Effect of continuous cuff pressure regulator in general anaesthesia with laryngeal mask airway

Postoperative pharyngolaryngeal complications (PPLC) occur during anaesthesia due to increased cuff pressure following the insertion of laryngeal mask airways. The use of a pressure regulator to prevent PPLC was evaluated in a prospective, randomized study. Sixty patients scheduled to receive general anaesthesia were randomly assigned to two equal groups of 30, either with or without the regulator. The 'just seal' cuff pressure (JSCP), cuff pressure at 5-min intervals during anaesthesia, incidence of pharyngeal sore throat (PST), dysphagia, dysphonia and other complications were evaluated at 1 and 24 h postoperatively. The combined mean ± SD JSCP of both groups was 20.3 ± 3.2 mmHg. In the group with the regulator, cuff pressure was maintained at a constant level during anaesthesia. This study demonstrated that the regulator is a simple, functional device that can reduce the incidence of PST significantly at 1 h postoperatively, following general anaesthesia.     

Using the inflating syringe as a safety valve to limit laryngeal mask airway cuff pressure

Objective  

Hyperinflation of the laryngeal mask airway (LMA) cuff is thought to be the etiology underlying many of the complications associated with the use of this device. Until now, there has not been a clinically acceptable method (besides direct measurement) to assure that the cuff pressure is maintained less than the recommended maximum value of 44 mm Hg (60 cm H₂O).     

The use of the laryngeal mask airway with mechanical positive pressure ventilation

The purpose of this article is to discuss the benefits, safety, and efficacy of the laryngeal mask airway (LMA) and identify the risks and misconceptions associated with LMAs when used with positive pressure ventilation (PPV). Despite the abundance of supporting evidence that LMAs may be used successfully in a variety of age groups and surgical procedures using PPV, many anesthesia providers are still reluctant to choose an LMA when PPV is needed. This reluctance emerges from the misconception that when using an LMA with mechanical ventilation, there is an increased incidence of gastric insufflation, failed ventilation, and pulmonary aspiration. When compared to other airway adjuncts, however, the LMA is a safe, effective means of delivering ventilation under anesthesia.     

Comparison of 2 cuff inflation methods of laryngeal mask airway Classic for safe use without cuff manometer in adults

Purpose

This single-center, prospective, randomized, double-blind, 2-arm, parallel group comparison trial was performed to establish whether the adult-sized laryngeal mask airway (LMA) Classic (The Laryngeal Mask Company Ltd, Henley-on-Thames, UK) could be used safely without any consideration of cuff hyperinflation when a cuff of the LMA Classic was inflated using half the maximum inflation volume or the resting volume before insertion of device.

Basic procedures

Eighty patients aged 20 to 70 years scheduled for general anesthesia using the LMA Classic were included. Before insertion, the cuff was partially filled with half the maximum inflation volume in the half volume group or the resting volume created by opening the pilot balloon valve to equalize with atmospheric pressure in the resting volume group. Several parameters regarding insertion, intracuff pressure, airway leak pressure, and leakage volume/fraction were collected after LMA insertion.

Major findings

The LMA Classic with a partially inflated cuff was successfully inserted in all enrolled patients. Both groups had the same success rate of 95% at the first insertion attempt. The half volume group had a lower mean intracuff pressure compared with the resting volume group (54.5 ± 16.1 cm H₂O vs 61.8 ± 16.1 cm H₂O; P = .047). There was no difference in airway leak pressure or leakage volume/fraction between the 2 groups under mechanical ventilation.

Conclusions

The partially inflated cuff method using half the maximum recommended inflation volume or the resting volume is feasible with the adult-sized LMA Classic, resulting in a high success rate of insertion and adequate range of intracuff pressures.     

Choosing the correct laryngeal mask airway sizes and cuff inflation volumes in pediatric patients

The laryngeal mask airway (LMA) is now standard airway management equipment in prehospital and Emergency Department (ED) care. Most providers may not be able to match the pediatric LMA sizes to the appropriate weights of pediatric patients. The exact inflation volumes are also difficult to memorize. To overcome this problem, we propose the following equations: Weight (kg) of patient = 2(2 x LMA), where LMA is the size; cuff inflation volume (mL) = 5 x LMA.     

Comparison of 2 cuff inflation methods before insertion of laryngeal mask airway for safe use without cuff manometer in children

Purpose

This prospective, randomized trial was conducted to establish whether the pediatric laryngeal mask airway (LMA) could be used without any concerns for abnormally high intra-cuff pressure when a cuff of the LMA was inflated with half the maximum recommended inflation volume or the resting volume before insertion.

Basic procedures

Eighty children 0 to 9 years of age and weighing of 5 to 30 kg scheduled for general anesthesia were included. Before insertion, the cuff of the LMA was filled with half the maximum recommended inflation volume in the Half volume group, or the resting volume by opening the pilot balloon valve to atmospheric pressure in the Resting volume group. After insertion of the LMA, intra-cuff pressure, oropharyngeal leak pressure, and leakage volume were investigated.

Major findings

The Half volume group showed lower mean intra-cuff pressure than the Resting volume group (49.6 ± 12.1 cm H₂O vs 58.1 ± 13.8 cm H₂O, P = .005). There was no difference in oropharyngeal leak pressure (22.1 ± 5.8 vs 21.7 ± 5.1 cm H₂O, P = .757) or leakage volume between the Half volume group and the Resting volume group (0.13 ± 0.13 ml/kg vs 0.11 ± 0.12 ml/kg, P = .494) under spontaneous respiration.

Conclusions

Both methods of the LMA cuff inflation before insertion provided an acceptable range of intra-cuff pressure with adequate pharyngeal sealing without any intervention after insertion.     

食管引流型与标准型喉罩通气道用于正压通气的自身对照研究

目的采用随机自身对照设计方法比较食管引流型喉罩通气道(PLMA)和标准型喉罩通气道(SLMA)用于间歇正压通气的有效性。方法选择50例经美国麻醉医师协会(ASA)身体状态分级标准分为1~2级、拟在全身麻醉下实施择期整形外科手术患者。在常规麻醉诱导后,顺序插入PLMA和SLMA,将通气罩内压充气至60cmH2O(1cm H2O=0.098kPa),评价两种喉罩通气道充气前后的肺通气满意度和气道密封压,同时进行光导纤维支气管镜(FOB)评分,确定通气罩的解剖位置。然后将潮气量设定为10ml/kg实施间歇正压通气,记录间歇正压通气后连续5次呼吸的平均呼潮气量和平均吸气峰压。结果在通气罩未充气情况下,插入PLMA后有46例(92%)患者获得了良好和尚可的肺通气效果,而插入SLMA后仅有22例(44%)患者获得了良好和尚可的肺通气效果;PLMA的气道密封压显著高于SLMA(P<0.05)。将通气罩内压充气至60cmH2O,采用PLMA的50例患者均获得良好的肺通气效果,但采用SLMA时仅有28例获得良好的肺通气效果;PLMA所需的充气量和充气后获得的气道密封压均显著高于SLMA(P均<0.05)。采用PLMA时所有患者的气道密封压均高于或等于采用SLMA时;采用PLMA时除2例患者外,其他患者所需的充气量也均高于采用SLMA时。PLMA通气罩位置的FOB评分显著低于SLMA(P<0.05)。采用PLMA维持气道的29例患者和采用SLMA维持气道的21例患者的平均呼潮气量、吸气峰压及维持气道时间差异均无显著性(P均>0.05)。结论与SLMA相比,PLMA可为正压通气提供更好的气道密封压,而且对声门和食管上端具有潜在的隔离作用,用于正压通气时PLMA比SLMA更有效、更安全。     

环状软骨压迫对食管引流型喉罩通气道插入操作和通气功能的影响

目的 评价环状软骨压迫(CP)对食管引流型喉罩通气道(PLMA)插入操作和正压通气功能的影响.方法 50例按美国麻醉医师协会(ASA)标准身体状态分级为Ⅰ级的择期整形外科手术患者被纳入研究.静脉麻醉诱导后,于CP下插入PLMA,保留专用引导器并将通气罩内压充气至60 cm H2O(1 cm H2O=0.098 kPa).观察肺通气满意度,测定气道密封压,并采用光导纤维支气管镜(FOB)评价通气罩的解剖位置.暂时终止CP,采用专用引导器进一步推送PLMA到达理想位置,并重新调整通气罩内压至60 cm H2O.再次评价上述指标,并记录CP下和非CP下正压通气时的呼潮气量和吸气峰压,观察经PLMA插入胃管的情况并评价引流管解剖位置的FOB评分.结果 与在CP下插入PLMA比较,在临时解除CP并进一步推送PLMA后,肺通气满意度(良好和尚可为50例比14例)、气道密封压[(27±7)cm H2O比(21±7)cm H2O]和通气罩解剖位置的FOB评分均显著改善(P均＜0.05).在将PLMA推送至理想位置后,虽然在CP和非CP时的正压通气呼潮气量差异无显著性,但CP时的吸气峰压[(28±5)cm H2O]却显著高于非CP时[(14±2)cm H2O,P＜0.05].结论 CP可阻碍将PLMA插入到理想位置,在暂时终止CP的情况下,采用专用引导器可将PLMA插入到理想位置,而且CP可显著增加正压通气的吸气峰压.     

胃镜喉罩在无痛超声胃镜检查中的应用效果

目的 评价胃镜喉罩应用于无痛超声胃镜检查的可行性和安全性。方法 选取该院行无痛超声胃镜检查的患者50例,随机分为胃镜喉罩组和气管插管组。记录两组患者插管前(T₀)、插管后1 min (T₁)、拔管前1 min (T₂)和拔管后1 min (T₃)的平均动脉压(MAP)、心率(HR)、经皮动脉血氧饱和度(SpO₂)、T₁至T₂时点呼气末二氧化碳分压(PetCO₂)和气道峰压;同时记录麻醉药用量、手术时间、拔管时间和PACU监护时间;记录反流误吸及术后咽喉部并发症。结果 两组患者手术时间、T₁至T₂时点PetCO₂及气道峰压比较,差异均无统计学意义(P>0.05)。与T₀时点比较,气管插管组T₁至T₃时点MAP明显升高,HR明显增快,且相应时点均高于胃镜喉罩组(P <0.05...     

The laryngeal mask airway in emergency medicine

The Laryngeal Mask Airway (LMA) is an upper airway adjunct lying intermediate in function between the endotracheal tube and the oropharyngeal airway. It has gained wide acceptance since its introduction into United Kingdom anaesthetic practice in 1988. We review the principles of advanced airway management in the emergency department and examine the application of the LMA to this area. We conclude that the LMA may have a small role in pre-hospital and CPR airway management, and a very significant role in the management of difficult or failed endotracheal intubation.     

气囊内压对气管内插管时受压气管黏膜的影响

目的 观察气管插管时不同气囊内压力下气管黏膜的病理改变.方法 选择气管内插管机械通气深昏迷患者60例,按随机原则分为囊内压25、30、35、40 mm Hg(1 mm Hg=0.133 kPa)组(分别记为A1、A2、A3、A4组),观察插管后1、24、48、72 h受压气管黏膜病理改变.结果 4组患者气管黏膜均有不同程度病理改变,但组内比较差异均无统计学意义.随气囊内压增加,气管黏膜损伤加重;A1组气管黏膜病理改变轻微,均为Ⅰ度;A2组未发现Ⅲ度损伤.损伤1 h时,A3组Ⅱ度损伤例数较A2组明显增多(10例比6例,P<0.05);A4组Ⅱ度及Ⅲ度损伤例数与A3组比较差异有统计学意义(Ⅱ度:7例比10例,Ⅲ度:6例比2例,均P<0.05);而且损伤1 h后,损伤程度不随时间变化而加重.结论 气管插管机械通气气囊内压低于30 mm Hg时气管黏膜病理改变轻微,气管插管时气囊内压低于30 mm Hg较为妥当.     

Tolerance of mice to nitrous oxide.

Mice continuously exposed to a subanesthetic dose of nitrous oxide (N2O) become tolerant to nitrous oxide, as measured by an increase in their ED50 (dose required to abolish the righting reflex in 50% of animals) for N2O. The maximum increase in ED50 is approximately 0.25 atm for mice exposed to 40, 50 or 70% N2O for 2 to 3 weeks. Mice exposed to 25% N2O for 3 weeks do not develop tolerance. Mice exhibit a withdrawal syndrome when removed from the subanesthetic environment after exposure to 40 to 70% but not 25% N2O for 3 weeks. Tolerance to 50 or 70% N2O develops within 1 week and is maximal at 2 weeks. Tolerance to nitrous oxide is lost within 6 days following removal of the animals from the subanesthetic environment. Synaptic membrane fatty acid, phospholipid, and cholesterol compositions of tolerant animals are not significantly altered.     

标准体质量在喉罩选择及其临床疗效中的价值

目的观察标准体质量在喉罩选择及其临床疗效中的价值。方法选取82例腹腔镜手术患者作为研究对象,按照随机数字表法分为观察组和对照组。对照组根据患者体质量选择喉罩,30~50、50~70、70~100kg分别对应3、4、5号。观察组根据Broca改良公式计算标准体质量,根据体质量区间选择喉罩型号。比较两组的血流动力学变化情况、插入时间、一次成功率、手术时间、胸骨上窝试验情况、固定片距离及喉罩密封压情况。比较两组并发症发生情况及VAS评分情况。结果观察组插入时间明显短于对照组,一次成功率明显高于对照组,差异均具有统计学意义(P0.05)。喉罩置入后,两组平均动脉压、血压饱和度、心率及呼气末二氧化碳分压比较,差异均无统计学意义(P0.05)。观察组喉罩密封压明显高于对照组,差异有统计学意义(P0.05)。观察组并发症发生率为9.8%,明显低于对照组的26.8%,差异具有统计学意义(P0.05)。结论根据标准体质量选择喉罩,有利于喉罩的置入,且并发症发生率低。