L2: Anesthesia Machine and Components (Garcia) Flashcards
how much pressure of oxygen can a tank hold?***
1900-2200 PSI
regulator takes pressure of oxygen from tank down to what pressure?***
55-75 PSI
slide 3 diagram
:)
why can tanks carry more nitrogen?**
stored in liquid form at high pressure
how many liters of oxygen and at what PSI can E tank hold?
660L
1900 PSI
how many liters of nitrogen and at what PSI can E tank hold?
1600L
750 PSI
how many liters of oxygen and at what PSI can H tank hold?
7000L
2200 PSI
how many liters of nitrogen and at what PSI can H tank hold?
16000L
750 PSI
pressure in tank is ____ proportional to volume
directly (for O2)
how do you gauge how much oxygen is left in tank?
pressure (pressure directly prop. to volume)
how do you gauge how much N2O is left in tank?
by WEIGHT (pressure will not decrease until liquid nigtrogen is extinguished)
what color is O2
green (white internationally)
what color is CO2
gray
what color is N2O (laughing gas)
blue
what color is He
brown
what color is N2
black
what color is air
yellow (black/white internationally)
safety systems
No interchangeable connections:
-Pin Index Safety System (PISS) and Diameter Index Safety System (DISS)
fx of flowmeter
- measures gas flow in L/min
- has knobs for O2 and N2O
- read at center of ball or top of float
max O/N ratio
1:3
fx of flush valve
-bypasses flowmeter and vaporizer and delivers oxygen at intermediate pressure (45-50 psi) at 35-70L/min to dilute the anesthetic gas
2 locations vaporizers can be
VOC (vaporizer out of the circuit)
VIC (in the circuit)
pop off valve
- usually left open
- closed intermittently to deliver breaths
- can be closed in the closed circuit system
- if accidentally left closed, pressure will rise inside patient’s lungs and venous return to heart decreases
scavenger
- passive or active
- has a charcoal absorber that avoids environmental contamination w/ short life but does NOT absorb N2O
- in passive, pressure > barometric; cheaper, simpler; whenever pressure builds up in system, it passively leaves as negative pressure
- active has a flow inducing device and is more expensive
2 main types of breathing systems
Circle (Rebreathing) System - used in most patients
Non-rebreathing system - more wasteful, no recycling of gas
Components of circle system
- unidirectional valves (inspiratory and expiratory)
- canister with absorber
- breathing bag
- rebreathing tube
- pressure gauge
- pop off valve
chars. of unidirectional valves
- allow flow only in 1 direction
- no rebreathing of CO2 (expiratory valve prevents)
- may stick with moisture
- may dislodge from housing
canister
- houses CO2 absorbent (sodalime, baralyme)
- should be >2x the tidal volume (Vt) of the patient
- great source of leaks
- should not be overfilled due to channeling
- granules turn purple when exhausted
MOA of sodalime and baralyme absorbents
- reacts with CO2 forming heat and H2O
- changes color with reaction
- changed when 1/2 of soda is purple
- pellets become harder after reaction
- caution: pellets won’t stay purple forever!
breathing bag
- used as a reservoir
- 6x the tidal volume of the patient
- used to deliver breaths manually
- can be used to count RR
- some protection against excessive pressure
most to least sites of leaks
canister unidirectional valves reservoir bag hoses connections *must close pop off valve to check for!*
advantages of circuit system
-rebreathing of expired gas after CO2 elimination
-keep heat and moist
-more economic (decreases O2 and inhalant used)
-lower O2 flows: less env. contamination
-
disadvantages of circuit system
- lots of parts
- more likely to leak
- difficult to clean
- not easily moved
- controlled ventilation can lead to hypocarbia (dec. CO2 in the blood)
chars. of semi-closed circuit system
- O2 is greater than p requirement
- O2 flow >20ml/kg
- CO2 elimination less dependent on absorbent
- no nitrogen accumulation due to low flow
- fast change in anesthetic concentration
chars. of semi-closed circuit system
- less economic
- less heat and moist conservation than closed
- more pollution
- high flows may increase resistance
adv. of low flow or closed system (same machine as semi-closed circuit system, but with low flow)
- more economic
- less pollution
- keep heat and moist
how much flow does a low flow system have?
8-15ml/kg
disadv. of low flow or closed system
- CO2 elimination dependent only on absorbent (not on scavenger)
- slower change in anesthetic conc.
- may cause incorrect vaporizer output (since vaporizer is flow dependent
- N accumulation
chars. of non-rebreathing systems
- elimination of CO2 by high O2 flow
- usually use on patients <3kg
- high O2 flow (100-200 ml/kg)
- Bain system most common
adv. of non-rebreathing system
- light, simple, low resistance
- no need for absorber
- fast change in depth
- inexpensive
disadv. of non-rebreathing system
- wasteful
- loss of heat and moisture
- pollution
- changes in EtCO2 (lvl of CO2 released at end of expiration) and gas analyzer readings
can leave pop-off valve closed in closed system?
yes
main use of low flow or closed system
to MAINTAIN animal in anesthesia
how to check for leaks
- close pop-off valve
- put thumb on patient’s end of breathing hose
- press flush valve until pressure gauge reads 30 cmH2O
- pressure should hold
- press flush valve
- p’s end of breathing hose open
- reservoir bag should deflate (if inflates, means inspiratory hose is leaking)
