increase in lamina propria thickness (P = .0013), mucosal thickness (P ≤ .0001), and in goblet cell areal density (P = .014). Analysis of mucin types found a significant decrease in acidic (P = .0001) mucin coinciding with a significant increase in mixed mucin types (P = .0013).

CONCLUSIONS

Our model provides a reliable and reproducible technique for acute/subacute injury to the subglottis secondary to intubation, which is consistent with previous histological findings of early changes associated with acquired subglottic stenosis (SGS). Future uses of this model could include the examination of current adjunctive therapies and their effects on limiting progression to SGS.

A model of canine tracheal stenosis induced by radiofrequency cauterization

OBJECTIVE

The current methods of management of tracheal stenosis have disadvantages and are controversial, therefore ideal experimental animal models for the further studies are required. The aim of this study was to establish a new model of canine tracheal stenosis by radiofrequency cauterization.

METHODS

The tracheal cartilage ring was injured by radiofrequency at the level of the sixth tracheal ring in 12 mongrel dogs. A fibrolaryngoscope was used to guide the procedure. The animals were observed after operation and examined after euthanasia. Endoscopic and histological examinations were undertaken to evaluate the progress of stenosis. The degree of stenosis was calculated using the formula: degree of stenosis=(initial lumen area-final lumen area)/initial lumen area × 100%.

RESULTS

Tracheal stenosis had developed in all dogs by the 21st day post operation. Costal retraction was observed in all dogs after the 18th day post operation. At the end of the study, gross and endoscopic examinations showed that stenosis had been induced to a satisfactory degree and without any complications. The median of the degree of stenosis was 92%, with a range of 84-94%. Histological examination showed that cartilage was damaged and that granulation tissue and collagen fibres had formed.

CONCLUSIONS

The model of canine tracheal stenosis induced by radiofrequency cauterization is a relatively simple, reliable, and reproducible animal model. This model may be useful in the development of new methods of treatment for tracheal stenosis.

Causes of headache in patients with a primary diagnosis of sinus headache

Headache is a common occurrence among the general population. Although the pain could be a symptom of acute sinusitis, chronic sinusitis is not considered as a usual cause of headache. In addition, autonomic-related symptoms in the sinonasal region may be associated with vascular pain. Confusion regarding these symptoms could lead to an incorrect diagnosis of sinusitis. A prospective cross-sectional study was conducted at two tertiary referral centers with residency programs in otorhinolaryngology, head and neck surgery and neurology. The study included 58 patients with a diagnosis of "sinus headache" made by a primary care physician. Exclusion criteria were as follows: previous diagnosis of migraine or tension-type headache; evidence of sinus infection during the past 6 months; and the presence of mucopurulent secretions. After comprehensive otorhinolaryngologic and neurologic evaluation, appropriate treatment was started according to the final diagnosis and the patient was assessed monthly for 6 months. The final diagnoses were migraine, tension-type headache and chronic sinusitis with recurrent acute episodes in 68, 27 and 5% of the patients, respectively. Recurrent antibiotic therapy was received by 73% of patients with tension-type headache and 66% with migraine. Sinus endoscopy was performed in 26% of the patients. Therapeutic nasal septoplasty was performed in 16% of the patients with a final diagnosis of migraine, and 13% with tension-type headache. Many patients with self-described or primary care physician labeled "sinus headache" have no sinonasal abnormalities. Instead, most of them meet the IHS criteria for migraine or tension-type headache.

Acute and chronic changes in the subglottis induced by graded carbon dioxide laser injury in the rabbit airway

OBJECTIVE

To investigate the repair process following carbon dioxide laser injury to the upper airway mucosa (UAM) during the development of chronic subglottic stenosis (SGS).

DESIGN

Animals were assigned to either sham control (cricothyroidotomy only) or injured (cricothyroidotomy and posterior subglottic laser) groups using various carbon dioxide laser exposures (8, 12, and 16 W) for 4 seconds.

SUBJECTS

Twenty-four New Zealand white rabbits.

INTERVENTIONS

The subglottis was approached via cricothyroidotomy. Sham control airways were immediately closed, whereas injured airways were subjected to graded carbon dioxide laser exposures prior to closure. Airways were endoscopically monitored preoperatively, postoperatively, and on postoperative days 7, 14, 28, 42, 56, 70, and 84. Animals were killed at 14 and 84 days. Subglottic tissue was harvested for histologic evaluation (reepithelialization, extracellular matrix, vascularity, and inflammation).

MAIN OUTCOME MEASURES

Endoscopic visualization and histologic analysis.

RESULTS

(1) Increases in UAM thickness (up to 5 times the thickness of normal mucosa) were observed but were limited primarily to the lamina propria. The mucosal epithelium regenerated without chronic changes. Focal areas of cartilage repair were encountered acutely after injury and to a greater extent in the chronic phases of repair. (2) Acutely, the thickened lamina propria comprised poorly organized extracellular matrix components and demonstrated increases in blood vessel size and number. (3) Histologic changes present in the acute phase only partially resolved in progression to chronic SGS. Chronic SGS was characterized by thick collagen fiber bundles extending into the remodeled subglottic cartilage.

CONCLUSIONS

The carbon dioxide laser induces acute changes to lamina propria architecture and vascularity that persist chronically. Elucidating responsible signaling pathways may facilitate the development of therapeutic agents to prevent or reduce the formation of SGS.

Anti-transforming growth factor beta as a treatment for laryngotracheal stenosis in a canine model

OBJECTIVES/HYPOTHESIS

Laryngotracheal stenosis (LTS) represents a significant treatment dilemma faced by otolaryngologists. Recent topical use of Mitomycin C as an adjunctive treatment has proved helpful but does not completely prevent stenosis. Current literature suggests that transforming growth factor beta (TGFB) plays a significant role in the development of subglottic stenosis. We modified an existing canine model to test antitransforming growth factor beta (anti-TGFB) as a possible treatment for laryngotracheal stenosis.

STUDY DESIGN

Pilot study in a modified canine model.

METHODS

Eight mixed-breed dogs underwent cautery injury to the subglottic region creating subsequent laryngotracheal stenosis. Four dogs were treated with saline injection into the injury site and four dogs were treated with a combination of intravenous (5 mg/kg on day 0 and 5 of the experiment) and local injection of anti-TGFB (50 micrograms).

RESULTS

In the canine model of induced subglottic airway injury, a combination of intralesional and intravenous anti-TGFB results in a reduction in tracheal stenosis (P < .05) and an increase in survival time (P < .03) when compared to the saline control subjects.

CONCLUSIONS

Anti-TGFB appears to be a useful adjunct in the treatment of LTS. Further study regarding the optimal dosing, route of administration, and timing of delivery is needed to understand the role of anti-TGFB in the treatment for laryngotracheal stenosis.

Electrocautery versus 23% NaOH infiltration to induce subglottic stenosis in a canine experimental model

Subglottic stenosis (SGS) is defined as the narrowing of the lower larynx. Difficulties in the management of subglottic stenosis, especially in the pediatric population, justify the development of experimental models. The objective of this study was to compare the two methods of experimental subglottic stenosis induction. Twenty-three dogs were randomly selected and assigned by lottery to either one of the two groups: Gp I (n = 10) of electrocoagulation; and Gp II (n = 13) of 23% NaOH injection. In Gp I, self-interruption electrocoagulation was applied to one point in each of the four quadrants of the cricoid cartilage. In Gp II, 0.2 ml of 23% NaOH was injected in the submucosal layer in the anterior and posterior portions of the cricoid cartilage. Once a week, endoscopy was performed and the caliber of the subglottic region was measured using endotracheal tubes, and the injection was repeated if there were no signs of subglottic stenosis. The animals were killed on day 21; animals that developed respiratory distress were killed before day 21. One animal in Gp I died on day 14 after the injection and during transportation; two animals in Gp II died, one on day 7 due to a tracheoesophageal fistula, and the other of unknown causes on day 5. Significant subglottic stenosis (over 51% obstruction) was found in 67% of the animals in Gp I and in 64% of those in Gp II (P = 0.99). Median time to development of significant stenosis was 21 days in both groups, and required either two or three injections. Mean time for the performance of the procedures was significantly shorter (P < 0.01) in Gp I (mean: 6.36 min) than in Gp II (mean: 14.88 min). Electrocoagulation and 23% NaOH injection in the subglottic region were effective in the development of significant subglottic stenosis in dogs, both methods leading to stenosis in the same period of time and after the same number of procedures. However, electrocoagulation was the fastest method.

Purulent chondritis of the thyroid cartilage

Purulent chondritis of the laryngeal cartilage is defined as a chondritis of the laryngeal framework cartilage with abscess formation between the inner and outer perichondria. To the best of our knowledge, only 1 report of purulent chondritis of the laryngeal framework cartilage has been published previously in the English language literature. Our patient suffered from generalized weakness, myalgias, and sore throat for 1 month and hoarseness for 10 days before diagnosis. Fiberoptic laryngoscopy demonstrated a granuloma-like, whitish, exophytic mass in the anterior commissure of the false vocal cords and erythema and edema in both the arytenoid and false vocal cord mucosa. A computed tomography scan revealed abscess formation between the intact inner and outer perichondria of the thyroid cartilage. The treatment included rigid endoscopy, external incision and drainage, and steroid and antibiotic therapy. The culture resulted in no growth. We report on a patient with a case of purulent chondritis of the thyroid cartilage, which requires a high index of suspicion for its diagnosis.

Halofuginone prevents subglottic stenosis in a canine model

OBJECTIVES

Halofuginone is a low-molecular weight quinazolinone alkaloid coccidiostat that inhibits collagen type I synthesis, extracellular matrix deposition, and angiogenesis. This study was conducted to assess its potential in preventing subglottic stenosis (SGS).

METHODS

We induced SGS in 10 dogs randomly divided into 2 groups. Each group received treatment between 3 days before and 21 days after the induction of SGS. One group received oral halofuginone 40 microg/kg, and the other was given placebo. The area of the subglottic lumen was measured at baseline and 3 months later. In addition, human tracheal fibroblasts were cultured. The inhibitory effect of halofuginone was compared to the effect of mitomycin.

RESULTS

All dogs survived throughout the study with no side effects. Three months after the operation, no halofuginone-treated dog had SGS, in contrast to a 66% to 80% stenosis rate (mean, 72%) in controls (p < .008). Thick fibrotic tissue was found in the placebo-treated larynges, whereas an almost normal architecture was observed in halofuginone-treated larynges. Halofuginone inhibited the growth of human tracheal fibroblasts by 75%, in comparison with 60% inhibition by mitomycin (no statistically significant difference).

CONCLUSIONS

This preliminary study shows that halofuginone is effective in preventing SGS caused by an acute injury. Halofuginone has a potential therapeutic role in preventing SGS in humans.

Midfacial segment pain: implications for rhinitis and sinusitis

During the past decade, studies on facial pain have shown that there is a distinct group of patients who have a form of facial neuralgia that has all the characteristics of tension-type headache, except that it affects the midface; it is called midfacial segment pain. The pain is described as a feeling of pressure, although some patients might feel that their nose is blocked when they have no nasal airway obstruction. Midfacial segment pain is symmetric, and it might involve areas of the nasion (the root of the nose), under the bridge of the nose, on either side of the nose, the peri- or retro-orbital regions, or across the cheeks. There might be hyperesthesia of the skin and soft tissues over the affected area. Nasal endoscopy and CT scans are typically normal. Most patients with this condition respond to low-dose amitriptyline, but noticeable improvement might require up to 6 weeks.

Mitomycin Does Not Prevent Laryngotracheal Repeat Stenosis After Endoscopic Dilation Surgery: An Animal Study

OBJECTIVES/HYPOTHESIS

Conflicting data exist in the literature regarding the role of mitomycin in the prevention and treatment of laryngotracheal stenosis. The purpose of the study was to assess the value of mitomycin in preventing repeat stenosis after endoscopic dilation surgery of well-established stenoses.

STUDY DESIGN

Prospective controlled animal study.

METHODS

Laryngotracheal stenosis was induced in 16 dogs. After a period of 3 months the dogs underwent endoscopic dilation and were randomly divided into two groups. The control group received immediate topical application of normal saline. Dogs in the mitomycin group received immediate topical application of 0.5 mg mitomycin. The animals were then observed for 3 more months before euthanasia. The laryngeal lumens were measured endoscopically at baseline, before dilation, and before euthanasia. A comparison was made between the two study groups by means of the Wilcoxon rank-sum test for change in the percentage of stenosis attained by the endoscopic dilation.

RESULTS

Nine dogs were included in the control group, and seven in the mitomycin group. Group comparison for initial occlusion before endoscopic dilation using Wilcoxon rank-sum test showed no difference between the two groups (z = 0.16 [P =.87]). Three months after endoscopic dilation, no difference was observed between the two groups regarding the change in the percentage of occlusion (z = -0.21 [P =.83]).

CONCLUSION

Mitomycin exerts a benefit equal to that of normal saline when applied to a well-established laryngotracheal stenosis in dogs and does not prevent repeat stenosis after endoscopic dilation surgery.

Prevention of laryngotracheal stenosis with carnitine after tracheotomy: an experimental study on rats

OBJECTIVE

We investigated the effect of carnitine on wound healing of trachea in tracheotomyzed rats. This study was undertaken to test the hypothesis that treatment with carnitine would protect the wound tissue, which was evaluated by measuring nitrite and nitrate, thus nitric oxide, malondialdehyde and cholinesterase in blood, and examining the histopathological changes.

METHODS

Standard vertical tracheotomy was performed on 24 Wistar-Albino type rats. Then the animals were randomly divided into two groups; group A (the study group) was administered intraperitoneal carnitine 100 mg/kg for 10 days; group B (the control group) was administered intraperitoneal saline for 10 days. On the 10th day, all animals were decanulated. Three weeks later, cardiac blood samples were taken for biochemical assays and trachea specimens were harvested for histopathologic examination.

RESULTS

In the carnitine-administered group, granulation tissue thickness resulting from the wound healing in the level of tracheotomy incision was lower compared to the control group (P < 0.01). When serum malondialdehyde levels were considered, a lower malondialdehyde level was found in the carnitine-administered group (P < 0.01). However, serum nitric oxide levels were close to each other in both groups (P > 0.05), while serum cholinesterase level was higher in the carnitine-administered group than in the control group (P < 0.01).

CONCLUSION

Carnitine treatment partially prevents and significantly reduces the severity of tracheotomy induced laryngotracheal stenosis.

Nasal polyposis and facial pain

A cohort of 973 patients with symptoms of rhinosinusitis and/or facial pain was followed up for a mean of 2 years 2 months and, within this, was a group of 220 with nasal polyps. Only 39 (18%) had pain or pressure as a symptom. Out of the 220 with nasal polyps, 190 had polyps without any purulent secretions and, of these, only 5 (2.6%) had pain attributable to their paranasal sinus disease. Ten out of the 15 with pain and polyps without pus were found to have pain as a result of neurological or medical cause after endoscopic sinus surgery and a trial of medical nasal treatment and, where necessary, drugs to treat neurological conditions. Thirty patients (13.6%) had nasal polyposis and purulent secretions, and, within this subgroup, 24 (79%) had pain as well. Of the 24 with pain and purulent secretions, 19 (80%) responded to treatment for their paranasal sinus disease, a far higher proportion than with nasal polyps without pus. In conclusion, in patients who have nasal polyps without purulent secretions, be cautious about attributing any symptoms of facial pain or pressure as being due to their paranasal sinuses as it is more probable that it is coincidental and the result of a neurological cause.

An investigation of airway wound healing using a novel in vivo model

OBJECTIVE

To study the amount of wound contraction and reepithelialization occurring in the healing process of full-thickness mucosal defects treated with and without mitomycin.

STUDY DESIGN

A new wound healing model was developed in which the tracheal mucosa was exteriorized without interference with the blood supply or with the cartilage support of the trachea. This was done by: 1) orthotopic tracheal revascularization in vascularized fascia; 2) isolation of revascularized segment after 14 days; 3) posterior longitudinal incision of revascularized segment; 4) exteriorization of tracheal mucosa with formation of anterior full-thickness mucosal defect; and 5) closure of posterior tracheal incision and reimplantation in the airway. This model was used to study airway wound healing in three groups of animals: 1) controls (revascularization, exteriorization, reimplantation) (N = 6); 2) full-thickness mucosal defect: patch defect (N = 5), circumferential defect (N = 3); and 3) full-thickness mucosal defect after topical mitomycin application: patch defect (N = 7), circumferential defect (N = 3). The animals were followed for periods varying from 2 to 4 weeks or until signs of dyspnea. The surface areas of the wounds before and after follow-up were measured. Wound healing was studied histologically on axial and longitudinal sections.

RESULTS

Group 1: All the animals survived for 1 month. No significant difference existed between surface area of isolated trachea and of reimplanted trachea after follow-up. Group 2: Five animals (patch defects) survived for 1 month. Full-thickness mucosal defects healed by reepithelialization and by a surface area reduction of 58.9% (mean - standard deviation = 10.5). The animals with the circumferential defects showed dyspnea after an average follow-up of 14 days as a result of excessive granulation tissue formation. Group 3: Mitomycin reproducibly inhibited wound closure, yielding wounds that on average closed 56% less than controls by day 14 (P <.001). Histologic comparisons showed that mitomycin blocks angiogenesis during wound healing.

CONCLUSIONS

A wound healing model based on tracheal revascularization, isolation, and reimplantation was developed in rabbits. This model allowed us to study the healing of full-thickness mucosal defects inside the airway.

Evaluating laryngotracheal stenosis in a canine model with virtual bronchoscopy

We performed a prospective masked animal study to determine whether virtual bronchoscopy, a noninvasive computed tomography technique, can accurately measure upper airway stenosis. Virtual bronchoscopy creates a 3-dimensional endoscopic image from spiral computed tomography data. Laryngotracheal stenosis was endoscopically induced in 18 dogs. The excised larynges were examined by endoscopy, virtual bronchoscopy, and macrodissection. Measurements were made of the anteroposterior (A-P) diameter, the left-right (L-R) diameter, the full length of stenosis in the sagittal plane, and the length of the tightest stenotic segment. Each measurement method was performed independently. All investigators were unaware of measurements made by others. The measurements obtained through virtual bronchoscopy and actual endoscopy were compared to those made at dissection by interclass correlation coefficients (ICCs). Endoscopy was better than virtual bronchoscopy in measuring the A-P diameter (ICC = .79, p < .0001; ICC = .42, p = .01). Both were equally effective in measuring the L-R diameter (ICC = .53, p = .0062; ICC = .52, p = .0064). The endoscopes could not assess the full length of the stenosis, whereas virtual bronchoscopy measured it fairly accurately (ICC = .72, p = .0001). Virtual bronchoscopy relatively accurately measured the length of the tightest stenotic segment (ICC = .68, p = .0002), whereas endoscopy produced measurements in only 11 of 18 larynges, and the measurements were less accurate (ICC = .45, p = .0068). Virtual bronchoscopy can provide good measurements of stenotic lesions in the airway. It is more accurate than actual endoscopy in determining the length of stenosis. It may therefore be useful as an adjunct imaging method in preoperative planning for reconstructive surgery.