1. PIPELINE/SUPPLY OF GASSES TO
OPERATING ROOM,
OXYGEN THERAPY
SPEAKER: DR.SUMAN GORAI
MODERATOR: DR.APURBA BISWAS
DR.JISHNU NAYEK
2. INTRODUCTION
Practice of anaesthesia involves the use of compressed gases day in and out.
Gases used in anaesthesia as well as medical practice are either provided in the form of
cylinders or medical gas piping system.
Smaller cylinders up to a certain specific size can be fitted to anaesthesia machine or work
station where as bigger cylinders are used in central manifold room (Bank of large cylinders)
and from there gases are supplied via pipelines to OT, CCU and Wards.
The central supply area can have Large cylinders or it can receive gases from a large insulated
tank of liquid gas. These gases are then delivered through pipelines to the wall outlets.
It is very important for anaesthesiologist to understand the complicacy of these system
,safety measures to be undertaken so as to be able to rectify and prevent the mishaps like
cross connection ,system running out of supply and so on that can lead to disasters.
Anaesthesia personnel should play a key role in designing the piping system.
3. SUPPLY OF GASSES
1. OXYGEN
MANUFACTURING:
The most common method of manufacturing oxygen commercially is by the
fractional distillation of liquefied air. This method produces oxygen which is over
99% pure.
Alternatively, oxygen concentrators containing zeolite adsorbents can be used.
Zeolite selectively adsorbs nitrogen and so delivers oxygen that is 90–95% pure.
The major contaminant is argon. Oxygen concentrators are commonly used in
aircraft, submarines, military field hospitals and at home.
4. STORAGE
The main hospital supply of oxygen comes from a vacuum-insulated evaporator
(VIE), which holds up to 1500 L of liquid oxygen. This is the most economical and
space-saving way of storing oxygen. The liquid oxygen is stored at a temperature
between −150 and −170 °C (below its critical temperature of −119 °C) and at a
pressure of 7bar (this is the saturated vapour pressure (SVP) of oxygen at its
stored temperature). One volume of liquid oxygen yields 842 times of its volume
of oxygen in gaseous form at 15°C temperature and one atmospheric pressure.
The hospital back-up oxygen supply comes from a cylinder manifold (size J
cylinders arranged in series), which stores oxygen as a compressed gas at room
temperature.
Oxygen on the anaesthetic machine is stored as a compressed gas in molybdenum
steel cylinders (size E cylinders) with black bodies and white shoulders at a
pressure of 137bar (13700kPa). Aluminium cylinders are used in MRI suites.
5. 2. NITROUS OXIDE
Nitrous oxide (N2O) is manufactured by the thermal decomposition of
ammonium nitrate.
The critical temperature of nitrous oxide is 36.5 °C and therefore at
room temperature N2O exists as a liquid with its vapour. On the
anaesthetic machine, N2O is stored as a liquid in molybdenum steel
cylinders with blue bodies and blue shoulders at a pressure of 52bar
(this is the SVP of N2O vapour above its liquid).
N2O cylinders have different filling ratios. In tropical countries the
filling ratio is 0.67 but in temperate climates it is 0.75.
The main hospital supply of N2O comes from a cylinder manifold
where once again the N2O is stored as a liquid at room temperature.
6. CYLINDER MANIFOLD
Manifolds are used to supply oxygen, nitrous oxide and
Entonox.
An average cylinder manifold configuration contains two
equal banks of gas cylinders with a centrally located control
panel, which provides a normal output pressure of four bar.
Large cylinders are usually divided into two groups: Primary
(duty bank) and secondary (standby bank). The two groups
alternate in supplying the pipelines.
All cylinders in each group are connected to the manifold via
a copper tail-pipe with a gas specific connection and seal.
Each connection has a non-return valve fitted to enable
single cylinder to be changed if a leak or tail-pipe rupture
occurs. The cylinders are held captive by individual chains to
the backbar. All the cylinders are connected through non-
return valves to a common pipe. This in turn is connected to
the pipeline through pressure regulators.
7. CYLINDER MANIFOLD (cont.)
In either group, all the cylinder valves are opened.
This allows them to empty simultaneously. The
supply is automatically changed to the secondary
group when the primary group is nearly empty. The
changeover is achieved through a pressure-sensitive
device that detects when the cylinders are nearly
empty.
The total storage capacity of the manifold should be
based on 1 weeks supply with a minimum of 2 days
supply on each bank and a supply of 3 days spare
cylinders held in the manifold room.
8. PIPELINES
The medical gas supply includes pipelines
linking VIEs, cylinder banks and air
compressors to terminal units (Wall outlets
,ceiling pendants and bed head panels.
The pipeline is made of a special high
quality(phosphorous containing de-oxidized,
non-arsenical copper to prevent corrosion or
contamination.
Gases are supplied at 400kPa (4Bar), with the
exception of air which is supplied at 400kPa
for therapeutic use and 700kPa to power
surgical equipments.
9. Pipeline distribution system
There are 3 general classes of piping:
Main lines :- Pipes connecting the source to risers or
branch lines or both.
Risers :- Vertical pipes connecting the main line with
branch lines on various levels of the facility.
Branch (lateral) lines :- The sections of the piping system
that service a room or group of rooms on the same level
of the facility.
10. Pressure Relief Valves
Each central supply system must have a pressure relief valve set at
33% above normal line pressure downstream of the line regulators and
upstream of any shutoff valve.
This relief valve prevents pressure buildup if a shutoff valve is closed.
The valve should close automatically when the excess pressure has
been relieved.
11. Shutoff Valves
Shutoff valves permit specific areas of the piping system to be isolated in
the event of a problem as well as for maintenance, repair,testing,or
expansion without the whole system being turned off.
There are 2 types of shutoff valves:
Manual: must be installed where they are visible and accessible at all
times for authorised persons.
Service shutoff valves: are designed to be used only by authorised
personnel. They are in locked cases or have their handle secured and
tagged to prevent accidental closing.
12. Alarms
Alarm types:
1.Master Alarm System:
A master alarm system monitors the central supply and
the distribution system for all medical gas systems.
To ensure continuous responsible observation, master
signal panels must be located in two separate locations,
wired in parallel to a single sensor for each condition.
A centralised computer system may be substituted for
one of the master alarms.
13. 2. Area Alarm System :
Critical life support areas, such as operating room suites,
postanesthesia care units, ICU, coronary care units, etc. must
have an area (local) alarm system to indicate if the pressure
increases or decreases 20% from normal line pressure.
It will be placed downstream of the shut-off valve for the area.
3. Local alarms:
Local alarms are installed to monitor the function of the central
medical and instrument air systems as well as the vacuum and
anesthetic gas scavenging systems.
The signals may be located on or in the control panel of the
machinery being monitored, within a monitoring device or on a
separate alarm panel.
15. TERMINAL UNIT
Component:-
1. Base block : This is the part of a terminal unit that is attached to
pipeline distribution system.
• Primary valve-(automatic shutoff valve ; terminal unit valve; self sealing valve;
primary check valve)
It opens and allows the gas to flow when the male probe is inserted and close
automatically when the connection is broken.
• Secondary valve-(shutoff valve; terminal stop valve; secondary check valve)
It is designed so that when primary valve is removed (e.g,, for cleaning or
servicing)the gas flow is shut off. When primary valve is in place secondary valve
stays open.
16. Gas specific Connection Point( Socket Assembly)
The receptor for a noninterchangeable gas specific connector that is either a
part of or attached to the base block is incorporated into each terminal unit.
The connector may be a threaded Diameter Index Safety System(DISS) or a
proprietary (manufacture specific) quick connector.
The corresponding male component of the noninterchangeable connection is
attached to the equipment to be used or to a flexible hose leading to the
equipment.
The female component is called an outlet connector or socket.The male
member is called an inlet connector, probe, plug, striker or jack.
Each DISS or quick connector must have backflow check valve to prevent gas
floe from the anaesthesia apparatus.
17. Diameter Index Safety System
• It consists of a body, nipple and nut combination.
• There are two concentric bores in the body which
connects with concentric and specific shoulders on the
nipple
• To achieve non-interchangeability between different
connectors, the two diameter on the body bores and the
nipple shoulder increases/decreases proportionally
which allows proper fitting.
18. Quick connectors
Quick connectors allow apparatus (hoses, flowmeters, etc.) to be connected
or disconnected by a single action using one or both hands without the use of
tools or undue force.
Quick connectors are more convenient than DISS fittings but tend to leak
more.
Each quick connector consists of a pair of gas-specific male and female
components.
A releasable spring mechanism locks the components together.
Hoses and other equipment are prevented from being inserted into an
incorrect outlet by using different shapes and/or different spacing of mating
portions
19. Types of Terminal unit
Wall Outlets:
Wall outlets are simple and well suited where the equipment to be connected is
near the wall.
However, it leads to personnel tripping over the hoses, difficulty in moving
equipment, wear and tear on the hoses.
For large room , more than one set of wall outlets may be advisable.
Ceiling-mounted Hoses:
Ceiling-mounted hoses with the terminal unit at the end of the hose may be
used.
A spring-actuated chain keeps the hose close to the ceiling.
20. FLEXIBLE HOSES
Flexible colour-coded hoses (O2-white,N2O-blue,Air-
black/white,vaccume-yellow) connect the outlets to the
anaesthetic machine.
They have a Schraeder probe at one end and a gas-specific
threaded connector at the other end. The gas specific
Schraeder valve, uses a unique collar indexing system with a
unique diameter that fits the matching recess on the terminal
outlet for a specific gas only.
The hose connects to the anaesthetic machine by means of a
Non-Interchangeable Screw Thread (NIST) which cannot be
attached to the wrong connector.In the USA a similar system is
employed called Diameter index safety system(DISS)
21. Testing Medical Gas Distribution System
After the pipeline have been installed but before installation of terminal units
and other system component ( source equipment, alarms, pressure gauge,
pressure relieve valve) the line must be blown clear of foreign materials by
using oil free nitrogen.
23. HYPOXIA
Hypoxia - reduced oxygen for tissue respiration.
Oxygen Delivery to the tissues depends on
1.) Supply of oxygen during inspiration
2.) Transfer of oxygen from the Alveoli to the pulmonary capillaries
3.) Transport of oxygen by blood to the tissue
26. ANAEMIC HYPOXIA
Anaemic hypoxia - due to decrease concentration of functional
hemoglobin.
1. Anaemia-reduced hb%.
2. CO Poisoning –affinity of Hb for CO is about 250 times higher
then O2.
3. Methaemoglobinaemia - Methemoglobin lacks the electron that
is needed to form a bond with oxygen and, thus, is incapable
of oxygen transport.
4. Sulphhaemoglobinaemia- rare blood condition that occurs
when a sulfur atom is incorporated into the hemoglobin
molecule.
27. STAGNANT HYPOXIA
Stagnant hypoxia –type of hypoxia which is caused by
inadequate blood flow which results in less oxygen
available to the tissues.
Decrease tissue perfusion is due to
General – Decrease Cardiac output.
Local – Arterial or venous occlusion e.g. atheroma,
embolism, trauma,
Vasoconstriction.
28. HISTOTOXIC HYPOXIA
Histotoxic hypoxia– adequate amount of oxygen is inhaled through the lungs
and delivered to tissue, but the tissues are unable to use the oxygen.
Sodium nitroprusside contains a cyanide radical, so overdose of this drug can
cause histotoxic hypoxia.
29. Post operative Hypoxia –
i. Fink effect
ii. Increase V / Q mismatch due to decrease FRC.
iii. Stagnant Hypoxia
iv. Hypoventilation
(a) Drugs
(b) Obstruction
(c) Pain
(d) Intra operative Hyperventilation.
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32. Objectives:
To correct documented or suspected acute Hypoxemia.
To Decrease symptoms associated with chronic Hypoxemia.
To Decrease workload that hypoxemia imposes on the
cardiopulmonary system.
34. ASSESSMENT
The need for oxygen therapy should be assessed
by
1. monitoring of ABG - PaO2, SpO2.
2. clinical assessment findings.
35. PaO2 as an indicator for Oxygen therapy
• PaO2 : 80 – 100 mm Hg : Normal
60 – 80 mm Hg : cold, clammy
extremities
< 60 mm Hg : cyanosis
< 40 mm Hg : mental deficiency
memory loss
< 30 mm Hg : bradycardia
cardiac arrest
PaO2 < 60 mm Hg is a strong indicator for oxygen therapy
37. Oxygen Delivery System
Oxygen delivery system is a device which is used to administer, regulate and
supplement oxygen to a subject to increase the arterial oxygenation.
Classification:
DESIGNS
o Low flow system
o Reservoir system
o High flow system
o Enclosure
PERFORMANCE (Based on predictability and consistency of FiO2 provided)
o Fixed
o variable
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61. HYPERBARIC OXYGEN THERAPY
DEFINITION: A mode of medical treatment wherein the patient breathes 100%
oxygen at a pressure greater than one atmosphere absolute (1 ATA)
1 ATA is equal to 760 mm of hg at sea level.
Basis of Hyperbaric O2 Therapy:
Dissolved o2 in plasma: 0.003ml/100 ml of blood/mm PO2
(Henry’s Law: The concentration of any gas in solution is proportional to its
partial pressure.)
Breathing Air(PaO2- 100 mmHg)=0.3ml/100ml of blood.
Breathing 100%O2(PaO2- 600 mmHg)=1.8ml/100 ml of blood.
Breathing 100% O2 at 3 ATA(PaO2- 2000 mmHg)=6ml/100 ml of blood.
71. 2. Depression of Ventilation
Seen in COPD patients with chronic hypercapnia
Mechanism
↑PaO2
suppresses peripheral V/Q mismatch
chemoreceptors
depresses ventilatory drive ↑ dead space/tidal
volume ratio
↑PaCO2
72. 3. Retinopathy of prematurity (ROP)
Premature or low-birth-weight infants who receive
supplemental O2
Mechanism
↑PaO2
↓
retinal vasoconstriction
↓
necrosis of blood vessels
↓
new vessels formation
↓
Hemorrhage → retinal detachment and
blindness
To minimize the risk of ROP - PaO2 below 80 mmHg
73. 4. Absorption atelectasis: Hypoxic Pulmonary
Vasoconstriction
Absorption atelectasis
refers to the tendency
for airways to collapse
if proximally
obstructed. Alveolar
gases are reabsorbed;
this process is
accelerated by nitrogen
washout techniques.
74. 5. Fire hazard
High FiO2 increases the risk of fire
Preventive measures
Lowest effective FiO2 should be used
Use of scavenging systems
Avoid use of outdated equipment such as aluminium gas regulators
Fire prevention protocols should be followed for hyperbaric O2 therapy
