Flashcards in Anesthesia devices and physics Deck (26)
What can transcranial doppler ultrasound detect?
1. Increases AND decreases in CBF
2. cerbral atherosclerotic plaque burden
When moving a blood pressure cuff distally, what changes occur in the readings? What is the most accurate reading on NIBP monitoring?
1. SBP increases and DBP decreases, leading to an increase in PP
2. MAP > SBP > DBP
What layer of the heart are permanent pacemaker leads placed?
Endocardium (innermost layer of the heart muscle)
What is the equation for lung compliance?
Compliance: Vt/(Plateau pressure - PEEP)
What is the PSI of a full tank of Nitrous and O2? What are the volumes for each?
1. Nitrous: 1590L at 750 PSI
2. O2: 625L at 2000 PSI
What is the molecular weight of nitrous oxide?
44gm, which occupies 22.4L (according to avogadros law)
How does tricuspid regurgitation change the thermoreader for CO? How do L to R shunts affect it?
1. Regurg leads to prolongation of fluid across PA, leading to underestimation of CO
2. Shunts decrease the amount of fluid passing the PA, making it seem like the fluid is passing faster and the CO is more
What are the VP for Halothane/Iso vs. Sevo/enflurane
1. HI: 240s
2. SE: 170s
What changes on capnography do you see with an incompetent inspiratory valve? How do you treat it?
1. Re-breathing (gradual increase in CO2 baseline)
2. Gradual inspiratory slope
3. treat by increasing fresh gas flows
What is the equation for CPP?
CPP: Aortic diastolic P - LVEDP
What gauge catheter do you use for transtracheal ventilation? What is the maximum PSI?
1. 16 or 18 gauge needle
2. Max is 55 but recommended max is 35
How do you calculate RSBI? What is predictive of a successful extubation?
1. RSBI: RR/TV
2. RSBI < 105 is good! This means that the patient is taking big TV and has a slow RR
What NIF is predictive of an unsuccessful extubation?
1. NIF > - 20 (I.e. 20 to 0)
What percentage of receptors are blocked when there are 0 twitches to 4 twitches?
0 twitches: 100 %
1 Twitch: 90%
2 twitches: 80 %
3 twitches: 70-80%
4 twitches 65-70 %
In an I to E ratio of 1:2, how many seconds are in the total breathing cycle, and how many are I vs. E?
There are three seconds total, with 1 of them devoted to inspiration and the other two to expiration
What is absolute humidity vs. relative humidity?
1. Absolute humidity: the mass of water per unit of gas
2. Relative humidity: the amount of water in a gas compared to how much water the gas can hold at a given temperature
What population are recruitment maneuvers NOT recommended?
Patients with ARDS, there are multiple complications and it is not beneficial
Explain how PCo2 and PaO2 change with increased temperature
The PaCO2 and PaO2 will increase in warmer samples. This is because at lower temperatures, the CO2 and O2 will be dissolved in the blood. With warming, they come out of the gas and are picked up by the analyzer, giving a falsely high CO2 and therefore falsely low pH
When are blind intubation techniques avoided?
When airway anatomy is compromised or during trauma.
What happens to Compound A when the soda lime is desiccated? What is the dye called that turns it purple?
1. Compound A actually decreases, whereas CO increases
2. Ethyl violate
What is the order of gases that increases CO production?
DIS is what causes CO production
Des > Iso >> Sevo
Describe a major downfall with puncture or needle cricothyroidotomy.
It requires high oxygen pressure for inspiration and a patent upper airway for expiration
How are gasses measured in the machine? What gas is not measured by this technique?
1. infrared absorption spectophotometry
2. O2 is not measured this way. There are paramagnetic, clark/galvanic, and polarographic instruments to measure O2
What instruments are used to detect pH, PCO2, and PO2 in a blood gas?
1. pH: sanz
2. PCO2: sveringhaus
3. PO2: Clark
True or false: In pacemaker dependent patients, you do not need to see an EP doc for analysis prior to surgery. You can simply place them in asynchronous mode
TRUE, but only if the patient is pacemaker dependent