Anesthetic equipment and breathing systems

1. Anesthetic equipment and Breathing
Systems

2. Introduction
• Delivery of known concentrations of inhaled an
esthetics and oxygen to the patient requires ap
propriate equipment including an anesthetic m
achine, vaporizer, and anesthetic breathing syst
em.

4. Anesthetic machines
• Anesthetic machines, regardless of their manu
facturer, consist of the same basic component
s.
These include:-
• A source of compressed gases
• Flow meters
• Means to vaporize
• Anesthetic Breathing Systems

5. Common features of anesthesia
machine
• Inlet of hospital pipeline for compressed gases
(oxygen, nitrous oxide, and air)
• Inlet of compressed gas cylinders
• Pressure regulators to reduce pipeline and cyli
nder pressure to safe and consistent levels
• Fail-safe device
• Flow meters to control the amount of gases de
livered to the breathing limb

6. Common features of anesthesia
machine cont'd..
• Vaporizers for adding volatile anesthetic gas to the
carrier gas
• Common gas line through which compressed gases
mixed with a volatile agent enter the breathing
limb

7. Breathing limb, including an
• Breathing limb, including an
– oxygen analyzer,
– inspiratory one-way valve,
– circle system,
– gas sampling line,
– spirometer to measure the
respiratory rate and volume,
– expiratory one-way valve,
– adjustable pressure-limiti
ng valve,
– carbon dioxide absorbent,
– reservoir bag,
– mechanical ventilator,
– scavenging system

8. Diagram of the internal circuitry of an anaesthesia machine

9. • The anesthetic machine may be equipped with
- a mechanical ventilator
- devices to monitor the ECG,B/P ,TO & inhale
d
and exhaled concentrations of oxygen and
carbon dioxide.
• Alarm systems to signal apnea or disconnection
of the anesthetic breathing system from the pati
ent are also available.

10. 1-Compressed Gases
• Gases used in anesthesia are available in cylinders.
• Oxygen stored in cylinders in the operating room is a
gas
• Oxygen and nitrous oxide may be piped to the opera
ting room from a central source for delivery to the a
nesthetic machine via pressure tubing.
• Gas cylinders are attached to yokes on anesthetic m
achine.
• Color - coded pressure gauges (green for oxygen, blu
e for nitrous oxide) on the anesthetic machine indic
ate the pressure of the gas in the cylinder.

11. 1-Compressed Gases
• The pressure in an oxygen cylinder is directly p
roportional to the volume of oxygen in the cyli
nder.
• For example, a full O2cylinder (E size) contains
625 liters of O2at a pressure of 2000 psi and o
ne-half this volume when the pressure is 1000
psi.

12. 1-Compressed Gases
• Therefore, it is possible to calculate accurately h
ow long a given flow rate of oxygen can be maint
ained before the cylinder is empty.
• When gas leaves the cylinder, it enters metal tubi
ng in the anesthetic machine and is directed thro
ugh a pressure- reducing valve or regulator
• some gases support combustion (oxygen, nitrous oxide

13. 1-Compressed Gases
• Calculation of cylinder contents: The content of th
e cylinder is depending on the pressure and the ori
ginal volume of the cylinder. For example if the cyli
nder normally contain 40 liter and pressurized to 1
20 bar/ atm, the total volume will be (40x 120) =4
800 liter. Therefore, if you constantly uses oxygen
4 liter/min your oxygen will be sufficient for 1200/
min (20 hrs).

14. Pressures in the Cylinder & anaesthetic
machine
• The pressure in the cylinder is 137 Bar; too high for
the anesthetic machine.
• The pressure is reduced to 4 Bar to protect the mac
hine (This pressure would still harm or kill a patient
).
• After the rotameters, the pressure is reduced to < 1
/3 Bar to protect the patient.
• This requires pressure regulators or pressure releas
e valves Pressure regulators and pressure release v
alves maintain a constant pressure

15. Pressures in the Cylinder...
• Different regulators may protect the anestheti
c machine (providing 4 Bar) or the patient (by
providing <35 kPa, or 1/3 Bar).

16. 2-Flowmeter
• measures gas flow
• Gas flow into the flow meter raises a float that
is shaped as a bobbin or ball.
• The float comes to rest when gravity is balance
d by the fall in pressure caused by the float.
• oxygen flows should meet or exceed metabolic
requirement
• 4-6 lit/min = metabolic requirement

17. 2-Flowmeter
• The flowmeters are initially calibrated for the i
ndicated gas at the factory.
• The scale accompanying an O2 flowmeter is gr
een and the scale for the nitrous oxide flowme
ter is blue.

18. 3-Vaporizers
Changes liquid agent (halothane, enflurane, isof
lurane) to a vapor
• To provide a means for anesthetic vapor to be
combined with the carrier gas in a controlled
manner

19. 3-Vaporizers

20. 3-Vaporizers
Vaporizers classification
• Vaporizers are classified as
1. flow - over or
2. bubble - through, depending on the meth
od for saturating the carrier gas that flows thr
ough the vaporizing chamber.

21. 3-Vaporizers
• Agent - specific vaporizers are flow- over vapo
rizers
• The copper kettle and vernitrol are bubble- t
hrough vaporizers.

22. 3-Vaporizers
a. Agent - specific vaporizers
• accept the entire fresh gas flow from the anes
thetic machine.
• Agent - specific vaporizers are temperature- c
ompensated by virtue of a heat - sensitive met
allic strip.
• the vapor concentration is maintained consta
nt within certain temperature and flow ranges
.

23. Flowmeter
Patient
VARIABLE BYPASS

24. 3-Vaporizers
b. Copper Kettle
• A copper kettle receives oxygen as the carrie
r gas from a separate dedicated flow meter o
n the anesthetic machine.
• The efficiency of vaporization is maximized b
y passing this carrier gas through a sintered
bronze disk at the bottom of the vaporizer (b
ubble through) to form streams of fine bubbl
es

25. Flowmeter
Patient

26. 3-Vaporizers
• The bubbles produce maximal vaporization eff
iciency by providing a large surface for the liqu
id-gas interface.
• Construction of the copper kettle with copper
facilitates the transfer of heat from the surrou
nding metal parts of the anesthetic machine a
nd environment

27. 4- Anesthetic Breathing Systems
• Consist of the components necessary to delive
r anesthetic gases and oxygen from the anesth
etic machine to the patient.
• Conceptually, the anesthetic breathing system
is a tubular extension of the patient's upper ai
rway.

28. 4- Anesthetic Breathing Systems
• The most commonly used anesthetic breathing syst
ems are the Mapleson F (Jackson-Rees system, Bai
n circuit, and circle system.
• Mapleson breathing system: Mapleson analyzed a
nd described five different arrangements of fresh g
as inflow tubing, reservoir tubing, facemask, reserv
oir bag, and an expiratory valve to administer anest
hetic gases.

29. 4- Anesthetic Breathing Systems
• The five different semi open anesthetic breath
ing systems are designated as Mapleson A to E
.
• The Mapleson F system, which is a Jackson-Re
es modification of the Mapleson D system, wa
s added later. The Bain circuit is a modification
of the Mapleson D system.

30. Mapleson breathing system

31. Mapleson breathing system
• Flow characteristics of the Mapleson systems ar
e characterized by the absence of valves to dire
ct gases to or from the patient and the absence
of chemical carbon dioxide neutralization.
• Because of no clear separation of inspired and e
xpired gases, rebreathing occurs when inspirato
ry flow exceeds the fresh gas flow.

32. Mapleson breathing system
• The composition of the inspired mixture depe
nds on how much rebreathing takes place. The
amount of rebreathing associated with each s
ystem is highly dependent on the fresh gas flo
w rate.
• The optimal fresh gas flow may be difficult to
determine.

33. Mapleson breathing system
• The fresh gas flow should be adjusted when cha
nging from spontaneous and controlled ventilati
on. Monitoring end-tidal CO2 is the best metho
d to determine the optimal fresh gas flow.

34. Efficiency of Mapleson
• The relative efficiency of different Mapleson s
ystems for preventing rebreathing during spon
taneous ventilation is A > DF > C > B.
• The relative efficiency of different Mapleson s
ystems for preventing rebreathing during cont
rolled ventilation is DF > B > C > A.

35. The Bain circuit
• Bain circuit is a coaxial version of the Mapleso
n D system in which the fresh gas supply tube
runs coaxially inside the corrugated expiratory
tubing.
• The fresh gas tube enters the circuit near the r
eservoir bag, but the fresh gas is actually deliv
ered at the patient end of the circuit.
• The exhaled gases are vented through the ove
rflow valve near the reservoir bag.

36. The Bain circuit
• The Bain circuit may be used for both spontan
eous and controlled ventilation.
• Prevention of rebreathing during spontaneous
ventilation requires a fresh gas flow of 200 to
300 mL/kg/min and a flow of only 70 mL/kg/
min during controlled ventilation.

37. Bain system

38. Mapleson breathing system

39. Advantages of the Bain circuit include:
• Warming of the fresh gas inflow by the surrounding
exhaled gases in the corrugated expiratory tube.
• Conservation of moisture as a result of partial rebr
eathing
• Ease of scavenging waste anesthetic gases from the
overflow valve.
• It is lightweight, easily sterilized, reusable, and usef
ul when access to the patient is limited, such as dur
ing head and neck surgery.

40. Disadvantages:
• Hazards of the Bain circuit include unrecognize
d disconnection or kinking of the inner fresh g
as tube.
• The outer expiratory tube should be transpar
ent to allow inspection of the inner tube.

41. Anesthetic breathing systems are classified as:
Open, Semi open,Semi closed and Closed, accor
ding to the presence or absence of:
• A gas reservoir bag in the system
• Rebreathing of exhaled gases
• Means to chemically neutralized exhaled carbon
dioxide and
• unidirectional valves,
• In addition, the composition and flow rate of th
e inflow gases should be stated when describing
an anesthetic breathing system.

42. Classification of anesthetic Breathing systems

43. The circle system
• It is the most popular anesthetic breathing system
in world.
• It is so named because its essential components
are arranged in a circular manner.
• The circle system prevents rebreathing of carbon
dioxide by chemical neutralization of carbon dioxi
de with carbon dioxide absorbents.
• A circle system can be classified as semiopen, sem
iclosed, or closed, depending on the amount of fr
esh gas inflow.

44. The circle system
• In a semi open system, very high fresh gas flo
w is used to eliminate rebreathing of gases.
• A semi closed system is associated with rebrea
thing of gases and is the most commonly used
breathing system.
• In a closed system, the inflow gas exactly matc
hes that being consumed by the patient.

45. • Rebreathing of exhaled gases in the semi close
d and closed circle systems results in:
• Some conservation of airway moisture a
nd body heat and
• Decreased pollution of the surrounding
atmosphere with anesthetic gases when
the fresh gas inflow rate is set at less tha
n the patient's minute ventilation.

46. Disadvantages of the circle system include:
• Increased resistance to breathing because of the
presence of unidirectional valves and carbon dio
xide absorbent.
• Bulkiness with loss of portability.
• Enhanced opportunity for malfunction because
of the complexity of the apparatus.

47. Impact of rebreathing
• Rebreathing of exhaled gases in a semi closed circle sys
tem influences the inhaled anesthetic concentrations o
f these gases.for example ,when uptake of the anesthet
ic gas is high; as during induction of anesthesia, rebreat
hing of exhaled gases depleted of anesthetic greatly dil
utes the concentration of anesthetic in the fresh gas inf
low.
• This dilutional effect of uptake is offset clinically by incr
easing the delivered concentration of anesthetic.
• As uptake of anesthetic diminishes, the impact of diluti
on on the inspired concentration produced by rebreathi
ng of exhaled gases is lessened.

48. Impact of rebreathing
• This dilutional effect of uptake is offset clinicall
y by increasing the delivered concentration of
anesthetic.
• As uptake of anesthetic diminishes, the impact
of dilution on the inspired concentration prod
uced by rebreathing of exhaled gases is lessen
ed

49. Components of the circle system
• A fresh gas inlet
• Inspiratory and expiratory unidirectional check val
ves
• Inspiratory and expiratory corrugated tubing
• A Y-piece connector
• An adjustable pressure-limiting (APL) valve, also re
ferred to as an overflow or “pop-off valve
• A reservoir bag
• A canister containing carbon dioxide absorbent
• A bag/vent selector switch
• A mechanical anesthesia ventilator.

50. Circle system

51. 1-Fresh gas inlet and unidirectional valves:
• Fresh gas enters the circle system through a connection fro
m the common gas outlet of the anesthesia machine.
• Two unidirectional valves are situated in different limbs of
the corrugated tubing such that one functions for inhalatio
n and the other for exhalation.
• These valves
• permit positive-pressure breathing and
• prevent the rebreathing of exhaled gases until they have
passed through the carbon dioxide absorbent canister and ha
ve had their oxygen content replenished.
•

52. • Rebreathing and hypercapnia can occur if the unidi
rectional valves stick in the open postion,and total
occlusion of the circuit can occur if they are stuck i
n the closed positon.
• If the expiratory valve is stuck in the closed postion
,breath stacking &barotraumas can occur.
• If the unidirectional valves are functioning properl
y, the only dead space in the circle system is betwe
en the Y-piece and the patient.

53. 2-Corrugated Tubing:
• The inspiratory and expiratory corrugated tubes se
rve as conduits for delivery of gases to and from th
e patient.
• Their large bore provides minimal resistance, and t
he corrugations provide flexibility, resist kinking, a
nd promote turbulent instead of laminar flow.
• During positive-pressure ventilation, some of the
delivered gas distends the corrugated tubing and s
ome is compressed within the circuit, which leads
to a smaller delivered tidal volume.

54. 3.Y-Piece Connector:
• A Y-piece connector at the patient end of t
he circuit has
• A curved elbow,
• An outer diameter of 22 mm to fit
inside a facemask, and
• An inner diameter of 15 mm to fit o
nto an endotracheal tube connector.

55. 4-Adjustable pressure-limiting valve:
• When the “bag/vent” selector switch is set to “bag,” t
he APL (overflow or “pop-off”) valve
• allows venting of excess gas from the breathing system
into the waste gas scavenging system
• can be adjusted to allow the anesthetist to provide assi
sted or controlled ventilation of the patient's lungs by m
anual compression of the gas reservoir bag.
• The APL valve should be fully open during spontaneo
us ventilation so that circuit pressure remains negligib
le throughout inspiration and expiration.

56. 5- Reservoir bag:
• When the “bag/vent” selector switch is set to “bag,
” the gas reservoir bag maintains an available reser
ve volume of gas to satisfy the patient's spontaneo
us inspiratory flow rate (up to 60 L/min), which gre
atly exceeds conventional fresh gas flows (common
ly 3 to 5 L/min) from the anesthesia machine.
• The bag also serves as a safety device because its di
stensibility limits pressure in the breathing circuit t
o less than 60 cm H2O, even when the APL valve is c
losed.

57. 6-Anesthesia machine ventilators:
• When the “bag/vent” selector switch is set to “vent,” t
he gas reservoir bag and APL valve are eliminated from
the circle anesthetic system and the patient's ventilatio
n is delivered from the mechanical anesthesia ventilato
r.
• Anesthesia ventilators are powered by compressed gas,
electricity, or both.
• Most conventional anesthesia machine ventilators are
pneumatically driven by oxygen or air that is pressurize
d and, during the inspiratory phase, routed to the spac
e inside the ventilator casing between the compressible
bellows and the rigid casing.

58. Humidification
• Is a form of vaporization in which water vapor
(moisture) is added to the gases delivered by t
he anesthetic breathing system to minimize w
ater and heat loss.
• The water formed and the heat generated by c
hemical neutralization of carbon dioxide help
humidify and heat the gases in the breathing c
ircuit.

59. Scavenging Systems
• Scavenging is the collection and subsequent r
emoval of vented gases from the operating ro
om.
• The excess gas comes from either the APL valv
e if the bag/vent selector switch is set to “bag
” or from the ventilator relief valve if the bag/
vent selector switch is set to “vent.”
• All excess gas from the patient exits the breath
ing system through these valves.

60. Scavenging Systems
• In addition, when the bag/vent selector switch is
set to vent, some anesthetic breathing systems di
rect the drive gas inside the bellows canister to th
e scavenging system.
• The amount of delivered gas used to anesthetize
a patient commonly far exceeds the patient's nee
ds.
• The anesthetist must be certain that the scavengi
ng system is operational and adjusted properly to
ensure adequate scavenging.

61. Closed anesthetic Breathing system(CABS)
• In CABS there is total rebreathing of exhaled g
ases after absorption of Co2 and the APL valve
or relief valve of the ventilator is closed.
• A closed system is present when the fresh gas
inflow into the circle system (150 to 500 mL/m
in satisfies the patient's metabolic o2 require
ments (150-250ml/min during anesthesia and
replaces anesthetic gases lost by virtue of tissu
e uptake.

62. Advantages of CABS
• Advantages of a closed circle anesthetic breathing sys
tem over a semiclosed circle anesthetic breathing sys
tem include:
1- Maximal humidification and warming of inhaled
gases.
2- Less pollution of the surrounding atmosphere wi
th
anesthetic gases.
3- economy in the use of anesthetics.

63. Danger of CABS
• Includes:
• Unpredictable and possibly insufficient concent
ration of o2 .
• Unknown and possibly excessive concentration
of potent anesthetic gases.

64. Elimination of Carbon dioxide
• Chemical neutralization of CO2 is achieved by
directing exhaled gases through a container (c
anister) containing a carbon dioxide absorbent
such as soda lime or bara lyme.

66. Composition of CO2 Absorbents
Soda Lime Baralyme
(Percent of net weight ) (Percent of net weight)
• Sodium hydroxide = 4 % Barium hydroxide = 20 %
• Potassium hydroxide = 1 % Calcium hydroxide = 80 %
• Water = 14-19 % Water = bound water of
crystallization in the
• Silica = 0.2 % octahydrate salt of barium
hydroxide
• Calcium hydroxide = 80% Silica = none

67. Soda lime
• Soda lime granules consist of calcium hydroxide
plus smaller amounts of sodium hydroxide and
potassium hydroxide that are present as activat
ors.
• A specific water content of soda lime granules i
s necessary to assure optimal activity.
• Silica is added to the granules to give hardness
and thus minimize the formation of alkaline dus
t.
• since its inhalation can produce irritation of the
airways manifesting as bronchospasm.

68. Soda lime
• Neutralization of carbon dioxide begins with the reactio
n of this gas with the water present in soda lime granul
es and exhaled gases to form carbonic acid.
• Carbonic acid then reacts with the hydroxides present i
n soda lime granules to form carbonates, water, and he
at.
• The water formed by the neutralization of carbon dioxi
de is useful for humidifying the inhaled gases and for di
ssipating some of the heat generated in the exothermic
neutralization reaction.
• The Maximum CO2 absorbed is 23-26lit per 100gm of a
bsorbent.

69. Soda lime
• Accumulation of this highly alkaline of water in
the bottom of the canister can produce burns o
n contact with the skin.
• The heat generated during neutralization of ca
rbon dioxide can be detected by warmness of t
he canister.
• Failure of the canister to become warm to touc
h should alert the anesthetist to the possibility
that chemical neutralization of carbon dioxide i
s not taking place.

70. Chemical Neutralization of Carbon dioxide
Soda lime…….
• CO2 + H2O → H2 CO3
• H2 CO3 + NaOH → Na2 CO3 (rapid) + 2 H2O + H
eat
• H2 CO3 + Ca (OH)2 → CACO3, (slow) + 2 H2O + H
eat

71. Baralyme
• Baralyme granules consist of barium hydroxide
and calcium hydroxide.
• Unlike soda lime, the addition of silica to baraly
me granules is not necessary to assure hardness
.
• hardness of baralyme granules reflects the pres
ence of bound water of crystallization in the oct
ahydrate salt of barium hydroxide.
• This bound water also accounts for the more rel
iable performance of baralyme than soda lime i
n dry environment.

72. • Baralyme…
• CO2 + H2O → H2CO3
• H2 CO3 + Ba (OH)2 → BaCO3 (rapid) + 2 H2O + Hea
t
• H2O3 + Ca (OH)2 → CaCO3 (slow) + 2H2O + Heat

73. • This checkout, or a reasonable equivalent, should
be conducted before administration of anesthesia
.
• Users are encouraged to modify this guideline to
accommodate differences in equipment design a
nd variations in local clinical practice. Such local
modifications should have appropriate peer
review.
• Users should refer to the appropriate operator m
anuals for specific procedures and precautions.

74. • 1. Verify backup ventilation equipment is availabl
e and functioning
High-Pressure System
• *2. Check O2 cylinder supply
a. Open O2 cylinder and verify at least half full
(about 1000 psig).
b. Close cylinder
• *3. Check central pipeline supplies; check that ho
ses are connected and pipeline gauges read abou
t 50 psig

75. Low-Pressure System
• *4. Check initial status of low-pressure system
a. Close flow control valves and turn vaporizers
off.
b. Check fill level and tighten vaporizers' filler ca
ps.

76. • 5. Perform leak check of machine low-pressure syst
em
a. Verify that the machine master switch and flow co
ntrol valves are off.
b. Attach suction bulb to common (fresh) gas outlet.
c. Squeeze bulb repeatedly until fully collapsed.
d. Verify bulb stays fully collapsed for at least 10 seco
nds.
e. Open one vaporizer at a time and repeat steps c an

77. 6. Turn on machine master switch and all other ne
cessary electrical equipment.
7. Test flowmeters
a. Adjust flow of all gases through their full range
,
checking for smooth operation of floats and
undamaged flowtubes.
b. Attempt to create a hypoxic O2/N2O mixture
and

78. Scavenging System
• 8. Adjust and check scavenging system
a. Ensure proper connections between the scaven
ging system and both APL (pop-off) valve and v
entilator
relief valve.
b. Adjust waste-gas vacuum (if possible).
c. Fully open APL valve and occlude Y-piece.

79. d. With minimum O2 flow, allow scavenger reserv
oir bag to collapse completely and verify that ab
sorber
pressure gauge reads about zero.
e. With the O2 flush activated, allow scavenger re
servoir bag to distend fully, and then verify that
absorber pressure gauge reads < 10 cm H2O.

80. Breathing System
• 9. Calibrate O2 monitor
a. Ensure monitor reads 21% in room air.
b. Verify low-O2 alarm is enabled and functioni
ng.
c. Reinstall sensor in circuit and flush breathing
system
with O2.
d. Verify that monitor now reads greater than 9

81. 10. Check initial status breathing system
a. Set selector switch to Bag mode.
b. Check that breathing circuit is complete,
undamaged, and unobstructed.
c. Verify that CO2 absorbent is adequate.
d. Install breathing-circuit accessory equipmen
t (eg,
humidifier, PEEP valve) to be used during the
cas

82. • 11. Perform leak check of the breathing system
a. Set all gas flows to zero (or minimum).
b. Close APL (pop-off) valve and occlude Y-piece
.
c. Pressurize breathing system to about 30 cm H
2O
with O2 flush.
d. Ensure that pressure remains fixed for at least
10

83. Manual and Automatic Ventilation Systems
• 12. Test ventilation systems and unidirectional
valves
a. Place a second breathing bag on Y-piece.
b. Set appropriate ventilator parameters for n
ext
patient
c. Switch to automatic-ventilation (ventilator)
mode.

84. e. Set O2 flow to minimum, other gas flows to ze
ro.
f. Verify that during inspiration bellows deliver a
ppropriate tidal volume and that during expira
tion bellows fill completely.
g. Set fresh gas flow to about 5 L min–1.
h. Verify that the ventilator bellows and simulate
d lungs fill and empty appropriately without s
ustained
pressure at end expiration.

85. i. Check for proper action of unidirectional valves.
j. Exercise breathing circuit accessories to ensure
proper function.
k. Turn ventilator off and switch to manual ventila
tion (bag/APL) mode.
l. Ventilate manually and ensure inflation and defl
ation of artificial lungs and appropriate feel of s
ystem resistance and compliance.
m. Remove second breathing bag from Y-piece.

86. Monitors
13. Check, calibrate, and/or set alarm limits of all
monitors: capnograph, pulse oximeter, O2 anal
yzer,
respiratory-volume monitor (spirometer), press
ure monitor with high and low airway-pressure
alarms.

87. Final Position
14. Check final status of machine
a. Vaporizers off
b. APL valve open
c. Selector switch to Bag mode
d. All flowmeters to zero (or minimum)
e. Patient suction level adequate
f. Breathing system ready to use