Anesthesia devices and physics

Question 1

What can transcranial doppler ultrasound detect?

Answer 1

1. Increases AND decreases in CBF

2. cerbral atherosclerotic plaque burden

Question 2

When moving a blood pressure cuff distally, what changes occur in the readings? What is the most accurate reading on NIBP monitoring?

Answer 2

1. SBP increases and DBP decreases, leading to an increase in PP
2. MAP > SBP > DBP

Question 3

What layer of the heart are permanent pacemaker leads placed?

Answer 3

Endocardium (innermost layer of the heart muscle)

Question 4

What is the equation for lung compliance?

Answer 4

Compliance: Vt/(Plateau pressure - PEEP)

Question 5

What is the PSI of a full tank of Nitrous and O2? What are the volumes for each?

Answer 5

1. Nitrous: 1590L at 750 PSI

2. O2: 625L at 2000 PSI

Question 6

What is the molecular weight of nitrous oxide?

Answer 6

44gm, which occupies 22.4L (according to avogadros law)

Question 7

How does tricuspid regurgitation change the thermoreader for CO? How do L to R shunts affect it?

Answer 7

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

Question 8

What are the VP for Halothane/Iso vs. Sevo/enflurane

Answer 8

1. HI: 240s

2. SE: 170s

Question 9

What changes on capnography do you see with an incompetent inspiratory valve? How do you treat it?

Answer 9

1. Re-breathing (gradual increase in CO2 baseline)
2. Gradual inspiratory slope
3. treat by increasing fresh gas flows

Question 10

What is the equation for CPP?

Answer 10

CPP: Aortic diastolic P - LVEDP

Question 11

What gauge catheter do you use for transtracheal ventilation? What is the maximum PSI?

Answer 11

1. 16 or 18 gauge needle

2. Max is 55 but recommended max is 35

Question 12

How do you calculate RSBI? What is predictive of a successful extubation?

Answer 12

1. RSBI: RR/TV

2. RSBI < 105 is good! This means that the patient is taking big TV and has a slow RR

Question 13

What NIF is predictive of an unsuccessful extubation?

Answer 13

1. NIF > - 20 (I.e. 20 to 0)

Question 14

What percentage of receptors are blocked when there are 0 twitches to 4 twitches?

Answer 14

0 twitches: 100 %
1 Twitch: 90%
2 twitches: 80 %
3 twitches: 70-80%
4 twitches 65-70 %

Question 15

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?

Answer 15

There are three seconds total, with 1 of them devoted to inspiration and the other two to expiration

Question 16

What is absolute humidity vs. relative humidity?

Answer 16

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

Question 17

What population are recruitment maneuvers NOT recommended?

Answer 17

Patients with ARDS, there are multiple complications and it is not beneficial

Question 18

Explain how PCo2 and PaO2 change with increased temperature

Answer 18

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

Question 19

When are blind intubation techniques avoided?

Answer 19

When airway anatomy is compromised or during trauma.

Question 20

What happens to Compound A when the soda lime is desiccated? What is the dye called that turns it purple?

Answer 20

1. Compound A actually decreases, whereas CO increases

2. Ethyl violate

Question 21

What is the order of gases that increases CO production?

Answer 21

DIS is what causes CO production
or DIS-CO
Des > Iso&raquo_space; Sevo

Question 22

Describe a major downfall with puncture or needle cricothyroidotomy.

Answer 22

It requires high oxygen pressure for inspiration and a patent upper airway for expiration

Question 23

How are gasses measured in the machine? What gas is not measured by this technique?

Answer 23

1. infrared absorption spectophotometry

2. O2 is not measured this way. There are paramagnetic, clark/galvanic, and polarographic instruments to measure O2

Question 24

What instruments are used to detect pH, PCO2, and PO2 in a blood gas?

Answer 24

1. pH: sanz
2. PCO2: sveringhaus
3. PO2: Clark

Question 25

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

Answer 25

TRUE, but only if the patient is pacemaker dependent

Question 26

When is use of a rigid fiberoptic scope indicated?

Answer 26

In cases of foreign body obstruction or tumor.