Clinical Monitoring 1 - Exam 1 Flashcards
When would we have ventilatory pressure monitoring?
- with invasive ventilation - LMA/ETT
- Ex: PEEP/PIP
What pt population & surgeries require strict temp monitoring/thermoregulation?
- children & elderly
- major surgeries, long surgeries w/ temp changes
What does a Left shift in the oxyhemoglobin curve mean?
What 6 things cause a left shift in the oxyhemoglobin curve?
- that Hb’s affinity for O2 is increased - not as much O2 released to tissues
1. alkalosis (increased pH)
2. Hypocarbia (low CO2)
3. Hypothermia
4. Decreased 2,3 DPG (metabolic byproduct)
5. COHb
6. Fetal Hb
What does a right shift in the oxyhemoglobin curve tell us?
What 4 things can cause a right shift?
- Hb’s affinity for O2 is lower - O2 released easier & used by tissues
1. Acidosis (low pH)
2. Hypercarbia (high CO2)
3. Hyperthermia
4. Increased 2,3 DPG
O2 saturation of Hb
PO2 60mmHg = ____ O2 sat
90%
O2 saturation of Hb
PO2 40mmHg = ____ O2 sat
75%
O2 saturation of Hb
PO2 27mmHg = ____ O2 sat
50%
What 3 things happen to light as it goes through matter?
- transmitted
- absorbed
- reflected
What is the Beer-Lambert Law of Absorption?
relates transmission of light through a solution to concentration of solute
- light absorption measured at wavelengths proportional to # of solutes
Beer-Lambert
What happens w/ low concentration Hb?
- the solutes are not absorbing all of the wavelengths
Beer Lambert
What happens w/ high concentration Hb?
There are way less wavelengths getting through
* the concentrated solutes blocks most of the light
Beer-Lambert
What happens w/ less light path length? What is the example of this?
- normal/constricted vessel - more light gets through
Beer-Lambert
What happens w/ more light path length? What is the example of this?
- Dilated artery/vein - more light is absorbed & less gets through
What are the types of Hb that could be circulating in adult blood?
- Oxyhemoglobin
- Deoxyhemoglobin
- Methemoglobin (Fe3+)
- Carboxyhemoglobin
- Sulfhemoglobin
What is Sulfhemoglobin?
- stable green pigment molecule
- made through oxidation of iron in Hb from sulfa containing drugs
What type of oximetry is the gold standard for measuring carboxyhemoglobin?
Co-oximetry
* regular pulse-ox demonstrates falsely elevated O2 sat
Wavelength Chart
Red light wavelengths
660nm
Infrared light wavelengths
940nm
Deoxyhemogobin (deO2Hb) absorbs more ____ light.
Red light (660nm)
Oxyhemoglobin (O2Hb) absorbs more ____ light.
Infrared (940nm)
What estimates SaO2?
pulsatility of arterial blood flow
What is pulse-ox light transmitted through?
- Skin
- soft tissue
- venous blood
- arterial blood
- capillary blood
- different tissue/solutes
What is the ratio of AC/DC light absorption?
the pulsatile component divided by the non-pulsatile component for each wavelength
- the more tissue your pt has or the more vasodilated = more light absorption
What is DC?
Direct current
* non-pulsatile
* deO2Hb
What is AC?
Alternating Current
* pulsatile
* O2Hb
Carboxyhemoglobin vs. Oxyhemoglobin
COHb absorbs as much light in 660nm (red) range as O2Hb
- falsely elevated SpO2
- Left shift in O2Hb curve - less release of O2
Each ____ increase in COHb will increase SpO2 by ____.
What % COHb do smokers have?
- 1% - 1%
- > 6% in smokers (6% falsely high SpO2)
What 6 things can interfere w/ the pulse-ox read out?
- Ambient light
- Low perfusion (low CO, shock, vasoconstricted)
- Venous blood pulsations = altered AC (pulsatile)
- Additional light absorbers (methylene blue)
- Additional forms of Hb (fetal Hb, COHb)
- Nail Polish
When would you have pulsatile venous blood flow?
- infant - transposition of great vessels
- alteration in R heart return
- AV fistulas
What types of surgeries would methylene blue be administered?
- Renal cases
- Cysto cases
- bladder cases
- in ICU for other indications (vasoplegia)
What happens w/ a pulse-ox reading in response to methylene blue admin?
- falsely low until methylene blue circulates & gets out of system
Pulse-ox and CO measurement
- pulse ox may indicate CO status
- looks like A-line waveform = GREAT CO
- Dampened = POOR CO
look for trends