anesthesia breathing systems Flashcards
What is the breathing system?
links the patient to the anesthesia machine by delivering oxygen and anesthetic gases and eliminating carbon dioxide
what are the types of breathing systems?
- resuscitation
- insufflation (open)
- open drop (open)
- draw over (semi open)
- maplesons (semi open)
- circle (semi closed or closed)
all circuits have some resistance, how can circuit resistance be decreased?
- decrease in circuit length
- increase circuit diameter
- avoid sharp bends
- eliminating valves (cant totally eliminate, need unidirectional flow)
- maintaining laminar flow
what happens when you have increased gas flows?
- decreased rebreathing (of O2, CO2, N2O, and volatile agent)
- decreased equilibration time between “dialed-in” concentration and inspired concentration
when do you use high flows?
- for induction to denitrogenate and get inspired gas concentration up
- for emergence to “wash out” anesthetic gases
- to prevent rebreathing
when do you use low flows?
-for maintenance to conserve heat, humidity, volatile agent, and minimize OR contamination
describe resuscitation breathing system.
-use of ambu (artificial manual breathing unit) bag
-self refilling with O2 or room air
-valves help with one way flow
>pt valve opens on inspiration
>exhalation ports allow venting during exhalation
>nonrebreathing valve
>intake valve closes with compression allowing for + pressure
*needs high flows for high FiO2
what are some advantages and disadvantages of the resuscitation breathing system?
- advantage: simple, portable, can deliver almost 100% O2
- disadvantage: difficult to determine mask to face seal
- with anesthesia bag, if there is no seal, bag will go flat
describe open-drop anesthesia breathing system.
-used ether or chloroform
-dripped onto gauze over a mask
-pt inhales -> air passing through vaporizes the liquid
agent -> mask gets cold -> condensation and decreased
vapor pressure
**completely open method, not in circuit, not controlled
*no longer used, historically important
describe draw-over anesthesia breathing system.
- ambient air is inhaled (drawn over) liquid agent
- pt inhalation “draws over” the vaporizer
- can be fitted with valves for O2, positive pressure ventilation and passive scavenging
- *amt of O2 and gas given is dependent on flow and temp
- *semi open method
ex: copper kettle
how does flow affect amount of O2 and gas in draw-over anesthesia?
- 1 L/min O2- FiO2 30-40%
- 4 L/min O2- FiO2 60-80%
what are the advantages of draw-over anesthesia?
- simple
- portable
- can be used without compressed gas or ventilators
- can be used with room air
- used in war zones
what is insufflation?
blowing gas across the face
*more a technique than a breathing system
what are some uses of insufflation?
- preoxygenation
- manual ventilation
- inhalation inductions (peds)
- under drapes during sedation
- flushed out CO2 but caused fires from accumulating O2
- apneic techniques
- airway surgeries cant have something in airway, keeps O2
- blowing O2 over airway, like with jet ventilators
- does not help with CO2, just keeps Sat up
- still have to take breaks & insert tube to blow off CO2
describe Mapleson systems?
-breathing systems with components added
-location of components determines classification
(A-F)
*total nonrebreathing
*use high gas flows
-dangerous with potent gases
-flushes out pt. moisture and heat
-wastes gases and contaminates OR
**semi open
how are Mapleson systems total nonrebreathing?
fresh gas comes in to patient during inhalation, exhalation goes out to APL valve to go to scavenging
what are the components of the Mapleson system?
- breathing tube
- fresh gas inlet
- adjustable pressure-limiting (APL) valve
- reservoir bag
describe the Mapleson breathing tube.
- corrugated (rubber or disposable synthetic)
- large (22mm) diameter for low resistance
- long tubes and/or high compliance equal large gradient b/w gas delivery to circuit and gas delivery to pt (takes longer)
describe the Mapleson fresh gas inlet.
- anesthetic gases (volatiles, N2O, O2, air) from anesthesia machine enter the Mapleson through the FGI
- location of FGI determines class
describe the APL valve or “pop-off” of the Mapleson system.
- controls pressure build up in the circuit (vents/pops off when a set pressure is reached)
- APL vents from circuit to scavenging system
describe the reservoir bag in the Mapleson system.
- 2 functions
1) anesthetic gas reservoir
2) positive pressure ventilation manually - protective from barotrauma (as volume increases, compliance increases; wont keep getting bigger so won’t back up pressure to pt)
what are the Mapleson characteristics?
- high flows to prevent rebreathing
- with spontaneous ventilation: fgf MUST equal minute ventilation (have to match how much they are taking in)
- with controlled + pressure ventilation (mechanical or manual): fgf must be 3x minute ventilation
what is the Bain Circuit?
a type of Mapleson D with the fresh gas inlet tube inside the corrugated tubing
- “tube in a tube”
- preserves some heat
- still used in some peds for short cases
- adapter needed d/t lack of outer tubing
describe the circle system.
- most common used in US
- more components added than Mapleson
- semi closed or closed
