Medical Oxygen System Shutdowns

Help your customer understand and beat the risks.

By Joseph Parenta

Compressed gas manufacturers and distributors often receive requests to assist healthcare facilities with medical gas system shutdowns. Medical oxygen, air, and nitrous oxide cylinders are the most common resources requested, along with technical support. Be cautious, and involve both risk management teams, yours and theirs.

Back Feeding
Many hospitals back feed their piped oxygen system through wall outlets from various points in the building. This is a very poor practice, as many of these buildings are old and are, in fact, several buildings cemented together. Thus, most do not have a certified pipe map for the entire facility.

Even with a certified map, outlets were designed to flow out to supply flow meters. The wall orifice is 1/8 to 3/16 inch inner diameter in size at this point and is further restricted by the check valve mechanism present in the outlet. Back feeding through these outlets have low flow volume characteristics and other issues, especially when trying to supply critical care areas containing high-volume equipment such as oxygen ventilators. These usually malfunction when being supplied by the wall back feed method.

Another weakness to back feeding the system is the wall zone valve. Typically, the hospital will turn the valves to the off position in order to isolate each area for back feeding. The question to ask is: “When was the last time these valves were turned off and tested for leakage?” Often you'll receive a blank stare. Sometimes the answer is: “We have always done it this way.”

New construction, cryogenic vessel upgrades and the requirement for a low-pressure emergency bypass valve/inlet are among the most common reasons hospitals need to shut down the medical gas systems at the bulk tank. Shutting off the valve at the pad eliminates the main and the back-up oxygen system. Back feeding does not address this situation with a sufficient margin of safety to satisfy risk management scrutiny. When a back-fed system crashes, there is no secondary or backup system in place.

Cylinder-By-Bedside
The safe method is cylinder-by-bedside. Place the appropriate cylinder in a safety stand or cart with the appropriate regulator attached next to the patient. A written recommendation to use the cylinder-by-bedside method will protect your company should the hospital's plan to utilize the back feeding method backfire.

The main objections to the cylinder-by-bedside method are cost, equipment and the human resources needed to execute the plan. The cost differential is usually small and in situations where new construction is involved, it is immaterial. Equipment and human resources, or lack of them, are other commonly cited objections to using the bedside method. A well-written shutdown plan minimizes the needs in both of these areas. A walk-through survey of the facility quantifies the actual equipment and labor requirements for the project. In many cases, the required resources are less than initially perceived.

Once the redundancy of the two oxygen sources that are present at all hospitals is lost, there is no way to protect the patient when an old valve fails, or system leaks that went unnoticed for years cause a precipitous drop in the system's oxygen pressure.

Oxygen system pressure drops and total pressure losses can be caused by many factors such as: freeze-ups of overdrawn liquid cylinder, construction workers cutting the wrong pipe or cutting in the wrong place, crushed pipes using the clamp method, etc. These and many other problems have caused the emergency halt of a project and sent respiratory department personnel franticly searching for enough cylinders and regulators to set up bedside oxygen service.

Other Considerations
There are additional important questions to be asked when assisting hospitals:

• Do you have a redundant system in case your back feed fails? If so, does it meet the regulatory standards?
• Do you have a certified medical gas system pipe map?
• Has there been any work done on the system since the certification?
• Have the zone valves been tested for leaks? If so, did the valves pass the test?
• Will disturbing these valves create problems for the system?
• How did you test the system prior to attempting the upcoming project?
• What standard did you use to validate that test?
• Do you understand the pressure to volume characteristics (i.e. Bernoulli's Principle) and flow properties of compressed gas regulators?

Remember, the hospital looks to you for expert help when dealing with compressed gases and related equipment. Protect your company and your healthcare facility customer. Instruct them to do it safely the first time. Risk managers, yours and theirs, will agree that cutting corners for cost and/or convenience can lead to disaster and subsequent litigation.