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==Introduction==
==Introduction==
Breathing systems are the connecting component between the anaesthetic machine and patient. Their role is to deliver oxygen and anaesthetic agent to the patient from the machine, remove exhaled carbon dioxide and provided a means of ventilatiion via pressure on the reservoir bag.
Breathing systems are the connecting component between the anaesthetic machine and patient. Their role is to deliver oxygen and anaesthetic agent to the patient from the machine, remove exhaled carbon dioxide and provided a means of ventilation via pressure on the reservoir bag.
Basic components of a breathing system are -
Basic components of a breathing system are -
*''Pressure relief valve'' - Limit pressure build up and allows for removal of waste gases.
*''Pressure relief valve'' - Limit pressure build up and allows for removal of waste gases.
*''Fresh gas inlet'' - Connects the circuit to the gas outlet on the anaesthetic machine.
*''Fresh gas inlet'' - Connects the circuit to the gas outlet on the anaesthetic machine.
==Classification==
==Classification==
===Non Rebreathing Systems===
===Non Rebreathing Systems===
====''T-piece''====
====''T-piece''====
*Used on patients less the 10kg.
*Used on patients less than 10kg.
*Circuit factor - 2-3x Minute Volume.
*Circuit factor - 2.5 - 3 x Minute Volume.
*Reservoir bag on expiratory limb.
*Reservoir bag on expiratory limb.
*'''Advantages'''
*'''Advantages'''
**Low resistance so suitable for small patients.
**Low resistance so suitable for small patients.
**Can use Inttermitent Positive Pressure Ventilation (IPPV).
**Can use Intermitent Positive Pressure Ventilation (IPPV).
*'''Disadvantages'''
*'''Disadvantages'''
**Cold dry gases delivered to patients.
**Cold dry gases delivered to patients.
**Unecomonical on larger patients.
**Uneconomical on larger patients.
====''Bain''====
====''Bain''====
*Either parallel or co-axial circuits.
*Either parallel or co-axial circuits.
*Used on patients between 10-20kg.
*Used on patients between 10-20kg.
*Circuit factor - 1-2x Minute Volume.
*Circuit factor - 2.5 - 3 x Minute Volume.
*Reservoir bag on expiratory limb.
*Reservoir bag on expiratory limb.
*'''Advantages'''
*'''Advantages'''
====''Magill''====
====''Magill''====
*Used on patients between 10-25kg
*Used on patients between 10-35kg
*Circuit factor - 1-1.5x Minute Volume.
*Circuit factor - 1-1.5x Minute Volume.
*Reservoir bag on inspiratory limb.
*Reservoir bag on inspiratory limb.
====''Lack''====
====''Lack''====
*Also parallel and mini circuits available.
*Also parallel and mini circuits available.
*Used on patients between 10-35kg (Mini lack used on patients less then 10kg)
*Used on patients between 10-35kg (Mini lack used on patients less than 10kg)
*Circuit factor - 1-1.5x Minute Volume.
*Circuit factor - 1-1.5x Minute Volume.
*Reservoir bag on inspiratory limb.
*Reservoir bag on inspiratory limb.
*Also mini circle circuit available.
*Also mini circle circuit available.
*Used on patients over 10kg.
*Used on patients over 10kg.
*Minimum gas flow = 10ml/kg.
*Minimum gas flow = 10ml/kg. It does not have a circuit factor!
*'''Advantages'''
*'''Advantages'''
**Patient breathes warm humidified air due to rebreathing.
**Patient breathes warm humidified air due to rebreathing.
#Open the pressure relief valve to ensure pressure relieved.
#Open the pressure relief valve to ensure pressure relieved.
#Ensure inspiratory and expiratory valves move freely on a circle circuit by squeezing reservoir bag and releasing thumb off the end of the circuit.
#Ensure inspiratory and expiratory valves move freely on a circle circuit by squeezing reservoir bag and releasing thumb off the end of the circuit.
==Calculating Fresh Gas Flow==
*The formula for working out the fresh gas flow rate is:
<center>
{| border="1" cellpadding="1"
|-style="background:#B0E0E6; color:black"
!'''Fresh gas flow''' = ''Tidal volume (weight x 10 - 15mls)'' x ''Respiratory rate'' x ''System factor''
|-
|}
</center>
*For patients under 10kg, the tidal volume is weight times 15mls, for patients over 10kg the tidal volume is weight times 10mls.
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[[Category:Anaesthetic Equipment]]
[[Category:To Do - Anaesthesia]]