December This Product Comparison covers the following device term and product code as listed in ECRI s Universal Medical Device

Transcription

1 December 2005 Product Comparison Anesthesia Units UMDN S information This Product Comparison covers the following device term and product code as listed in ECRI s Universal Medical Device Nomenclature System (UMDNS ): Anesthesia Units [10-134] Table of Contents Scope of this Product Comparison...3 Purpose...3 Principles of operation...3 Gas supply and control...4 Vaporizers...4 Ventilation...5 Breathing circuits...6 Scavenging system...7 Monitors and s...7 Automated anesthesia record keepers/anesthesia information management systems...8 Reported problems...9 Purchase considerations...11 ECRI recommendations...11 Other considerations...12 Cost containment...13 Stage of development...14 Bibliography...14 Standards and guidelines...15 Anesthesia breathing circuits...15 Anesthesia equipment...15 Anesthesia unit vaporizers...17 Anesthesia ventilators...17 Anesthetic reservoir bags...18 Medical gas piping...18 Scavenging systems...18 Citations from other ECRI publications...19 Supplier information...21 About the chart specifications

2 Policy Statement The Healthcare Product Comparison System (HPCS) is published by ECRI, a nonprofit health services research agency established in HPCS provides comprehensive information to help healthcare professionals select and purchase diagnostic and therapeutic capital equipment more effectively in support of improved patient care. The information in Product Comparisons comes from a number of sources: medical and biomedical engineering literature, correspondence and discussion with manufacturers and distributors, specifications from product literature, and ECRI s Problem Reporting System. While these data are reviewed by qualified health professionals, they have not been tested by ECRI s clinical and engineering personnel and are largely unconfirmed. The Healthcare Product Comparison System and ECRI are not responsible for the quality or validity of information derived from outside sources or for any adverse consequences of acting on such information. The appearance or listing of any item, or the use of a photograph thereof, in the Healthcare Product Comparison System does not constitute the endorsement or approval of the product s quality, performance, or value, or of claims made for it by the manufacturer. The information and photographs published in Product Comparisons appear at no charge to manufacturers. Many of the words or model descriptions appearing in the Healthcare Product Comparison System are proprietary names (e.g., trademarks), even though no reference to this fact may be made. The appearance of any name without designation as proprietary should not be regarded as a representation that is not the subject of proprietary rights. ECRI respects and is impartial to all ethical medical device companies and practices. The Healthcare Product Comparison System accepts no advertising and has no obligations to any commercial interests. ECRI and its employees accept no royalties, gifts, finder s fees, or commissions from the medical device industry, nor do they own stock in medical device companies. Employees engage in no private consulting work for the medical device industry. About ECRI ECRI (formerly the Emergency Care Research Institute) is a nonprofit health services research agency. Its mission is to improve the safety, quality, and cost-effectiveness of healthcare. It is widely recognized as one of the world s leading independent organizations committed to advancing the quality of healthcare. ECRI s focus is healthcare technology, healthcare risk and quality management, and healthcare environmental management. It provides information services and technical assistance to more than 5,000 hospitals, healthcare organizations, ministries of health, government and planning agencies, voluntary sector organizations, associations, and accrediting agencies worldwide. Its more than 30 databases, publications, information services, and technical assistance services set the standard for the healthcare community. ECRI s services alert readers to technology-related hazards; disseminate the results of medical product evaluations and technology assessments; provide expert advice on technology acquisitions, staffing, and management; report on hazardous materials management policy and practices; and supply authoritative information on risk control in healthcare facilities and clinical practice guidelines and standards. 2

3 December 2005 Anesthesia Units Scope of this Product Comparison This Product Comparison covers anesthesia systems that can have the following components: mainframes, hanger yokes and gauges, flowmeters, vaporizers, flush valves, carbon dioxide (CO2) absorbers, ventilators, scavenging systems, monitors, and s. Not included are separate analyzers designed to measure concentrations of halogenated anesthetics and gases supplied to the unit or to detect levels present in the operating room; also not included are separate stand-alone physiologic monitoring systems. For information on these devices, see the following Product Comparisons: Halogenated Anesthetics Analyzers Multiple Medical Gas Monitors, Respired/Anesthetic Oxygen Monitors Physiologic Monitoring Systems, Acute Care; Neonatal; ECG Monitors Pressure Monitors, Airway These units are also called: anesthesia machines. Purpose Anesthesia units dispense a mixture of gases and vapors and vary the proportions to control a patient s level of consciousness and/or analgesia during surgical procedures. Basically, anesthesia units perform the following four functions: Provide oxygen (O2) to the patient Blend gas mixtures, in addition to O2, that can include an anesthetic vapor, nitrous oxide (N2O), other medical gases, and air Facilitate spontaneous, controlled, or assisted ventilation with these gas mixtures Reduce, if not eliminate, anesthesiarelated risks to the patient and clinical staff The patient is anesthetized by inspiring a mixture of O2, the vapor of a volatile liquid halogenated hydrocarbon anesthetic, and, if necessary, N2O and other gases. Because normal breathing is routinely depressed by anesthetic agents and by muscle relaxants administered in conjunction with them, respiratory assistance either with an automatic ventilator or by manual compression of the reservoir bag is usually necessary to deliver the breathing gas to the patient. Principles of operation An anesthesia system comprises four basic subsystems: a gas supply and control circuit, a breathing and ventilation circuit, a scavenging system, and a set of system function and breathing circuit monitors (e.g., inspired O2 concentration, airway pressure). Also included in some anesthesia systems are a number of monitors and s that indicate levels and variations of several 3

4 physiologic variables and parameters associated with cardiopulmonary function and/or gas and agent concentrations in breathed-gas mixtures. Manufacturers typically offer a minimum combination of monitors, s, and other features that customers must purchase to meet standards and ensure patient safety. To meet the minimum standard of care in the United States, the American Society of Anesthesiologists (ASA) states that anesthesia systems must continually monitor the patient s oxygenation, ventilation, circulation, expired CO2 levels, and temperature. Integrated or stand-alone monitors may be used. Gas supply and control Because O2 and N2O are used in large quantities, they are usually drawn from the hospital s central gas supplies. In some countries, cylinders containing compressed O2, N2O, and sometimes other gases are mounted on yokes attached to the anesthesia machine and can serve as an emergency gas supply in case central supplies fail. Cylinder connections generally include indexing systems (e.g., specific patern of pins), which are intended to prevent accidental mounting of a gas cylinder on the incorrect yoke. Each gas entering the system from a cylinder flows through a filter, a one-way check valve, and a regulator that lowers the pressure to approximately 45 pounds per square inch (psi). There is no need for a separate regulator when the central gas supply is used because the pressure is already at about 50 psi. Most anesthesia machines have an O2-supply-failure device and an that protect the patient from inadequate O2 supply. If the O2 supply pressure drops below about 25 to 30 psi, the unit decreases or shuts off the flow of the other gases and activates an. The flow of each gas in a continuous-flow unit is controlled by a valve and indicated by a flowmeter. The flowmeter can be a purely mechanical arrangement, with a flow tube in which a bobbin moves up and down depending on the flow, or it can be an electronic sensor with an LCD (liquid crystal display). After the gases pass through the control valve and flowmeter, enter the low-pressure system, and, if required, pass through a vaporizer, they are administered to the patient. The N2O and O2 flow controls are interlocked so that the proportion of O2 to N2O can never fall below a minimum value (generally 0.25) to produce a hypoxic breathing mixture. An O2 monitor that is located on the inspiratory side of the breathing circuit analyzes gas sampled from the Y-piece of the patient s breathing circuit and displays O2 concentration in volume percent. O2 monitors should sound an if the O2 concentration falls below the preset limit. If the flow of anesthetic gases to the patient must be interrupted for any reason, an O2 flush valve can be activated to provide a large flow of central-source O2 to purge the breathing circuit of anesthetic vapors. The O2-flush flow bypasses the flowmeters and vaporizers. In some units, the anesthetic gas flow momentarily shuts off. Vaporizers Because the inhaled anesthetic agents, with the exception of N2O, exist as liquids at room temperature and sea-level ambient pressure, they must be evaporated by a vaporizer. Vaporizers add a controlled amount of anesthetic vapor to the gas mixture. Some anesthesia units can accommodate up to three vaporizers. Most units have a lockout mechanism that prevents the use of more than one vaporizer at a time. There are several types of vaporizers, including variable bypass 4

5 Reserve Cylinders Gas Supply Gas/Vapor Blending System Gas Control and Flowmeters Vaporizer O Flush Valve 2 Fresh Gas Flow Breathing Circuit Selector Valve Patient APL Valve N O Shutoff/Low O Pressure Alarm 2 2 Gas Pipelines To Atmosphere Ventilator Scavenging System Reservoir Bag C866UN7A-01 Figure 1. Continuous-flow anesthesia system (conventional), heated blender, measured flow, and draw-over. Variable bypass vaporizers can be either mechanically or electronically controlled. Variable bypass and heated blender vaporizers are concentration calibrated and thus can deliver a preselected concentration of vapor under varying conditions. In a variable bypass vaporizer, such as one used for enflurane, isoflurane, halothane, or sevoflurane, a shunt valve divides the gas mixture entering the vaporizer into two streams; the larger stream passes directly to the outlet of the vaporizer, while the smaller stream is diverted through an internal chamber in which vapor fills the space over the relatively volatile liquid anesthetic. The vapor mixes with the gas of the smaller stream, which then rejoins the larger stream as it exits the vaporizer. In a mechanically-controlled variable-bypass vaporizer, a bimetallic thermal sensor that regulates the shunt valve to divert more or less gas through the chamber compensates for temperature changes that affect the equilibrium vapor pressure above the liquid. Each variable bypass vaporizer is specifically designed and calibrated for a particular liquid anesthetic. The heated blender vaporizer was introduced for use with the anesthetic agent. In this type of vaporizer, is heated in a sump chamber. A stream of vapor under pressure flows out of the sump and blends with the background gas stream flowing through the vaporizer. Desflurane concentration is controlled by an adjustable, feedback-controlled metering valve in the vapor stream. Measured-flow vaporizers (also known as copper kettle or flowmeter-controlled) are not concentration calibrated; in this type of vaporizer, a measured flow of carrier gas is used to pick up anesthetic gas. This type of vaporizer has become almost obsolete in the United States since the adoption of an ASTM International standard that requires all vaporizers to be concentration calibrated; it may still be in use outside the United States. Draw-over vaporizers are sometimes used by the military in the field, but they are not typically used in the United States. They are usually employed in situations or countries in which pressurized gas sources are unavailable. Such units offer low resistance to gas flow and are relatively simple. A few anesthesia units now have a liquid-injector type of vaporizer. This vaporizer is electronically controlled and injects the liquid anesthetic agent directly into the stream of gases. Ventilation Manual ventilation, which requires that an operator manually squeeze the reservoir bag for each patient breath, can be tiring during long procedures and can compete with other tasks; therefore, an automatic ventilator is generally used to mechanically deliver breaths to the patient. These ventilators use a bellows or piston in place of the manually-compressed reservoir bag. The ventilator 5

6 forces the anesthesia gas mixture into the patient s breathing circuit and lungs and, in a circle breathing system (discussed below), receives exhaled breath from the patient as well as fresh gas. The anesthetist can vary the volume of a single breath (tidal volume) and the ventilation rate, either directly by setting them on the ventilator or indirectly by adjusting parameters such as the duration of inspiration, the inspiratory flow, and the ratio of inspiratory to expiratory time. The ventilatory pattern is adjusted to the varying needs of the patient. Minute ventilation, the total volume inspired or expired during one minute, can be evaluated as the product of the expired tidal volume and the ventilation rate. It requires careful monitoring, not only because it is physiologically important to the patient, but also because it can indicate malfunctions of the ventilation delivery system (e.g., leaks in the breathing circuit). The expired tidal volume can be measured with a flowmeter, with a spirometer, or with a sensor placed in the expiratory circuit. Most ventilators are capable of providing controlled ventilation and can maintain a positive airway pressure during the expiratory phase of the breath (positive end-expiratory pressure [PEEP]). Many ventilators can be equipped with modes that permit spontaneous breathing during mechanical ventilation. Fresh Gas Flow C866UN7A-02 One-Way Valve CO Absorber 2 One-Way Valve To Mechanical Ventilation and the Scavenging System Fresh Gas Flow To Mechanical Ventilation and the Scavenging System Circle Breathing System Idealization of T-Piece System Figure 2. Examples of breathing circuits Breathing circuits Most anesthesia systems are continuous-flow systems (see Fig. 1), which provide a continuous supply of O2 and anesthetic gases. There are two basic types of breathing circuits used in these systems: the circle system and the T-piece system (see Fig. 2), each of which can assume various configurations. (A common configuration of the T- piece system is the Bain modification of the Mapleson D system.) A higher proportion of anesthetic gases is rebreathed in the circle system, which uses check valves to force gas to flow in a loop and returns expired gases (minus the CO2), plus fresh gas, to the patient. In the T- piece circuit, most of the exhaled gas is vented out of the system, and the portion rebreathed depends on the fresh-gas flow rate. In the circle system, fresh gas from the anesthesia machine enters the inspiratory limb of the breathing circuit and mixes with gas in the system before the resulting mixture flows through a one-way valve to the patient. Expired gas flows from the patient through a second (expiratory) limb of the circuit, passing another one-way valve, into either a reservoir bag or a ventilator. When positive pressure is generated in the system, either by a manual squeeze of the reservoir bag or by compression of the bellows or piston by a mechanical ventilator, collected gas that does not escape via an adjustable pressure-limiting (APL) valve to the scavenging system is driven through a CO2 absorption canister where CO2 is removed from the gas before it is returned to the patient. In circle breathing systems, a fresh-gas flow of 1 L/min or less is typically considered low-flow anesthesia (4 to 10 L/min is typically considered the usual fresh-gas flow rate). A fresh-gas flow of 0.5 L/min is generally considered minimal-flow anesthesia. In situations in which the cost of anesthetic agents is high, low-flow anesthesia may be the preferred option. Machines with a T-piece design have corrugated tubing in which fresh gas and some expired gas mix before entering the patient at each inhalation. Partial rebreathing is controlled by the supply rate of fresh gas, and the exhaled anesthetic mixture leaves the circuit through an APL valve. Elimination of rebreathed CO2 depends on fresh-gas flow and occurs in direct proportion to that flow. 6

7 This system, although adaptable to a variety of anesthetic procedures, is used most often in pediatric anesthesia. Circle systems offer advantages over T-piece systems in that they conserve a greater proportion of the anesthetic gases and conserve body heat and moisture from the patient. The advantages of T- piece systems include a lower circuit compliance, easier circuit sterilization, and a less complex design requiring fewer valves and no CO2 absorber (although one can be used with it). Because excess pressure imposed on the patient s lungs can cause serious lung damage, either an APL valve or a valve in the ventilator allows excess gas to escape when a preset pressure is exceeded. There are two types of APL valves: spring-loaded and needle valves. The spring tension in spring-loaded APL valves can be adjusted to control the pressure at which the valve will open. At lower pressures, the valve is closed. The pressure in the breathing system maintained by the needle valve depends on the flow through the valve. Therefore, when the valve is not fully closed, gas will always leak from the system. The minimum exhaust pressure required to refill a ventilator bellows is usually 1 to 2 cm H2O; for maximum pressure, both types of valve are fully closed. Because many APL valves do not have calibrated markings, the anesthetist must adjust them empirically to give a desired peak inspired pressure. Circle systems and T-piece systems also include a pressure gauge for monitoring circuit pressure and setting the APL valve. An electronically controlled, settable, and calibrated APL valve is available on some anesthesia machines. Scavenging system A scavenging system captures and exhausts waste gases to minimize the exposure of the operating room staff to harmful anesthetic agents. Scavenging systems remove gas by a vacuum, a passive exhaust system, or both. Vacuum scavengers use the suction from an operating room vacuum wall outlet or a dedicated vacuum system. To prevent positive or negative pressure in the vacuum system from affecting the pressure in the patient circuit, manifold-type vacuum scavengers use one or more positive or negative pressure-relief valves in an interface with the anesthesia system. In contrast, open-type vacuum scavengers have vacuum ports that are open to the atmosphere through some type of reservoir; such units do not require valves for pressure relief. Passive-exhaust scavengers can vent into a hospital ventilation system (if the system is the nonrecirculating type) or, preferably, into a dedicated exhaust system. The slight pressure of the waste-gas discharge from the anesthesia machine forces gas through large-bore tubing and into the disposal system or directly into the atmosphere. Monitors and s Anesthesia systems incorporate a set of equipment-related monitors, including those for airway pressure, expiratory volume, and inspired O2 concentration. They can also include exhaled gas monitors, such as those for CO2 concentration, N2O concentration, and agent concentration, or physiologic monitors such as those for blood O2 saturation by pulse oximetry, electrocardiogram, invasive and noninvasive blood pressure, and temperature. Anesthesia systems are typically configured with respect to their monitors in one of two ways: as modular systems or as preconfigured systems. In the modular approach, an anesthesia machine with a basic set of equipment monitors (usually airway pressure, inspired O2 concentration, and expired volume) is used as a physical platform for the system. Additional physiologic monitors, individually or in a monitoring system (with its own display and s), along with other devices as needed, are obtained separately and added to the system. The preconfigured approach involves a more completely integrated, manufacturer-assembled system that already includes all physiologic and equipment monitors and displays in a turnkey unit. Some units may have methods of integrating, analyzing, displaying, and recording the information generated by the monitors sensors and s. Microprocessors have been incorporated into the systems to implement these functions. Stand-alone microprocessor-controlled data collection and display units have been used to integrate modular anesthesia systems. These units can also be 7

8 used as part of an anesthesia information management system (AIMS). Integration of the information and s from each of the monitors into a single display has become very important. An integrated display gives the anesthetist a single point of reference for a wide variety of equipment and physiologic information. Anesthesia machines that lack integrated s can sometimes cause confusion among anesthetists and operating room teams by sounding numerous s simultaneously. In an integrated system of information and s, visual messages appear on a central display; furthermore, audible and visual s are prioritized so that the more urgent sounds and visual signals are associated with the more vital monitored variables. An anesthesia workstation is designed to centralize system control and to integrate the display of information. This involves continuous acquisition, recording, and presentation on a central display of selected monitored physiologic and equipment variables (in real time or using historical trends) along with limit settings and the status of all s, plus explanatory messages. Several models exist to predict the level of wakefulness in anesthetized patients, such as the Ramsay Scale and the Modified Observer s Assessment of Alertness/Sedation Scale. However, in lieu of a direct method of monitoring brain activity during surgery, users may rely on indirect means of assessing consciousness, such as blood pressure and vital signs. According to proponents, one indirect method, level-of-consciousness monitoring (e.g., Bispectral Index [BIS] or Physiometrix s Patient State Index), measures the effectiveness of painkilling agents while ignoring the sedative and paralytic elements that constitute a significant portion of anesthetic agents. Some anesthesia units may incorporate this technology as an additional tool to monitor the patient. Level-ofconsciousness monitors use a metered scale (0 to 100) to indicate the degree of patient wakefulness based on collected and processed data. A digital meter indicates the number on the scale that corresponds to the patient s degree of wakefulness, with a higher number representing a higher degree of consciousness and awareness of sensation despite the presence of anesthetic agents. One supplier offers an Entropy module that provides information on the central nervous system during general anesthesia. The information is acquired based on the acquisition and processing of raw electroencephalogram (EEG) and frontalis electromyography (FEMG) signals using a proprietary algorithm. The Entropy module is designed to assist clinicians in delivering the appropriate amount of anesthetic agents. ASA states that there is not enough evidence to warrant mandatory use of these technologies for patients under general anesthesia. However, ASA stated it may be useful for at-risk patients to be monitored for intraoperative awareness. For additional information, visit ASA s Website at Automated anesthesia record keepers/anesthesia information management systems Automated anesthesia record keepers (AARKs) are available either as an option on some anesthesia units or from third-party suppliers. They are used for collecting data from electronic ventilation and monitoring equipment that has appropriate outputs. Vital signs such as blood pressure, heart rate, end-tidal CO2, and oximeter values are recorded at specific intervals and plotted in graph form. Drug dosages, lab data, intraoperative events, and gas delivery rates are entered into the system either manually or by some semiautomated means; comments can also be entered directly onto the record. An AARK produces a formatted hard copy of the anesthesia record for the patient s files. Gathering and storing such data can expedite individual patient management and billing, quality assurance, critical incident analysis, and teaching. However, automated record keeping has not achieved wide acceptance, in part because of many clinicians concerns about misleading artifacts being entered into the record, hospital personnel s resistance to change, and the cost of implementing an automated record keeper. An AIMS can receive, analyze, store, and distribute information relating to the clinical and administrative management of anesthesia. Information can be collected from numerous sources associated both directly with anesthesia administration (e.g., an AARK system) and indirectly with the surgical procedure (e.g., preoperative evaluation, laboratory, and pharmacy records). Long-term storage capabilities aid in quality assurance and anesthesiology research. Some systems may also 8

9 incorporate administrative management tools such as room scheduling and patient billing. (For further information, see the Product Comparison titled DATA MANAGEMENT SYSTEMS, ANESTHESIA.) Reported problems Problems have been reported in all areas of anesthesia systems. Because patients under general anesthesia depend entirely on others for life support, errors caused by machine failure, faulty adjustments, or the operator can be critical. Pre-use checklists, regular inspections, and preventive maintenance are critical to minimizing anesthesia unit hazards. One of the greatest dangers of general anesthesia is a lack of O2 delivered to the patient (hypoxia), which can result in brain damage or death. Conversely, the administration of O2 in a concentration of 100%, even for a short duration, may be toxic. Inhalation of 100% O2 may cause resorption atelectasis. The danger of inhaling 100% O2 is particularly acute in neonatal anesthesia, during which retrolental fibroplasia and bronchopulmonary dysplasia can be caused by inhalation of 100% O2 even for a very short duration. Inadequate O2 delivery can be caused by any number of conditions, including disconnection of the patient from the breathing circuit; accidental movement of the O2, N2O, or other gas flow control setting knobs; changes in the patient s lung compliance; and gas leaks. One common safety measure is the inclusion of an O2 monitor and a CO2 monitor or an expired volume (in an anesthesia unit with an ascending bellows or piston) in the anesthesia system. An O2 monitor warns of inadequate O2 concentration in the inspiratory limb. A CO2 monitor or a spirometer (in an anesthesia unit with an ascending bellows) in the breathing circuit can alert the anesthetist to inadequate ventilation such as that caused by a disconnection. ECRI has investigated incidents of patient exposure to carbon monoxide (CO) during the administration of inhaled anesthetics through semiclosed circle anesthesia systems. Once in the blood, CO binds tightly with hemoglobin, forming carboxyhemoglobin and diminishing the ability of hemoglobin to transport and release O2. A reaction between halogenated anesthetic agents and commonly used CO2 absorbents can produce CO if the CO2 absorbent is excessively dry. Drying out can occur when (1) an anesthesia machine has been idle (e.g., over a weekend), and (2) there is a continuous flow of medical gas (which is very dry) through the CO2 absorber. When dry, the absorbent becomes highly reactive in the presence of certain halogenated agents, resulting in the production of CO as the agent flows through the machine s CO2 absorber. ECRI recommends that the absorbent material in both canisters of an absorber be replaced whenever there is reason to believe that a machine has been left idle with gas flowing for an undetermined time. Fresh absorbent materials are sufficiently hydrated and normally remain hydrated by exhaled water vapor in the circle system, thereby preventing reaction with halogenated agents. For more information, please see the Health Devices citation in this report. Some anesthesia system malfunctions can cause delivery of gas with excessive CO2 concentration, an inadequate or excessive amount of anesthetic agent, or dangerously high pressure. Hypoventilation, compromised cardiac output, air in the pleural cavity (pneumothorax), and asphyxiation are possible consequences of such problems. Improperly calibrated vaporizers can result in the delivery of the wrong concentration of anesthetic agent to the patient. Removing some vaporizers from the anesthesia machine and transporting them can disturb their calibration and could eventually cause delivery of too much or too little anesthetic. However, many tip-proof vaporizers have been released to reduce calibration errors. The output of an anesthesia vaporizer should be tested each time the vaporizer is removed from a system and each time it is returned to service. Each vaporizer should be inspected and the calibration verified at least twice a year. Contamination of any part of the anesthesia breathing circuit, including the breathing tubes, Y- connector, face mask, and reservoir bag, may lead to nosocomial infections. Reported cases include infections of the upper respiratory tract or the lungs and, in one instance in Australia, transmission of hepatitis C. The Centers for Disease Control and Prevention (CDC) and the American Association of Nurse Anesthetists recommend single use of disposables or high-level disinfection of reusables or disposables between patients to prevent cross-contamination. There has been some controversy 9

10 concerning the use of disposable bacteria filters to prevent patient cross-infections (Berry and Nolte 1991, Brooks et al. 1991, Dorsch and Dorsch 1998, Hogarth 1996, Komesaroff 1996, Snowdon 1994). CDC has not made a definitive recommendation concerning the use of bacterial filters with anesthesia machines. Possible hazards, such as the increased impedance to gas flows and obstruction of the circuit, are associated with these filters. Also, because many viruses are difficult to culture, the efficacy of viral filters that attempt to reduce viral contamination of breathing systems is not established. Frequent replacement of disposable filters can prevent inadequate gas delivery due to clogging and some filters can be sterilized and reused. The piping connections for O2 and N2O within the hospital walls can be accidentally interchanged during installation or repair of medical gas systems, potentially for causing patient injury or death. After any such work, careful inspection and testing with an O2 analyzer are vital. Gas lines should also be checked for liquid, gaseous, solid particulate, and microorganism contamination after installation or repair and periodically thereafter. In the United States, a diameter index safety system (DISS) is used to prevent the connection of gas hoses from the machine to the wrong wall outlet, and a pin index safety system is used to prevent the connection of the wrong cylinders to the yokes in the anesthesia machine. The pin index safety system employs pins protruding from the yoke that correspond to holes in a specific type of gas cylinder post. Only a cylinder post with the corresponding holes can fit properly onto the yoke. Countries outside the United States have similar requirements to ensure the proper connection of all medical gas hoses to the anesthesia machine. ECRI has seen instances of improper connections in which damaged pins allowed users to force the wrong cylinder into place. ECRI recommends that damaged indexing components should never be used. Faulty or inoperative scavenging systems are responsible for most anesthetic gas pollution in the operating room; other causes include improper anesthesia administration technique and leaks in anesthesia equipment. Common sources of leaks include hose connectors, the CO2 absorber, the APL valve, and the endotracheal tube or mask. Current scientific and epidemiologic studies have shown that exposure to trace levels of anesthetic gases continually present in the operating room can cause adverse health effects in operating room personnel, such as an increased incidence of spontaneous abortion and congenital anomalies in offspring. In addition, trace gas levels in the air may have a slight anesthetizing effect on the anesthetist and surgeon. The increased interest in low-flow anesthesia to reduce costs has increased the potential danger associated with leaks in the anesthesia unit. Because low-flow anesthesia requires very little fresh gas flow, a leak in the equipment can result in inadequate delivery of O2 and anesthetic gases. Regular testing of the anesthesia equipment using standard leak tests should minimize the risk of leaks during the administration of anesthesia. Inadequate evacuation of some scavenging systems can cause pressure to build up in the breathing circuit, with the potential for pneumothorax. Another common problem is circuit obstruction due to the presence of a foreign object (e.g., needle caps) or a manufacturing defect. This problem occurs most often when a pre-use check is omitted. As mentioned previously, anesthesia units that lack integrated monitors and s can cause confusion by sounding numerous s simultaneously. While integrated monitors and s are becoming more widespread, both modular and integrated systems are subject to the confusion caused by false s. A false, caused by accidental patient movement or other nonphysiological reasons, can confuse operating room staff and possibly draw attention away from other s that may truly indicate a change in the patient s physiologic condition. Ensuring that the limits are properly set and positioning sensors and electrodes in such a way as to minimize artifacts can reduce the incidence of false s. Also, ECRI recommends that users do not set physiologic limits below normal values in order to reduce nuisance s. The magnetic fields created by magnetic resonance imaging (MRI) equipment may interfere with the function of conventional anesthesia units and electronic monitoring equipment when used in proximity to such equipment. Conversely, magnetic materials and electronic monitors may interfere with MRI scanner function and degrade image quality. Also, anesthesia machines are designed to be 10

11 compatible with MRI units when used in accordance with the instructions and precautions contained in the operation manual and on the unit itself. If the instructions are not followed, the anesthesia units could be attracted to MRI units, potentially causing user or patient injury. Many MRIcompatible anesthesia machines have restrictions or limitations to their use in the MRI environment. If they are not used in accordance with these restrictions/limitations, MRI-compatible devices can pose the same types of hazards in the MRI environment as devices that are not MRI compatible. For instance, if some MRI-compatible devices are positioned closer to the MRI unit than is specified by the device supplier, they can become airborne and crash into the magnet. Also, some MRI-compatible devices that come into physical contact with a patient, if used inappropriately, can cause burns (or the sensation of heat) to a patient. The hazards posed by the inappropriate use of MRI-compatible devices in the MRI environment can cause injury to the patient or staff and/or damage to equipment (e.g., the MRI-compatible device or the MRI unit itself). A few suppliers offer MRI-compatible anesthesia machines, and a line of MRI-compatible monitors is available. Users should be careful not to hang any extraneous materials (e.g., polyethylene garbage bags) or equipment from anesthesia units. If accidentally bumped, the hanging objects may compromise the anesthesia unit s stability and be sucked into the receiving end of the anesthesia unit. This could cause the full negative pressure to be transmitted to the patient breathing system, collapsing the reservoir bag. Purchase considerations ECRI recommendations Included in the accompanying comparison chart are ECRI s recommendations for minimum performance requirements for anesthesia units. The recommendations are listed in two categories: basic and high performance. ECRI considers certain minimum safety measures necessary for all anesthesia units. Among these measures are O2 fail-safe and hypoxic mixture fail-safe systems, gas cylinder yokes for O2 in case central supplies fail, and an internal battery (for units with automatic ventilators) capable of powering the unit for at least 30 minutes. An anesthesia unit should consist of a gas supply and control circuit, a breathing and ventilation circuit, and a scavenging system (not required on basic systems). The unit must be able to measure O2 concentration, airway pressure, and either the volume of expired gas or the concentration of expired CO2 (ETCO2). (Note: ASA recommends monitoring of ETCO2 in all intubated patients; this can be accomplished by the anesthesia unit or by a separate device [e.g., capnograph, multigas monitor].) Gas cylinders should be attached through hanger yokes with the proper pin index safety system and check valves. Each pipeline gas cylinder supply should have a pressure gauge with scale numbers large enough to be easily read. Gas hoses and machine receptacles should use DISS fittings to prevent misconnection. It is advantageous if the anesthesia unit accepts medical-air input to allow delivery of either air and/or N2O as the gas carrier. In the event of a partial or complete loss of O2 supply, an undefeatable audible should activate and the flow of N2O gases should automatically shut off or decrease proportionately to the flow of O2 to prevent a hypoxic condition. Also, flows and the mixture ratios determined from flowmeter settings should be accurate to within 10% of set values. Anesthetic vapor concentration delivered to the common gas outlet should be accurate to within 0.2% vapor concentration of agent or 10% of the set value (whichever is greater) at any gas flow. It is preferable that ventilation rate and PEEP values be monitored. It should not be possible to silence or disable a ventilator monitor for longer than two minutes. Line-powered units should have a power-loss and battery-powered units should have an automatic low-battery. All line-powered units should include a backup battery to guard against power loss. The anesthesia unit should automatically switch to the internal battery if line power is interrupted; also, the loss of line power should be accompanied by an. The battery 11

12 should also operate the anesthesia unit and integral monitors for at least 30 minutes. A low-battery should visually and audibly indicate when the battery voltage falls to a level below which the unit may fail to perform satisfactorily. If the battery is rechargeable, it should not require more than 16 hours to recharge after depletion. High-performance systems are distinguished largely by their ability to serve a wide range of patients and to operate with little or no supplemental equipment. Features that make this possible include ventilator modes and tidal volume ranges suitable for neonates and adults, as well as integrated gas and sometimes physiologic monitoring. High-perfomance units generally include more automated features, including storage of trends and self-tests at the beginning of each procedure. Basic systems include only the most vital monitoring capabilities (i.e., O2 and CO2 volumes or pressures) and have only one or two automatic ventilator modes. When equipped with appropriate stand-alone monitors, these units are adequate for treatment of most patients but may remain illsuited for use on neonates and very sick patients, as well as for monitoring-intensive procedures (e.g., certain types of cardiac surgery). These fundamental systems may also include units designed for military or field use, which often lack ventilators and pipeline gas inlets. Other considerations Some anesthesia units require stand-alone physiologic monitors (modular approach) and/or anesthetic agent monitors, while others have integrated monitors (preconfigured approach). The advantages of preconfigured monitoring include convenience and electronically integrated displays and prioritized s. Modular systems can be less expensive than preconfigured systems, especially if the facility already owns the monitors. Hospitals can purchase customized modular systems assembled from standard components, or they can assemble their own modular systems. These systems must meet all national and regional safety standards. Advantages of the modular approach include flexibility in choosing and upgrading monitors and ease of service; drawbacks include assembling a system that may not be successfully integrated and thus has multiple s and/or multiple displays. Anesthesia units and patient monitoring systems should be carefully chosen to ensure that all the essential monitoring functions recommended by the American Society of Anesthesiologists are obtained and to ensure optimal integration and an adequate standard of care. For legal reasons, the level-of-monitoring and anesthesia-delivery capabilities for each anesthesia station should be uniform so that all patients receive the same standard of care for the same surgical procedures. Integrated anesthesia workstations, along with the gas/vapor dispensing subsystem and individual physiologic and equipment monitors, may also include a device for automatically dispensing injectable drugs. Consequently, the anesthesia workstation can be viewed as an integrated monitoring system that dispenses anesthetic drugs. Hospitals should also consider the standardization of anesthesia equipment; that is, purchasing systems that are compatible with equipment already in operating rooms or other areas of the hospital (e.g., intensive care units). The purpose of standardization is to allow a reduced parts inventory, minimize the number of suppliers and service personnel, and reduce confusion among the staff. Pulse oximetry is considered a standard of care for monitoring arterial O2 saturation in the operating room during procedures requiring anesthesia and in intensive care units and recovery. Pulse oximeters noninvasively measure O2 saturation of blood hemoglobin (SpO2) and, along with O2 monitors and CO2 monitors, are increasingly being required for anesthesia units by state law. Some U.S. states have specified their own requirements for anesthesia units. Hospitals should check with their state s department of health for any regulations that may apply to their area. Pulse oximeters provide a spectrophotometric assessment of hemoglobin oxygenation by measuring light transmitted through a capillary bed, synchronized with the pulse. The detection system consists of single-wavelength LEDs (light-emitting diodes) and microprocessors located within a sensor. For more information on pulse oximeters, see the Product Comparison titled OXIMETERS, PULSE. 12

13 CO2 monitors measure end-tidal CO2 and can help identify leaks and misconnections as well as indicate when the trachea has not been properly intubated. Many features of anesthesia systems are optional, allowing hospitals to choose the ones that best fit their needs. Among anesthesia units with essentially equivalent mechanical gas/vapor dispensing subsystems, the monitors included in the system and the ways in which information is integrated and displayed are often the primary distinguishing features. Cost containment Because anesthesia systems entail ongoing maintenance and operational costs, the initial acquisition cost does not accurately reflect the total cost of ownership. The anesthetic agents are the biggest ongoing expense associated with anesthesia units. Therefore, a purchase decision should be based on issues such as life-cycle cost (LCC), local service support, discount rates, and non-pricerelated benefits offered by the supplier. An LCC analysis should be conducted to determine the cost-effectiveness of all the units that meet the users needs. Although costs associated with many of the following may be similar for a number of anesthesia units, they should still be carefully considered to determine the total LCC for budget purposes: Maintenance, service, and inspection Accessories, such as monitoring equipment, necessary to comply with standards Optional accessories Vaporizers (some have been offered at discounted prices or at no cost upon the introduction of a new anesthetic agent) Gases, including O2, N2O, and anesthetic agents Anesthesia circuits Recording and storage of anesthesia-related data Disposables Utilities When selecting a vaporizer, consider the type of anesthetic agent required for the hospital s patient mix in conjunction with the types of procedures being performed. Users should ask the supplier if the anesthetic gas monitor will be able to identify and measure all anesthetic agents used (i.e., some models may not recognize sevoflurane). Hospitals can purchase service contracts or service on a time-and-materials basis from the supplier. Service may also be available from a third-party organization. The decision to purchase a service contract should be carefully considered. Most suppliers should provide routine software updates, which enhance the system s performance, at no charge to service contract customers. Purchasing a service contract also ensures that preventive maintenance will be performed at regular intervals, thereby eliminating the possibility of unexpected maintenance costs. Also, many suppliers do not extend system performance and uptime guarantees beyond the length of the warranty unless the system is covered by a service contract. Hospitals that plan to service their anesthesia units inhouse should inquire about the availability and cost of service training and the availability and cost of replacement parts. ECRI recommends that, to maximize bargaining leverage, hospitals negotiate pricing for service contracts before the system is purchased. Additional service contract discounts may be negotiable for multiple-year agreements or for service contracts that are bundled with contracts on other similar equipment in the department or hospital. Discounts will depend on the hospital s negotiating skills and knowledge of discounts offered to other customers, the system configuration and model to be purchased, previous experience with the supplier, and the extent of concessions granted by the supplier, such as extended warranties, fixed prices for annual service contracts, and guaranteed onsite service response. Buyers should make sure that applications training and service manuals are included in the purchase price of the system. Some suppliers offer more extensive on- or off-site training programs for an additional cost. For customized analyses and purchase decision support, readers should contact ECRI s SELECT Group. 13

14 Stage of development Efforts to improve the design of anesthesia units center on gas supply and proportioning systems, breathing circuits, gas scavenging and humidification devices, gas monitors, ventilators, vaporizers, and data-handling (display, processing, and reporting) software. There is also an effort to decrease the overall size of anesthesia units. Although anesthesia systems are fundamentally unchanged, manufacturers have made a handful of improvements. Among them are: The introduction of low-volume breathing circuits The increasing availability of ventilation modes Increasing automation of pre-use checks Bibliography Block FE Jr, Schaaf C. Auditory s during anesthesia monitoring with an integrated monitoring system. Int J Clin Monit Comput 1996 May;13(2):81-4. Bromley HR, Tuorinsky S. An uncommon leak in the anesthesia breathing circuit [letter]. Anesth Analg 1997 Sep;85(3):707. Centers for Disease Control and Prevention. Guidelines for prevention of nosocomial pneumonia. Hospital Infection Control Practices Advisory Committee. MMWR Recomm Rep 1997 Jan 3;46(RR-1):1-79. Chant K, Kociuba K, Munro R, et al. Investigation of possible patient-to-patient transmission of hepatitis C in a hospital. New South Wales Pub Health Bull 1994 May;5(5): Davey A, Moyle JT, Ward CS. Ward s anaesthetic equipment. 4th ed. London: WB Saunders; Dorsch JA, Dorsch SE. Understanding anesthesia equipment. 4th ed. Baltimore: Lippincott, Williams & Wilkins; Ehrenwerth J, Eisenkraft JB, eds. Anesthesia equipment: principles and applications. St. Louis: Mosby-Year Book; Eisenkraft JB, Leibowitz AB. Ventilators in the operating room. Int Anesthesiol Clin 1997 Winter;35(1): Elliot B, Chestnut J. Dangers of s [letter]. Anaesthesia 1996 Aug;51(8): Failure to test anesthesia machine prior to surgery and to properly monitor patient during surgery. Med Malpract Verdict Settlements 2002 Jun;18(6):4. Heaton J, Hall AP, Fell D. The use of filters in anaesthetic breathing systems [letter]. Anaesthesia 1998 Apr;53(4):407. Hobbhahn J, Hoerauf K, Wiesner G, et al. Waste gas exposure during and isoflurane anaesthesia. Acta Anaesthesiol Scand 1998 Aug;42(7): Hogarth I. Anaesthetic machine and breathing system contamination and the efficacy of bacterial/viral filters. Anaesth Intensive Care 1996 Apr;24(2): Holak EJ, Mei DA, Dunning MB, et al. Carbon monoxide production from sevoflurane breakdown: modeling of exposures under clinical conditions. Anesth Analg 2003 Mar;96(3): Jack T. A leak of concern [letter]. Br J Anaesth 1998 Jun;80(6): Komesaroff D. Disposable and autoclavable anaesthetic circuits: the future is now. Anaesth Intensive Care 1996 Apr;24(2): McMahon DJ. A synopsis of current anesthesia machine design. Biomed Instrum Technol 1991 May- Jun;25(3):

15 Petty WC. New anesthetic requires new vaporizers for safety. J Clin Monit 1996 Nov;12(6):483. Rogers S, Davies MW. My anaesthetic machine s on fire [letter]. Anaesthesia 1997 May;52(5):505. Sivalingam P, Hyde RA, Easy WR. An unpredictable and possibly dangerous hazard of an anaesthetic scavenging system [letter]. Anaesthesia 1997 Jun;52(6): Snowdon SL. Hygiene standards for breathing systems? [editorial]. Br J Anaesth 1994 Feb;72(2): Somprakit P, Soontranan P. Low pressure leakage in anaesthetic machines: evaluation by positive and negative pressure tests. Anaesthesia 1996 May;51(5): Standards and guidelines Note: Although every effort is made to ensure that the following list is comprehensive, please note that other applicable standards may exist. Also, there are many state rules and regulations in the United States regarding anesthesia machines; consult ECRI s Healthcare Standards Directory or your state department of health for more information. Anesthesia breathing circuits ASTM International. Specification for particular requirements for anesthesia workstations and their components [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (revised 2000). Specification for anesthetic breathing tubes [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1999) (reapproved 1999). Specification for minimum performance and safety requirements for components and systems of anesthetic gas monitors [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1992) Australian and New Zealand College of Anaesthetists. Protocol for checking the anaesthetic machine. PS (revised 1997). European Committee for Standardization/Danish Standards Association. Breathing tubes intended for use with anaesthetic apparatus and ventilators [standard]. DS/EN 12342: Hong Kong College of Anaesthesiologists. Protocol for checking an anesthetic machine before use [policy statement] International Organization for Standardization. Breathing tubes intended for use with anaesthetic apparatus and ventilators [standard]. 4th ed. ISO 5367: Inhalational anaesthesia systems part 2: anaesthetic circle breathing systems [standard]. 2nd ed. ISO : (revised 1999). Anesthesia equipment American Association of Nurse Anesthetists. Infection control guide [guideline] (revised 1997). American National Standards Institute. Minimum performance and safety requirements for components and systems of continuous-flow anesthesia machines for human use [standard]. ANSI Z American Society of Anesthesiologists. Recommendations for infection control for the practice of anesthesiology. 2nd ed

16 Standards for basic anesthetic monitoring (reaffirmed 15 Oct 2003). Association of Perioperative Registered Nurses. Recommended practices for cleaning and processing anesthesia equipment [recommended practice] (revised 2004). ASTM International. Specification for particular requirements for anesthesia workstations and their components [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (revised 2000). Specification for signals in medical equipment used in anesthesia and respiratory care [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1999) (revised 1999). Specification for anesthetic equipment oropharyngeal and nasopharyngeal airways [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (2000) (revised 2000). Australian and New Zealand College of Anaesthetists. Recommendations on checking anaesthesia delivery systems (revised 2003). British Standards Institution. Anaesthetic and analgesic machines. Specification for continuous flow anaesthetic machines [standard]. BS : Anaesthetic and analgesic machines. Specification for intermittent (demand) flow analgesic machines for use with 50/50% (V/V) nitrous oxide and oxygen [standard]. BS : (revised 1996). Canadian Anesthesiologists Society. Guidelines to the practice of anaesthesia (revised 2003). Canadian Standards Association. Anaesthetic machines for medical use [standard]. CSA Z (R2001) (reaffirmed 2001). Danish Standards Association/European Committee for Standardization. Anaesthetic workstations and their modules particular requirements [standard]. DS/EN740: European Committee for Standardization. Anaesthetic and respiratory equipment conical connectors part 1: cones and sockets [standard]. EN : (revised 1997). International Electrotechnical Commission. Medical electrical equipment part 1: general requirements for safety [standard]. IEC ( ) Medical electrical equipment part 1: general requirements for safety. Amendment 1 [standard]. IEC am1 ( ) Medical electrical equipment part 1: general requirements for safety. Amendment 2 [standard]. IEC am2 ( ) Medical electrical equipment part 1-1: general requirements for safety. Collateral standard: safety requirements for medical electrical systems. 2nd ed. IEC ( ) (revised 2000). Medical electrical equipment part 1-2: general requirements for safety. Collateral standard: electromagnetic compatibility requirements and tests. IEC ( ) (revised 2001). Medical electrical equipment part 1-4: general requirements for safety. Collateral standard: programmable electrical medical systems. IEC ( ) (revised 2000). 16

17 Medical electrical equipment part 2-13: particular requirements for the safety of anesthetic workstations [standard]. IEC ( ) International Organization for Standardization. Anaesthesia and respiratory care signals part 1: visual signals [standard]. 1st ed. ISO 9703:Part 1: Anaesthesia and respiratory care signals part 2: auditory signals [standard]. 1st ed. ISO : Anaesthesia and respiratory care signals part 3: guidance on application of s [standard]. 1st ed. ISO : Anaesthetic and respiratory equipment conical connectors part 1: cones and sockets [standard]. 2nd ed. ISO 5356: (revised 1996). Anaesthetic and respiratory equipment conical connectors part 2: screw-threaded weightbearing connectors [standard]. 1st ed. ISO : Anaesthetic and respiratory equipment heat and moisture exchangers (HMEs) for humidifying respired gases in humans part 1: HMEs for use with minimum tidal volumes of 250 ml [standards]. 1st ed. ISO : Anaesthetic and respiratory equipment heat and moisture exchangers (HMEs) for humidifying respired gases in humans part 2: HMEs for use with tracheostomized patients having minimum tidal volumes of 250 ml [standard]. 1st ed. ISO : Anaesthetic gas monitors [standard]. 1st ed. ISO 11196: Inhalational anaesthesia systems part 4: anaesthetic vapor delivery devices [standard]. ISO : Jun. Standards Australia/Standards New Zealand. Anaesthetic machines non-electrical for use with humans [standard]. AS/NZS Underwriters Laboratories, Inc. Electrically conductive equipment and materials for use in flammable anesthetizing locations [standard]. 3rd ed (revised 1997). U.S. Department of Health and Human Services. Food and Drug Administration. Anesthesiology devices. 21 CFR Part U.S. Department of Labor. Occupational Safety and Health Administration. Anesthetic gases: guidelines for workplace exposures Jul 20 (revised 2000 May 18). Anesthesia unit vaporizers European Committee for Standardization. Agent specific filling systems for anaesthetic vaporizers part 1: rectangular keyed filling systems [standard]. EN : Internation Organization for Standardization. Anaesthetic vaporizers agent-specific filling systems [standard]. 1st ed. ISO 5360: Anesthesia ventilators ASTM International. Specification for minimum performance and safety requirements for anesthesia breathing systems [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1994) (reapproved 1994). 17

18 Specification for particular requirements for anesthesia workstations and their components [standard]. ASTM Committee F29 Anesthetic and Respiratory Equipment. F (revised 2000). Specification for ventilators intended for use during anesthesia [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1996) (revised 1996). Canadian Standards Association. Anaesthesia ventilators [standard]. CAN/CSA-Z (R2001) (reaffirmed 2001). Center for Devices and Radiological Health. Anesthesia apparatus checkout recommendations International Organization for Standardization. Breathing tubes intended for use with anaesthetic apparatus and ventilators [standard]. 4th ed. ISO 5367: Anesthetic reservoir bags American Society for Testing and Materials. Specification for anesthesia reservoir bags [standard]. ASTM Committee F29 on Anesthetic and Respiratory Equipment. F (1998) (reapproved 1998). Medical gas piping Canadian Standards Association. Low-pressure connecting assemblies for medical gas systems [standard]. CAN/CSA-Z305.2-M88(R2001) (reaffirmed 2001). Medical oxygen concentrator central supply system: for use with nonflammable medical gas piping systems [standard]. CAN/CSA-Z (R2001) (reaffirmed 2001). Danish Standards Association/European Committee for Standardization. Medical gas pipeline systems part 2: anaesthetic gas scavenging disposal systems basic requirements [standards]. DS/EN 737-2: European Committee for Standardization. Medical gas pipeline systems part 4: terminal units for anaesthetic gas scavenging systems [draft standard]. EN 737-4: International Organization for Standardization. Terminal units for medical gas pipeline systems part 2: terminal units for anaesthetic gas scavenging systems. 1st ed. ISO : National Fire Protection Association/American National Standards Institute. Fire protection in health care facilities [standard]. ANSI/NFPA In the United States, medical-gas pipeline systems must be constructed and maintained to meet the requirements of NFPA 99. Chapter 4 of this code specifically covers medical-gas and vacuum systems. A number of other countries, including Britain, France, and Japan, have requirements based on this code. Scavenging systems American National Standards Institute. Scavenging systems for excess anesthetic gases [standard]. ANSI Z European Committee for Standardization. Medical gas pipeline systems part 4: terminal units for anaesthetic gas scavenging systems [draft standard]. pren 737-4: International Organization for Standardization. Inhalational anaesthesia systems part 3: anaesthetic gas scavenging systems transfer and receiving systems [standard]. 1st ed. ISO : Medical gas pipeline systems part 2: anaesthetic gas scavenging disposal systems. 1st ed. ISO 18

19 7396-2: National Institute for Occupational Safety and Health. Development and evaluation of methods for elimination of waste anesthetic gases and vapors in hospitals. NTIS No. PB Waste anesthetic gases and vapors [recommendation]. NTIS No. PB Citations from other ECRI publications Health Devices Concentration calibrated vaporizers [hazard] Mar-Apr;16(3-4):112. Pre-use testing prevents helpful reconnection of anesthesia components [hazard] May;16(5): Who should service anesthesia equipment? [User Experience Network ] Feb;17(2):70-1. Barotrauma from anesthesia ventilators [hazard] Nov;17(11):354. Oxygen regulator fire caused by use of two yoke washers [hazard] Nov;19(11): Risk of barotrauma and/or lack of ventilation with ventilatorless anesthesia machines [hazard] Jan-Feb;23(1-2):54-5. False CO2 readings from disposable anesthesia breathing circuits with an internal gas-sampling line [hazard] Apr;24(4): Fires from oxygen use during head and neck surgery [hazard] Apr;24(4): Anesthesia systems [evaluation] May-Jun;25(5-6): Anesthesia ventilators with descending bellows: the need for appropriate monitoring [hazard] Oct;25(10): Leaching of the plasticizer from PVC tubing in heart-lung bypass unit tubing circuits [User Experience Network ] Oct;25(10): Anesthesia systems [update evaluation] Jan;27(1):4-27. Surgical fires: learning prevention [Talk to the specialist] Sep;28(9): Carbon monoxide exposures during inhalation anesthesia: the interaction between halogenated anesthetic agents and carbon dioxide absorbents [hazard report] Nov;27(11): Anesthesia systems [update evaluation] Apr;31(4): Anesthesia carbon dioxide absorber fires [hazard report online preview] Nov [cited 2003 Nov 19]. Available from Internet: Nov- AnesthesiaCO2Fires.pdf. Ventilator failures on Draeger Medical Fabius GS and Fabius Tiro anesthesia units [problem report] 2005 Jul;(34(7):23-5. Health Devices Alerts This Product Comparison lists Health Devices Alerts (HDA) citations published since the last update of this report. Each HDA abstract is identified by an Accession Number. Recalls and hazard reports include descriptions of the problem involved; abstracts of other published articles are referenced by bibliographic information. HPCS subscribers can call the Hotline for additional information on any of these citations or to request more extensive searches of the HDA database. 19

20 A5794 The U.K. Medicines and Healthcare Products Regulatory Agency (MHRA) has issued a Medical Device Alert notifying healthcare workers that the Association of Anaesthetists of Great Britain and Ireland (AAGBI) has published an updated version of its guideline "Checking Anaesthetic Equipment." The document was developed to prevent inadequate pre-use checks of anesthetic equipment. Use of inadequately checked anesthetic equipment has been associated with serious patient consequences, such as hypoxic brain damage or death. AAGBI and MHRA recommend that all U.K. anesthesia practitioners follow the updated AAGBI checklist, which is available online at Laminated copies of the 2-page checklist are available from AAGBI and should be attached to every anesthesia unit. Inquiries to AAGBI should be addressed to the Association of Anaesthetists of Great Britain and Ireland by mail at 21 Portland Place, London W1B 1PY, England; by telephone at (0207) ; by fax at (0207) ; or by at info@aagbi.org. Technical inquiries to MHRA should be addressed to Douglas McIvor or Nigel Richards, MHRA, by mail at Hannibal House, Elephant and Castle, London SE1 6TQ, England; by telephone at (0207) or 8277, respectively; by fax at (0207) ; or by at douglas.mcivor@mhra.gsi.gov.uk or nigel.richards@mhra.gsi.gov.uk, respectively. Clinical inquiries to MHRA should be addressed to Dr. Susanne Ludgate, MHRA, by mail at the above address, by telephone at (0207) , by fax at (0207) , or by at susanne.ludgate@mhra.gsi.gov.uk. All inquiries to MHRA should quote reference no Source: Great Britain. Medicines and Healthcare Products Regulatory Agency. Anaesthetic equipment and associated devices. London: Department of Health; 2004 Jan p. (Medical device alert; no. MDA/2004/003). A6015 FDA has designated this Class II Recall No. Z for certain Draeger Medical anesthesia units. In some cases, the rotary-knob-style APL valve of these anesthesia machines may separate from the unit. The APL valve is located on the breathing system, and the rotating knob is used to adjust airway pressure during manual ventilation. If the APL valve separates during use, manual ventilation will not be possible. Spontaneous and automatic ventilation will not be affected by APL valve separation. The manufacturer states that the failure rate is approximately 1% and that there have been no reported injuries resulting from this malfunction. The manufacturer initiated a recall by letter dated September 15, Verify that you have received the September 15, 2004, letter from Draeger. Identify any affected product in your inventory by removing the APL valve from the breathing system so that you can view the retaining nut, which will have the part number, revision level, and serial number stamped on the bottom. A DraegerService representative or authorized service organization will contact you to schedule replacement of affected APL valves. As standard practice and as referenced in the pre-use check in the operator s instruction manual, you should always have emergency ventilation equipment, such as a manual resuscitator, available for use with any anesthesia machine. For further information, contact Mike Kelhart, Draeger regulatory affairs, by telephone at (800) , ext. 2349, within the U.S. or at (215) outside the U.S. For further information regarding replacement of your APL valve, contact Draeger Service technical support by at techsupport@draegermed.com or by telephone at (800) (press #3 at the prompt) within the U.S. Source: FDA Enforcement Rep 2004 Nov 24; letter submitted by manufacturer. A6296 FDA has designated this action Class II Recall No. Z for certain Maquet anesthesia systems. A software update (version 7.0) has been released for these anesthesia systems. The manufacturer notified U.S. customers by letter dated January 11, The firm states that all systems have been updated or returned. No further action is required of customers. Source: FDA Enforcement Rep 2005 Apr 20; Manufacturer. D6528 FDA has designated this Class II Recall No. Z complete for certain Datascope anesthesia delivery units. The alternating current (AC) mains switch may fail, resulting in a loss of AC power. If AC power loss were to occur during device operation, the system would shift to battery operation to maintain pneumatic ventilation, sound an audible, and display intermittent 20