阿克玛麻醉机与ARF-850E呼吸机联用时对麻醉机吸入气体浓度的影响

天津组装的阿克玛麻醉机,由于配套的是非麻醉专用的ARF-850E呼吸机(采用无重复呼吸式回路),故联用时会对麻醉机回路内的气体浓度产生稀释影响。为寻求解决的方法,本文监测了使用80ml、160ml和240ml不同容积的衔接管,在麻醉机氧流量0.5～10L/min下吸入氧浓度的变化。结果表明,对吸入氧浓度的稀释影响与麻醉机氧流量和衔接管容积呈反比关系,与潮气量呈正比关系。氧流量愈大,衔接管愈长,潮气量愈小,稀释程度愈轻。增加衔接管容积,实质上是增加呼吸机仪器的无效腔,而呼吸机输出的潮气量与其仪器无效腔愈接近,对麻醉机回路内气体的影响愈小。当氧流量等于分通气量时,用240ml的衔接管基本可避免对吸入氧浓度的影响。但此联用方法不适用于低流量的麻醉管理。     

应用进口麻醉机施行低流量麻醉的若干体会

我院自1985年后先后进口了一些现代麻醉机,经使用及对通气系统的分析,我们认为Aika 60v、Sul-la808、Narkomed2A、Penlon AM 1000等麻醉机不作任何改动或稍加调整,是可以施行低流量甚至紧闭麻醉的,这样可节省药费、减轻对手术室空气污染,也符合我国国情,有一定的现实意义。现将有关体会介绍如下。一、现代麻醉机通气系统的组成和特点大部分现代麻醉机的通气系统是循环式的。挥发器都位于循环圈外。新鲜气流经过挥发器连续进入循环圈,当新鲜气流量大于人体摄取量时,多余气体必定从系统中排出。手控或自主呼吸时多余气体经APL活     

回路内麻醉气体吸附器的临床应用

目的在吸入麻醉术后恢复阶段,观察回路内麻醉气体吸附器是否可缩短吸入麻醉的苏醒时间。方法在固定潮气量、每分通气量和新鲜气体流量的条件下,术毕关闭挥发罐后,比较使用回路内麻醉气体吸附装置对回路内麻醉气体浓度变化的影响。结果使用吸附器后,回路内麻醉气体浓度降至MAC0．3所需时间,异氟醚由20．0±0．3分钟降至3．3±0．5分钟(P＜0．01)。安氟醚由25．0±0．1分钟降至3．5±0．5分钟(P＜0．01)。结论应用回路内麻醉气体吸附器可显著缩短病人苏醒时间,并减少气源浪费和环境污染。     

Gambro-Engstrom Eas 9010麻醉机电控定量注射蒸发器的准确度判定

目的 评价Gambro-Engstrom Eas9010麻醉机采用的全新蒸发原理的蒸发器的准确度.方法 用芬兰产Capnomac Datex AS/3多功能麻醉气体监护仪监测不同气体流量,不同气道压力、不同载气配比及快速充氧时对蒸发器输出浓度的影响.结果 该麻醉蒸发器在气体流量小于0.5L·min-1或设置浓度大于8%时,输出浓度小于设置浓度(P＜0.05)(前者误差可通过采用自身监测系统避免),除此之外,该蒸发器输出浓度不受气体流速、气道压力、载气配比及快速充氧的影响.结论 该新型电控定量注射系统蒸发器可安全地用于低流量、最低流量及全紧闭麻醉.     

麻醉及苏醒期间监测规范要点(英国麻醉学会1988年7月制订)

1.在整个麻醉过程中麻醉者务必在场并负责记录操作过程。2.在麻醉诱导前即应开始监测,并不间断地进行,直至病人从麻醉状态中完全恢复而后止。3.对麻醉机性能的监测必须包括氧(浓度)分析仪(能报警)以及能测知漏气、脱接、重复吸入或呼吸系统压力过高的装置。4.必须连续监测通气和循环。可适当地应用监测仪以增强麻醉者的感知(senses)能力,临床观察包括病人肤色、对手术刺激的反应,胸廓和贮气囊的活动幅度,摸数脉搏和听诊呼吸、心音。连续监测包括脉搏容积图、脉搏测氧仪、心电图、(呼出气)二氧化碳测定仪,以及测量血管(内)压力和体温的设备。     

安氟醚最低流量麻醉

目前临床使用的麻醉机吸入全麻药均经呼吸回路外的挥发罐挥发,由于功能残气量和呼吸回路具有很大的容积,因此常需较大的新鲜气流量进行调控吸入麻醉药浓度,其结果必然造成药物的浪费和环境污染。为此我们选择安氟醚采用最低流量麻醉法进行临床研究。资料与方法一般资料　22例ＡＳＡⅠ～Ⅱ级脊柱和脑外科择期手术病人,男14例,女8例,年龄22～64岁(492±63岁),体重621±57ｋｇ,术前心、肺、肝、肾功能均正常。麻醉方法　术前1小时肌注苯巴比妥钠01ｇ、阿托品03～04ｍｇ。硫喷妥钠6ｍｇ/ｋｇ、芬太尼4～5μｇ/ｋｇ及琥珀胆碱100ｍｇ静注后气管内…     

地氟醚、七氟醚与安氟醚低流量麻醉临床观察

比较地氟醚、七氟醚、安氟醚用于低流麻醉时ＢＰ和ＨＲ改变,苏醒过程、不良反应以及药物费用。方法：４２例ＡＳＡＩⅠ－Ⅱ级择期腹部外科手术病人随机分成地氟醚,安氟醚和七氟醚三组。麻醉诱导后连接Ｃｉｃｅｒｏ麻醉机。降低新鲜气流,地氟醚和安氟醚为０．３－０．５Ｌ／ｍｉｎ,七氟醚为０．８－１．０Ｌ／ｍｉｎ,从回路呼出端向麻醉机回路内注入液吸入麻醉药４－５分钟内使三组病人呼气末麻醉药浓度达到１ＭＡＣ左右,即地氟     

用全自动电动麻醉机进行低流量麻醉的临床观察

目的 采用高精密度监测设备和手段对全自动电动麻醉机物理性能测定后进行低落充量麻醉观察。方法 将４８例胸外科 手术病人随机分成两组,分别给予４Ｌ．ｍｉｎ＾－１和０．８Ｌ．ｍｉｎ＾－１流量麻醉,采用Ｃａｐｎｏｍａｃ Ｄａｔｅｘ ＡＳ／３多功能麻醉气体监测仪与麻醉机自身监测系统同时监测环路内各气体浓度（Ｎ２０、０２、ＣＯ２、Ｉｓｏ）,并记录各气体（Ｎ２Ｏ、Ｏ２、Ｉｓｏ）及钠石灰消耗量,将两监测系统监测值     

经麻醉机笑气通路吸入低浓度一氧化氮的可行性

为了探讨术中将一氧化氮气体经麻醉机笑气通路安全地引入呼吸环路的可行性，选择ＳＩＥＭＥＮＳ Ｖｅｎｔｉｌａｔｏｒ ７１０及ＮＡＲＫＯＭＥＤ ２Ｂ麻醉机分别与模拟肺相连组成环路。在新鲜氧气流量分别为２、３、４、５和６Ｌ／ｍｉｎ，ＮＯ浓度分别为１０、２０、４０、６０和８０ｐｐｍ条件下，对环路内一氧化氮和二氧化氮浓度进行观察。结果表明：经麻醉机笑气通路引入８００ｐｐｍ一氧化氮，试验条件下环路内二氧化氮浓度     

活性炭可有效吸附麻醉机内的吸入麻醉药

目的如果一个恶性高热易感者需要进行麻醉，就要求对先前使用过吸入麻醉药的麻醉机以高流量新鲜气流进行冲洗。关于冲洗时间，既往的研究结果各异，从10—104分钟不等。在先前提出的替代净化技术中，有研究者提出在呼吸回路吸气端安装活性炭过滤器。方法本研究中，我们将活性炭过滤器安置于几种分别受异氟烷、七氟烷和地氟烷污染的麻醉机呼吸回路的吸气和呼气两端，测出为使上述3种麻醉药浓度降至5ppm，用新鲜气流冲洗麻醉机所需要的时间。接下来我们还模拟了临床上麻醉诱导90分钟后被诊断为恶性高热的患者，评估用活性炭过滤器减少麻醉药接触的有效性。结果活性炭过滤器放置于呼吸回路的吸气端和呼气端后，使挥发性麻醉药浓度降低至低于5ppm所需要的时间小于2分钟。麻醉药的浓度可保持远低于5ppm至少60分钟。麻醉诱导后，一旦患者确诊为恶性高热，由于活性炭过滤器的存在，在吸入麻醉药浓度超过5ppm前，可使用同一麻醉机至少67分钟。结论用新鲜气流冲洗的方法清洗用过吸入麻醉药的麻醉机通常需要10—104分钟，安装活性炭过滤器给我们提供了一种取而代之的新方法。     

Inside anesthesia breathing circuits: time to reach a set sevoflurane concentration in toddlers and newborns: simulation using a test lung

We measured the time it takes to reach the desired inspired anesthetic concentration using the Primus (Dr?gerwerk, AG, Lübeck, Germany) and the Avance (GE Datex-Ohmeda, Munich, Germany) anesthesia machines with toddler and newborn ventilation settings. The time to reach 95% of inspired target sevoflurane concentration was measured during wash-in from 0 to 6 vol% sevoflurane and during wash-out from 6 to 0 vol% with fresh gas flows equal to 1 and 2 times the minute ventilation. The Avance was faster than the Primus (65 seconds [95% confidence interval (CI): 55 to 78] vs 310 seconds [95% CI: 261 to 359]) at 1.5 L/min fresh gas flow, tidal volume of 50 mL, and 30 breaths/min. Times were shorter by the same magnitude at higher fresh gas flows and higher minute ventilation rates. The effect of doubling fresh gas flow was variable and less than expected. The Primus is slower during newborn than toddler ventilation, whereas the Avance's response time was the same for newborn and toddler ventilation. Our data confirm that the time to reach the target-inspired anesthetic concentration depends on breathing circuit volume, fresh gas flow, and minute ventilation.     

FACTORS AFFECTING CARBON DIOXIDE HOMEOSTASIS DURING CONTROLLED VENTILATION WITH CIRCLE SYSTEMS

An experimental lung model was used, with controlled ventilation,to determine the effect of different circle arrangements andvarying ventilatory frequencies on the efficiency of carbondioxide removal from a circle system without carbon dioxideabsorption. Greater efficiency was found when fresh gas enteredthe system between the unidirectional inspiratory valve andthe subject than when the fresh gas inlet was on the ventilatorside of this valve. At any fresh gas flow and minute volume,efficiency was greater at low respiratory frequencies. Goodcorrelations existed between carbon dioxide concentration inthe model lung, fresh gas flow and minute ventilation when respiratoryfrequency was constant. Paradoxical results were obtained whenminute volume was varied by changes in frequency at a constanttidal volume. The major cause of the various differences inperformance has been ascribed to variations in the degree ofmixing of fresh and expired gas within the system.     

Distribution of Expiratory Gas and Rebreathing in a T-piece Modification Combined with a PEEP Valve

T-piece modifications with PEEP valves are often used in weaning from mechanical ventilation or for intubated patients not requiring ventilatory support. Distribution of expiratory gas and the extent of rebreathing in a T-piece modified with an inspiratory reservoir (ICR) and with a PEEP valve were studied in a model with various fresh gas flows (FGF), tidal volumes and frequencies at three valve settings: 0 cmH2O (ZEEP) and PEEP of 5 and 10 cmH2O (0.490-0.981 kPa). Two types of distribution of expiratory gas were delineated: type one with expiratory gas in the inspiratory limb (IL) and a high ratio of the maximum CO2 content and corresponding end-expiratory CO2 concentration in the expiratory limb (EL) (FmaxCO2/FECO2) and a type 2 with no detectable alveolar gas in the IL and a low ratio of FmaxCO2/FECO2. The use of PEEP did not increase the amount of alveolar gas in the system, and no increase occurred in the end-expiratory CO2 concentration. The investigated system is in fact a Mapleson A system. The ratio of FGF to minute ventilation just preventing rebreathing during spontaneous ventilation is approximately 1, in contrast to 3 in other modifications. These advantages minimize the risk of rebreathing, even when the minute ventilation rises to that of the fresh gas flow. The T-system with a compliant inspiratory reservoir and a PEEP valve can, in most clinical weaning situations, satisfy the inspiratory peak flow of different respiratory patterns with a standard FGF of 15 l X min-1.     

Functional analysis of the smart vent compensation system and the fresh gas decoupling system

BACKGROUND: In MIPPV mode, an anesthetic machine supplies a fixed amount of tidal volume (TV) corresponding to changes of fresh gas flow (FGF) in a certain period of time. In this research, we examined discrepancy of delivered TV and preset TV, after a change of FGF in both fresh gas decoupling system (FGDS) and smart vent compensation system(SVCS). METHODS: FGF value was changed from 0.1 l x min(-1) to 12 l min(-1), and after 10 times of ventilation, we measured TV and peak pressure of inspiratory circuit pressure(PIP). RESULTS: Following a gradual FGF increase, PIP dramatically increased in FGDS. TV and PIP; however, remained unchanged in SVCS. CONCLUSIONS: FDGS has a valve for closing FGF in the inspiratory phase and it makes the gas circuit over volume, but SVCS changes the volume of gas delivery to the ventilator by CPU according to FGF changes. Therefore it is assumed that the safety system of SVCS is superior to FDGS in high and low FGF.     

Leak of anesthetic gases inside the anesthesia machine

We experienced the leak of anesthetic gases inside the anesthesia machine in spite of performing the leak test before its use. After induction of anesthesia, a laryngeal mask airway was inserted and the patient was ventilated manually. At the beginning we could not find any signs of machine troubles. High airway pressure occurred immediately after switching to the mechanical ventilation. Because we could not detect the details of the machine trouble, tidal volume was set lower and the surgery was continued. After surgery, we found a crack in a fresh gas circuit valve. We have to check the anesthesia machine regularly and know its duration of use.     

Air contamination of a closed anesthesia circuit

Closed-circuit anesthesia (CCA) has certain advantages such as decreased cost, decreased anesthetic gas pollution, improved in-halational gas humidity and temperature in comparison to conventional inhalational anesthesia using a high fresh gas flow, i.e. more than 2 L. min^-1, with a semi-closed breathing circuit. The main disadvantage of CCA is the possibility of hypoxic anesthetic gas delivery. This potentially lethal situation is caused by an insufficient oxygen flow rate for the body metabolism or by the accumulation of inactive gas, usually nitrogen, within the breathing circuit in spite of a sufficient oxygen concentration in the fresh gas supply to the breathing circuit. In the latter case, the accumulation of inactive gas may also lead an increased risk of awareness because of its dilution effect on the concentrations of inhalational anesthetics. We herein present a case of air contamination of the breathing circuit through a sampling line of an anesthetic gas monitor. The air caused a decrease in the oxygen concentration during closed circuit anesthesia.     

Wasted ventilation measured in vitro with eight anesthetic circuits with and without inline humidification

Compression of gases (Boyle's law) and circuit compliance are major determinants of anesthesia circuit function. The materials of which circuits are constructed and the use of heated humidifiers may result in clinically important variations in delivered minute ventilation (VE) secondary to variations in compression volume. We examined eight anesthetic circuits both with and without a heated humidifier in an in vitro setting. Compression volume was determined with a large calibrated syringe. Circuit efficiency was determined by measuring VE at multiple peak inflation pressures (PIP) while using a pediatric ventilator with fixed VE, respiratory rate, fresh gas flow, and I/E ratio. As expected, both compression volume and delivered VE highly correlated with the type of circuit and the pressure at which it was examined (P less than 0.001). Mapleson D circuits had the lowest compression volume and were the most efficient circuits (P less than 0.0001). Pediatric circle systems were intermediate and adult circle systems had the largest compression volume and were the least efficient. Humidifiers uniformly increased compression volume. The following conclusions were drawn: 1) the anesthetic circuit, its material, and the pressure at which it operates are important determinants of circuit function; 2) humidifiers increase compression volume; 3) Mapleson D circuits had the lowest compression volume and therefore were the most efficient; 4) highly compliant adult circuits may result in compression volume losses that exceed the tidal volume of a pediatric ventilator; 5) humidifiers with low volume and rigid tubing should have the least effect on minute ventilation; and 6) highly compliant adult circuits when used in the care of infants and small children must be used with caution.     

Managing fresh gas flow to reduce environmental contamination

Anesthetic drugs have the potential to contribute to global warming. There is some debate about the overall impact of anesthetic drugs relative to carbon dioxide, but there is no question that practice patterns can limit the degree of environmental contamination. In particular, careful attention to managing fresh gas flow can use anesthetic drugs more efficiently--reducing waste while achieving the same effect on the patient. The environmental impact of a single case may be minimal, but when compounded over an entire career, the manner in which fresh gas flow is managed by each individual practitioner can make a significant difference in the volume of anesthetic gases released into the atmosphere. The maintenance phase of anesthesia is the best opportunity to reduce fresh gas flow because circuit gas concentrations are relatively stable and it is often the longest phase of the procedure. There are, however, methods for managing fresh gas flow during induction and emergence that can reduce the amount of wasted anesthetic vapor. This article provides background information and discusses strategies for managing fresh gas flow during each phase of anesthesia with the goal of reducing waste when using a circle anesthesia system. Monitoring oxygen and anesthetic gas concentrations is essential to implementing these strategies safely and effectively. Future technological advances in anesthetic delivery systems are needed to make it less challenging to manage fresh gas flow.     

Physiological effects of flow and pressure triggering during non- invasive mechanical ventilation in patients with chronic obstructive pulmonary disease

BACKGROUND: The effect of the type of trigger system on inspiratory effort has been studied in intubated patients, but no data are available in non-invasive mechanical ventilation where the "trigger variable" may be even more important since assisted modes of ventilation are often employed from the beginning of mechanical ventilation. METHODS: The effect of flow triggering (1 and 5 1/min) and pressure triggering (-1 cm H2O) on inspiratory effort during pressure support ventilation (PSV) and assisted controlled mode (A/C) delivered non-invasively with a full face mask were compared in patients with chronic obstructive pulmonary disease (COPD) recovering from an acute exacerbation. The patients were studied during randomised 15 minute runs at zero positive end expiratory pressure (ZEEP). The oesophageal pressure time product (PTPoes), dynamic intrinsic PEEP (PEEPi,dyn), fall in maximal airway pressure (delta Paw) during inspiration, and ventilatory variables were measured. RESULTS: Minute ventilation, respiratory pattern, dynamic lung compliance and resistances, and changes in end expiratory lung volume (delta EELV) were the same with the two triggering systems. The total PTPoes and its pre-triggering phase (PTP due to PEEPi and PTP due to valve opening) were significantly higher during both PSV and A/C with pressure triggering than with flow triggering at both levels of sensitivity. delta Paw was larger during pressure triggering, and PEEPi,dyn was significantly reduced during flow triggering in the A/C mode only. CONCLUSIONS: In patients with COPD flow triggering reduces the inspiratory effort during both PSV and A/C modes compared with pressure triggering. These findings are likely to be due to a reduction in PEEPi,dyn and in the time of valve opening with a flow trigger.


     

The measurement of expiratory oxygen as disconnection alarm

The efficacy of an oxygen-monitoring alarm in the expiratory limb of an anesthetic circuit was evaluated as a method of detecting disconnections of the patient from the anesthetic machine. Oxygen concentrations were determined in the expiratory limb of a semiclosed anesthetic circuit with a ventilator and a 2-1 reservoir bag serving as a simple lung model. Adjustments of ventilation during the different measurements were a PEEP of 5 cmH2O, respiratory rates of 10/min and 5/min, and tidal volumes of 1,000 and 500 ml, respectively. The alarm time measured with a stopwatch was the time that elapsed between disconnection and the acoustical alarm. The circuit was always disconnected at the y-piece when the reservoir bag had been fully expanded after an inspiration. With various fresh flow rates and oxygen concentrations ranging from 33% to 52%, disconnection always was evident within 30 s. Measurement of the oxygen concentration with an alarm time of 30 s after disconnection may be an effective backing system for detecting a disconnection.