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Using a supply system with redundancy, combined with telemetry, a hospital can be guaranteed of an uninterrupted supply of medical oxygen

The paper details the various modes of medical oxygen supply employed in a hospital, from cylinder manifold to liquid medical oxygen setups and contingency backup systems. It discusses the introduction of telemetry as an industry solution for medical oxygen storage and supply, the elimination of oxygen dry-out instances, stock monitoring, tanker tracking, and automated communication set up between supply source and destination. It also highlights the advantages associated with telemetry in terms of asset management, just in time delivery concepts, utilization metrics and improving customer satisfaction.

Introduction

Leveraging information technology to improve the supply chain of medical oxygen is a step towards customer satisfaction. Medical oxygen sourcing and supply have witnessed tremendous advances to meet the growing awareness and competition in the medical utility and commodity service segment but there are new issues and challenges for the hospital management to keep the oxygen supply delivery error free. Sourcing medical oxygen and assuring the availability is now not only a procurement task but can be seen as analogous to a dynamic inventory management concept ensuring the inventory is ready whenever the shop floor demands it. This involves not only intra-house management but also synchronization of various external parameters including hospital stores, transporters, supply plant and logistics.

The majority of hospitals worldwide dispense oxygen from a central source. Numerous problems can occur with liquid oxygen delivery systems, in part because of the complexities of such systems. Some hospitals have witnessed the occurrence of serious or potentially serious accidents related to their medical oxygen delivery systems that have even resulted in patient deaths. More than half of the reported incidents were decreases in oxygen pipeline pressure, often resulting in insufficient delivery of oxygen for clinical use. As an essential hospital facility, the central oxygen supply system should be designed with monitoring features allowing backup and the ability to trigger immediate restoration in the event of system failure

Medical Oxygen Cylinder Manifold System

This is the primary form of a centralized medical oxygen distribution system that has been adopted in a medical unit. With this system, medical oxygen cylinders are connected to a cylinder manifold system by means of high pressure copper pigtails. These cylinders are connected at all supply points provided on each bank of the manifold. A manifold is designated by the number of banks and the number of cylinder connectivity joints available on either bank. Figure 1 illustrates a 2 (number of banks) X 4 (number of cylinder connectivity points on each bank) manifold.

The cylinders are filled at designated liquid compression stations as per the pressure ratings specified for each cylinder type. Commercially available cylinders are normally filled at 150 kg(f)/ cm² and certain high pressure cylinders (depending on local statues) are filled up to a pressure of 200 kg(f)/cm². However, the settle pressures of cylinders are slightly less than the filling pressures due to the behavior of the gases. Output pressure and flow from each bank is controlled by a double stage step down pressure regulator. Spring loaded safety valves or pressure relief valves are provided on each bank of the manifold to vent off any excess pressure built up within the bank. Pressure gauges mounted on each bank indicate the respective bank pressure which in turn is a measure of the content level of the connected cylinders. The flow from each bank is routed through a final pressure regulator which controls the pressure and flow rate of medical oxygen supplied to the hospital wards. Each bank of the manifold is subjected to a differential pressure concept so that under ideal condition one bank at a time is consumed and the other acts as a back up or standby source. The individual pressure regulators of either bank are adjusted to have an output pressure different from each other but sufficient enough to meet the flow and pressure demand.

Once the content of cylinders connected to a particular bank is emptied, the standby bank automatically starts feeding the demand without any fluctuation of flow or pressure at the receiving end. The empty cylinders are then replaced with filled ones. The cycle is repeated to assure uninterrupted flow of medical oxygen in the hospital wards. With advancement of technology and safety regulations, manifold banks are now equipped with low pressure alarms that signal to the medical oxygen control room attendant of cylinder content levels. Best practices on the use of medical gases always suggest that both banks should be kept turned on. However due to lack of training and understanding of the process, users often keep the standby bank turned off in the belief it will minimize gas loss. Such acts can and have resulted in serious patient consequences.

Liquid Medical Oxygen Supply

As hospitals grow and expand, they are looking for alternative sources of medical oxygen feed as the cylinders no longer appear to be appropriate. What they seek are:

• Availability
• Quality standards
• Easy handling
• Cost effectiveness
• Product safety

Liquid Medical Oxygen (LMO) is the optimum solution and almost all major hospitals around the world have moved to this source. The growing oxygen demand in industrial sectors has resulted in the establishment of air separation units (ASU) by leading major gases manufacturers. Their products usually include liquid oxygen, liquid nitrogen and liquid argon depending on the type of ASU and its air separation cycle. The liquid oxygen from an ASU conforms to the statues and standards of medical oxygen.

Healthcare is eyed as a major line of business for these gases companies.

Quality has never been an issue with LMO as the manufacturing process does not involve any external product or catalyst. In a nut shell, air and power are the only two raw materials consumed by these units. Due to less handling, the direct consumption of the end product as a supply feed, and its cryogenic nature, the chances of external adulterants are minimized compared to a compressed cylinder.

One of the major advantages that LMO enjoys over compressed medical oxygen (CMO) cylinders is the ease of handling. No time is wasted in moving pallets of cylinders with the associated manual or automated labor required. The supply is simply fed from the cryogenic tank where the LMO is stored to the hospital through a dedicated pipeline circuit encompassing all respective units of the hospital. A cryogenic transport tank, commonly referred to as the tanker usually transports LMO from the manufacturing unit and decants the contents into a local storage tank at the hospital.

The LMO option initially faced stiff competition to its counter part, the CMO, because of a one time initial cost for the installation of storage tanks and an aluminum vaporizer. Also required are storage licenses and periodic renewal costs. However the operating cost becomes dramatically reduced when compared to rental charges associated with CMO cylinders and the transportation costs involved with such cylinders.

To become more competitive, gases companies have now designed promotional packages in which the entire set up and subsequent routine maintenance are provided by them, and any facility charges associated are also waived as an entry strategy. Moreover, CMO cylinders usually have a residual gas content that can never be used.

Safety also plays a role with LMOs. LMO handling and operation is quite safe when compared to CMO, the primary reason being the need to store the cylinders under pressure. While the LMO is stored at a maximum pressure of 6kg(f )/cm² in the storage tank, the latter is compressed and bottled at 150 kg(f )/cm². Cylinder handling also involves great care and concern especially regarding valve and spindle damage. While there are hazards associated with the cryogenic properties of LMO, trained, skilled personnel can make the handling much simpler assuring convenience and product friendliness at the same time.

The Inside Story

LMO is usually stored in a cryogenic storage tank, a double-walled, vacuum insulated tank with an inner shell of stainless steel and the outer shell of carbon steel. The annular space is filled with a powder, usually perlite, to insulate the annular space; a vacuum is maintained in this annular space. It is analogous to a thermos flask which preserves the content temperature irrespective of the external environment, thus eliminating the heat and evaporation impact caused by the outer environment. LMO is stored inside at a temperature of almost -183°C. Mountings such as pressure gauges monitor the tank pressure and differential pressure gauges sense the content level. Tanks come with accessories like rupture discs and spring loaded safety valves to counter any circumstances of pressure build-up and thus avert emergencies. A pressure regulator maintains a constant vapor pressure inside the tank. LMO is decanted into this tank from the cryogenic tanker by specially designed transfer hoses.

LMO expands greatly in volume when exposed to ambient environment. It is this property that is exploited in a LMO circuit. LMO from the tank is passed through an atmospheric vaporizing coil usually made of aluminum where it comes in contact with ambient conditions and changes its state to a vapor phase. The output is then controlled with pressure regulating valves and is fed to the hospital unit.

As an essential hospital system, the central oxygen supply should be designed with features allowing backup in the event of system failure (see Figure 2). Not surprisingly, most hospitals in urban areas use LMO systems (with primary and reserve liquid reservoirs) as the main central supply source, with some having CMO cylinder manifold as backup. Contingency planning to lessen the risk of an interrupted supply should involve back-up systems with physically separated feed lines, as well as CMO cylinder manifolds along the course of the main hospital oxygen circuit line. Supply feed from all sources is kept live with a differential pressure system so that one source at a time provides the medical oxygen, and the stand-by comes into play instantaneously whenever there is a pressure drop in the primary supply source. Of course, LMO systems must comply with guidelines of the local statutes.

Using Telemetry

One of the key considerations in choosing a supplier is supply assurance. A way of accomplishing this is be means of telemetry. Telemetry allows remote measurement and reporting of information to the operator. Telemetry typically refers to wireless communications i.e. using an RF signals to implement the data link, but can also involve data transfer over other media, such as a telephone, a computer network, or via an optical link (See Figures 3 and 4).

To utilize telemetry in an oxygen supply system, the storage tank is equipped with a telemetry system that provides hospitals with a valuable tracking tool. It consists of a strain gauge calibrated to the content gauge of the tank and connected with the telemetry device to easily monitor oxygen supply levels. It also assists in cost-effective delivery scheduling and allows hospitals to track consumption patterns to economize usage.

The device communicates with a signal routing satellite, which in turn communicates with the servicing plant. Cryogenic transport tankers can also be equipped with a telemetry module fitted to the tanker that can communicate periodically to a server over the mobile phone network. Enterprise resource planning (ERP) servers at the plant can be integrated into this network. This set up will assist in the following areas:

Stock Monitoring

The control room of both the servicing plant and the hospital can directly monitor the content level to know exactly how much oxygen is left in the tank. Low level alarms can be set that will trigger signals at both ends thus ensuring attention both from supplier and consumer ends. Integration into the mobile service provider's network will also trigger an SMS text message on the sales personnel's cell phone indicating a potentially critical need for restocking. A 24/7 customer support center can also be integrated to this network to provide additional surveillance and take necessary steps to prevent emergencies.

Supply Scheduling and Demand Management

Equipped with the data of exactly how much oxygen is left in the tank, both hospitals and servicing plants can schedule deliveries at the most convenient time, for example avoiding the busiest of times when parking lots are full. More importantly, deliveries can be scheduled only when they are really needed, reducing the number and cost of deliveries.

Return Asset Management

Cryogenic tankers often return with surplus loads that cannot be taken back inside the manufacturing premises owing to local statues. In such circumstances, the servicing plants equipped with real time data of all hospitals in the city are in the position to divert the returning tanker to a hospital that can receive the load remaining in the tanker.

Tanker Fleet Management

Servicing plants can also monitor the status of the tankers; plant control room personnel can exactly pin point the location of the tanker at the click of a button. Vehicle parameters can also be monitored such as location and speed, as well as other matters relating to vehicle mobilization, alerting the plant of potential hazards, accidents and driver issues. Information can also be sent to managers at any time via SMS text messages. Should a vehicle leave the compound out of normal hours or leave its designated working area, Geo-fences can be incorporated and alarms triggered. Delivery cost can be minimized and tanker utilization metrics highly improved by scheduling deliveries for a collective group of hospitals.

Accounts Reconciliation

One of the biggest hindrances to the smooth procurement of supplies is a credit blockage of the customer account in the books of the supplier. Telemetry extends its support here too. Based on consumption data and trends, the sales force is now geared with an additional tool of preplanning the supplies and streamlining the payment issues before hand. The integration of the ERP server to the mobile network allows sales personnel to review account statements before the next scheduled delivery. When the number of deliveries is reduced to a minimum, there are administrative savings in invoice reduction. Hospital administrations invest considerable amounts of time and money in processing of paperwork and invoices.

Conclusion

Gases companies are designing packages that offer each hospital a customized system for delivering LMO based on reliability and cost effectiveness. The suppliers also take on the responsibility the for maintenance of equipment, and provide a total supply solution with an assurance of safety and a guarantee of continuity of supply.

Jaideep Das is a Domain Consultant with the Resource, Energy and Utilities division of M/S Infosys Technologies Limited, a global IT service provider. He has over 7 years of experience in operations, customer engineering services, business development and consulting in chemical industry. He is experienced with cryogenic, heat treatment and LPG manufacturing processes and is conversant in sales of industrial gases along with customer engineering services in both the industrial and medical divisions. Prior to Infosys Technologies Limited, he has been associated with Repsol Gas and BOC India Limited (now a member of the Linde Group). His work is primarily focused on best practices in procurement, purchase, materials planning, inventory management, stock valuation, consignment and pipeline stocks and enterprise asset management.

He graduated with a degree in mechanical engineering. he can be reached on jaideep_das@infosys.com.

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