Volume 7, No. 1 • Spring 1992

European “Workstation” Rules Will Influence U.S. Anesthesia Machines

Stanley Weitzner, M.D.

Anesthesia equipment standards now being formulated in Europe may well have a significant influence on American anesthesia gas machines in the near future, particularly regarding mandatory monitoring of volatile anesthesia agents and the interrelationships of monitors and their alarms with anesthesia machines.

American anesthesiologists have been active for a quarter of a century in the development of minimum safety and performance standards for anesthesia equipment. As a result, when the International Standards Organization (ISO) Technical Committee on Anesthesia and Respiratory Equipment was approached by European delegations to prepare a safety and performance standard covering the essential requirements of an Anesthesia Workstation for the recently constituted European Economic Community (EEC), a “neutral North American expert” long active in this area (this author) was asked to chair this effort. In September, 1989, the formation of a joint IS0/IEC (International Electrotechnical Commission) working group was approved by the ISO Technical Committee. The working group consisted originally of experts nominated as national representatives from six European community countries plus Japan, Canada, Sweden, the Netherlands, and the United States.

Although there are many extant national and international anesthesia gas machine standards, the anesthesia workstation, for purposes of this European community standard, not only was to include the traditional components of an anesthesia gas machine such as vaporizer, flow control modules, breathing system, absorber, etc. but was also to include such devices as a pulse oximeter, ECC, non-invasive blood pressure monitor and other monitoring and/or protective devices. It was of interest to many of the committee members and others that various practice guidelines developed by different national professional societies (including the American Society of Anesthesiologists) were influential in convincing members of the working group that standards restricted to anesthesia gas machine safety and function only would be inadequate; for example, ECG and temperature monitoring are considered in these standards, although traditionally they are not part of the anesthesia gas machine, nor are they covered in any other anesthesia gas machine standards known.

The concept basic to the entire development of the workstation standard was that each anesthesia workstation is operated with ‘delivery system” devices (an ‘actuator’ that delivers either energy or drugs) and specific, associated devices designed for protection against the hazards from the delivery of this energy or substance to the patient. In other words, the intent was that for every specific delivery system (actuator) there would be a specific ‘hazard protection device’ associated with it (e.g. when a ventilator is in use, a pressure monitor with a high pressure alarm-the hazard protection device also must be in use).

Development of the new workstation standard is almost complete and it is expected to be submitted soon for ballot by the national delegations within the ISO Committee on Anesthesia. It is assumed that a similar, if not identical, standard then will be adopted by the European Community. The European Community mechanism routinely is charged with adopting, or very closely adapting, an already existing ISO standard, and only as a last resort writing a new standard.

The workstation standard originally was intended to apply to electronically controlled anesthesia gas machines that offer functional integration of both anesthesia delivery and comprehensive monitoring. It was further intended that the apparatus be supplied complete by one manufacturer, or possibly be assembled and integrated by one supplier, or assembled by the user. It should be noted that within U.S. law, each of these three approaches has different, and extensive, legal implications. Repair and service responsibility, product warranty, and FDA regulation would be different in each case. This has been the subject of much debate within the committee. The draft standard calls for the breathing system to have pressure monitoring, exhaled volume monitoring, ventilatory C02 monitoring and expired oxygen monitoring. Prioritized alarms with separate requirements for their audible and visual components are also mandated. The document will take advantage of, and incorporate or modify, existing ISO standards relating to 15/22mm fittings, anesthesia ventilators, gas mixers, and anesthetic gas scavenging systems. In most cases, the relevant ISO standards are very similar, if not identical, to current U.S. (ASTM F-29) standards.

It is the intention, and the agreement, of the member countries, for manufacturers to be able to .certify” that their anesthesia workstation meets the ISO standard’s requirements (with an independent “test house” confirming this). Once having achieved ft, manufacturers win be able to sell the apparatus throughout the EEC without restriction and without having to test and certify to 12 or more different national standards. This would offer a very significant commercial advantage since the EEC is one of the world’s largest markets.

The standard follows the format of IEC 6011:1988 “Medical Electrical Equipment General Requirements for Safety’ and deals with these areas: 1) terminology and definitions; 2) general requirements for electrical safety (e.g. single-fault conditions, operating temperature limits, etc.); 3) general test conditions needed to certify that the anesthesia workstation complies with the standard; 4) identifications, markings, and documents (e.g. color-coding of gas tanks, flowmeters, etc.), as wen as detailed information to be provided by the manufacturer in accompanying documents and manuals provided to the user, 5) sections relating to mechanical strength and stability; vibration and noise; hazards from, and susceptibility to, excessive radiation; excess humidity; accidental leakage of fluids into the workstation; sterilization and disinfection; and 6) requirements dealing with traditional components like gas cylinder and pipeline connections, pressure gauges, etc.

IEC 601-1 is the ‘mother document” for most if not all IEC Standards and also is providing the dominant format for ISO and ASTM Standards. Therefore the particular device standard on anesthesia workstations may say, for example, that ‘Section I of 601-1 applies unchanged”, or ‘Section 11 applies with the following additions’, or ‘Section III applies but with the following deletions,” etc. The numbering of the majority of clauses in the standard therefore will be identical to the numbering in IEC 601-1. Sections relating to the particular characteristics of a specific device are added to the standard for that specific device at the end of the sections already numbered within IEC 601-1. One such example is the requirement that limits the surface temperature of an electronic component when it operates in an oxygen-enriched atmosphere. For anesthesia workstations, these additional sections cover such items as gas pipeline connections, flow control systems, flowmeter calibration, vaporizing systems, etc.

In addition, the particular device standard will contain referee test methods that can be used for type testing to determine (certify) that a particular device meets the requirements of the standard. The pervasive influence of IEC 601-1 is so great that the Canadian Standards Association as well as Underwriters Laboratories have begun to change their major standards to parallel or match IEC 601-1.

E.C. Will Differ from U.S.

Details of peculiarities of the new workstation standards, how they differ from U.S. practice, and how they may affect U.S. manufacturers, and consequently U.S. practice, follow.

The most intense and prolonged debate within the working group centered around the question of whether or not the standard should be written to provide for an integrated workstation essentially provided by one manufacturer (or supplier), or one that could be assembled by the user from components obtained from different manufacturers or suppliers. Several paragraphs from the ‘Scope” section of the document are quoted here:

“This standard presents essential requirements for an anesthesia workstation supplied complete, as well as essential requirements for individual devices which together make up a complete anesthesia workstation.”

“It is the intent of this standard that both complete anesthesia workstations and the individual devices become commercially available to allow users to configure an anesthesia workstation to meet the needs of their clinical practice in conformance with their national regulations. To this end the standard has been structured in such a way as to clearly identify requirements pertinent to specific devices currently available. Different configurations of workstations are illustrated in the document.”

“Attention is drawn to recommendations for patient monitoring during anesthesia made by many national, clinical and regulatory bodies. These recommendations include monitoring of the patients’ ECG, blood pressure, body temperature, and pulse oximetry.”

“NOTE: Although this standard does not mandate the use of the monitoring devices referred to in the paragraph above, manufacturers of Anesthetic Workstations are encouraged to make provisions for such monitors so that the user can more easily assimilate their data output and so that the alarm function of the various monitors can be integrated.”

Some Manufacturers Concerned

The above represents the “final” decision of the parent ISO Committee (June 1991) and reflects the voting interest of many small European manufacturers. These manufacturers felt that if only an anesthesia workstation ‘supplied complete’ were described they would rapidly be excluded from the marketplace. One can readily see how a manufacturer of capnographs or pulse oximeters would have such apprehension. The ‘Overview’ portion of the document states that the user may assemble the components himself. This is, in actual fact, a complicated task; in the past the melding of different monitors to an anesthesia machine by the user has led to many reported difficulties. It is for this reason that American practice has tended toward fewer manufacturers supplying more and more integrated workstations. As a matter of fact, there are approximately five manufacturers in the world today who can supply an integrated workstation, only two of them based in the United States. On the other hand, the argument has been made that depending on one supplier for all equipment may limit the variety, design, and character of the equipment offered for purchase and thus, in fact, may alter practice.

A clear example of design limitation is the fact that within the standards writing group, manufacturers (who are invited and who do actively participate) proposed and supported what became the requirement of having an anesthetic agent analyzer in use every time an anesthetic vaporizer is in use. The majority of current U.S. practitioner opinion does not favor the mandatory use of anesthetic agent analyzers while administering anesthesia. This is not to argue the analyzer’s utility, its potential safety, and its desirability as a teaching tool; literature review simply does not support a high incidence of, nor significant hazard from, vaporizer malfunction. It should be noted that within the ASTM writing group currently generating an anesthesia agent analyzer standard for the U.S., the presence of such an analyzer is not mandated during the administration of inhalation anesthetics.

Gas Analyzers Coming

Nevertheless, because U.S. manufacturers actively sell their anesthesia machines overseas and because of the virtual economic mandate of manufacturing similar models for national and international sales, it appears essentially certain that in the near future, American anesthetists will have no choice but to buy anesthesia gas machines that incorporate anesthetic agent analyzers.

Another contentious point which required resolution by the parent ISO committee related to the requirement (adapted from the existing U.S. ASTM Standard) for mandatory monitoring devices to “be enabled and automatically functioning whenever the anesthesia machine is in use.” Related to the issue described above, the question centered on whether or not one could buy a capnograph or pulse oximeter, put it with an existing anesthesia gas machine, and then cause the capnograph or pulse oximeter to be enabled and automatically functioning whenever the anesthesia machine was in use. This is easy to engineer when both the anesthesia gas machine and the monitor are integrated in one frame or supplied by one manufacturer (who provides for the automatic power-on of the monitoring device when the anesthesia gas machine is turned on). When one is dealing with retrofitting an oxygen analyzer, it is also relatively easy to do this. It is merely a question of providing a courtesy or additional electrical outlet at the back or the side of the anesthesia gas machine wired to the master on-off switch. This switch is present on all modern anesthesia gas machines, domestic and foreign. This “automatic enabling’ requirement was included for all currently mandated monitoring in the U.S. ASTM Standard because reports in the literature clearly indicated that often appropriate monitors, although in place, were not in use when critical incidents developed. This is a very important concept that is believed by standards writers to provide significantly increased safety.

Despite the many arguments in favor of adopting the automatic-enabling feature in the ISO standard, the vote of the parent committee was slightly different and, thus, the draft standard now states, for example, that the anesthetic gas monitor and its alarm module shall be in operating condition by one of toe following: a) functioning automatically; or b) generating an alarm signal when not enabled or functioning; or c) being enabled and functioning following the pre-use checklist procedure as specified in the standard.” It may appear ironic that when the working group voted on this subject, resolution was not obtained because the vote was evenly divided; virtually all of the anesthesiologists voted for automatic functioning and enablement, and virtually all of the manufacturers voted for the system of various different methods to ensure that the monitor is turned on and functions.

This rewording of the originally proposed requirements will not affect the design of U.S. anesthesia machines in any way.

Alarm Priorities

The prioritization of alarms is provided for in the anesthesia workstation standard, calling for alarm characteristics of monitors to be grouped into three categories; 1) high priority, which indicates a condition requiring urgent and immediate action; 2) medium priority, requiring prompt action on the part of the anesthetist and; 3) a low priority alarm which is a signal indicating a condition that the anesthetist must be aware of, but may or may not necessarily respond to (e.g., battery-powered instrument has only one hour of battery supply left). Usually these monitors are provided with both audible and visual alarms, the audible alarms being intended to capture the anesthetist’s attention and indicating the degree of urgency with which he should respond, while the visual alarm confirms the alarm situation and points to the probable site or cause of the alarm condition. It is becoming rapidly obvious in this field that the prioritization of alarms will succeed more effectively if, instead of a simple visual alarm, there is a central monitor which can annunciate a brief written message indicating the site or cause of the alarm condition. This type of organization may offer major advantages when multiple (especially stand-alone) monitors are used in combination. Unfortunately, it is not easy or inexpensive to achieve.

“To facilitate data transfer capability between different monitoring devices, a BUS or data transfer system may be used”. This is the last sentence of the “Scope” statement of the ISO/IEC draft standard and is the expression of the hope and belief of many of the working group that all anesthesia workstations in the near future will be able to network with other data generators (in the clinical laboratories, recovery room, ICU, etc.) and to be part of a continuous chain of devices that add to, share, manipulate, and analyze relevant patient care information.

Reviewed here are only some of the highlights of the draft ISO standard (which is not yet completely finished, but already twice as long as the U.S. standard). The ISO/IEC working group has yet to settle such questions as the use of “failsafes” or “oxygen ratio controllers” when air is in use, how and what gases should be automatically shut off when the oxygen supply fails, and the accommodation of the monitoring requirements to “closed system (closed-circuit)” anesthesia.

It cannot be emphasized too strongly that this standard will establish de facto the requirements and the design of the Anesthesia Workstation that will be forthcoming in the not too distant future. U.S. manufacturers have already said they cannot afford to manufacture different models for two very different markets. Economically, this standard may functionally set limits to new designs for some time to come. It is vital that the views and technical guidance of the U.S. medical community especially, as well as of U.S. manufacturers, influence this standard as both will have to live with the results of its approval.

Dr. Weitzner is Professor of Anesthesiology at Duke Medical Center, Durham, NC and Chairman of the ISO working group on the anesthesia workstation as well as Secretary of the ASTM F-29 standards committee for anesthesia and respiratory equipment.