Feasibility of the laryngeal tube airway for artificial ventilation in pigs and comparison with the laryngeal mask airway

Airway management in anesthetized pigs is known to be technically demanding, and the 'gold standard' technique of endotracheal intubation is particularly difficult to master. The authors investigated the feasibility of the laryngeal tube as an alternative technique for airway management in German Landrace pigs (n = 5). They compared this method with the laryngeal mask, which is considered to be an effective yet relatively straightforward tool for porcine airway management. One after the other, investigators attempted to establish an airway in each anesthetized, artificially ventilated pig using each device. The laryngeal tube was too short to intubate the largest pig (weighing 45 kg), and it took investigators slightly longer to insert this device compared with the laryngeal mask. With the laryngeal mask, there were several incidents of gastric insufflation. Despite these complications, all investigators were able to establish a secure airway and maintain oxygenation with the laryngeal tube, and all subjectively rated both devices as easy to use.     

The laryngeal mask airway in experimental pig anaesthesia

The pig is used as a large animal model in many research projects. Standard practice for airway maintenance under general anaesthesia is using endotracheal (ET) intubation after intravenous induction to a near surgical plane. This is a technically demanding skill, requiring the assistance of an experienced technician. A technique is required which simplifies pig anaesthesia. This study examined the feasibility and potential advantages of using the laryngeal mask airway (LMA) in 10 pigs during laparotomy under spontaneous breathing anaesthesia. The results show that the LMA can be inserted rapidly, with minimal time for airway control by researchers relatively inexperienced in anaesthesia and is associated with few complications. By removing the need for intravenous induction, an entire step in the anaesthetic process is removed. The LMA designed for humans fits well in the pig hypopharynx; all pigs could be manually ventilated with no detectable gas leak. Although the pigs in this study were spontaneously breathing it is proposed that the LMA should be further investigated in studies of artificially ventilated pigs.     

Videoendoscopic endotracheal intubation of the rat

Mechanical ventilation is essential to the proper maintenance of anaesthesia in research animals undergoing laparoscopic research investigations with prolonged pneumoperitoneum. Ventilatory assistance is greatly aided by endotracheal intubation, which in rats can be a challenging procedure with a substantial risk of complication. The difficulty of the procedure arises primarily from the limited exposure and access to the laryngeal opening. We describe a simple and safe technique for endotracheal intubation in the rat that permits the introduction of a large-bore tube under direct visualization using equipment commonly found in the endosurgical research setting.     

Endotracheal Tube Perforation of the Hypopharynx

Perforation of the hypopharynx or esophagus is a serious though not often reported complication of endotracheal intubation. Only 12 cases had been reported before the eight which are presented here to emphasize this hazard of intubation. The early symptoms of perforation, which occurred during insertion of the tube, were: subcutaneous emphysema (seven patients), mediastinal emphysema (six), pneumothorax (two), cardiac arrest (one). One patient had no recognized early signs of perforation, but presented with an abscess of the mediastinum six weeks later. The site of perforation, determined by endoscopy in six patients, was the lateral hypopharynx in four, and the vallecula in two. The outcome of the eight perforations was as follows: two patients recovered on conservative management; in two, abscesses of the neck and in one an abscess of the mediastinum developed. All three recovered after drainage of the abscesses. Three patients died. Two outstanding characteristics of these eight cases were that in all of them intubation was attempted by physicians relatively inexperienced in the technique, and in all but one it was done in emergency. Since the use of intubation in emergency situations is increasing, all physicians in training should receive formal instruction in technique.     

喉罩与气管插管在呼吸衰竭患者院前和急诊急救中的应用效果比较

目的:探讨喉罩与气管插管在呼吸衰竭患者院前和急诊急救中的应用效果。方法:选择2016年1月至2018年5月由中国人民解放军第174医院急诊医学科出诊抢救的呼吸衰竭患者92例,所有患者根据通气方法的不同分为A组和B组。其中A组使用喉罩人工通气方法进行急救,共有47例,而B组则使用气管插管人工通气方法进行急救,共有45例,比较两组患者治疗前与治疗1 h后呼吸频率(RR)、心率(HR)以及血氧饱和度(SpO_2)等生命体征指标,对比喉罩与气管插管置入时间、一次性成功率、心肺复苏成功率情况,记录两组并发症发生情况。结果:两组患者治疗前HR、RR以及SpO_2比较差异无统计学意义(P0.05),两组患者治疗1 h后HR、RR均较治疗前降低,SpO_2较治疗前升高(P0.05),两组患者治疗1h后HR、RR以及SpO_2比较差异无统计学意义(P0.05)。A组的喉罩插管置入时间明显短于B组的气管插管置入时间,且A组插管一次性成功率明显高于B组,两组比较差异具有统计学意义(P0.05),而两组心肺复苏成功率比较差异无统计学意义(P0.05)。A组并发症发生率为2.13%(1/47),低于B组的并发症发生率13.33%(6/45),差异具有统计学意义(P0.05)。结论:喉罩通气与气管插管通气效果基本一致,但其操作更简单更安全,可缩短插管置入时间,提高一次性成功率,争取抢救时间。     

Airway management with the laryngeal tube in rabbits

The rabbit's oropharyngeal anatomy complicates the use of endotracheal intubation for airway management during surgical procedures. To determine if the laryngeal tube is useful for airway management in rabbits, the authors applied the device and evaluated its efficacy to ventilate the lungs. The laryngeal tube was inserted blindly and without difficulty in six healthy male New Zealand White rabbits; all of the rabbits were ventilated adequately with and without neuromuscular blockade. The authors conclude that the laryngeal tube can be used as an alternative means of airway management in rabbits.     

Voice changes after thyroidectomy: role of the external laryngeal nerve.

Hitherto voice changes have been regarded as an infrequent complication of thyroidectomy and damage to the recurrent laryngeal nerve has been given as their major cause. Voice function was assessed in 325 patients after thyroidectomy. Permanent changes occurred in 35 (25%) after subtotal thyroidectomy and in 19 (11%) after lobectomy. The commonest cause of voice change appeared to be injury to the external laryngeal nerves on one or both sides. Damage to the recurrent laryngeal nerve, which was routinely identified and protected, was rarely a cause. When the external laryngeal nerves were identified and preserved, permanent voice changes occurred in only 5% of cases; this was similar to the incidence of 3% in controls after endotracheal intubation alone. The course of the external laryngeal nerve is variable, and consequently mass ligation of the vessels at the top of the upper pole will damage it in a high proportion of cases. To minimise this serious complication these nerves should be identified and protected as well as the recurrent nerves and voice function should be assessed early in the postoperative period by laryngoscopy and by a speech therapist.     

Oral endotracheal intubation of rats for intratracheal instillation and aerosol drug delivery.

As reported in the literature, oral endotracheal intubation of rats is considered to be very difficult. Specialised equipment and complicated techniques have been described to perform this procedure. In our experiment we adopted a simple method, which allowed-without any complicated equipment-the insertion of a relatively wide tube into the trachea of rats, allowing drug administration.     

Use of the laryngeal mask airway in rabbits: placement and efficacy

The laryngeal mask airway (LMA) has been used in various animal species anesthetized for the purpose of device evaluation, but the device has not been evaluated in rabbits during surgery. The authors tested the feasibility and potential advantages of using the LMA in 50 rabbits undergoing surgery under spontaneous-breathing inhalational anesthesia, focusing mainly on the technique of insertion and its efficacy. The LMA was easily inserted and no air leakage at the larynx was detected. Although four rabbits developed lingual cyanosis, this was reversible and most likely due to lingual vascular compression by the LMA. The authors conclude that the LMA is an attractive alternative to endotracheal intubation, as the mask can be inserted easily and rapidly and its correct placement is easily confirmed.     

Simplified rat intubation using a new oropharyngeal intubation wedge.

Our new oropharyngeal intubation wedge made from a plastic 3-ml syringe has been used successfully for the expansion of the oropharyngeal cavity and visualization of vocal cords for endotracheal intubation in the rat. All the animals we used tolerated the intubation and ventilation procedures in a series of experiments. After the proper setting of the respirator, vital signs were maintained within normal range. The postmortem examination and measurements in the upper airway confirmed that the endotracheal tube was properly sited and also demonstrated the precise size of the device that should be used. The main advantages of this method include low cost, simplicity, and reliability. Furthermore, because no expensive, elaborate, difficult-to-operate, or hard-to-get special equipment is needed, this technique can be used in every laboratory.     

大鼠气管插管方法学概述

由于大鼠呼吸频率较快、口腔狭小、声门较高,医学实验中气管内插管操作具有较多困难,多年来很多学者对大鼠气管内插管方法进行了大量研究。本文主要对大鼠气管内插管时动物和气管导管的选择、麻醉方式、插管的体位以及各种插管工具和方法等作一简要的综述。     

A case of mistaken identity: accidental ingestion of coins causing esophageal impaction in an elderly female

Coin impaction of the esophagus is infrequently seen in adults, and multiple coin impaction has not been described. The patient was an 85-year-old blind female who presented with 2 days of dysphagia and odynophagia following an attempt to take her medications at bedtime. She reported an esophageal injury from endotracheal intubation during a surgery 6 months earlier. Radiographs showed a radiopaque circular mass in the midesophagus. Endoscopy showed 3 US coins--a nickel, a dime, and a penny--stacked together and impacted on a stricture at 27 cm from the gums. An overtube was planned, but preplacement evaluation showed the lumen was smaller than the coin diameters. An attempt with a retrieval net was unsuccessful. The patient then underwent endotracheal intubation and the coins were removed individually with rat-tooth foreign body forceps. She recovered and underwent successful endoscopic dilation 3 weeks later. She remains asymptomatic since dilation. A brief review of coin impaction and endoscopic management is discussed. Endotracheal intubation for airway protection during endoscopy is recommended for these patients.     

发光管芯引导插管在感染手术气道处理中的应用

目的:观察和评估发光管芯在感染手术患者麻醉常规气管内插管和预测困难气管内插管的适用性与安全性,并比较改变光棒前端弯曲角度的临床实用效果。方法:选择136例ASA I~Ⅲ级全麻下行择期手术的肝炎后肝硬化患者,其中正常气道120例,可顺利气管插管,120例患者按照插管时弯曲光棒角度不同随机分为A组(60°)和B组(90°);困难气道插管患者分为C组(90°)。分别记录各组插管时间、插管次数、插管的成功率、插管期间血流动力学变化以及术后并发症情况,同时测量医生与患者呼吸道之间的距离。结果:A、B和C组的一次插管成功率分别为100%、96.6%和81.2%,时间分别为(12.3±3.8)s、(13.2±4.1)s和(18.2±5.5)s,三组各自的插管总成功率均为100%。而且改变光棒前端角度的A组插管时间均较B、C组短,发现光棒插管对循环功能的影响小,术后并发症少,医生与患者呼吸道之间的距离为(34±4)cm。结论:在感染手术患者气管插管过程中使用发光管芯引导插管成功率高、对患者的循环影响低且术后并发症少,更为重要的是降低了医务人员与传染性患者近距离接触的机率。     

A simple laryngoscopic technique for the endotracheal intubation of rabbits

A safe and reliable technique for the endotracheal intubation of rabbits is described. Direct laryngoscopy is followed by intubation of the trachea with a fine catheter, and subsequent advancement of the endotracheal tube over this catheter.     

An improved method for direct laryngeal intubation in the guineapig.

A novel method of direct laryngeal intubation in the guineapig, using a modified laryngoscope blade, is described. The method has been used in over 400 animals and has proved suitable for recovery procedures and repeated intubation.     

The oesophageal obturator airway: a new device in emergency cardiopulmonary resuscitation.

Experience with 29 000 cases in which the oesophageal obturator airway has been used in cardiopulmonary resuscitation indicates its safety, efficacy, and ease of use. Blood gases, fractional inspired oxygen, and pH were measured in 18 patients given both the oesophageal obturator airway and the endotracheal tube; there was no significant difference between the two. The former was found to be inserted more rapidly and reliably; moreover, paramedical staff are quickly trained to use it. It is concluded that the oesophageal obturator airway provides the technique of choice whenever ideal conditions and facilities--and trained staff--for endotracheal intubation are not immediately available.     

Velocity profiles in central airways with endotracheal intubation: a model study

Steady inspiratory velocity profiles were measured at two flow rates in a 3:1 scale model of the human central airways in the presence of five modes of endotracheal intubation. The presence of an orifice or a short endotracheal tube had no significant effect on the velocity profiles distal to the carina. Long endotracheal tubes change the profiles in both main bronchi. A significant peak occurred in the frontal plane near the walls, and the maximum velocity in the airway was almost identical to the endotracheal tube center-line velocity. The flow impinging on the medial wall of the main bronchus was redirected up around the anterior and posterior walls yielding bipeak velocity profiles in the sagittal plane. A tube placed eccentrically in the trachea over the right main bronchus did not alter the velocity profiles in the left main bronchus, suggesting a redirection of flow over the carina into the left lung. An endobronchial tube at the mouth of the right main bronchus did change the shape of the velocity profiles in the left main bronchus. In the left upper lobar bronchus the presence of trachea intubation had no effect on the velocity profiles. However, in the right upper lobar bronchus, the long endotracheal tube flattened the velocity profiles from the strongly skewed ones seen in the absence of the endotracheal inserts. These results not only are relevant to distribution of ventilation and aerosol particle deposition, but also have strong implications in intrapulmonary gas mixing, especially when high-frequency low tidal-volume ventilation is involved.     

Transoral tracheal intubation of rodents using a fiberoptic laryngoscope

A fiberoptic laryngoscope which allows direct visualization of the deep pharynx and epiglottis has been developed for transoral tracheal intubation of small laboratory mammals. The device has been employed in the intubation and instillation of a variety of substances into the lungs of rats, and with minor modification, has had similar application in mice, hamsters, and guinea pigs. The simplicity and ease of handling of the laryngoscope permits one person to intubate large numbers of enflurane anesthetized animals either on an open counter top or in a glove-box, as may be required for administration of carcinogenic materials. Instillation of 7Be-labeled carbon particles into the lungs of mice, hamsters, rats, and guinea pigs resulted in reasonably consistent interlobal distribution of particles for each test animal species with minimal tracheal deposition. However, actual lung tissue doses of carbon exhibited some species dependence.     

Simplification of rat intubation on inclined metal plate

Small-animal intubation is often necessary during inhalation anesthesia to allow steady-state conditions for large operations and in vivo experiments in all fields of experimental surgery. In rats, placing an orotracheal tube is technically difficult primarily because of the small size of the subject and the lack of equipment specifically designed for this task. We describe a simple rat intubation technique in which the animal is suspended in dorsal recumbency on an inclined metal plate. The animal, anesthetized with ether, is fixed to a 70 degrees-inclined metal plate in a dorsal position by means of a Mersilene ribbon hooked around the upper incisors. This method of positioning the animal is the most important step in the intubation process and further facilitates the technique already described by other authors. A human otoscope was used as a laryngoscope, intubation was performed using the Seldinger technique, and a 14-gauge intravenous catheter served as an endotracheal tube. This inexpensive technique is quickly learned and can be used in any laboratory. Safe and reliable airway management can thus be achieved, permitting in vivo examinations and operations.     

Anaesthetics for General Anaesthesia in Growing Pigs

A comparison was made between different anaesthetics for general anaesthesia in growing pigs, with focus on minor surgery under field conditions and for experiments in clinical research. Healthy crossbreed pigs (HampshirexYorkshirexSwedish Landrace) weighing 20–45 kg were used. The anaesthetics combinations compared were 1) azaperone plus metomidate (AM), 2) Zoletil® (zolazepam + tiletamine) plus xylazine (ZX), and 3) Zoletil® plus xylazine plus ketamine (ZXK). Parameters measured were: heart rate, respiratory rate, blood pressure, body temperature, and depth of analgesia (pin-prick). Minor surgery was performed to test the reliability of the “pin-prick” tests. It was clearly shown that AM produces anaesthesia with good cardiovascular stability and is a drug combination that is suitable for minor surgery. ZX also produces a good anaesthesia characterized by reliable and rapid induction. Good cardiovascular function is maintained, and the laryngeal relaxation makes intubation possible. These characteristics are very useful in a laboratory environment, as easy handling to avoid stress is necessary for research. Although it is difficult to evaluate the quality of analgesia from this study, it is concluded that ZX did not provide a superior anasthesia and analgesia compared to AM in crossbreed pigs. However, these drugs are too expensive for regular use in ambulatory practice. The effects of ZXK resemble those of ZX, but the ZXK-drug combination has no anaesthetic advantages and is more laborious to work with. kw|Keywords|k]azaperone; k]metomidate; k]Zoletil®, xylazine; k]ketamine