- Equipment 3
- gases and their storage
- heliox
- 21% oxygen, 79% helium
- properties
- less dense
- will reduce the Reynold’s number and therefore the chance of turbulent flow
- similar viscosity
- will not significantly change the flow when using the Hagan-Poiseuille formula so less useful if flow is already laminar
- uses
- upper airway obstruction
- deep diving
- prevents nitrogen narcosis
- prevents oxygen toxicity
- Bert effect
- hyperbaric hyperoxia effects on CNS
- 2bar
- parasthesia, nausea, twitching, myopia
- 3bar
- Smith effect
- hyperbaric hyperoxia effects on lungs
- 2bar
- VC drop after 4 hours
- significant changes after 12 hours
- entonox
- pseudo-critical temp = -6 C
- 50:50 by volume
- horizontal storage will increase the surface area for diffusion of oxygen back into liquid nitrous (if below pseudo-critical temp)
- O2
- critical temp = -118C
- VIE
- steel
- vacuum of 0.16 - 3 kpa between skins
- -160 - 180 C
- SVP 10 bar
- blow off valve opens at 15 bar
- cooled by latent heat of vapourisation
- expands to 840 x its volume at 20 C
- demand
- low
- reduced cooling effect by LHV causes pressure to increase —> safety valve opens at 15 bar
- high
- rapid vapourisation causes reduction in SVP and insufficient vapour for demand, so some oxygen is tapped from the bottom, warmed by environment and added to circuit
- CYLINDERS
- C = 170L
- CD = 460L 20,000kPa
- D = 340L
- E = 680L
- the size on the anaesthetic machine
- F = 1360L
- G = 3400
- H =
- J = 6800L
- N2O
- produced by heating ammonium nitrate
- filling ratio
- weight of nitrous should be 75% of the weight of water that would completely fill the cylinder
- 67% in warmer climates
- remember weight, NOT volume
- measurement
- cannot use pressure as gas is below critical temperature
- measured by gross weight - tare weight
- when in constant use, the bourdon gauge will steadily decrease due to the cooling effect of the latent heat of vapourisation!
- CYLINDERS
- C = 450L
- D = 900L
- E = 1800L
- G = 9000L
- J = 18,000L
- Critical temps and pressures
- triple points
- STP
- low pressure circuit
- breathing systems
- open
- drape
- Schimmelbusch mask
- oxygen masks
- Venturi
- 28 - 50%
- entrainment ratio
- 1:25
- e.g. 1:10 at 6L/min = ((6x1)+(60x0.21)) / 66 = 28%
- 1:8
- 1:5
- 1:3
- 1:1.7
- semi-open
- Mapleson
- A
- alveolar MV (70mL/kg/min) for spont.
- 2-3x MV for controlled
- B
- C
- T-PIECES!
- D
- alveolar MV for controlled
- 2-3x MV for spont.
- E
- F
- semi-closed
- circle
- reservoir bag
- APL valve
- 2 uni-directional valves
- CO2 absorber
- FGF and vapours
- closed
- circle with APL valve fully closed
- Ventilators
- negative pressure
- positive pressure
- classification
- powering mechanism
- pneumatic
- pneumatic with electric control
- electric
- inspiratory/expiratory cycling mechanism
- time cycled
- pressure cycled
- volume cycled
- flow cycled
- inspiratory driving mechanism
- minute volume dividers
- bag squeezers
- Ohmeda anaesthetic machine ventilator
- intermittent blowers/constant flow generators
- Penlon Nuffield 200
- Oxylog 1000
- mechanical thumbs/pressure generator
- neonatal ventilators
- Penlon with a Newton valve
- jet
- low frequency
- high frequency
- reduces airway vibration
- 12 - 600 cycles/min
- oscillators
- active inspiration and expiration
- 3-15Hz (180 - 900 breaths/min)
- examples
- bag in bottle
- pneumatically powered, electronically controlled, time cycled, bag squeezer
- Oxylog
- 1000
- pneumatically powered, time cycled intermittent blower
- 2000/3000
- pneumatically powered, electronically controlled, time cycled, intermittent blower
- Penlon Nuffield 200
- pneumatically powered, time cycled intermittent blower
- Manley
- pneumatically powered, time cycled, minute volume divider
- modes
- mandatory
- VC
- constant flow, varying pressure
- volume maintained when compliance changes
- good for tight CO2 control
- PC
- constant pressure, varying flow
- able to compensate for leaks
- better for paeds (uncuffed tubes)
- higher MAwP
- PRVC
- support
- spontaneous