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Anesthesia Breathing Systems
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For a comprehensive understanding of 'Anesthesia breathing circuits' click here for a review. It opens a new window, close the window to return to this section again.
The following section contains pertinent features of anesthesia circuits and their functional analysis for easy understanding facilitated by animations.
DEFINITION
A
breathing system is defined as an assembly of components which connects the
patient’s airway to the anaesthetic machine creating an artificial atmosphere,
from and into which the patient breathes.
It
primarily consists of
a)
A fresh gas entry port/delivery tube through which the gases are delivered from
the machine
to the systems;
b)
A port to connect it to the patient’s airway;
c)
A reservoir for gas, in the form of a bag or a corrugated tube to meet the peak
inspiratory flow requirements;
d)
An expiratory port/valve through which the expired gas is vented to the
atmosphere;
e)
A carbon dioxide absorber if total rebreathing is to be allowed and
f)
Corrugated tubes for connecting these components.
Flow
directing valves may or may not be used.
Classification
| BREATHING SYSTEMS WITHOUT CO2 ABSORPTION | BREATHING SYSTEMS WITH CO2 ABSORPTION. |
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Unidirectional
flow: a) Non rebreathing systems. B) Circle systems.
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Unidirectional
flow Circle system with absorber.
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Bi-directional
flow: a) Afferent reservoir systems. Mapleson A Mapleson B Mapleson C Lack’s system. B) Enclosed afferent reservoir systems Miller’s (1988) c) Efferent reservoir systems Mapleson D Mapleson E Mapleson F Bain’s system d) Combined systems Humphrey ADE |
Bi-directional
flow To and Fro system.
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Mapleson circuits
In 1954 Mapleson described and analyzed five different semiclosed anesthetic systems, and they are classically referred to as Mapleson systems and designated A to E. In 19 , Willis et al added the F system to the five original systems. The table below shows appearance and description of each system. For functional analysis of each of these systems, click on the hyperlink to open a new window. Close the window to return back to this section.
Fresh gases CO2 containing gases There is mixing of these two in rebreathing systems
| Type | Appearance | Description |
| Mapleson A |  |
Expiratory valve close to face
mask, separated by corrugated tube (
) from reservoir bag and supply of fresh gases
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| Mapleson B |  |
Expiratory valve and supply of
fresh gases close to face mask, separated by corrugated tube (
) from reservoir bag
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| Mapleson C |  |
Expiratory valve, supply
of fresh gases and reservoir bag , all close to face mask (No corrugated
tube ( )
|
| Mapleson D |  |
Supply of fresh gases close to
face mask, separated by corrugated tube (
) from reservoir bag and expiratory valve
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| Mapleson E |  |
Supply of fresh gases close to
face mask. Open length of corrugated tube (
). No reservoir bag or expiratory valve.
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| Mapleson F |  |
Supply of fresh gases close to
face mask. Corrugated tube (
) present. . Reservoir bag with expiratory port, but no expiratory
valve.
Mapelson E with reservoir bag.
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Relative efficiency of rebreathing among various Mapleson circuits |
| Spontaneous ventilation |
A>DFE>CB |
| Controlled ventilation |
DFE>BC>A |
| Mapleson A is most efficient during spontaneous ventilation. It is worst for controlled ventilation. |
| Mapleson D is most efficient during controlled ventilation |
Circle system
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Bain system
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Non rebreathing system
| This is a unidirectional non rebreathing system with out CO2 absorption. A non rebreathing valve is located near the patient end. |
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