Machine Scavenging And Capnography Flashcards
NIOSH recommended levels of anesthetic gases in OR Volatile alone N2O alone Both Over what time period
2 ppm
25 ppm
0.5 ppm
8 hr concentration
5 components of scavenging system
Gas collecting assembly Transfer means Scavenging interface Gas disposal tubing Gas disposal assembly
Size of transfer tubing to scavenging interface
19 mm or 30 mm
Gas collecting assembly
What it does
Outlet connection usually what
Why connection size imp
Captures excess gas at emission site, delivers to transfer means tubing
30 mm male fitting
So it doesnt connect to other parts of system
Transfer means
Also called what 2
Delivers gas from where
Exhaust tubing or hose and transfer system
Conveys gas from collecting assembly to the interface
Transfer means
Tube has what on both ends
Traits of tube, must be what (2)
Female fitting connectors both ends
Short, large diameter, carries high flow w.o increase in pressure
Kink resistant and diff color
Scavenging interface
Prevents what
Also called what
Limits what and where
- Pressure increase or decrease in scavenging sys transmitted to breathing sys
- balancing valve
- limits pressure downstream of gas collecting assembly to -0.5 to+5 cmh20
3 basic elements of scavenging interface
- Pos pressure relief- protects in case system occluded
- Neg pressure relief- limits subatmospheric p
- Reservoir capacity matches intermittent gas flow from gas collecting assembly to the continuous flow of disposal system
Open interface
Doesnt have what
Requires use of what
No valves- open to atmosphere via holes in reservoir
Use of central vacuum and reservoir
What vacuum needs to be on open interface
Must be greater than excess gas flow rate to prevent OR pollution
Two types of closed interfaces
Positive pressure relief only or
Positive pressure and negative pressure relief
Traits of positive pressure relief closed interface
Single positive pressure relief valve, opens when max pressure reached. Passive disposal w no vacuum or reservoir bag
\+ pressure - relief closed interface 3 components What disposal sys is Gas vented to atm when what Room air entrained if what
+ p relief valve, - p relief valve, reservoir bag
Vacuum control valve, activ is reservoir bag is over distended or deflated.
If system p exceeds 5 cm h20
If p less than -0.5 cm h20
Gas disposal tubing
Should be diff what
With passive sys should be what
Where tubing goes
Color and size from breathing system
Short and wide
Overhead to prevent kink
Gas disposal
Active needs what
Passive needs what
A- neg pressure in tubing, neg pressure relief valve
P- pt exhales, manual squeeze of vent or bag. Needs pos pressure.
Passive sys
Gases go 3 places
Pros
Cons
Window, pipe to outside wall, extractor fan to outside
Cheap, easy
Impractical in some bldgs
Active system
- connect what to what
- pro
- con
Most commonly used
- exhaust of breathing sys to hospital vacuum by needle valve
- convenient where many machines in use in large hospital
- expensive. Needle valve may need adjustment
How to do scavenging system check
Connections b/w scavenge and APL and vent relief valve and waste gas vacuum. Open APL, occlude Y. Allow scaveng bag to collapse, verify p is 0. O2 flush, distend bag, p should be <10.
Gold standard of ETT placement
Capnography
Capnography
- guides what
- detects which abnormalities
- contraindications
Vent settings
- PE, arrest, disconnect, obstructed airway
- none
Pa CO2 ____ PEtCO2
>
Average gradient between paco2 and petco2
2-5mmHg under GA
Capnography can evaluate what, what indicates it
If gradient wider than 2-5, less gas exchange occurring= dead space
2 methods of measuring co2 in expired gases
Calorimetry or infrared absorption spectrophotometry (most common)
Colorimetric
___ assessment of co2
Uses what indicator, what changes it
Rapid
Metacresol purple paper, changes color in presence of what, co2 w water- carbonic acid changes paper
Infrared absorption Spectro.
__ __ analyzed
Determines what of contents
Gas in mixture absorbs what
Gas mixture
Proportion
Infrared radiation at different wavelengths
Capnography measurements techniques
2, which most common
Mainstream and sidestream
Sidestream More common
Mainstream capnopgraphy
Pro
Con
Only gives what
Real time measurement, not delayed
Potential burn and kink of ett from weight
Expired co2, not inspired
Sidestream capnography
What it does
Con
Aspirates fixed amt of gas, if analysis with comparison to know quantity
Time delay and potential disconnect
Capnogram 1 2 3 4
1- inspiration, no co2
2- beginning of expiration, rises
3- plateau, before end expiration
4- inspiring, back down to baseline
Phase 1 Inspiratory \_\_\_ \_\_ co2 \_\_ and first part of \_\_ \_\_ \_\_ \_\_ exhaled
Baseline
No
Ins, exp
Dead space gas
Phase 2 \_\_\_ upstroke Represents rise in \_\_ level Slope determined by evenness of \_\_ \_\_ Mixture of \_\_ \_\_ and \_\_ \_\_
Expiratory
Co2
Alveolar emptying
Dead space, alveolar gas
Phase 3 \_\_ plateau Constant or slight \_\_ \_\_\_ phase \_\_ \_\_ sampled
Alveolar
Upstroke
Longest
Alveolar gas
Phase 3
Peak at end is where reading is taken: ___
Normal value= __-__
Reflection of __ and __
PEtCO2 end tidal partial pressure of CO2
30-40
PACO2, Paco2
Phase 4
Beginning of __
CO2 conc
Inspiration
Rapid decline
