In vivo measurement of vocal fold surface resistance

OBJECTIVES/HYPOTHESIS

A custom-designed probe was developed to measure vocal fold surface resistance in vivo. The purpose of this study was to demonstrate proof of concept of using vocal fold surface resistance as a proxy of functional tissue integrity after acute phonotrauma using an animal model.

STUDY DESIGN

Prospective animal study.

METHODS

New Zealand White breeder rabbits received 120 minutes of airflow without vocal fold approximation (control) or 120 minutes of raised intensity phonation (experimental). The probe was inserted via laryngoscope and placed on the left vocal fold under endoscopic visualization. Vocal fold surface resistance of the middle one-third of the vocal fold was measured after 0 (baseline), 60, and 120 minutes of phonation. After the phonation procedure, the larynx was harvested and prepared for transmission electron microscopy.

RESULTS

In the control group, vocal fold surface resistance values remained stable across time points. In the experimental group, surface resistance (X% ± Y% relative to baseline) was significantly decreased after 120 minutes of raised intensity phonation. This was associated with structural changes using transmission electron microscopy, which revealed damage to the vocal fold epithelium after phonotrauma, including disruption of the epithelium and basement membrane, dilated paracellular spaces, and alterations to epithelial microprojections. In contrast, control vocal fold specimens showed well-preserved stratified squamous epithelia.

CONCLUSIONS

These data demonstrate the feasibility of measuring vocal fold surface resistance in vivo as a means of evaluating functional vocal fold epithelial barrier integrity. Device prototypes are in development for additional testing, validation, and for clinical applications in laryngology.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E364-E370, 2017.

Histopathologic Changes in Laryngeal Mucosa of Extremely Low-Birth Weight Infants after Endotracheal Intubation

Objectives:

Advances in medicine have improved the survival of infants with increasingly lower birth weights. The histopathologic changes of intubation-related laryngeal injury in extremely low-birth weight infants (less than 1,000 g) have not been well known. We examined histopathologic changes in infant larynges, including extremely low-birth weight infants, after endotracheal intubation.

Methods:

Forty-four infants, including 21 extremely low-birth weight infants, who had been intubated for periods ranging from 10 minutes to 138 days, were examined in a whole organ serial section study.

Results:

As the duration of intubation increased, the ulceration was found to be larger and deeper. The injury at the subglottis and posterior glottis was greater than that at other portions. The perichondrium of the cartilage was exposed in many cases intubated longer than 8 days. Repaired epithelium that was composed of squamous epithelium was present in 6 of 7 larynges that had been intubated more than 20 days, indicating that not only injury but also the healing process occurred during long intubation. There were no obvious relationships between the degree of intubation injury and the birth weight of the infants.

Conclusions:

Prolonged intubation is better tolerated by infants than adults. The intubation-related laryngeal injuries of extremely low-birth weight infants were histopathologically the same as those of infants of other birth weights.

Noninvasive Measurement of Ablation Crater Size and Thermal Injury after CO2 Laser in the Vocal Cord with Optical Coherence Tomography

OBJECTIVES: To characterize tissue destruction after CO2 laser-ablation of the vocal cords with the use of optical coherence tomography (OCT).

STUDY DESIGN AND SETTING: OCT was used to image fresh porcine vocal cords after laser ablation. OCT and histology estimates of the ablation crater dimensions and the depth of thermal injury were obtained.

RESULTS: The vocal cord substructures up to 2.29 mm in depth at 10 μm resolution, and the thermal disruption after laser ablation were identified by OCT. OCT and histology estimates of the lesion dimensions showed no significant differences. Crater depth is directly proportional to laser power, whereas crater width and the zone of thermal injury appear to be unrelated to laser power.

CONCLUSIONS: OCT may be used to accurately characterize the native states and the laser-induced thermal injury of laryngeal mucosa, within the inherent limitation in its depth of penetration. OCT may be a useful diagnostic and monitoring tool in an otolaryngology practice.

A new rat model for investigation of subglottic stenosis

CONCLUSION

This study attempted to develop a new rat model of subglottic stenosis (SGS), resulting from subglottic mucosal injury administered by electrocauterization. Despite failure of the posterior SGS model, the anterior SGS model was considered feasible.

OBJECTIVE

To investigate the feasibility of using rats as an animal model for SGS.

METHODS

Thirty-seven female Sprague-Dawley rats were assigned to the control group or to the anterior or posterior subglottic injury group. Electrical cauterization was performed on the anterior or posterior 180° of the subglottic mucosa. Animals were euthanized at 4 weeks after injury. Histologic features of the subglottis were evaluated as regards changes in the subglottic lumen, lamina propria, cartilage, and epithelium after hematoxylin and eosin and Masson trichrome staining.

RESULTS

Survival in the anterior injury group was 80% (13/15) until 4 weeks, and results of histologic evaluation showed an increase in thickness of lamina propria with fibrosis and cartilage damage, resulting in luminal narrowing. A high rate of mortality was observed in the posterior injury group.

Endoscopic management of blunt pediatric laryngeal trauma

OBJECTIVES

Blunt laryngeal trauma in the pediatric population is an uncommon but unique entity that can be potentially life-threatening. Given the infrequency of these events, its management can pose a clinical dilemma. The authors review the evaluation and treatment of blunt pediatric laryngeal trauma.

METHODS

We present a case report and a review of the literature.

RESULTS

We describe the case of a 3-year-old boy who presented with laryngeal injury following blunt trauma. The patient sustained endolaryngeal hematomas and mucosal lacerations with exposed cartilage. After mucosal approximation, the patient was successfully managed in a critical care setting without a tracheostomy.

CONCLUSIONS

With an appropriate and thorough evaluation of the pediatric patient, endoscopic management without a surgical airway may be considered as a viable alternative for blunt laryngeal trauma.

Arytenoid mucosal injury in young Thoroughbred horses — investigation of a proposed aetiology and clinical significance

AIM

To determine whether trauma to the larynx caused by nasotracheal intubation induced mucosal ulceration of the arytenoid cartilages of adult horses, and to determine the incidence of such ulceration in yearling Thoroughbred horses and its effect on athletic performance.

METHODS

Laryngeal trauma was induced in a group of 21 adult horses by introduction of a nasogastric tube into the trachea three times within 5 min. Injury to the arytenoid cartilages or vocal cords was subjectively assessed immediately after intubation, and thereafter at weekly intervals for 10 weeks. The outcome and athletic performance of 33 Thoroughbred yearling horses with idiopathic disease of the arytenoid cartilages, diagnosed at the yearling sales, were evaluated and compared to those of control horses of the same gender and age, from the same sale.

RESULTS

Mucosal injury was noted immediately after intubation in every horse. Evidence of injury to the vocal or corniculate processes of the arytenoid cartilages or vocal cords was still apparent in 10/21 (48%) horses 1 week after intubation, five of which developed persistent lesions that remained present and unchanged from 28 days following intubation until the end of the 10-week observation period. All persistent lesions were nodules or focal swellings of the vocal cords or arytenoid cartilages, and there was no evidence of mucosal ulceration, infection or discharge. Mucosal ulceration of the vocal processes was the most common abnormality detected in the yearlings, affecting 16/33 (48%) that were diagnosed with idiopathic arytenoid disease at the yearling sales. Five of the 33 (15%) horses were diagnosed with arytenoid chondritis at the time of sale and were excluded from the performance outcome analysis. Of the 28 horses diagnosed with arytenoid abnormalities excluding chondritis, 19 (68%) raced with no history of respiratory-related problems, two (7%) were subsequently diagnosed with laryngeal hemiplegia, and seven (25%) were lost to follow-up. The case animals were 2.7 times more likely to race than control horses, but there was no difference between cases and controls in the likelihood of starting more than three times.

CONCLUSIONS

This study showed that nasotracheal intubation in adult horses could result in immediate mucosal trauma, persistent swelling, and focal scarring of the arytenoid cartilages, but this did not mimic mucosal ulceration or chondritis of the arytenoid cartilages observed in yearling Thoroughbred horses. The population studied, however, may not accurately represent the population in which idiopathic disease occurs. In this study, arytenoid mucosal ulceration detected at sale did not commonly progress to arytenoid chondritis. However, a study of a larger population of horses with untreated, naturally occurring disease is required to confirm these findings.

CLINICAL RELEVANCE

It is unlikely that trauma from nasogastric intubation caused arytenoid mucosal ulceration, therefore this procedure should not necessarily be discouraged. This study did not find evidence that horses diagnosed with arytenoid mucosal ulceration at yearling sales had a reduced performance history, therefore it is reasonable to continue to pass horses with uncomplicated arytenoid mucosal ulceration during post-sale endoscopic examination. However, monitoring of the lesions and treatment, if required, may be indicated in the post-sale period.

The laryngeal mask airway Unique versus the Soft Seal laryngeal mask: a randomized, crossover study in paralyzed, anesthetized patients

We tested the hypothesis that ease of insertion, oropharyngeal leak pressure, fiberoptic position, ease of ventilation, and mucosal trauma are different for the Soft Seal laryngeal mask airway (SSLM) and the laryngeal mask airway Unique (LMA-U). Ninety paralyzed, anesthetized adult patients (ASA I-II; 18-80 yr old) were studied. Both devices were inserted into each patient in random order. Oropharyngeal leak pressure and fiberoptic position were determined during cuff inflation from 0-40 mL in 10-mL increments and at an intracuff pressure of 60 cm H(2)O. Ease of ventilation was determined by controlling ventilation for 10 min at 8 and 12-mL/kg tidal volume and recording hemoglobin oxygen saturation, end-tidal CO(2), leak fraction, peak airway pressure, and the presence or absence of gastric insufflation. Mucosal trauma was determined by examining the first randomized device for the presence of visible and occult blood. Insertion time was shorter (P = 0.0001) and fewer attempts were required (P = 0.005) for the LMA-U. There were no failed uses of either device. Oropharyngeal leak pressures were similar, but fiberoptic position was superior with the LMA-U (P < or = 0.0003). There were no differences in hemoglobin oxygen saturation, end-tidal CO(2), leak fraction, or peak airway pressure at either tidal volume. Gastric insufflation was not detected in either group at either tidal volume. The frequency of visible (P = 0.009) and occult blood (P = 0.0001) was less with the LMA-U. We conclude that the LMA-U is superior to the SSLM in terms of ease of insertion, fiberoptic position, and mucosal trauma, but similar in terms of oropharyngeal leak pressure and ease of ventilation.

A Comparison of Sex- and Weight-based ProSeal™ Laryngeal Mask Size Selection Criteria

Background

The authors compared the manufacturer's weight-based formula (size 3 for weight &lt; 50 kg, size 4 for weight 50-70 kg, and size 5 for weight &gt; 70 kg) with a sex-based formula (size 4 for women and size 5 for men) for selecting the appropriate size of ProSeal laryngeal mask airway.

Methods

Two hundred thirty-seven healthy, anesthetized, paralyzed adult patients (American Society of Anesthesiologists physical status I or II; age, 18-80 yr) were randomly allocated for weight- or sex-based size selection. An experienced user inserted the ProSeal laryngeal mask airway with the digital technique. The following were compared: ease of insertion, oropharyngeal leak pressure, ease of ventilation, gas exchange, location of gas leak, anatomic position, mucosal injury, and postoperative pharyngolaryngeal problems. Intraoperative and postoperative data collection were unblinded and blinded, respectively.

Results

Ease of insertion, anatomic position, gas exchange, mucosal injury, and postoperative pharyngolaryngeal problems were similar between groups. For the sex-based group, larger ProSeal laryngeal mask airways were selected more frequently (P &lt; 0.0001), oropharyngeal leak pressure (P = 0.02) was higher, leak volume (P = 0.004) and leak fraction (P = 0.007) were lower, and oropharyngeal leaks (P = 0.03) were detected less frequently.

Conclusion

Size selection for the ProSeal laryngeal mask airway is equally effective using the manufacturer's weight-based formula or the sex-based formula in healthy, anesthetized, paralyzed adult patients, but leakage of small volumes of air from the mouth occurs less frequently with the sex-based formula.

Thermische Belastung der gesunden Larynxschleimhaut bei Einsatz des CO 2 -Lasers*

BACKGROUND

The carbon dioxide (CO(2)) laser in endolaryngeal surgery is a successful tool because of its implementation of the thermally induced hematostatic incision technique. We investigated the problem of thermal damage of surrounding tissue during laser surgery. Until now a potential damage of surrounding healthy mucosa caused by laser surgery through general heating up, hot gases and steam has scarcely been noticed. During prolonged tumor surgery the tender mucosa of the surrounding healthy tissue can be irreversible affected and damaged due to thermal exposure above 45 degrees C.

METHOD

The study was performed on the larynx of a pig cadaver. Temperature probes were placed under the epithelium of the vocal cords on the opposite side of the surgical field to detect any increase in temperature during laser application.

RESULTS

A rise in temperature of up to 32 degrees C was observed in the vocal cord opposite the surgical field after 70 s of laser surgery (output power: 4 W, continuous wave mode) even with continuous aspiration. Protection of the healthy mucosa against thermal radiation caused a rise in temperature of only 3.5 degrees C. An increase in temperature of up to 16.1 degrees C was observed, if intermittent exposures (output power: 4 W, pulse length: 0.5 second, repeat time: 0.1 second) were used.

CONCLUSION

Transferring the presented cadaver studies to in vivo surgery, the laryngologist should take into account heating of collateral healthy tissue up to 69 degrees C (37 degrees C body temperature plus 32 degrees C heating by thermal radiation).

Gross and histologic changes in the developing rabbit subglottis in response to a controlled depth of injury

OBJECTIVE

Our goal was to determine the effects of both perichondrial and intracartilaginous injury in the developing rabbit subglottis versus normal development.

DESIGN

We conducted a descriptive, pilot study of changes in the shape and histology of the subglottis after a controlled depth of injury in 27 New Zealand White rabbits, ages 4 weeks, 8 weeks, and 1(1/2) years.

INTERVENTION

Within each age group, 3 animals underwent no surgery, 3 underwent perichondrial injury, and 3 underwent intracartilaginous injury.

RESULTS

Perichondrially injured animals in the 4-week age group developed a marked abnormality in the shape of the cricoid cartilage in the injured region. Cartilage of the perichondriallly injured animals in the 8-week and 1(1/2)-year groups became histologically consistent with fibrous tissue. The cartilage of all animals that underwent intracartilaginous injury was replaced with fibrous tissue.

CONCLUSION

In this observational study, we identified 3 relevant findings. First, the responses of the cartilage to a perichondrial injury suggest that the luminal soft tissues may exert some morphologic control in developmentally young animals. Second, only the 4-week-old group's cartilage was tolerant of a perichondrial injury with continued growth of the ring. Third, no animal's cartilage could withstand an intracartilaginous injury regardless of age.

[Perforation of the laryngeal mucosa caused by closed trauma: comparison of laryngoscopic and CT findings]

INTRODUCTION

Laryngeal mucosal perforation is a frequent event whose diagnosis is based on clinical, laryngoscopic and CT findings.

MATERIAL AND METHODS

We reviewed retrospectively the data relative to 77 patients with blunt neck trauma examined October, 1991, to June, 1996. All patients were submitted to clinical examination first and then, to fiberoptic laryngoscopy and CT on the clinician's request.

RESULTS

Nineteen patients with small skin tears and no signs and symptoms of laryngeal injury were immediately discharged while 37 patients were submitted to surgery: 17 to remove cerebral hematomas, 13 to stabilize cervical fractures and 7 because of hemodynamic instability. Twenty-one patients underwent laryngoscopy which showed laryngeal lesions in 12: wide mucosal disruption with fractures of the laryngeal skeleton and hematomas were observed, which needed immediate surgery with airway reconstruction in 7 cases; small mucosal tears and hematomas were seen and laryngeal CT examination was requested to establish the possibility of conservative management in 5 cases which are the subject of the present study. Laryngoscopic findings were: 1) laryngeal mucosal tear near the thyroid cartilage with quadrangular membrane edema, 2) thyroid mucosal tear with thyrohyoid muscle edema, 3) edema of the left false vocal cord, 4) edema of the oblique arytenoid muscle, 5) posterior cricothyroid muscle edema with bleeding near the cricoid ring. In cases 1, 2 and 3 CT showed gas bubbles in the paralaryngeal space, where laryngeal tear or edema were indicated at laryngoscopy.

DISCUSSION

CT does show the "gas bubbles" in the paralaryngeal space when laryngoscopy cannot distinguish laryngeal mucosal perforation from tear.

CONCLUSIONS

The routine use of CT in minor, laryngeal injuries in the emergency department is useful for the early diagnosis of laryngeal mucosal perforation.

Dexamethasone treatment does not ameliorate subglottic ischemic injury in rabbits

BACKGROUND

Following tracheal intubation, a small proportion of patients develop laryngeal inflammation or tissue necrosis severe enough to result in clinical symptoms. Although corticosteroids are frequently advocated to prevent such injury, human studies have been inconclusive because of the low incidence of the problem. This study developed a rabbit model of endotracheal tube-induced laryngeal injury to test the hypothesis that a corticosteroid, dexamethasone, could ameliorate the inflammation and necrosis.

METHODS

Subglottic injury was induced in 21 anesthetized rabbits by inflating the cuff of an endotracheal tube to 100 mm Hg with the cuff just below the vocal cords. Every 30 min for 2 h, the cuff was deflated, the tube turned 90 degrees, and the cuff then reinflated. After 2 h, the rabbits' tracheas were extubated. Rabbits were divided into two groups: the treatment group received dexamethasone (1 mg/kg) i.v. 1 h prior to extubation with the dose repeated 6 h following extubation; the untreated group received a saline solution placebo. Four additional rabbits were anesthetized for the same period but did not have a tracheal tube inserted. All rabbits were killed 24 h later and the larynxes were harvested. Sections through the larynx at the level of the cricoid cartilage were randomized and submitted blindly to a veterinary pathologist. Larynxes were scored and ranked according to the severity of mucosal inflammation and necrosis, and submucosal hemorrhage, edema, inflammation, and necrosis. Specimens were also evaluated for focal vs diffuse disease.

RESULTS

Injured rabbits demonstrated focal to diffuse mucosal and submucosal inflammation and necrosis. Inflammatory exudates were present in sections from most of the injured rabbits and large sections of the larynxes were denuded of epithelium. There were no differences in injury scores between the treated and untreated rabbits. The four uninjured control rabbits had normal larynxes.

CONCLUSIONS

Two hours of endotracheal tube cuff inflation to 100 mm Hg causes an inflammatory laryngeal injury. The histologic features of the injury are unaltered by treatment with 2 mg/kg dexamethasone.

Bilateral vocal cord paralysis associated with diabetes mellitus: case reports

The manifestations of diabetic neuropathy are diverse. However, cases affecting the lower cranial nerves are rarely seen. We report three cases of previously unreported, bilateral, vocal-cord palsy associated with diabetes mellitus: a presumed relationship.

Laryngeal complications of prolonged intubation

In this study, 82 patients who experienced translaryngeal intubation (TLI) for more than four days were prospectively evaluated for laryngeal complications. At the time of extubation or tracheostomy, direct laryngoscopy was performed in these patients and laryngeal damage evaluated. A typical pattern of laryngeal damage was seen, consisting of mucosal ulcerations along the posterior-medial aspects of both vocal cords and varying degrees of laryngeal edema in 77 patients (94 percent). Performance of a tracheostomy and presence of neuromotor activity were associated with the severity of laryngeal damage, but duration of TLI was not. Laryngoscopy was repeated at two-week intervals in 54 patients and laryngeal damage was resolved within four weeks in 63 percent. These 54 patients were evaluated for adverse clinical effects arising from TLI-induced laryngeal pathology and no relationship was found between laryngeal pathology seen at initial laryngoscopy and the development of adverse effects.

Laryngeal injury from prolonged endotracheal intubation

This project was undertaken to develop models of acute and chronic laryngeal intubation as a format for testing a newly designed endotracheal tube. The tube has a specially created laryngeal cuff designed to reduce pressure exerted against the laryngeal soft tissues. The laryngeal foam cuff was shown to prevent the injurious sequence of mucosal ischemia, ulceration, and cartilage damage. A laryngeal foam cuff has the potential to significantly reduce laryngeal injury from prolonged endotracheal intubation. A prospective randomized clinical trial has been initiated and will be reported subsequently.

Airway reconstruction following laryngotracheal thermal trauma

Care of burn patients is a complex problem for the trauma team involving management of fluid and electrolyte imbalances, infections, and ultimately reconstruction. Patients with burns of the head, neck, and upper thorax present a series of unique problems because of a high incidence of associated upper and lower airway thermal trauma necessitating intubation and ventilatory support. A series of cases requiring laryngotracheal reconstruction following severe burns to the head and neck region is reported. Methods of treatment are discussed as well as modifications of standard burn therapy to decrease the incidence of severe scarring.

Unilateral degloving injuries of the arytenoid cartilage

Arytenoid cartilage dislocations and avulsions are often seen as a part of severe laryngeal injuries due to blunt trauma. An uncommon type of injury is the unilateral degloving of an arytenoid cartilage following laterally directed trauma to the thyroid cartilage. It may occur without additional cartilaginous or mucosal damage. The arytenoid cartilage is squeezed between the thyroid ala and the cervical spine and stripped of its mucosal covering. It may retain mobility and be exposed only on adduction, or it may lose mobility due to dislocation and be tipped into the laryngeal lumen. Prognosis for vocal cord mobility and voice production is good for the degloving injury alone, but poor if the arytenoid cartilage is also dislocated. Cases are discussed to illustrate the mechanism, treatment, and outcome of such injuries.

Early recognition and treatment of postintubation dysphonia

The most common complication of prolonged endotracheal intubation is vocal change. This dysphonia is a result of the laryngeal pathology produced by the recurrent frictional irritation of the endotracheal tube with each respiratory exchange. The purpose of this paper is to present three representative cases, stress early recognition, and outline a course of vigorous early treatment which has proved to be successful in alleviating and reducing the prolonged symptoms of this iatrogenic dysphonia.

[Extension of traumatic mucosal changes and their relevance in reconstructive surgery in laryngeal and tracheal stenoses following long-term intubation (author's transl)]

Serial light and electron microscopy studies done to determine the earliest that significant mucosal changes occur after translaryngeal intratracheal long-term intubation show that, as well as a penetrating lesion at the site of the pressure effect of the tube, there is a mucosal injury which extends up and down away from the focus of the lesion. This is a consequence of trauma, and away from the site of the trauma, three differing zones of mucosal change can be identified. Cognisance of this explains the healing problems that can occur following reconstructive surgery, particularly in the border area between seemingly undamaged tissue and preserved or directly grafted tissue. Instructions in regard to avoiding unsatisfactory surgery is given.