delivery systems Flashcards
essential elements of breathing system
1 - deliver gases from machine to alveoli in same conc as set, in shortest ant time
2 - elim CO2
3 - min apparatus dead space
4 - low resistance
desirable elements of breathing system
1 - economy of fresh gas 2 - conservation of heat 3 - adequate humidification of inspired gas 4 - light weight 5 - convenience during use 6 - efficiency during spon/controlled breathing 7 - adaptability for children/adults 8 - reduce environmental pollution
low resistance
- short tubing
- large diameter
- avoid sharp bends
- caution with valves
- minimize connections
rebreathing
may be beneficial
- cost reduction
- adds humidification/heat to gases
don’t want to rebreathe CO2
higher FGF associated w less rebreathing in any type of circuit
dead space
increases chance of rebreathing CO2
ends where inspiratory and expiratory gas streams diverge
apparatus dead space can be minimized by separating inspiratory and expiratory streams as close to patient as possible
Open system
- no gas reservoir bag
- no valves
- no rebreathing of exhaled gases
types:
1 - insufflation/blowby
2 - open drop
insufflation
open system
blowby, tent, bronchoscopy port, nasal cannula, steal induction
advantages of insufflation
avoids direct patient contact
no rebreathing of CO2
no reservoir bag or valves
disadvantages of insufflation
no ability to assist or control vent
may have CO2/O2 accumulation under drapes
no control of anesthetic depth/fiO2
environmental pollution
schimmelbusch mask
true open circuit,
consisted of bit of cloth saturated w ether or chloroform or halothane and held over patients face
open drop method
ether mask (schimmelbusch)
advantages of open drop
simplicity
low cost apparatus
portable
disadvantages of open drop
poor control of inspired concentration of anesthetics accumulation of CO2 under max predisposes to hypoxia risk spontaneous vent only/cannot control OR pollution/health care provider risk
semi open 5 characteristics
1 - facemask or ETT 2 - pop off valve 3 - reservoir tubing 4 - fresh gas inlet 5 - reservoir bag
mapleson A-F, Bain, circle
functional group 1
mapleson A
pop off located near face mask
FGF located at opposite end
functional group 2
Mapleson B/C
pop off and FGF located near facemask
functional group 3
Mapleson D, E, F
FGF located near face mask and pop off located at opposite end
opposite landscape of mapleson A
CO2 rebreathing depends on
1 - fresh gas inflow rate
2 - min vent of patient
3 - type of vent (spon vs controlled)
Mapleson D
reversed config of A
can be used for both soon and controlled vent
during spon… FGF: 2-3 x MV
controlled… FGF: 1-2 x MV
most efficient mapleson during controlled vent
Mapleson E (T piece)
modification of ayres T piece (used to give O2 in ICU/PACU)
NO RESERVOIR BAG or POP OFF
SV… FGF: 2-3 x MV
Mapleson F (Jackson-Rees)
modification of mapleson E/t piece w adjustable pop off valve at end of reservoir bag
popular in peds
Bain
coaxial mod of Map D
FGF tubing within large bore corrugated tubing
allows exhaled gas to wam inspired gas, preserves heat and humidity
used for controlled or spon vent
FGF same as map D
disadvantage - potential for inner tube leaks, kinking or disconnection
ambu bag
modified map Awith non-rebreathing valve
capable of delivering high fiO2
reservoir self filling
requires high fresh gas flow
depends on min vent
advantages of mapleson system
1 - simple components 2 - lightweight 3 - can provide positive pressure vent 4 - low resist 5 - portable 6 - if using inhaled anesthetics, more predictable anesthetic conc and decreased room pollution
disadvantages of mapleson system
1 - requires calc of FGF (both SV & CV)
2 - control of anesthesia depth variable, diluted as FGF increases but better control than open system
3 - if FGF not maintained, CO2 buildup and rebreathing
4 - min rebreathing of other gases, poor conservation of heat/humid
5 - FGF costly
6 - requires special assembly and function complex
components of circle system
1 - fresh gas flow source
2 - inspiratory/expiratory unidirectional valves
3 - inspiratory/expiratory limbs/corrugated tubing
4 - Y piece connector
5 - adjustable pressure limiting valve (APL, over flow, pop off)
6 - reservoir bag
7 - CO2 absorber
Circle system
can be used as semi-open, semi-closed, or closed
(depends on adjustment of APL valve… FGF rate differs for each system)
prevents rebreathing of CO2 by chemical neutralization
allows rebreathing of other exhaled gases
reservoir bag
“breathing bag” “resp bag”
neoprene or rubber
neck - 22mm female fitting to male system
tail - end opposite neck
functions of reservoir bag
1 - accumulation of gas during exhalation
2 - assist/control of vent
3 - visual/tactile monitor to observe spon resp
4 - protect against excessive pressure reservoir of gas
breathing tubes
large bore, non rigid corrugated tubing
rubber or clear plastic (see foreign obj through)
22mm female fitting w machine
patient end - T piece 22mm male, 15mm female coaxial fitting
functions of breathing tubes
flexible, low resistance, light weight connection
reservoir
APL
pressure relief, popoff, safety relief
releases gases to scavenge or atm exhaust port
user adjustable, clockwise, closes valve and increases pressure in system
rpovides control of pressure in system - pressure gauge on absorber
APL for spon resp
valve fully open
close partially only if reservoir bag collapses
APL for assisted vent
valve partially ope
bag squeezed on inspiration
careful and frequent adjustments necessary
APL for mech vent
valve closed (if machine not equipped with switch)
where is dead space in circle system?
if unidirectional valves working properly, only dead space is between Y piece and patient
what rules must circle arrangement follow?
1 - unidirectional valves must be located between patient and reservoir bag on both insp and exp limbs of circuit
2 - FGF cannot enter system between exp valve and patient
3 - APL cannot be located between patient and insp valve
Semi Open circle system
- not used often, occasionally for sedation ( mask placed over face to increase FiO2)
- no rebreathing occurs
- requires very high FGF (10-15L/min) to elim rebreathing of gas
- no conservation of wastes gases and heat
- APL valve open all the way
semi closed circle system
- most commonly used breathing system in US practice
- requires relatively low flow rates (1-3L/min)
- conserves some heat and gases
- some rebreathing of a agents and exhaled gases (minus CO2)
- APL valve partially closed and adjusted as needed
closed circle system
- 3rd world countries
- inflow fas exactly matches metabolic needs/ O2 consumption of patient using very low flows (O2 flow = 200ml/min)
- total rebreathing of all gases after CO2 absorption
- total conservation of all exhaled gases
- APL valve closed
O2 Consumption
VO2 = 10 x Kg 3/4
70kg patient: 10 x 70 3/4 = 242ml/min
advantages of circle system
- relative stability of inspired gases
- conservation of moisture and heat
- prevention of OR pollution
- can be used for closed system anesthesia
- can be used with daily low flows with no rebreathing of CO2
- economy of anesthetics and gases
- can scavenge waste gases
disadvantages of circle system
- complex design
- has at least 10 connections (potential leaks, obstruction, disconnection)
- 1/3 malpractice claims resulted form disconnects of circuit
- potential of malfunctioning valve
- increased resistance to breathing
- less portable and convenient than mapleson systems due to bulkiness
leak test
set all gas flows to zero occlude Y piece close APL pressurize to 30cm water using O2 flush hold pressure 10 sec listen for sustained pressure alarm open APL and see that pressure decreases
(doesn’t assess integrity of unidirectional valves)
flow test
attach breathing bag to Y piece
turn on vent
assess integrity of unidirectional valves
