Equipment Flashcards
What is the pin index system
Safety feature
Prevent delivery of incorrect gases
Drilled holes on gas cylinder valve which correspond to pins on the equipment.
Nitrous 3,5 , Oxygen 2,5, Air1,5
What is filling ratio, why important
The amount of gas/liquid contained in a filled cylinder as a percentage of what a full cylinder with water would contain.
Issue for N2O and CO2- liquid with vapour. Vapour produces pressure, as it is used more liquid vapourises. Temperature changes may cause a dangerous rise in pressure as it affects the SVP.
UK -0.75, hot climates .67
VIE key features (6)
Temp and pressure?
-150 to -180’C P10 ATM
Dual walled chamber with vacuum to reduce conductive heat loss
Blow off excess pressure valve
Pressure raising vaporiser to heat liquid oxygen and increase vaporisation in time of excess usage
Weighing scale to estimate remaining oxygen
connection to pipeline distribution system with pressure contrl panels and safety shut off valvs
O2 boiling point and TCT?
BP -183’c, CT -118’c
relative humidity of oropharynx and temp
27-32g/m3 , temp 30-37’c
Dry gases issues?
Increased viscosity of secretions, disruption of mucocilary clearance, damage to respiratory mucosa. Atelecasis, shunt, reduced FRC.
How do HMEF work
Conservation of heat/moisture from patients expired gases.
Exhaled gas cools - water vapour condenses on hygroscopic material.
inhaled gas dry - moisture picked up as it is heated and delivered to patient.
Efficiency 80%.
Problems with HMEF
- Retention of secretions/blockage
- Increase in deadspace, resistance gas flow
- Takes time to heat up
- unsuitable for long term ventilation
Describe what Beer-Lambert law is
The absorbance of light is proportional to the concentration of the medium it passes through and the path length that the light has to travel through
Absorbance = molar absorbivity x path length x concentration
How can you classify breathing systems?
4 categories, ?examples
Open, semi-open, closed, semi-closed
Open: Schimmelbusch mask, ‘cupped hand’
Closed: Circle system
3 key roles of breathing systems
1) Supply oxygen 2) remove CO2 and prevent rebreathing 3) deliver anaesthetic gas
Clinical and practical
Ideal properties of a breathing system
Clinical: Efficient in SV (low resistance) and CV, low deadspace volume, apply to wide patient population, economical for FGF/VA, low pollution and allow CO2 absorption for rebreathing of exhaled gases, protection from barotrauma and minimal risk of disconnection.
Practical: cheap, lightweight, easy to use, portable, disposable, no/easy maintainance, easy to connect to pressure monitoring equipment.
List names of the breathing systems (mapleson)
A - Magill, also have Parallel and Co-axial/LACK system (takes APL valve away from face) - spontaneous ventilation most efficient (70% mV)
B - not really used
C - Water’s circuit
D - D circuit and Bain modification (Controlled ventilation most efficient 1-2x minute volume FGF)
E - Ayres T-piece
F - Ayres T -piece with Jackson-Rees modification
3 Purposes of reservoir bag and adult volume
1) Reservoir of FGF/O2 if patient’s minute ventilation exceeds fresh gas flow from machine
2) Conserve FGF during expiratory pause
3) Means of ventilation on manual spont.
Which breathing system is most efficient for SV and CV
SV - Mapleson A
CV - Mapleson D
