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A Solution For Providing an Uninterrupted Medical Oxygen Supply
By Jaideep Das
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.
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
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
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
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
- 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
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
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.
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:
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
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
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.
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.
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.
has over 7 years
of experience in operations,
customer engineering services,
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
and pipeline stocks and enterprise asset management.
He graduated with a degree in mechanical engineering. he can be reached
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