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8 Cards in this Set

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Phase 1:
No CO2
Inspiration & 1st part of expiration
Dead Space gas exhaled

Phase 2:
Sharp upstroke represents rising CO2 level in sample
Slope determined by evenness of alveolar emptying
Mixture of dead space and alveolar gas

Phase 3:
Alveolar Plateau
Constant or slight upstroke
Longest phase
Alveolar gas sampled
Peak at end of plateau is where the reading is taken – End Tidal Partial Pressure of CO2 (PEtCO2)
Norm value = 30-40mmHg
Reflection of PACO2 & PaCO2

Phase 4:
Beginning of inspiration
CO2 concentration
Rapid decline to inspired value
Interpret the shape of the normal capnogram
(Identify the phases)
Methods for measurement and detection of CO2: (2 main methods
Mainstream Capnography a.k.a. “Flow Thru”
Heated infrared measuring device placed IN circuit
Sensor window must be clear of mucus
Less time delay, quick reading
Potential burns
Weight of it can cause kinks in the ETT and leave marks on pt

Sidestream Capnography
Aspirates fixed amt gas/minute, range is 50-500ml, but usually 100-150ml
Transports expired gas to sampling cell via tubing
Near ETT is best location for sampling
Big time delay
Potential disconnect source
Pediatric sampling (TV’s 100-200)
Water vapor – condensation, traps & filters can clog up filter causing EtCO2 to stop working
Methods of measuring CO2 in expired gases: (4)
Mass Spectrometry
Switching device directs gas from sampling line @ T-Piece to mass spec
Sample is ionized & exposed to magnetic field in vacuum chamber
Ionized gases then separated based on mass/charge ratio
Allows for analysis of multiple gases w/increased accuracy
Large and expensive

Raman Analysis (RASCAL)
Photons generated by increased intensity argon laser collide w/gas molecules
Gas molecules momentarily excited to unstable vibrational & rotatory states
Gases return to normal state, photons of characteristic frequency are emitted
Scattered photons are measured as peaks in spectrum – determines concentration and composition of respiratory gases

Colorimetric
Rapid assessment of CO2 presence, not as accurate
Metacresol purple impregnated paper
CO2 + H2O = Carbonic Acid (changes color in presence of acid)
Off-site anesthesia, a/w management, ICU/ER/code intubations
Can be reliable indicator of proper ETT placement when used in combo w/auscultation of breath sounds

Infrared Absorption
Most common, rapid and reliable
Infrared light transmission thru gas sample is measured and compared to gas that is free of CO2
. Compare & contrast capnometry, capnogram, and capnography
Capnometry – numeric representation e.g. EtCO2 30mmHG
Capnogram – time/concentration e.g. the actual curve itself
Capnography – con’t monitor of capnogram e.g. multiple capnogram tracings
Interpret the shape of the normal capnogram:
Phase 1:
No CO2
Inspiration & 1st part of expiration
Dead Space gas exhaled

Phase 2:
Sharp upstroke represents rising CO2 level in sample
Slope determined by evenness of alveolar emptying
Mixture of dead space and alveolar gas

Phase 3:
Alveolar Plateau
Constant or slight upstroke
Longest phase
Alveolar gas sampled
Peak at end of plateau is where the reading is taken – End Tidal Partial Pressure of CO2 (PEtCO2)
Norm value = 30-40mmHg
Reflection of PACO2 & PaCO2

Phase 4:
Beginning of inspiration
CO2 concentration
Rapid decline to inspired value
Identify pt problems that can be detected by use of capnography:
Detects changes in ventilation, PaCO2, metabolic activity, & pulm bld flow; will produce characteristic waveform changes
May be used as estimate of PaCO2; average gradient is 2-5mmHg under GA
Can determine incr. in metabolism such as malignant hyperthermia.
MH produces incr. in CO2 before other s/s arise such as incr. temp
Blocked pulm bld flow – CO2 on arterial side never makes it to alveoli – dramatic decrease of EtCO2. In order for EtCO2 to pick up anything, it needs to get to alveoli, detecting expired CO2.
Obstructive Lung Dz’s (COPD, asthma, bronchoconstriction, acute obstx) will show slow rise in Phase 2 and little-no Phase 3. Smooth alveolar emptying not occurring. Gas trapping then happens.
Increased CO2 (w/unchanged ventilation)
MH
Szr
Shivering
TQT release
Release aortic vessel clamp
IV bicarb
Insufflation of CO2 into peritoneal cav
Equipment defects (exp valve stuck, exhausted CO2 absorbers)
Decreased CO2
Hyperventilation
Gradual decr relects increased minute vol (MV)
Rapid decr reflects possible PE (thrombus, fat, amniotic fluid, air), V/Q mismatch, incr in PaCO2 & PEtCO2 gradient
Cardiac Arrest – no C.O., no EtCO2 during MI
Sampling error – disconnect, high sampling rate w/elevated FGF, esp on peds
Decr BP – if pt becomes hypotensive, they won’t get enough bld flow to pulm circulation, causing a decr in ETCO2.