pulm intraop monitoring and difficult airway Flashcards
pulse ox measures a difference between background absorption in ___ and peak absorption in ___.
diastole, systole
plethysmography displays as a waveform the differences in absorption during
arterial pulsation in systole
infrared nm
940
infrared is for
oxyhemoglobin
infrared corresponds to ___ saturation
100
red light nm
660
red is for
deoxyhemoglobin
red light corresponds to ___ saturation
50
PAO2 ___ ___ __ for Sat ___ ___ ___
40 50 60 . 70 80 90
mixed venous blood in PA
75, 40
tissue damage by pulse ox caused by
heat from light source (rare) or sensor pressure (more common) may cause tissue damage
what happens if you use standard pulse ox in MRI
patient gets burned
endobronchial intubation and pulse ox
undetected
limitations of pulse ox.
HYPO tension, thermia, volemia (shock), perfusion. vasoconstriction. asystole. vfib. BP cuff inflation, tourniquet
carboxyhemoglobin on pulse ox
shows spo2 of 100 (overestimates)
methemoglobin on pulse ox
absorbs equally at both wavelengths, shows SPO2 of 85% regardless of the true oxygen saturation
what causes methemoglobinemia
nitrates, benzocaine spray, nitro, sulfonamides, nitrites, nitroprusside
how to treat methemoglobiema
give methylene blue or ascorbic acid
2 things that do not affect pulse ox
fetal hemoglobin and bilirubin
poor accuracy at SPO2
30
if Hb
3-4
venous pulsations
SPO2 thinks they are arterial. like R heart failure (cor pulmonale) or tricuspid regurg . seen in dependent down limb
malpositioned sensor
penumbra effect - shows SPO2 of 90-95
capnography rapidly and reliably indicates ____ intubation but does not reliably detect ____
esophageal. endobronchial
gold standard for tracheal intubation
ETCO2
capnograph
records and displays CO2
CO is depicted graphically as a ___ recorded by a ____ and measured by a
capnogram, capnograph, capnometer
aspiration (sidestream) capnograph
continual suction of gas from breathing circuit.
aspiration (sidestream) capnograph aspiration rates
50-250ml/min
aspiration (sidestream) capnograph CO2 concentration is determined by
infrared absorption
aspiration (sidestream) capnograph is prone to
water precipitation and erroneous readings
AB
beginning exhalation, dead space gas
CB
exhalation, mixing of gases
CD
alveolar plateau, alveolar rich gas
D
highest CO2
DE
start inspiration
early spont breath capnogram
muscle relaxant wearing off
exp valve failure or depleted CO2 absorber shows
elevation of baseline
inspiratory valve failure allows you to
exhale up the insp limb. causing rebreathing. go up on your flows
dCO2 definition
normal ETCO2 to arterial CO2 gradient
dCO2 normal
2-5mmhg
dCO2 reflects
alveolar dead space
any significant reduction in lung perfusions ___ alveolar dead space and ___ dCO2
increases, increases
PaCO2 will always be ___ than ETCO2 why?
mixing and dilution with the dead space gases
what increases dCO2
decreased pulm artery pressure, upright posture, PE, COPD, mechanical obstruction oF PA, cuff leak, tracheal disruption, bronchopleural fistula, decreased CO or decreased BP
hypoventilation causes ____ etco2
increased
MH causes ___ etco2
increased
laparoscopy causes ____ etco2
increased
CO2 inflation causes ____ etco2
increased
hyperthermia causes ____ etco2
increased
improved blood flow to lungs after hypotension resuscitation causes ____ etco2
increased
water in capnograph causes ____ etco2
increase
tourniquet released causes increased
increased
CO2 absorber exhausted causes ____ etco2
increased
inadequate fresh gas flow causes
increased
faulty valves in circuit causes ____ etco2
increased
most common cause of decreased ETCO2
hyperventilation
airway leak, leak around cuff
decreased
decreased blood flow to lungs causes ___ etco2
decreased
PE causes ____ etco2
decreased
arrhythmias causes ___ etco2
decreased
incipient pulm edema causes ____ etco2
decreased
hypothermia causes ___ etco2
decreased
inadequate sample volume causes ____ etco2
decreased
sample catheter misplaced causes ____ etco2
decreased