Characteristics of medical gas systems

In hospitals, medical gas implants are of fundamental importance, in fact, a minimum interruption in their supply is enough to put at risk the lives of the patients who must use them. The purpose of these systems is in fact to supply patients with vital substances such as oxygen. For this reason, in the planning phase, we must first worry about supply security.

Other aspects that must be carefully considered in the design phase are:

• The purity and quality of the output, both in reference to patients and to the machines that use them.
• The pressure, which must be constant and in accordance with the limits set by the system administrators.
• The safety of patients and operators.
• Efficiency, that is the ability to offer the best result at the lowest possible cost.

The ISO reference standards are the UNI 11100 of 2011, which integrates the two previous standards UNI EN ISO 7396-1 (2010) and UNI EN ISO 7396-2 (2007).

The main types of medical gas systems in healthcare facilities.

Currently, there are two types in hospitals:     

• Distribution plants for compressed and vacuum medical gases
• Anesthetic gas evacuation systems.

The first type includes a complete system, capable of distributing medical gases to patients who need them or to the instruments that use them, in addition to the vacuum, that is a pressure lower than the atmospheric one generally used for the aspiration of blood or other liquids.The second one serves to convey and discharge the anesthetic gases after use in the operating theater. 

THE IMPORTANCE OF CENTRALIZATION

The most recommended choice for hospitals regarding this type of system is centralized. In this way numerous benefits are obtained:

• Safety: avoid dispersing potentially dangerous power sources such as pressure cylinders around the structure.
• The convenience of use: medical gases are supplied via easily accessible wall outlets.
• Economy: maintenance and installation costs are optimized and reduced.In the case of the anesthetic gas distribution system, there is also a reduction in the exposure of health personnel to them.

The characteristics of the distribution systems of compressed and vacuum medical gases (IDGM)

The main components of an IDGM (which stands for Medicinal Gas Distribution Plant) are the following:

• Power supply unit, ie the source that supplies the system by supplying gas and vacuum.
• Distribution network, which conveys the gases to the supply terminals.
• Dispensing terminals, or outlets, ie the withdrawal and use points of medical gases within the facility.
• Monitoring and alarm systems. They keep the system under control, signaling potential critical situations (for example, blocking of some outlets, changes in pressure in the pipes, anomalies in the operation of the power station's machinery). 

IN PARTICULAR, THE POWER STATION

Power sources can consist of compressors, vacuum pumps, gas stored in liquid or cryogenic state in cylinders, oxygen concentrators and filtration systems.These machines are not necessarily all concentrated in the same place, even if the system is centralized. This is because the treatment of each medical gas poses different problems.

For example, fixed evaporators have construction, control and maintenance needs different from a compression unit for medical air, and are therefore subject to specific  regulations.Therefore it is always essential to ensure continuity of service and delivery. This occurs, at the design level, using redundancy, ie building a power plant that can provide at least three times the maximum demand required by the healthcare facility. 

THE PROBLEM OF CONTINUITY OF THE DISTRIBUTION

We have said that the need to ensure continuity of supply is the most important point to keep in mind when planning a hospital medical gas distribution system.The regulatory solution required is to adopt at least three sources:

• A primary, destined to be used in the ordinary regime.
• A secondary one, which is activated in case of failure of the previous one.
• A reserve, or tertiary, which must guarantee continuity of service until the situation returns to normal.

The three sources do not necessarily have to be machines for generating medical gases; you can use containers in whole or in part, as long as they are large enough to ensure continuity of service delivery.

THE CALCULATION OF STORAGE

The legislation does not set specific criteria on the quantities to be stocked, leaving to each healthcare facility the development of a policy on this point. It will therefore be necessary to calculate the maximum possible demand required of the system in stress conditions, to evaluate:

• The probability of exceptional events that could compromise the operation of the plant.
• The distance from the supplier.
• Road or environmental conditions, their effect on logistics. 

This work is essential especially for medicinal gases that cannot be produced locally, which must necessarily be provided periodically by the supplier according to contractual conditions and carefully evaluated and considered supply plans. 

THE TECHNICAL AND PROJECT REQUIREMENTS

Typically, medical air is supplied by a compression unit, which must be placed in suitable indoor rooms. Conversely, the other medical gases (nitrogen, oxygen) are stored in particular areas generally in cylinders or other suitable containers. There are numerous requirements to be met. In summary, among the most important ministerial guidelines are:

• Easy access to the area for the staff in charge.
• Location on flat land.
• Respect minimum safety distance of at least 15 meters.If placed in rooms, these must be adequately ventilated and built with fireproof material.
• The cryogenic tanks must be installed outdoors and surrounded by a wire mesh fence wall at least 2 meters high.
• Arrangement of the necessary prohibition and warning signs.

Anesthetic gas evacuation systems (SDEGA)

The purpose of this system is to aspirate, convey and expel anesthetic gases out of the operating room. There are two types of evacuation: 

• Active type, which uses a venturi tube fed by compressed air.
• Passive type, which use a blower with adjustable depression downstream of the evacuation system.

An anesthetic gas evacuation system typically consists of the following elements: 

• Generator: provides the negative pressure necessary to suck the gases to be expelled.
• A Drainage network.
• Terminal units. In this case, they are outlets that provide operators with the negative pressure needed to discharge.
• An indication system, which indicates that the system is working.
• A system of drain pipes and related discharge point.
• Pressure and flow rate adjustment systems.
• Generator power supply (can be compressed air, electric or pneumatic). 

For reasons that can be easily understood, the discharge point of the anesthetic gas evacuation systems (also indicated with the acronym SDEGA) must not be near the power outlets of the medical air or ventilation and ventilation systems. The problems posed at the design level concern above all the safety of the operators and patients, linked to the risk of environmental dispersion of anesthetics or their incomplete evacuation. 

We remind the reader that BOGE is at the forefront of solutions in the production of compressed air for hospitals with a wide range of products. In addition, it offers a consultancy and guidance service on the specific problems of medical gas systems. For those who want more information, contact our BOGE Australia offices or the nearest dealer.