Physics and Monitoring Flashcards
3 ways to minimize oxygen when using anesthesia machine as an ICU ventilator
- Use electrically powered ventilator
- Converting ventilator drive gas to air instead of oxygen for pneumatically driven bellows ventilators
- Using low fresh gas flows
Pneumatically-driven bellows ventilators generate (inspiratory/expiratory) effort. Volume of ventilator drive gas that is roughly equivalent to ______ is injected into the bellows chamber.
inspiratory
the pt’s tidal volume
In most pneumatically-driven bellows ventilators, the ventilator drive gas is _________. But it can be converted to use ____ instead to conserve it.
oxygen
air
The auxiliary oxygen tank will begin to deliver oxygen to an anesthesia machine if the pipeline pressure drops below __ PSI
45
Ultrasound is a high frequency sound with vibrations above _____ cycles per second
20,000
A full E-cylinder contains ___ L of oxygen at ____ PSIG
660L
2000 PSIG
How to calculate time remaining before a tank is depleted
Liters remaining / (current flow rate in Liters/min)
or
take current pressure (PSIG) divided by 3, then dividing by flow rate
When a vaporizer is designed for a volatile anesthetic with a lower saturated vapor pressure (SVP)is misfilled with a volatile anesthetic with a higher SVP, the output volume percentage will be (higher/lower) than the [ ] set with the dial
higher
- the higher the SVP, the higher the partial pressure of anesthetic, and therefore the higher percentage of total gas leaving the chamber
the adjustable pressure limiting (APL) valve, aka the _______ valve, cannot be positioned between the ____ and the _____ to prevent rebreathing of CO2 in a traditional circle system
pop off valve
patient and inspiratory
_______ is the most common breathing system in the US
The circle system
A unidirectional valve must be positioned between the ______ and _____ in order to prevent rebreathing of CO2 in a traditional circle system
patient
both the inspiratory and expiratory limbs
Fresh gas flow cannot come into the circle system between the ____ and the ____ in order to prevent rebreathing of CO2 in a traditional circle system
patient and expiratory valve
The circle system can be used in 3 different ways depending on the fresh gas flow
- semi-open system
- semi-closed system
- Closed system
Semi-open system
high fresh gas flows with no rebreathing
Semi-closed system
lower fresh gas flows with some rebreathing
Closed system
fresh gas flow matches pt consumption with complete rebreathing
_______ protect persons from electrocution by turning a normal “grounded system” (that exists outside the OR) which only needs a single fault to cause electrocution into a “protected” system in which two faults are needed to deliver a shock
Line isolation systems
- Isolation transformer + line isolation monitor
Lasers in the OR is assoc with (4)
- gas embolism
- retinal injury
- OR fires
- laser plume creation
*NOT shown to cause defibrillator discharge
Wandering baseline ECG tracing, especially in leads III and aVR, is commonly caused by _____
loose ECG electrode
Poor skin contact
moving pt (respirations)
Lead II measures the voltage between the ___ and ___ electrodes
Red (left leg)
white (right arm)
Lead III measures the voltage between the ___ and ___ electrodes
red (left leg)
black (left arm)
Lead aVR (augmented vector right) measures the voltage between the ___ and ___ electrodes
white (right arm)
combination of black (left arm) and red (left leg)
Color code these gas types: Carbon dioxide - Nitrous oxide - Nitrogen - Helium - Oxygen - Air -
Carbon dioxide - gray
Nitrous oxide - blue
Nitrogen - black
Helium - brown
Oxygen - green
Air - yellow
The doppler effect can be used in ECHO to determine both the ____ and ____
direction
speed of flow
_____ technique is the most commonly utilized invasive method for assessing cardiac output
Thermodilution cardiac output
Induction agent that most enhances motor evoked potential amplitudes
Ketamine
Somatosensory evoked potentials (SSEP) provides information regarding the integrity of the _____ and are measured by stimulating the peripheral or cranial nerve and measuring the resultant EEG
ascending neurons
Motor evoked potentials (MEP) are used to evaluate the integrity of the ______.
descending motor neuronal pathways
Etomidate may enhance ____ evoked potentials but does not increase ____ evoked potentials
somatosensory evoked potential
motor evoked potential
a 5 MHz probe will provide (better/worse) tissue penetration than a 7.5 MHz probe
better
Higher frequency (lower wavelength) means better ______ but worse _____
resolution
penetration (depth)
Lower frequency (increased wavelength) gives better _____ but sacrifices _____
penetration (depth)
resolution
Velocity =
frequency * wavelength
VWF
In a pt with Fontan circulation, ______ circulation bypasses the heart to reach the lungs. Used for pts with ______ cardiac system.
venous univentricular - tricuspid atresia - hypoplastic L or R heart - double inlet L ventricle
In Fontan circulation, ______ pacing leads may be placed for permanent pacing rather than _____ pacing, d/t access.
Epicardial
Transvenous
A curved array US probe maximizes _____, and is better at _____.
returning US waves
deeper structures
A Linear array US probe maximizes _____, at the expense of _____
resolution
less penetration
Cerebral perfusion pressure =
Spinal cord perfusion pressure =
MAP - ICP
MAP - CSF pressure
*Two most common way to improve SCPP during aortic surgery is either increase MAP or decrease CSF pressure using lumbar CSF drain
SVR = ?
80 * (MAP - RAP) / CO
R atrial pressure = CVP
Half tank of N2O would read a pressure of ___
745 psig
- regardless of the volume of N2O in the tank, the pressure will read 745 psig until ALL liquified gas is used up (~250 L or 16%)
A full tank of N2O contains ____ at a pressure of 745 psig
1590L
atmospheric pressure at sea level is ____
14.7 psig
A full and Half tank of O2 would read a pressure of ___
Full: 2200 psig
Half: 1100 psig
A full tank of O2 contains ____ at a pressure of 2200 psig
660L
Raising or lowering a pressure transducer (ie. art line, pulm a. cath, intracranial pressure) relative to the pt will alter the pressure reading.
a 10 cm change in height will alter pressure reading by _____ mmHg
- 5mmHg
- Raising transducer (lowering pt): lowers the pressure reading
- Lowering transducer (raising pt): increases the pressure
What happens to the pressure reading if you:
- Raising transducer (lowering pt):
- Lowering transducer (raising pt):
- Raising transducer (lowering pt): lowers the pressure reading
- Lowering transducer (raising pt): increases the pressure
- 10 cm change in height will alter pressure reading by 7.5mmHg
The bellows within the circle system is in a (high/low) pressure system, and will STILL function in the presence of leaks in the low pressure system
High
The flowmeters and vaporizers within the circle system is in a (high/low) pressure system, and will NOT still function in the presence of leaks in the low pressure system.
low
- could lead to administration of hypoxic gas mixtures or insufficient amts of anesthetics
The adjustable pressure limiting (APL) valve is typically taken out of the circuit when the ventilator is switched to mechanical ventilation mode. What does this mean?
The system will function the same regardless of whether the APL valve is open or closed
Which one consumes more gas, using gas from the pipeline supply or E-cylinders?
E-cylinders
- so you should hand ventilate if there is a failure with the pipeline supply
The a typical ascending (standing) bellows ventilator, the bellows (rise/fall) during pt exhalation
rise
*the bellows can act as an indicator of a leak or disconnected circuit
The a typical ascending (standing) bellows ventilator, the bellows (rise/fall) during pt inhalation
fall
*the bellows can act as an indicator of a leak or disconnected circuit
3 most important preop anesthesia machine checks
- Oxygen analyzer calibration
- low pressure circuit leak
- circle system test
A suction bulb is attached to the _____ and must remain collapsed for at least _____ seconds to pass a negative pressure leak test. If this is successful, the flowmeter or vaporizer is considered safe.
Common gas outlet
10 s
Fresh gas flow must be greater than or equal to ___ times minute ventilation in Mapelson ____ circuits.
1-2x
D, E, F
Mapelson D, E and F are ____ circuits that are not very efficient for spontaneous ventilation, but is most efficient for ______.
Semi-open circuits
Controlled ventilation
Advantages of a Bain circuit (Mapelson D) (4)
- conservation of moisture d/t partial rebreathing
- warming of fresh gas inflow
- scavenging waste is easier from APL valve
- advantageous when access to the pt is limited
Which mapelson circuit requires higher fresh gas flows (2.5x minute ventilation)?
D (bain)
Mapleson __ is better for spontaneous respirations, and ___ is better for controlled ventilation
A - spontAneous
D - controlleD
If a pt is able to do a head lift, or hand grip, or effective cough, the TOF ratio is ____
0.7 < TOF Ratio < 0.9
T4:T1 height ratio
How much receptor is suppressed? 1 Twitch 2 Twitch 3 Twitch 4 Twitch
1 Twitch: > 90%
2 Twitch: 80-90
3 Twitch: 70-80%
4 Twitch: 65-75%
Limitations to:
MAP = 2/3 diastolic BP + 1/3 Systolic BP
Can only calc if systolic and diastolic P are known (ie: auscultation)
Heart rate dependent (only good if HR are normal, not fast)
During oscillometric non-invasive BP measurement, how is MAP determined?
Point of maximal amplitude of oscillations
- point when inflated cuff is completely compressing artery
- point when deflated cuff is not able to sense oscillations
The ______ leak test may check for leaks in the low-pressure system of the anesthesia machine.
- ie: suction bulb compression
negative pressure leak test
ECG “wandering baseline” usually happens in leads ____, which is commonly caused by _____
Leads III and aVR
Loose ECG electrodes
What does interference from an alternating current (AC) on ECG look like?
Thick ECG tracing that alternates up and down 60 times/second (60 hertz)
What is the first sign that a hypoxic mixture is being delivered (ie. pipeline crossover or mix-up where O2 switched with another gas)?
What should you do?
alarming of oxygen analyzer
- at this point, disconnect the pipeline supply gases
The oxygen supply alarm goes off, the oxygen analyzer detects _______, you should now disconnect the machine from the hospital’s oxygen supply (pipeline supply gases)
decreasing FiO2 delivery
- hypoxic mixture is being delivered (ie. pipeline crossover or mix-up where O2 switched with another gas)?
Which lead is most sensitive for monitoring atrial electrical activity on ECG? Second most?
Lead II
- parallel to normal axis of atrial depolarization
- p waves are most prominent
*lead V1 is second most sensitive
Which lead is most sensitive for monitoring arrhythmias on ECG?
Lead II
Three lead (RA, LA, and LL) ECG monitoring allows for uninterrupted monitoring of Lead I, II, or III, which is good for monitoring for ______, but poorly sensitive for ______.
Good
- atrial arrhythmias
- R wave changes
Bad
- ST segment changes
- Complex ventricular arrythmias
What do these leads contribute to sensing on ECG?
- V1
- V4
- V5
- V1: arrhythmia detection
- V4 or V5: ischemia detection
WHat happens to BP cuff reading if the point of measurement is elevated above the heart?
Decrease
- inversely proportional to height of the heart
- 0.75 mmHg per cm
Sites correlating with core temperature
- Esophageal
- Tympanic
- Pulmonary artery
- Nasopharyngeal
How does a microshock occur?
How to prevent it?
Result of a new grounded current that can result in electric shock with small current values
Prevention:
- Equipment ground wire
- prevent grounding of anesthesiologist and pt
What device is placed to monitor current imbalance in grounded circuits?
- Breaks the current flow if there is an imbalance of current flow btwn “hot” and “neutral” wires
- Threshold is 5 mAmps (prevents macroshocks)
ground fault circuit interrupter (GFCI)
What device is used to measure the total leakage current of the non-grounded isolated power circuit in the OR?
Line isolation monitor
What device is a very low impedance wire that is used to allow leakage current to pass through to prevent build up of leakage current? It also prevents electric shock with pt grounding (electricity follows path of least resistance - wire instead of pt)
Equipment ground wire
What device prevents macroshock?
microshock?
macroshock
- ground fault circuit interrupter
- line isolation monitor
microshock
- Equipment ground wire
The radius of a vessel is directly proportional to ____ and inversely proportional to ____
flow
resistance
How do these changes affect blood flow:
- Double blood viscosity
- Half the blood viscosity
- Double radius of artery
- Half the radius of artery
Double blood viscosity
- half the flow
Half the blood viscosity
- double the flow
Double radius of artery
- exponentially increase blood flow (Q ~ r^4)
Half the radius of artery
- exponentially reduce blood flow
Which Law dictates flow in relation to radius, viscosity, and length?
Poiseuille Law
Rebreathing of exhaled gases will occur if _____ exceeds fresh gas flow, which causes lower FiO2
minute ventilation
- average ~ 5L/min
*need to keep FGF at least equal to MV to prevent rebreathing
What is the vital capacity of an average 70kg pt with nl PFT?
How much would their minute ventilation be if they took 2 vital capacity breaths in 1 minute?
5 L
5 L * 2 = 10L/min
What is SUPERIOR when it comes to preoxygenating pts, 4 deep breaths (vital capacity) over 30 seconds, or 3 min of tidal volume breathing?
3 min of TV
How is pressure of inspired oxygen (PiO2) correlated to fraction of inspired oxygen (FiO2)?
Directly proportional
- doubling PiO2 -> doubling FiO2
At sea level with room air, FiO2 =
21%
When is the sub-ambient pressure alarm on the ventilator triggered?
*This is different from high or low pressure alarm
Pressure in the breathing circuit falls below atm pressure (typically -10cm H2O)
- NG tube placed in trachea
- Pt inhaling against collapsed reservoir bag
The ____ electrode is used to measure partial pressure of oxygen and required a voltage/ power source (ie. battery) to maintain linearity btwn measurements
Clark
- ie: ABG or anesthesia machines
A _____ electrode is used to measure oxygen content, through electrons and their relation to electrolyte fluid. A batter is not needed.
Galvanic
- ie: scuba equipment
A _____ electrode is used to measure pCO2, based on the principle that pH and pCO2 change in a linear fashion with temp.
Severinghaus
Infrared (IR) absorption spectrophotometry is used to detect _____, bc each gas absorbs a different wavelength of infrared light.
It is the most commonly used method for gas analysis with anesthesia machines.
Volatile anesthetics
CO2
N2O
Clark, galvanic, and paramagnetic electrodes measure _____.
Severinghaus electrode measures _____.
Sanz electrode measures ____.
Oxygen
CO2
pH
How do different elevations affect the MAC of anesthetic gases delivered through a variable bypass vaporizer (sevo, iso, enflurane)?
Minimal effect on MAC at higher / lower elevations
How do different elevations affect the MAC of anesthetic gases delivered through a dual-gas blender (desflurane)?
Anesthetic gas will be directly proportional to atmospheric pressure change
- aka gas delivered will be inversely proportional to altitude
- ie: normal atm = 760 mmHg
if pt was at sea level and atm = 380 mmHg, MAC of desflurane is 0.5.
6% desflurane at 0.5 atm = to __% desflurane at 1 atm, or about ___ MAC
3% desflurane
0.5 MAC
Desflurane
6% Des is 1 MAC at 1 atm (760 mmHg)
- To achieve 0.25 MAC, barometric pressure needs to be ___
- To achieve 1 MAC at 0.5 atm, des dial needs to be ___
190 mmHg
- Anesthetic gas will be directly proportional to atmospheric pressure change
12%
- gas delivered will be inversely proportional to altitude
In the absence of electricity, what can you still provide under GA?
- Manual positive pressure ventilation
- breathing bag w/ APL valve - Air and N2O
- Oxygen delivery
- Anesthetic gases if Vaporizer is mechanical (variable bypass)
In the absence of electricity, what CAN’T you provide/monitor under GA?
- Capnography
- mass spectrometer and IR analyzer both use electricity - Monitoring capabilities
- Desflurane
- requires proper heating - Cassette-type vaporizers
_____ law indicates that at a constant temp, the [ ] of a dissolved gas in solution is DIRECTLY proportional to partial pressure of that gas
Henry’s law
C = kP
K = solubility constant
*increasing volume % of anesthetic gas -> increases alveolar partial pressure -> increases speed of induction
_____ law indicates that a fixed mass of gas at a constant temp will have a constant pressure-volume
Boyle’s law
P1V1 = P2V2
- If gas is pressurized, it takes up a smaller volume
- Water boyles at a constant temperature
_____ law states that the pressure of a given mass of gas is DIRECTLY proportional to its temperature when at a constant volume
Guy-Lussac’s law
P1/T1 = P2/T2
*Air in ETT cuff at room temp, gradually warms to body temp, and pressure in cuff increases as well
_____ law states that the volume of a given mass of gas is directly proportional to its temperature when at a constant pressure
Charles law
V1/T1 = V2/T2
*prince Charles is under constant pressure to be king
_____ law indicates that the total pressure exerted by a mixture of gases is the sum of the individual gases’ partial pressures.
Dalton’s law
- Pt = P1 + P2 + P3 ect
- explains why pts with elevated PaCO2 will have a reciprocal decrease PaO2
- explains why E-cylinders containing a mixture of different gases, will have the partial pressures equal the total gas pressure
(True/False) A noncompensating pneumatic bellows ventilator system takes into account the added volume of fresh gas flow during inspiration when delivering a set tidal volume
False
- You need to also factor in fresh gas flows on top of the set delivered tidal volume
- ie: if you set 800mL, but pt is also getting O2 and Air fresh gas flow, you need to know that the pt is getting actually more than 800 mL per breath
Minute ventilation is ____
TV * RR
amt of air person breaths / min
What types of carbon dioxide absorbents are more likely to cause formation of carbon monoxide?
Absorbents with Strong bases (KOH or NaOH)
- Baralyme (4.6% KOH)
- Sodalime (2.5% KOH)
Which new absorbents contain mostly Ca(OH)2 and almost no strong bases (KOH and NaOH), making them at little risk of Carbon monoxide formation?
Sodasorb Sodalime II Spherasorb Lithium hydroxide Amsorb
Carbon dioxide absorbents are used in modern anesthetic practice in ____ and _____ systems
semi-closed
closed
All volatile anesthetics undergo degradation by absorbents that contain sodium and/or potassium hydroxides.
Sevoflurane, desflurane, enflurane, and isoflurane degrade into ____
Sevo: compound A
Desflurane, enflurane and Isoflurane: Carbon monoxide
______ allows preferential use of the pipeline oxygen when the higher pressure in this system is sensed, sparing the lower pressure, back up oxygen tank for emergencies.
First stage oxygen regulator
What nail polish color is LEAST likely to interfere with pulse oximeters (which analyzes two wave light: red 660 and infrared 940 nm light)?
Red
- absorbs little light at 660 and 940, so causes minimal interference
The potency of volatile anesthetics is a function of ______ (NOT inspired percent concentration).
Partial pressure
- changes with altitude
The international color code of oxygen containers
White
*in the US its green
Quick way to calculate volume remaining in oxygen tank
Pressure (PSIG) / 3
Then divide that by flow (L/min), and you should get time remaining
A _____ circuit system is a low flow technique using a circle system in which total fresh gas flow (oxygen and inhalational anesthetic) is equal to oxygen consumption and inhalational anesthetic metabolism
Closed circuit
In a ______ circuit system, the majority of the gas inhaled with each breath is that which was exhaled in the previous breath (nitrogen, water, unmetabolized volatile anesthetic)
Closed circuit
Advantages of closed circuit or low flow circuit (5)
- decrease use of fresh gas
- decrease volatile anesthetic use
- conservation of heat and humidity
- improved mucociliary function
- decreased microatelectasis
Disadvantages of closed circuit or low flow circuit
- Rebreathing noxious gases (acetone, CO)
2. Increase risk PONV
The rate of rise of the fractional concentration of inspired anesthetic (FI), initially follows which order kinetics?
First order
- rate of rxn depends on [ ] of one reactant
Gas flow rate through the annular space of a conventional flowmeter is primarily affected by _____ at low fresh gas flow (FGF) rates
gas viscosity
- laminar flow
- Hagen-Poiseuille equation
Gas flow rate through the annular space of a conventional flowmeter is primarily affected by _____ at high fresh gas flow (FGF) rates
gas density
- turbulent flow
- Graham’s law
The (ascending / descending) bellows will CONTINUE to fill the ventilator chamber with a leak in the system
Descending
- not reliable sx of leak
- continue to fill with room air
*ascending bellows have advantage of providing a visual sx of a system leak
(ascending/descending) bellows have advantage of providing a visual sx of a system leak
ascending
When pts have decreased compliance (obesity, laparoscopic sx, pneumothorax, supine), they will need an increase in (pressure / volume)
pressure
_____ will cause an abrupt drop in ETCO2 to zero on capnography
acute obstruction of ETT
Circuit disconnect
_____ will cause a sudden drop in ETCO2, (value above zero)
Partial airway obstruction
Circuit leak
When measuring blood flow velocity using doppler US, accuracy is significantly affected by _____.
the ANGLE btwn the US beam and the direction of blood flow velocity
The higher the blood-gas solubility coefficient, the (faster / slower) the uptake in the blood
fastest
*the blood-gas coefficient is a representation of solubility of volatile anesthetics
The uptake of volatile anesthetics is (directly / inversely) proportional to the rise in FA/FI.
Inversely
- low solubility = faster onset
- If there is quick uptake in the alveoli, there is less anesthetic available to create a [ ] gradient.
- agents with lower solubility will have a lower uptake of anesthetic into the blood, more of a gradient available, faster onset
Desflurane has a (high/low) blood-gas coefficient and therefore the lowest anesthetic uptake, and the FA/FI rapidly equilibrates and speed of anesthetic equilibration is rapid
lowest
*the blood-gas coefficient is a representation of _____ of volatile anesthetics
solubility
Isoflurane has a (high/low) blood-gas coefficient and therefore the highest anesthetic uptake, and the speed of anesthetic equilibration is slower
high
Solubility from most to least for anesthetic gases
*Highly soluble drugs: larger uptake into blood: FA/FI ratio is lowered
Halothane > isoflurane > Sevoflurane > nitrous oxide > desflurane
Why do certain dyes (methylene blue, indocyanine green, indigo carmine, nitrobenzene) show a falsely low oxygen saturation?
These dyes absorb light at 660 nm more than 940 nm.
- Pulse ox interprets this as greater [ ] of DEOXYHEMOGLOBIN (relative to oxyhemoglobin)
What happens when a Line isolation monitor begins to sound (exceeds 2mA)?
Unplug the last item that was plugged in
- if it still goes off and you can’t ID source, cancel the elective case
Pulse oximetry operates on the principle of the _____ law, which correlates [ ] with light absorption
Beer-Lambert law
The intensity of light detected by infrared spectrophotometer is (directly / inversely) proportional to the CO2 partial pressure
INVERSELY
- A greater partial pressure of CO2, will absorb a greater amount of infrared light, thus less will reach the detector
(Increased/Decreased) atmospheric pressure will result in an increased vaporizer output
DECREASED
- ie. moving from sea level (760 mmHg) to Denver (632 mmHg),
Partial pressure or anesthetic potency of gases will (increase/decrease) with altitude
remain unchanged
If you fill sevoflurane (lower vapor pressure 160 mmHg) into a vaporizer that is calibrated for isoflurane (higher vapor pressure 240 mmHg), you will have a (Higher / Lower) concentration of delivered gas
Lower vaporizer output
The gauge pressure of nitrous oxide remains 745 PSIG (full) until approximately ____ % or ____ L of Nitrous oxide remains
16%
253L
Examples of non-liquified gases (permanent gases that do NOT become liquid at room temp, even at very high pressures)
Oxygen
Air
Helium
Nitrogen
Examples of Liquified gases (gases that become liquid at room temp when stored under pressure)
Carbon dioxide
Nitrous oxide
Propane
- as gas is removed, liquid is vaporized to restore equilibrium, this is why the pressure gauge remains constant until the gas is nearly empty.
- more reliable to determine amt left base on weight than pressure
Nitrous oxide and Carbon dioxide
- PSI of full cylinder
- L of full cylinder
PSI of full cylinder
- Nitrous oxide: 745 PSIG
- CO2: 830 PSIG
L of full cylinder
- Nitrous oxide: 1590 L
- CO2: 1590 L
Oxygen and Air
- PSI of full cylinder
- L of full cylinder
PSI of full cylinder
- Oxygen: 1900 PSIG
- Air: 660 PSIG
L of full cylinder
- Oxygen: 1900 PSIG
- Air: 660 PSIG
The only type of fresh gas used in a closed circuit technique is ____
oxygen
- possible to maintain FiO2 < 30%, safe for head/neck surgery
relative contraindications to closed circuit or low flow anesthetic techniques
- Sevoflurane (compound A)
- Alcohol intoxication (acetone intox)
- Manutrition (ketoacid intox)
- Heavy smokers (carboxyhemoglobin)
- Cirrhosis
- Ketoacidosis
PLacement of the APL valve between the patient and the inspiratory valve can lead to _____
rebreathing
3 requirements to avoid rebreathing of carbon dioxide in traditional circle system
- unidirectional valve must be positioned btwn pt and both inspiratory and expiratory limbs
- FGF cannot come into the circle system btwn the pt and expiratory valve
- APL valve cannot be positioned btwn pt and inspiratory valve
The circle system can be used 3 ways depending on fresh gas flows:
- Semi-open
- High FGF with no rebreathing - Semi-closed
- lower FGF with some rebreathing - Closed
- FGF matches pt consumption with complete rebreathing
Rank vapor pressures of volatile anesthetics from greatest to least
*vapor pressure indicates substance is MORE likely to evaporate at a given temp than a substance with a lower vapor pressure
Desflurane > isoflurane > sevoflurane
Des: 681
Iso: 240
Sevo: 160
mneumonic to help remember useful circuits for spontaneous ventilation
All Dogs Can Bite
A > D > C > B
mneumonic to help remember useful circuits for controlled ventilation
Dead Bodies Can’t Argue
D > B > C > A
