Developmental changes of laryngeal dimensions in unparalyzed,sedated children

BACKGROUND: Knowledge of the influence of age on laryngeal dimensions is essential for all practitioners whose interest is the pediatric airway. Early cadaver studies documented that the larynx is conically shaped, with the apex of the cone caudally positioned at the nondistensible cricoid cartilage. These dimensions change during childhood, as the larynx assumes a more cylindrical shape. The authors analyzed laryngeal dimensions during development to determine if this relationship continues in unparalyzed children in whom laryngeal muscles are tonically active. The authors determined the relationships between the vocal cord, sub-vocal cord, and cricoid ring dimensions and the influence of age on these relationships. METHODS: Infants and children undergoing magnetic resonance imaging with propofol sedation had determinations of the transverse and anterior-posterior (AP) dimensions of the larynx at the most cephalad level of the larynx (vocal cords) and the most caudad level (cricoid). Most patients had an additional measurement (sub-vocal cord) at a level between the vocal cords and the cricoid ring. Relationships were obtained by plotting age against laryngeal dimensions and the ratio of laryngeal dimensions at different levels within the larynx. RESULTS: The authors measured transverse and AP laryngeal dimensions in 99 children, aged 2 months-13 yr. The relationship between the transverse and AP dimensions at all levels of the larynx did not change during development. Transverse and AP dimensions increased linearly with age at all levels of the larynx. In all children studied, the narrowest portion of the larynx was the transverse dimension at the level of the vocal cords. Transverse dimensions increased linearly in a caudad direction through the larynx ( P< 0.001), while AP dimensions did not change relative to laryngeal level. The shape of the cricoid ring did not change throughout childhood. CONCLUSIONS: In sedated, unparalyzed children, the narrowest portions of the larynx are the glottic opening (vocal cord level) and the immediate sub-vocal cord level, and there is no change in the relationships of these dimensions relative to cricoid dimensions throughout childhood.     

The effect of cricoid pressure on the cricoid cartilage and vocal cords: an endoscopic study in anaesthetised patients

Cricoid pressure is used to protect the lungs from contamination with gastric contents during tracheal intubation. We studied the effect of cricoid pressure applied with a yoke on 30 anaesthetised patients examined fibreoptically through a laryngeal mask airway. We assessed the effect of 20, 30 and 44 N on the internal appearance of the cricoid and vocal cords. Difficulty in ventilation was also recorded. At 44 N, cricoid deformation occurred in 27/30 patients (90%) and 15/30 (50%) had cricoid occlusion [13/30 (43%) had cricoid occlusion at 30 N and 7/30 (23%) at 20 N]. Associated difficulty in ventilation was present in 15 patients (50%) and 18/30 (60%) had vocal cord closure with associated difficult ventilation, at forces up to 44 N. Cricoid occlusion was unrelated to age and body mass index but females were at greater risk. Orthodox values of cricoid pressure, applied with a yoke, may produce obstruction at the level of the cricoid cartilage or vocal cords, with implications for tracheal intubation and ventilation by mask.     

Primary tracheal anastomosis after resection of the cricoid cartilage with preservation of recurrent laryngeal nerves.

Resections at the cricoid level pose the problems of damage to the recurrent laryngeal nerve and loss of circumferential cartilaginous support. Strictures within the cricoid ring have usually been managed with keels or stents, whereas neoplasms have been managed by laryngectomy. This paper reports on 6 patients with lesions involving the cricoid who were successfully treated by segmental tracheal resection and removal of all but a thin shell of posterior cricoid plate. The distal trachea was anastomosed at the subglottic level within 1 cm. or less of the vocal cords. Two patients had traumatic transection at the cricotracheal level with disruption of cricoid cartilage and avulsion of both recurrent nerves. Of the other 4 patients with tracheal lesions involving the cricoid, 2 had postintubation strictures, another had chemical burns, and the fourth had adenoid cystic carcinoma. Primary healing and good clinical results were obtained in all 6 patients. In the 4 patients with intact recurrent nerves, nerve function was preserved. This technique provides a method for resection and reconstruction in one stage for selected lesions at the cricoid level.     

Simultaneous determination of neuromuscular blockade at the adducting and abducting laryngeal muscles using phonomyography

Phonomyography (PMG) is a new method for measuring neuromuscular blockade (NMB) at the larynx. In this study, we used PMG to compare NMB at the posterior cricoarytenoid (PCA) and the lateral cricoarytenoid muscle (LCA) in humans. Twelve patients were included in this study. Endotracheal intubation was performed without aid of neuromuscular blocking drugs. One small condenser microphone was inserted beside the vocal cords into the muscular process at the base of the arytenoid cartilage to record acoustic responses of the LCA (vocal cord adduction), and a second microphone was placed behind the larynx to measure NMB of the PCA (vocal cord abduction). Stimulation of the recurrent laryngeal nerve was performed using superficial electrodes placed at the neck (midline between jugular notch and cricoid cartilage) using train-of-four (TOF) stimulation every 12 s. After supramaximal stimulation, mivacurium 0.1 mg/kg was injected and onset, peak effect, and offset of NMB measured and compared using t-test (P < 0.05). The data are presented as mean (SD). Peak effect, onset time, and early recovery to 25% of control twitch height were not significantly different between PCA and LCA at 86% (13) versus 78% (16), 2.3 min (0.45) versus 2.3 min (1.0), and 9.55 min (3.05) versus 8.5 min (4.7), respectively. However, recovery to 75%, 90% of control twitch height, and recovery to a TOF ratio of 0.8 were significantly longer at the PCA than at the LCA at 14 min (4) versus 11 min (5), 17 min (5) versus 11.8 min (5.6), and 17.5 min (5.6) versus 12.3 min (5.5), respectively. The authors conclude that recovery of NMB at the PCA takes longer than at the LCA in humans after mivacurium. IMPLICATIONS: After neuromuscular blockade in humans, the recovery of the ability to open the vocal cords takes longer than the ability to close the vocal cords.     

Opening and closing mechanisms of the larynx

Opening and closing of the larynx are determined by the intrinsic and extrinsic muscles acting on the elastic forces in the tongue, pharynx, larynx, and trachea. The pharynx is opened or closed by two mechanisms: (1) Contractions of the cricothyroid and of the intrinsic muscles of the larynx open and close the vocal cords. (2) The false cords, ventricle, and true cords accordion open or close in a bellows mechanism. We conclude that the posterior cricoarytenoid opens the laryngeal airway. The cricothyroid together with the posterior cricoarytenoid accentuates this opening. The larynx is also opened by the geniohyoid, mylohyoid, sternothyroid, and middle constrictor. The thyrohyoid, cricothyroid, sternohyoid, and inferior constrictor close the laryngeal airway. Abnormalities in the soft tissues of the neck or of the innervation of the larynx, pharynx, and neck muscles may severely interfere with patency of the laryngeal airway. This occurs in such conditions as vocal cord paralysis, sleep apnea, multiple sclerosis, amyotrophic lateral sclerosis, spastic dysphonia, mandibular fractures or hypodevelopment, and cerebrovascular disease.     

Transcutaneous electrical stimulation of the recurrent laryngeal nerve: a method of controlling vocal cord position

This study was designed to examine the feasibility of transcutaneous stimulation of the recurrent laryngeal nerve. Electrical activation of the recurrent laryngeal nerve was achieved by applying a blunt electrode to the intact neck skin at specific points along the tracheoesophageal groove in anesthetized adult dogs. The stimulus consisted of 10 mA cathodal pulses, each of 1 msec duration, delivered at a frequency of 10 Hz and increased by 10 Hz increments up to 100 Hz. Vocal cord excursion was directly related to the frequency of applied current. In all six dogs studies, stimulation at 30 Hz resulted in maximal ipsilateral vocal cord abduction, while stimulation at frequencies greater than 40 Hz resulted in ipsilateral vocal cord adduction up to or across the midline. Vocal cord movement was immediate and persisted for the duration of the stimulus train. Surrounding neck muscles were not visibly activated. We propose that the observed frequency-dependent movement of the vocal cords occurred because of the difference between the contraction times of the intrinsic abductor and adductor muscles of the larynx. Transcutaneous recurrent laryngeal nerve stimulation appears promising, both as a diagnostic aid in laryngoscopy and as a therapeutic tool in controlling the glottic aperture.     

Upper airway dimensions in children using rigid video-bronchoscopy and a computer software: description of a measurement technique

Background: Pediatric airway management decisions are based primarily on results derived from indirect measures of laryngeal and tracheal dimensions. More recent methods could provide more direct information about absolute and relative changes in airway dimensions associated with growth and development. Study Objectives: The aims of this study were (i) to determine whether a ‘video‐bronchoscopic’ measurement method could be used to reliably measure airway dimensions in children and (ii) to provide a preliminary assessment of dimensions of the glottis and cricoid in children of various ages. Methods: Following approval from the institutional review board, validation experiments were performed to determine whether measurements obtained from the video image from the bronchoscope provided accurate measurements of tubular objects of known dimensions. The reliability of the measurements was determined by using two independent trained observers to measure video‐bronchoscopic images of the larynx at the level of the glottis and the cricoid in 11 children. The observers measured the video‐bronchoscopic images and airway measurements were obtained in 16 additional children to determine the utility of the measurement method. Results: There was good agreement between the direct and video‐bronchoscopic measurement techniques (Bland and Altman plot) for both the cross‐sectional area (CSA) and the diameter of objects. The interobserver measures for cricoid and glottis were reproducible as indicated by the concordance correlation coefficient (CCC) for cricoid anteroposterior diameter (CCC = 0.98, r = 0.98, accuracy = 0.99) and transverse diameter (CCC = 0.93, r = 0.8, accuracy = 0.99) as well as for the glottic anteroposterior diameter (r = 0.8, accuracy = 0.8, CCC = 0.6) and the glottic transverse diameter(r = 0.8, accuracy = 0.74, CCC = 0.6). Overall, for the 27 children studied [mean age 73 months (±24.7, range 30–140], the mean value of the cricoid CSA [45.3 mm² (±13.9)] was found to be greater than the glottic CSA [16.2 mm² (±10.1)]. Conclusions: The video‐bronchoscopic imaging method provided an accurate, reliable measure of pediatric airway dimensions. This technique could be applied to assess absolute and relative airway size associated with growth and development. The relationship between glottic and cricoid dimensions during growth and development in children needs further investigation across various age groups.     

Laryngeal reflex before and after placement of airway interventions: endotracheal tube and laryngeal mask airway

BACKGROUND: Previous reports indicate that detrimental laryngeal function persists over several hours after tracheal extubation even in patients who have regained full consciousness from anesthesia. The authors hypothesize that even after minor surgery, the presence of an endotracheal tube (ETT) impairs the receptors at the vocal cord and diminishes the defensive laryngeal function. The hypothesis was tested by comparing types of experimentally induced laryngeal airway reflexes before and after surgery in anesthetized patients with use of either an ETT or a Laryngeal Mask Airway. METHODS: Twenty adult patients undergoing elective minor surgeries were randomly allocated into two groups, the ETT and Laryngeal Mask Airway groups, depending on the airway management method used during surgery. While maintaining sevoflurane at 1 minimum alveolar concentration, laryngeal and respiratory responses were elicited by instillation of distilled water on the vocal cords immediately before and after surgery. Furthermore, the vocal cord angles were endoscopically measured under complete paralysis. RESULTS: Some laryngeal reflex responses of both groups, particularly the cough reflex, were significantly attenuated after minor surgery. Significant narrowing of the glottic aperture was evident in patients with ETT placement but not in patients with Laryngeal Mask Airway placement. CONCLUSIONS: With either airway intervention, laryngeal defensive reflexes are depressed immediately after surgery even without visible laryngeal swelling. The sensory impairment attributable to the presence of an ETT cannot be the solo factor responsible for the modification of the defensive airway reflexes elicited from the larynx.     

Unsuspected difficult intubation caused by a laryngeal web

We report a case of unsuspected difficult intubation in an adult caused by laryngeal web formation in the anterior commissure of the larynx. After induction of anaesthesia, most parts of the posterior commissure of the vocal cords were seen clearly at laryngoscopy, but a 7.5-mm internal diameter (id) tracheal tube could not be advanced below the level of the vocal cords because of resistance. Intubation was re- attempted several times after oxygenation by mask with trials of smaller tubes. Finally, a 5.0-mm id cuffed tube was passed successfully through the vocal cords, and secured in place. Because of the unexpected difficulties in intubation, an otolaryngologist was consulted to examine the larynx with a microscope. A web of 0.5 cm in the anterior commissures was found which caused subglottic stenosis.      

A cadaver study to measure the adult glottis and subglottis: defining a problem associated with the use of double-lumen tubes

OBJECTIVE: To test the hypothesis that the adult cricoid diameter is the same or less than that of the glottis. DESIGN: Prospective. SETTING: A city mortuary. PARTICIPANTS: Adult cadavers undergoing autopsy. INTERVENTIONS: After removal of the organs, the trachea was opened above the first ring to allow access to the cricoid from below, and the cricothyroid membrane was cut so that passage of measuring sounds through the vocal cords from above could be confirmed. MEASUREMENTS AND MAIN RESULTS: In 79 male and 55 female cadavers, the largest of a graduated series of cylindrical sounds that the cricoid ring would accommodate was noted. Then the biggest size possible that could pass through the glottis was measured. Height and weight were recorded. In 68% of males and 76% of females, glottic diameter was greater than subglottic; in all other cases, it was the same. In none was it smaller. Correlation between height and cricoid diameter was 0.24 for male cadavers and 0.21 for female cadavers. Regression analysis showed females to average a cricoid diameter 3.5 mm less than males of the same height. CONCLUSIONS: The ruling diameter of the adult larynx is not the glottis but the cricoid ring. Its correlation with height is extremely poor, and it averages 3.5 mm less in females than males of the same height. These findings are important for thoracic anesthesiologists.     

Laryngeal Resistance before and after Minor Surgery: Endotracheal Tube versus Laryngeal Mask Airway™

Background: The placement of an endotracheal tube (ETT) may promote laryngeal swelling, which is an important cause of upper airway obstruction after extubation. The authors hypothesized that laryngeal swelling after ETT placement increases laryngeal resistance and tested that hypothesis by comparing postoperative laryngeal patency between patients with ETT placement and those with a Laryngeal Mask Airway(TM) (LMA(TM)).

Methods: Fourteen adult patients who underwent elective minor surgeries were randomly allocated to two groups whose airway would be managed through ETTs (the ETT group) or LMAs(TM) (the LMA(TM) group) during the surgery. While maintaining at sevoflurane 1 minimum alveolar concentration, the authors measured laryngeal resistance before and after surgery, during both spontaneous breathing and mechanical ventilation under complete paralysis. In addition, they endoscopically measured the vocal cord angle under complete paralysis.

Results: In association with marked swelling of the vocal cords, the vocal cord angle significantly decreased after surgery in the ETT group, whereas the angle did not change in the LMA group. Laryngeal resistance during mechanical ventilation significantly increased only in the ETT group. Laryngeal resistance during spontaneous breathing significantly increased after surgeries in both groups.     

A method to measure elicited contraction of laryngeal adductor muscles during anesthesia

The recurrent laryngeal nerve was stimulated with surface electrodes to produce vocal cord adduction, and the response was measured as pressure changes in the inflatable cuff of a tracheal tube positioned between the vocal cords. To test the linearity of the system, a model of the larynx consisting of a syringe barrel was constructed, and weights were applied to two bands of tissue simulating the vocal cords. Tests on Mallinckrodt size-7.5 tubes showed that the pressure increase produced by a given force was independent of baseline pressure in the range 10-30 mmHg. In addition, the pressure inside the inflatable cuff was linear with increasing weight (or force) for a baseline pressure of 10 mmHg. Thirty ASA physical status 1 or 2 adults were anesthetized with propofol and fentanyl. Tracheal intubation was performed in the absence of muscle relaxants, and the inflatable cuff of the tracheal tube was positioned between the vocal cords. Pressure inside the cuff was measured with an air-filled transducer. Stimulation was produced at different sites along the course of the recurrent laryngeal nerve. A surface electrode placed over the notch of the thyroid cartilage produced consistent adduction of the cords, measured as an increase of 8.9 +/- 5.1 mmHg (mean +/- standard deviation [SD]) in the cuff pressure. Neuromuscular blocking drugs produced train-of-four fade, and large doses abolished the response completely, ruling out direct muscle stimulation. It is concluded that this assembly can provide useful information on intrinsic laryngeal muscle function.     

Interscalene brachial plexus block: assessment of the needle angle needed to enter the spinal canal*

Attempts were made to place 8‐cm 22G needles into the spinal canals of four preserved cadavers using the skin entry point most commonly associated with the lateral interscalene brachial plexus block or Winnie approach (that is, at the level of the cricoid cartilage). Eleven successful attempts were confirmed by computed tomography. Needle angles that were cephalad, transverse or slightly caudad were associated with entry into the spinal canal at depths of 5.0 cm or less from the skin. The only needle entry into the spinal canal with a needle angle of > 50 degrees to the transverse plane (< 40 degrees to the sagittal plane) entered the intervertebral foramen at a depth of 7.7 cm from the skin. We conclude that the use of markedly caudad angulations of needles no longer than 5.0 cm may minimise the chances of spinal canal entry and spinal cord damage.     

Video imaging to assess neuromuscular blockade at the larynx

We describe video imaging as a technique for assessing neuromuscular blockade at the larynx. We sought to determine the stability and reproducibility of this technique and to compare the effect of succinylcholine at the adductor pollicis and the larynx. Ten patients were studied. Anesthesia was induced and maintained with propofol. The recurrent laryngeal nerve was stimulated superficially and movements of the vocal cords were recorded on videotape by using a fiberoptic bronchoscope passed via a laryngeal mask airway. Neuromuscular function was recorded at the adductor pollicis by using a mechanomyograph. Twenty images of the vocal cords were examined repeatedly by one investigator and by ten independent observers. The mean difference between the two sets of observations was 0.86 degrees with a correlation coefficient (r) of 0.997. For 3 min before the administration of relaxant the coefficient of variation in the cord movement during supramaximal stimulation ranged from 1%-4% (median 2.7%). After the administration of succinylcholine 1 mg. kg(-1) the times to loss of T1 at the larynx and hand were 63 +/- 15 s and 63 +/- 12 s respectively. Times to 25% recovery were 215 +/- 36 s at the larynx and 436 +/- 74 s at the hand and times to 75% recovery were 285 +/- 55 s and 525 +/- 85 s respectively. These results indicate that video imaging may be a useful research technique for estimating neuromuscular blockade at the larynx and that the time to onset of succinylcholine at the larynx is similar to that at the hand, whereas the duration of blockade is significantly shorter at the larynx. Implications: Assessment of neuromuscular blockade at the larynx is possible by using a video imaging technique. By using this technique, the time to onset of neuromuscular blockade at the larynx is similar to that at the hand after the administration of succinylcholine; this finding is different from previously published data obtained by using a cuff pressure measurement technique.     

Inhalational induction of anaesthesia with 8% sevoflurane in children: conditions for endotracheal intubation and side-effects

BACKGROUND AND OBJECTIVE: This study was designed to assess the conditions for endotracheal intubation or insertion of a laryngeal mask airway following an inhalational induction using 8% sevoflurane and nitrous oxide without the use of muscle relaxants or opioids. METHODS: There were two groups: 30 children had endotracheal intubation and 30 children had a laryngeal mask airway inserted. Induction of anaesthesia was accomplished using an inspiratory concentration of sevoflurane 8% in a nitrous oxide and oxygen mixture. After an end-expiratory concentration of sevoflurane of at least 4% had been reached, when the pupils were miotic and centred, the trachea was intubated or a laryngeal mask inserted. The time to loss of consciousness and successful airway management was recorded. Jaw relaxation, movements, visibility, and position of the vocal cords and vital parameters were monitored. RESULTS: Jaw relaxation was complete in all children. The vocal cords were completely visible in all patients of the tracheal intubation group, whereas vocal cord relaxation was incomplete in five children. Nevertheless, all children had an atraumatic intubation or insertion of the laryngeal mask without the use of a muscle relaxant. Vital signs were stable in both groups. There were no cases of restlessness and/or postoperative shivering. Four patients in the endotracheal group (13.3%) were nauseous and three (10%) vomited, while two children (6.6%) in the laryngeal mask group experienced nausea and vomiting. CONCLUSIONS: Induction with sevoflurane in nitrous oxide and oxygen leads to fast loss of consciousness and provides ideal conditions for managing the airway without supplemental opioids or muscle relaxants. Furthermore, sevoflurane using this technique was very well tolerated, indicated by high haemodynamic stability and a reduced rate of postoperative restlessness, shivering, nausea and vomiting.     

Laryngeal resistance before and after minor surgery: endotracheal tube versus Laryngeal Mask Airway

BACKGROUND: The placement of an endotracheal tube (ETT) may promote laryngeal swelling, which is an important cause of upper airway obstruction after extubation. The authors hypothesized that laryngeal swelling after ETT placement increases laryngeal resistance and tested that hypothesis by comparing postoperative laryngeal patency between patients with ETT placement and those with a Laryngeal Mask Airway trade mark (LMA). METHODS: Fourteen adult patients who underwent elective minor surgeries were randomly allocated to two groups whose airway would be managed through ETTs (the ETT group) or LMAs (the LMA group) during the surgery. While maintaining at sevoflurane 1 minimum alveolar concentration, the authors measured laryngeal resistance before and after surgery, during both spontaneous breathing and mechanical ventilation under complete paralysis. In addition, they endoscopically measured the vocal cord angle under complete paralysis. RESULTS: In association with marked swelling of the vocal cords, the vocal cord angle significantly decreased after surgery in the ETT group, whereas the angle did not change in the LMA group. Laryngeal resistance during mechanical ventilation significantly increased only in the ETT group. Laryngeal resistance during spontaneous breathing significantly increased after surgeries in both groups. CONCLUSIONS: Postoperative laryngeal resistance increases at least in part because of laryngeal swelling in patients with ETT placement, whereas alteration of laryngeal neural control mechanisms has been also indicated. The use of the LMA trade mark has an advantage over ETT placement in order to avoid postoperative laryngeal swelling.     

Experimental studies for correction of superior laryngeal paralysis by fusion of the thyroid to cricoid cartilages

Contraction of the cricothyroideus muscles (CTMs), innervated by the superior laryngeal nerves (SLNs), modulates the voice by tilting the thyroid cartilage anteriorly onto the top of the cricoid and tensing the vocal cords. Either unilateral or bilateral paralysis of the SLNs is disabling for individuals with above-average voice demands. Some patients never compensate for this paralysis; there is no surgical procedure recognized to correct it. This study tested the hypothesis that surgical fusion of the thyroid and cricoid cartilages anteriorly can correct the problems of SLN injury by duplicating the mechanical tilt of the thyroid onto the cricoid cartilage normally produced by the CTMs. The SLNs were cut in 12 dogs. In six the cricoid and thyroid cartilages were fused anteriorly. Vocal cord and airway function was assessed preoperatively, immediately postoperatively, and 6 to 10 weeks after surgery. Following surgery there was no airway compromise and there appeared to be a more satisfactory compensation for the SLN paralysis in the fused larynges as compared with the unfused controls as determined by cinelaryngoscopic analysis.     

CO2激光经口微创手术治疗喉部良、恶性病变

目的观察经口显微镜支撑喉镜下CO2激光治疗喉部良恶性病变的临床疗效,探讨激光喉部手术适应证。方法回顾性分析2008年11月～2012年5月经CO2激光治疗的喉部良恶性病变33例。上海得邦得力公司DJL-40C CO2激光机,激光波长为10600nm,脉冲模式0．1s,功率3～8w,光斑直径O．7—1．0mm。CO2激光机通过耦合器与Leica F40手术显微镜连接。良性病变18例,其中声带息肉3例,声带角化1例,喉乳头状瘤6例,声带白斑5例,喉蹼2例,双侧声带麻痹1例。恶性病变15例,其中声门上型喉癌4例,声门型喉癌11例。均采用经口显微镜支撑喉镜下CO2激光治疗。结果良性病变术后随访3—6个月,除1例喉乳头状瘤术后复发行二次激光手术外,其余全部一期愈合。恶性病变术后随访11—28个月,平均19月。术后复发1例,声带粘连1例,其余术后病变清除彻底,喉功能保存良好,无严重并发症发生。结论显微镜支撑喉镜下CO2激光治疗喉部良、恶性病变疗效可靠,能较好地保留喉结构和功能,是治疗喉疾病的重要手段。     

Post traumatic disruption of the laryngo-tracheal junction

Of 43 tracheo-bronchial ruptures, 19 patients presented with disruption of the laryngo-tracheal junction which would appear to be a very specific anatomical lesion. The disruptions were secondary to blunt cervical trauma in 11 cases and strangulation in 8 cases. The disruption was complete in 14 cases and incomplete in 5. The lesion is very complex and involved the retraction of the lower part of the trachea into the mediastinum (14 cases), fracture of the cricoid ring (9 cases), bilateral recurrent nerve tears (14 cases), unilateral (4 cases) and retraction of the laryngeal mucosa with exposure of the cricoid cartilage in all cases. According to the complexity of the lesion, the treatment was: laryngo-tracheal resection and end-to-end anastomosis with treatment of the vocal cord palsy in 13 patients; simple end-to-end anastomosis in 4 patients who had an unilateral vocal cord palsy; 2 patients with a partial disruption were treated medically with endoscopic stenting and laser photocoagulation. All had restoration of airway patency and recovery of voice. The results contrast with the failures and reoperations reported in the literature and underline the necessity of complete evaluation and treatment of these complex lesions.     

Noninvasive measurement of ablation crater size and thermal injury after CO2 laser in the vocal cord with optical coherence tomography.

OBJECTIVE: To characterize tissue destruction after CO(2) 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 microm 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.