Term
|
Definition
| Minute volume (Vm) = tidal volume (Vt) x resp rate |
|
|
Term
| estimate minute volume (Vm) |
|
Definition
Minute volume ~ 150-250ml/kg/min
NB: smaller animals have a higher minute vol. per kg than larger animals |
|
|
Term
| estimate tidal volume (Vt) |
|
Definition
Vt ~ 10-15ml / kg
(consider body shape / physique - overweight animal may have small lung size and tidal vol. relative to overall weight) |
|
|
Term
|
Definition
5ml/kg/min in LA
10ml/kg/min in SA |
|
|
Term
| Reservoir bag approximation |
|
Definition
| reservoir bag should be 3-6x tidal volume |
|
|
Term
| Sodalime canisters approximation |
|
Definition
| sodalime canisters should be 2x tidal volume |
|
|
Term
|
Definition
|
|
Term
|
Definition
| inspired fraction of anaesthetic agent |
|
|
Term
|
Definition
-connects the anaes. machine to the ETT/mask of the patient - may be rebreathing or non-rebreathing
-conveys O2 and anaes. vapour to the patient
-allows the removal of CO2 to prevent rebreathing - by chemical removal, high FGF rates or via non-rebreathing valves
-enables ventilation to be assisted in IPPV |
|
|
Term
|
Definition
90% CaOH
5% NaOH
1% KOH
plus silicate, moisture and dye |
|
|
Term
| minimising R in breathing systems |
|
Definition
-large diameter ETT
-short, wide smooth hoses
-avoid kinks
-minimal absorbant (for soda lime have 2x minute volume)
-IPPV |
|
|
Term
| deciding which breathing system to use |
|
Definition
-size of animal - consider R, dead space, economy (e.g. v. high flow rates wasted on LA)
-heat and moisture retention (in rebreathing syst)
-ease of cleaning and sterilisation
-ease of scavenging
-valve position
-suitability for IPPV
-use of nitrous oxide |
|
|
Term
|
Definition
| reuses some of expired gas - CO2 abosorbed by soda lime |
|
|
Term
| Closed re-breathing systems |
|
Definition
|
|
Term
| Semi-closed rebreathing systems |
|
Definition
FGF > oxygen consumption
Valve is open to allow excess gas to pass into scavenging |
|
|
Term
|
Definition
| entirely fresh gas from the anaesthetic machine w. every breath - CO2 removed from the system by high FGF |
|
|
Term
|
Definition
-economy of O2 and inhaled agents - only need low FGF and vol. agents
-inhaled gases warm and humidified
-suitable for IPPV
-reduced pollution risk |
|
|
Term
| Rebreathing disadvantages |
|
Definition
-inr R to breathing
-conc. of inspired anaes. agent is unknown
-can't alter FiAA quickly at low flow rates
-denitrogenation required
-can only use N2O at higher flow rates and only in semi-closed systems - inspired O2 must be measured
-more difficult to sterilise
-soda lime required
-expensive purchase
-cumbersome machinery |
|
|
Term
|
Definition
the use of higher flow rates in first 15-20mins to eliminate N2
-needed to prevent mixing and hence dilution of expired N2 with circulating O2 |
|
|
Term
| in rebreathing systems, why can N2O only be used at higher flow rates in semi-closed systems, and if insp. O2 measured? |
|
Definition
can result in dec. proportion of O2 compared to N2O
expired O2 > inspired O2 c.f.
inspired N20 = expired N20 |
|
|
Term
| Non-rebreathing system advantages |
|
Definition
-low R to breathing
-FiAA on vaporiser dial = that inhaled i.e. know conc. of inspired agent
-rapid changes in FiAA possible
-denitrogenation not required
-safe to use N2O
-easy to clean and sterilise
-soda lime not required
-inexpensive initial purchase
-not cumbersome |
|
|
Term
| Non-rebreathing system disadvantages |
|
Definition
-high running costs - need high FGF and volatile agents - impracticle for LA
-loose heat and moisture
-IPPV may or may not be possible
-higher pollution risk |
|
|
Term
|
Definition
circle system
to-and-fro-system |
|
|
Term
|
Definition
-rebreathing system - exhaled air through one-way valves around a circular breathing system
-have gas outlet w. scavenging system
-soda lime
-FGF in
-reservoir bag
-back into patient |
|
|
Term
|
Definition
-constant dead space
-unlikely to inhale soda lime
-no channeling of sodalime
-bulk of equipment away from head |
|
|
Term
| Circle system disadvantages |
|
Definition
-complex and expensive
-not easily transported
-esp. slow change in FiAA (i.e. more than other rebreathing system)
-incr. R to breathing due to valves etc |
|
|
Term
| Suitability of patients for circle systems |
|
Definition
-not generally used in very small animals due to R
-popular w. LA |
|
|
Term
|
Definition
a rebreathing system - air from patient exhaled through sodalime into reservoir bag and then then inspired back into patient
-valve next to patient, then FGF inlet |
|
|
Term
| To-and-fro-system advantages |
|
Definition
-simple system
-easy to clean and sterilise
-inexpensive
-more rapid FiAA c.f. circle system |
|
|
Term
| To-and-fro-system disadvantages |
|
Definition
-not used very much
-cumbersome
-dead space increases as soda lime used - expired air has to traval further before reaching it
-risk of inhlaing soda lime dust and chemical bronchiolitis
-risk of channeling of soda lime and so CO2 retention
-risk of hyperthermia |
|
|
Term
| How can the risk of soda lime inhalation be reduced in a to-and-fro system? |
|
Definition
|
|
Term
|
Definition
-Magill
-parallel lack
-lack
-Ayres' T piece w. or w/o Jackson modification
-Bain |
|
|
Term
|
Definition
a non-rebreathing system
patient --> valve --> long corregated tube --> reservoir bag --> FGF entry at end of tube |
|
|
Term
|
Definition
FGF = 1 x Vm (efficient)
-suitable for animals 5kg+ (due to dead space and expiratory R) |
|
|
Term
|
Definition
-inconvenient valve placment
-not use in very SA
-can not be used for prolonged IPPV |
|
|
Term
|
Definition
a non-rebreathing system
Similar to Magill, but valve at end of separate limb so not next to patient
i.e. 2 limbs - ins. and exp. which are parallel
patient --> long corregated tube w. valve at end
Also patient --> long corregated tube -->tube w. reservoir bag --> FGF entry at end of tube |
|
|
Term
|
Definition
FGF = 1 x Vm (efficient)
-disconnection or kinking easy to see
-valve away from animal's head |
|
|
Term
| Parallel lack disadvantages |
|
Definition
-can not use in SA <10kg
-can not be used for prolonged IPPV |
|
|
Term
|
Definition
a non-rebreathing system similar to a parallel lack but limbs are coaxial
- inspitory limb is outer, expiratory is inner
-FGF and bag at end of insp. tube at opposite end to patient
-valve and open end of exp. limb at opposite end to patient |
|
|
Term
|
Definition
FGF = 1 x Vm (efficient)
less drag than Magill - valve not near head |
|
|
Term
|
Definition
-some have higher exp. R
-can not use in SA <10kg
-can not be used for prolonged IPPV |
|
|
Term
Ayres' T piece system
w. or w/o Jackson Rees Modification |
|
Definition
a non-rebreathing system
patient --> tube w. FGF inlet --> corregated tube with air outlet at end
Jackson Rees modification involves open ended bag at end of corregated tube |
|
|
Term
Ayres' T piece system
w. or w/o Jackson Rees Modification advantages |
|
Definition
-IPPV can be performed by occluding end og bag, sqeezing content into patient and releasing
-low R - suitable for very SA up to ~10kg
-minimal dead space |
|
|
Term
Ayres' T piece system
w. or w/o Jackson Rees Modification disadvantages |
|
Definition
FGF = 2.5-3x Vm (high)(need to flush out exp. gases)
-scavenging may be difficult - connectors can twist and cause rapid over-distenstion of bag |
|
|
Term
|
Definition
a non-rebreathing system -coaxial
-inner limb is insp. (baIn), outer is exp.
-FGF at end of insp. tube at opposite end to patient
-valve and bag at end of exp. limb at opposite end to patient - note not open as in lack |
|
|
Term
|
Definition
-exp. down outer limb so decr. R
-can get valveless versions w. open end, suitable for very SA
-expirate may warm inspired air and conserve patient temp (only minor effect)
-suitable for IPPV |
|
|
Term
|
Definition
-if valve present suitable for 8kg+
-usually FGF 2-3x Vm (high) (need to flush out exp. gases) |
|
|
Term
|
Definition
breathing system that can rebreathing ot non-rebreathing depending on w. or w/o soda lime
-w. soda lime - functions as a circle system
-w/o soda lime - like a parallel lack
-expiratory valve is v. low R - suitable for SA
-versatile
-limitations esp for LA (e.g. small cannister) |
|
|
