Airway equipments

1. ANAESTHESIA MACHINE
AND EQUIPMENTS

3. ANAESTHESIA MACHINE
 First Boyles machine was made by Edmund
Gaskin Boyle in 1917.
 The Boyles machine is continuous flow type of
machine used for administration of Anaesthesia.

7. MECHANICS OF GAS FLOW IN ANAESTHESIA
MACHINE
 Gases in cylinders are at high Pressure (2000psi for oxygen
and 760 psi for nitrous oxide ) which are reduced to 45 to
60psi by pressure regulator (1st pressure reducing valve)) .
 The newer machines have second pressure reducing valve
which further decrease the pressure to 15 to 20 psi

8.  Gases from pressure reducing valve reach flow meters
where flow is regulated by flow control knobs.
 These gases mix in a common manifold at the top of flow
meter from where they pass through a vaporizer containing
inhalational agent ,the vapor's of which get incorporated in
gaseous mixture which finally reaches the machine outlet at
a pressure of 5 to 8 psi.

10. Anesthesia machine is divided into 3 parts:
 High pressure system
 Intermediate pressure system
 Low pressure system

11.  High pressure system which includes cylinders ,pressure
regulators (also called as 1st pressure reducing valve),yoke
assembly and oxygen flush.
 Intermediate pressure system which starts from 2nd pressure
reducing valve to flow control valve. It includes 2nd
pressure reducing valve ,oxygen failure alarms and fail safe
valve.

12.  Low pressure system includes downstream to flow
control valve up to machine outlet.
 It includes rotameter, vaporizers, check valve.

13. HIGH PRESSURE SYSTEM
1.CYLINDERS
 Cylinders are made up of molybdenum steel because
molybdenum steel can withstand high pressures.
 Some of the newer cylinders contains chromium alloy to
decrease their weight .
 Since steel is not compatible with MRI therefore aluminum
cylinders are used in MRI suites.

15. CYLINDER VALVES
 It is fitted at the top of cylinder.
 Different type of cylinder valves are available
like flush type ( most commonly used) ,bull
nosed etc.,
 To start and close gas these valves are rotated
anticlockwise and clockwise respectively.

16. PRESSURE GAUGE
 It is used to measure the cylinder pressure .
 Most commonly used type is
Bourdon type.

17. 2.YOKE ASSEMBLY
 It is the portion of machine at which cylinder get
fitted.
 It consists of index pins ,a gas seal
( Bodok seal ) to prevent leak between
cylinder and yoke and a filter .

19. PIN INDEX SYSTEM
 This is the safety mechanism so that one cylinder can not be
fitted at the others position.
 It consists of 2 pins ,4mm and 6mm long on yoke of the
anaesthesia machine.
 The pins are so positioned that the cylinder with
corresponding hole can only be fitted.

20. MAKING OF PIN INDEX SYSTEM
 A 9/16 inch circumference semicircle is made and 6 equidistant
points are made on arc ( additional 7th point if entonox is to be
used).
 The pins for oxygen are at 2 and 5 position and
oxygen cylinders have holes at the same position.

21.  Similarly , for nitrous oxide pin are at 3,5 position
and nitrous oxide cylinder has holes at same
position. It is not possible to fit any other cylinder
at this position.

24. CENTRAL SUPPLY OF GASES:
 In large hospitals where consumption of gases is more
oxygen ,Nitrous oxide and air are supplied through central
supply pipelines.
 In central supply rooms oxygen and nitrous oxide are stored
in a set of 4 to 8 large H type cylinders connected to a
common manifold.

25.  (Many hospitals use liquid oxygen tanks instead of
cylinders).
 In India ,oxygen and nitrous oxide are supplied at
a pressure of 60psi through central supply.

26. There is color coding for central supply pipelines .
 White for oxygen, blue for nitrous oxide and black for air.(
fourth ,yellow color pipe is for central suction)
 Like pin index system which prevent wrong fitting of
cylinders to machine Diameter index safety system DISS ,
to prevent wrong fitting of central supply pipes to machine.

27. 3.OXYGEN FLUSH ( EMERGENCY OXYGEN FLUSH)
 It is a bypass system which bypasses
the intermediate and low pressure
System and oxygen directly reaches
at machine outlet.
 It delivers 35 liter's of oxygen per minute at a pressure
of 60psi.

28. 4.1ST PRESSURE REDUCING VALVE
 It is also known as pressure regulator or
pressure preset valve .
 It converts high variable pressure in cylinder
to Constant working pressure suitable for anesthesia machine.
 This reduces the pressure to 45 to 60 psi.
 (In most of the machines in India it is set at a pressure of 60psi)

30. INTERMEDIATE PRESSURE SYSTEM
It includes :
1.2nd PRESSURE REDUCING VALVE
It reduces the pressure to 15 to 20 psi.
2.OXYGEN FAILURE ALARMS
Machine starts alarming if the pressure of oxygen falls below
a preset pressure (usually 30psi).

31. 3.FAIL SAFE VALVE:
 This is very important safety device which in case of
decreased oxygen pressure either cut off or proportionately
decreases the flow of nitrous oxide and other gases( that’s
why also called as oxygen supply failure protection devices)
thus preventing the delivery of hypoxic mixture.
 It usually shuts off if oxygen pressure becomes less than
25psi.

33. LOW PRESSURE SYSTEM
ROTAMETER
 One of the most important component of low
pressure system is Rotameter which contains
flowmeter tubes specific for each gas and flow
control knobs controlling the flow of gas through each tube.

34.  Flowmeter tubes are glass tubes which are
transparent and tapered(narrow at base and wider
at apex) with markings on each tube indicating
flow.
 These tubes are also called as Thorpe's tube.

35.  In each tube there Is a float called as Bobbin
which keeps on rotating by the gas stream passing
all around the bobbin and the upper end of the
Bobbin determines the flow rate.
 The whole unit with different Thorpe's tubes and
control knobs is called as Rotameter .

36.  Bobbin is made up of aluminum and it is made antistatic
to prevent it from sticking to wall of flow meter.
 The flow to each tube us adjusted by flow control valve.
 These flow control valve are also color coded i.e., blue
for nitrous oxide ,grey for carbon dioxide and white
for oxygen and black for air.

37.  To prevent the error of opening wrong knob and oxygen
knob is made physically different from other knobs like
more fluted, more prominent and large in diameter.
 The flow at low flow rates is laminar and viscosity
determines the flow at low flow rates.
 Density of gas is important at high flow rates where flow is
turbulent due to high flows.

38. SAFETY FEATURES OF ROTAMETER
1.POSITION OF FLOW METER TUBES:
 Most vulnerable point of leakage is the junction of flow
meter tube and common manifold at the top of machine.
 If oxygen tube is upstream it can leak at 6 points
(1,2,3,4,5,6) while if it is most downstream then possibility
of leakage Is only at 2 points ( 5 and 6).
 Therefore oxygen tube should be most downstream i.e.,
oxygen should be the last gas to enter the Rotameter.

39. 2.OXYGEN NITROUS RATIO CONTROLLER / OXYGEN
NITROUS PROPORTIONING SYSTEM
 Oxygen and nitrous oxide knobs are interconnected by a pulley
in such a manner that a rotation of nitrous oxide knob will
automatically start oxygen flow so it is not possible to deliver
singular flow of nitrous oxide.
 This ensures a minimum FIO2 of 25% which is mandatory to
prevent hypoxia.

40.  3. Florescent back panel of rotameter so that it can
be visualized in dark.
 4.Rotameters are hand calibrated to minimize
errors.

41. Other types of flowmeter:
 HEIDBRINK FLOWMETER:
 It is used in past ,it consists of metal tapered tube
with inverted black float.

42. CONNELL FLOWMETER:
 Again used in past it contains a round float
(bobbin) .
 Reading is taken from the centre of float.

43. 2 .VAPORIZERS :
 Vaporizers are the devices used to deliver inhalational
agents.
 Inhalational agents are in liquid form in vaporizer.
 Since inhalational agents are volatile therefore fresh gases
passing over the agent vaporizes it and its vapours get
incorporated in fresh gases and are delivered to patient.

44.  The vaporizer material should have high specific
heat and high thermal conductivity.
 Copper possess these properties so vaporizers are
made up of copper.

45. The characteristics of new vaporizers are:
 Temperature compensated (vaporizer output not effected
by changes in temperature).
 Variable bypass (by rotating the dial knob, it can be
decided that how much fresh gas will pass through
vaporizer and how much to be bypasses ( therefore called as
spliting ratio) this decides the concentration of

46. Anaesthetic agent to be delivered i.e., at 5% concentration
most of the gas will pass through the vaporizer and at 0.1%
most of gas will be bypasses)
 Flow over i.e., gas flow passes over the agent. other type is
bubble through in which gas passes through the agent.
 Not affected by pumping effect( back pressure).

47.  Agent specific. Although all vaporizers used now a days
are agent sepcific .
 However the agents with similar vapour pressure can be
used interchangeably.
 For example halothane and isoflurane with almost identical
vapour pressure can be used interchangeably with accurate
delivery.

48.  Different vaporizers:
 Old vaporizers :Boyles vaporizers for ether ( ether bottle) and trielene
(trielene bottle) and
Goldman vaporizer.
 BOYLE ETHER VAPORIZER: It consists
of ether bottle ,a lever for on and off,
U tube and a plunger with hood over U tube.

50.  Ether bottle is calibrated up to 300ml. When the plunger is
brought down, the hood comes under the surface of liquid
and the gas pass through liquid delivering high
concentrations.
 U tube is made up of copper which acts as anticatalyst to
prevent decomposition of ether.
 Ether bottle can deliver an arbitarary 5 to 15%

51. Goldman vaporizer:
 It is a simple glass bottle used to deliver
halothane.
 In these old vaporizer ,output is effected by
changes in temperature and they do not deliver
accurate concentrations.

52. NEWER VAPORIZERS
 Vapor 19.1,fluotec III,IV,V and VII are used for
delivery of halothane, isoflurane and sevoflurane .
 Tech VI is specifically designed for desflurane.

53.  Aladin cassette vaporizer is the latest vaporizer
which can be used to deliver all inhalational
agents.
 It just requires insertion of colour coded cassette
of each agent, rest everything is automatically
adjusted by vaporizer.

54.  SEQUENCE OF VAPORIZERS
 One machine contains more than one vaporizer at a time.
The agent with lower boiling point should be placed first
i.e. ,near to Rotameter otherwise the condensed particles
will be removed from the second vaporizer.
 That is why isoflurane is placed before halothane and
sevoflurane.

55. Agent Boiling point Vapour pressure
( mmHg)
Sevoflurane 58°C 160
Halothane 50°C 243
Isoflurane 49°C 240
Desflurane 23.5°C 680

56. SAFETY FEATURES IN VAPORIZERS
 Newer vaporizers are agent specific. Fluotec 5
and 7 have special key filling system specific for
each agent.
 There are color coded markings Mentioned in
vaporizers and the same color is for filling system.

57. Color code is
 Red for halothane
 Purple for isoflurane
 Orange for enflurane
 Blue for desflurane

58. ONE WAY CHECK VALVE
 It is placed just before machine outlet to prevent
backflow effect of positive pressure ventilation.

59.  Anaesthesia workstation
 Anaestheisia machines used now a days and are called as
Anaesthesia work stations because these are not only the
machines but are the compact systems having all essential
monitors ( capnograph , pulse oximeter , oxygen analyzer ,
spirometer ,airway pressure monitor) all essential alarms ,
ventilators, storage drawers

60. for equipment's, suction port, auxiliary oxygen
source, provision for closed and semi closed circuits,
scavenging systems and electric plugs integrated as a
single unit.

61. SAFETY FEATURES OF ANAESTHESIA MACHINE
 1.Antistatic rubber tyres( to prevent current flow).
 2.Pin index system to prevent wrong cylinder placement
and diameter index safety system to prevent wrong fitting of
central supply pipelines.
 3.Pressure reducing valves.

62.  4.Fail safe valve
 5.Oxygen failure alarms.
 6.Colour coding of flow control knobs.
 7.Different physical appearance of oxygen knob.
 8.Oxygen nitrous proportioning devices.
 9.Fluorescent back panel of Rotameter.
 10.Oxygen flow meter tube placed most downstream

63.  11.Trielene lock for closed circuits ( in old machines)
 12.pressure relief valve( open when there is excessive
pressure in machine)
 13.Oxygen flush can deliver high flow in emergency.
 14.One way valve before machine outlet to prevent
backpressure effects of positive pressure ventilation.