Anesthesia Machine Flashcards
(140 cards)
0
Q
What are 5 pathways of oxygen in the anesthesia machine?
A
- flow to gas flowmeters, 2. powers the oxygen flush valve, 3. activates the fail-safe mechanisms, 4. activates oxygen low-pressure alarm, 5. compresses the bellows of ventilator
1
Q
What government agency oversees the anesthesia machine before the year 2000? After the year 2000?
A
before 2000: ANSI (american national standards institute)
after 2000: ASTM (american society for testing and materials)
2
Q
What is included in the high pressure system? What is the pressure?
A
Cylinders/ tanks of O2/nitrous gases
Pressure of 2200 gets down regulated to 45 by check valves
3
Q
What is in the intermediate pressure system?
A
Pipeline (oxygen, nitrous, air), pressure regulators, oxygen pressure failure device, oxygen flush valve, flowmeter control valves, pneumatic part of master switch
4
Q
What is in the low pressure system?
A
vaporizer, flowmeter tubes, flow control valve, check valve (unidirectional valves), pressure relief devices, common gas outlet, hypoxia prevention device
Note: pressure is slightly higher than atmospheric pressure
5
Q
What is DISS?
A
Diameter Index Safety System, provides non-interchangable connections for gas lines (pipelines), required on every anesthesia machine
Composed of body, nipple, and nut
6
Q
What is the O2 pressure sensor shut-off valve?
A
A safety valve downstream from N20, it decreases or shuts off anesthetic gases that are allowed into the machine if oxygen PRESSURE decreases
(It shuts off when oxygen gets less than 25 psi)
Note: it doesn’t completely prevent a hypoxic mixture, it only detects pressure
7
Q
What is PISS? What are the numbers for nitrous, oxygen, and air?
A
Pin index safety system, the pins have positions based on the gas that is delievered
Nitrous #3 #5
O2 #2 #5
Air #1 #5
8
Q
How much oxygen do E-cylinders hold? (psi and L)
A
2000-2200 psi
625-700 L
9
Q
What colors are associated with the gases? N2O, O2, Air
A
N2O: blue
O2: green
Air: yellow
10
Q
What is the fail-safe feature on the flowmeter?
A
When oxygen PRESSURE decreases, this feature makes sure that oxygen CONCENTRATION doesn’t decrease and pressure alarms are activated
This feature tries to prevent from giving a hypoxic mixture of gases (hypoxic mixture is still possible)
11
Q
What is the flow of the O2 flush, when is it used?
A
35-75 L/min
Used for machine check and to fill bellows on expiration
Note: use with caution, risk of barotrauma
12
Q
What is the proportioning link system on the flowmeter?
A
If adjustments in gases try to go under fiO2 of 21%, the link system engages like a bike chain, it prevents the hypoxic mixture from getting to the patient
13
Q
What is checked daily? What is checked between each case?
A
Daily machine check
Circuit check between each case
14
Q
What monitor is best for revealing a disconnect?
A
ETCO2- capnography
15
Q
What is the oxygen analyzer?
A
ONLY monitor that detects problems downstream from the flow control valves (after common gas outlet)
16
Q
What is the negative pressure leak test?
A
Turn machine master switch, flow control valves, and vaporizers OFF
Squeeze suction bulb to the common gas outlet several times until it is collapsed creating vacuum in the low pressure circuit
Bulb must remain collapsed for 10 seconds, this shows that the machine is leak free
17
Q
What are some ways that the anesthesia machine was created in order to maintain low resistance? (low resistance is an essential part of the machine)
A
Short tubing, large diameter tubing, no sharp bends, caution with valves (because valves create resistance), minimal connection pieces
18
Q
Where is the equipment dead-space?
A
The Y piece is the dead space where gas exchange can’t take place
Note: dead space increases the chance of rebreathing CO2
19
Q
How are open systems characterized?
A
No gas reservoir bag, valves, or rebreathing
2 types: 1. insufflation (blow by, nasal cannula, bronchoscopy port), 2. open drop (chloroform/ether mask, old technique, no control of inspired concentration of anesthetics, the anesthetic is dropped into a cloth or mask that the patient breathes in)
20
Q
What are the 5 components to semi-open systems?
A
- facemask/ETT, 2. pop-off valve (APL), 3. Reservoir tubing, 4. fresh gas inlet, 5. reservoir bag
Examples: Mapleson A-F, Bain, Circle
21
Q
How do you distinguish the different types of Mapleson? (A,B,C,D,E,F)
A
Mapleson A: pop-off near facemask, FGF (fresh gas flow) at other end
Mapleson B,C: pop-off and FGF near facemask
Mapleson D,E,F: opposite of Mapleson A, FGF near facemask, pop-off on other end
Note: Mapleson D is most efficient during controlled ventilation (used at Georgetown)
22
Q
What is a T-Piece, and which Mapleson does it correspond with?
A
Mapleson E with no reservoir bag and no pop-off valve, it is used to administer oxygen
23
Q
What is a Bain Circuit and which Mapleson is it like?
A
Modified Mapleson D, it is fresh gas flow tubing within large bore tubing so that exhaled gas will warm the inhaled gas
24
What is an Ambu bag and which Mapleson is it like?
Modified Mapleson A with non-rebreathing valve, it can deliver high FiO2, but you can't feel compliance
25
What are advantages and disadvantages of the Mapleson System?
Advantages: Simple, lightweight, can give positive pressure ventilation, low resistance, portable, it can give predictable concentration of anesthetic and decreased room pollution
Disadvantages: requires calculation of FGF, depth can't be controlled, CO2 buidup/rebreathing is possible, poor conservation of heat/humidity, FGF costly, special assembly
26
How does a circle system work and what are the 7 components?
Can be used as a semi-open, semi-closed, or closed system based on how the APL valve is adjusted, prevents re-breathing of CO2 but allows rebreathing of other gases
1. Y piece 2. insp/exp limb 3. insp/exp unidirectional check valve 4. FGF 5. CO2 absorber 6. APL/ pop-off valve 7. reservoir bag
27
What position (open/closed) is the APL valve in for spontaneous respiration? Assisted ventilation? Mechanical ventilation?
Spontaneous: open
Assisted: partially open
Mechanical: closed
Note: when on ventilator mode, APL doesn't matter bc its not in use
28
Circle system must follow which 3 rules?
Unidirectional valves must be located between the patient and reservoir bag on inspiratory and expiratory limbs
Fresh gas flow CAN'T enter the system between the expiratory valve and patient
The APL CAN'T be located between the patient and inspiratory valve
29
What is used more commonly in the U.S., semi-open, semi-closed, or closed? What are the differences?
Semi-closed is the most common because is conserves some heat and gases, some re-breathing, the APL is partially closed, requires low flow (3L)
Semi-open has the APL open all the way, so no heat is conserved, no re-breathing, requires high flow (10-15L)
Closed is used in third world countries, APL is closed, total re-breathing
30
For a closed system, how is oxygen consumption calculated?
10 x kg^3/4
31
How is the leak test performed, how often is it performed?
Perform the leak test between each case
1. set gas flow to 0 2. occlude Y-piece, 3. close APL, 4. use O2 flush valve to pressurize circuit to 30, 5. hold for 10 sec and listen for alarm, 6. open APL valve and watch pressure decrease
32
When performing the leak test, the integrity of unidirectional valves are NOT tested, which test will cover this? How is it performed?
Flow test: to test integrity of unidirectional bags, attach breathing bag to Y-piece and turn on the ventilator
33
How are ventilators characterized?
According to inspiratory characteristics:
Time (I:E ratio)
Volume (TV in mL)
Pressure (impedance of lungs and circuit overcome with pressure)
Flow (flow rate, volume/time)
Note: Most of our machines are time cycled with a volume limiting aspect
34
What direction do the bellows move during expiration?
Ascend-ascend: bellows move up with expiration
| descend/descend are old, it is not as easy to determine a leak with this type of bellows system
35
How do the bellows move during inspiration and expiration?
Inspiration: driving gas enters the chamber and increases pressure which causes the ventilator relief valve to close and compresses the bellows so that what is contained INSIDE the bellows can be delivered to the patient
Expiration: drive gas exits the bellow chamber, the pressure drops to zero causing the ventilator relief valve to open, exhaled patient gas fills the bellows BEFORE scavenging
36
When does the relief valve of the bellows system open?
ONLY after the bellows have been completely filled during expiration, this allows extra expiration gases from the patient to go to the scavenging system
37
Does air move through the CO2 scrubber/absorber during inspiration or expiration?
INHALATION, because it would be wasteful to scrub out CO2 before it got sent to scavenging
38
What does the inspiratory pause/sigh do?
Increases inhalation time by 25%, flow of gas stops and is held in lungs until exhale, then more gas exchange can take place
Note: this option is good for sicker patients
39
What is the formula for oxygen delivery? Oxygen content?
CO x O2 content
| O2 content = (hgb x sats x 1.39 mL) + (PaO2 x 0.003 mL)
40
Each gram of hemoglobin binds to how much O2?
| For each mmHg of PO2, there is how much mL O2 of blood?
1. 34 (or 1.39) mL for each gram of hgb
| 0. 003 mL O2 for each mmHg of PO2
41
What is the coorelation between FiO2 and PaO2?
As FiO2 increases by 10%, PaO2 increases by 50 mmHg
| PaO2 of 100 = 21%, PaO2 of 150 = 30%, PaO2 of 200 = 40%
42
How do ICU and OR ventilators differ?
ICU vents are more powerful, OR vents have CO2 absorber, ICU vents have more modes, no bellows on ICU vent (so the gas suppled directly ventilates patient, in the OR, driving gas never reaches the patient)
43
Modes of ventilators: What are SIMV and IMV?
IMV: vent delivers a preset volume at a specific interval with continous flow of gas, it senses patient's breaths and reschedules based on settings, used for weaning, not synched with pt
SIMV (synchronized intermittent mandatory ventilation): like IMV, but synched with patient, can be given with pressure support, for waking pt up in OR
44
Vent Modes: What is CV?
Controlled ventilation by ventilator
45
Vent Modes: What is AC?
(Assist Control) Settings can be pressure or volume controlled. Intermittent mode of positive pressure ventilation. The pt's inspiratory effort creates a sub-baseline pressure in the inspiratory lib of the vent circuit which triggers the vent to deliver a predetermined TV. If the pt's rate drops below the minimum, the machine takes over
46
Vent Modes: What is Pressure Support?
Aids in normal breathing with a predetermined level of positive pressure. It is similar to IMV except pressure is constant through inspiration period. It is used for support when patients come out of surgery, especially obese patients, bc it decreases work of breathing.
47
Vent Modes: What is jet ventilation/ high frequency ventilation?
Indicated for gas exchange at lower pressure, used in electro-shock for renal stones. Low TV set and high rate (100-200 bpm), IT 33%, driving pressure 15-30 psi.
48
Vent Modes: What is pressure control ventilation?
Pt or time triggers pressure limited, time-cycled mode of vent support. Gas flow decreases as airways pressure rises and stops when pressure equals the set peak pressure. TV is NOT fixed. Useful when pressures can be high (GI surgeries) and in neonates.
49
Vent Modes: What is CPAP?
Continuous positive airway pressure, positive pressure is maintained during inspiration and expiration. Pt must be spontaneously breathing. Can be provided with mask or vent. Caution: with pressures over 15, aspiration can occur. Good for weaning and sleep apnea
50
According to NIOSH, what is the max dose of volatile anesthetic exposure we can be exposed to? What is the max volatile anesthetic with nitrous oxide?
Volatile anesthetic alone: 2 ppm
| Volatile anesthetic with nitrous oxide: 0.5 ppm
51
According to NIOSH, what is the max nitrous oxide we can be exposed to?
25 ppm
52
What are the 5 components of the scavenging system?
1. gas collecting assembly
2. transfer means
3. scavenging interface
4. gas disposal tubing
5. gas disposal assembly
53
What is the gas collecting assembly of the scavenging system? What size is the connection?
Captures excess gas at site of emission and delivers them to transfer means tubing.
The outlet connection is usually 30mm (19mm on old machines), male-fitting, and doesn't connect to breathing system components
54
What is the transfer means part of the scavenging system?
Conveys gas from the collecting assembly to the interface, kink resistant
The tube has a female-fitting connector on each end, wide diameter and short tubing for high flow of gas without an increase in pressure
55
What are the three basic elements of the interface of the scavenging system?
1. Positive pressure relief (protects patient in case of occlusion)
2. Negative pressure relief (limits sub-atmospheric pressure)
3. Reservoir capacity (matches the intermittent gas flow from gas collecting assembly to the continuous flow of disposal system)
56
What is the purpose of the scavenging interface?
Prevents pressure increases or decreases (keeps downstream gases between -0.5 to 5 cmH2O) in the scavenging system from being transmitted to the breathing system
57
What is the difference between open and closed interface of the scavenging system?
Open: has no valves, is open to atmosphere to avoid buildup of pressure (requires vacuum or high flows to prevent pollution)
Closed: positive pressure relief (passive disposal, relief valve opens for too much pressure) or positive and negative pressure relief (active disposal, vacuum and reservoir bag used to keep system between -0.5 and 5 cmH2O pressure)
58
What is the gas-disposal assembly of the scavenging system?
Active or passive components to remove wastes from the OR
Active: mechanical flow (vacuum system, hospital evacuation system)
Passive: pressure is raised above atmosphere by patient exhaling (vented to a fan and out a window usually at the top of the facility)
Note: active is common in hospitals, passive is inexpensive but may be impractical
59
How do you perform a scavenge system check?
Ensure proper connection, fully open APL valve and occlude Y-piece. Turn on low oxygen flow and allow scavenger bag to collapse so that pressure gauge reads zero. With oxygen flush activated, allow scavenger bag to fill and verify pressure reads less than 10 cm pressure
60
What is the purpose of capnography?
Gold standard of confirming ETT placement, determines patient is being ventilated, guides vent settings, disconnect indicator, detects quality of CO2 absorption, detects abnormalities (perfusion, PE, MH, disconnect, obstruction)
61
If the patient is hypotensive, what will the ETCO2 show? What will it show if the patient is having a PE?
hypotensive: low perfusion, LOW levels of ETCO2
PE: ventilation isn't normal, shows LOW levels of ETCO2
62
Which has a higher reading, PaCO2 or PEtCO2? Why?
PaCo2 will read a little bit higher due to dead space making PEtCO2 a diluted reading
63
What causes an increase in CO2?
Hypoventilation, COPD (longer I:E ration, increased metabolism (MH, stress, fever, sepsis), rebreathing CO2 (if CO2 absorber is exhausted), release of tourniquet (tourniquet builds up lactic acid and other metabolic byproducts like CO2 that are released when the tourniquet is released), bicarb drip was started
64
What causes a decrease in CO2?
Hyperventilation (shown by GRADUAL decrease in CO2), if patient is hypothermic, PE or VQ mismatch (shown by RAPID decrease in CO2), leak in system or disconnect, low CO (low perfusion, cardiac arrest)
65
How does the Infrared Absorption Spectrophotometry work?
It measures amount of CO2 in expired gases by detecting how much CO2 is absorbed by infrared radiation at specific wavelengths related to other gases
66
What is mainstream vs. sidestream capnography?
Mainstream (aka Flow-Through): infrared devise placed in circuit, con- gets hot and can burn the patient
Sidestream: diverts sample through tubing, takes about 50 mL away and uses an infrared devise, con- potential disconnect source and time delay
67
What are the 4 phases on the capnogram?
Phase 1: flat line, inspiration and first part of expiration (dead space)
Phase 2: upstroke, expiration shows rising CO2 in sample, mixture of dead space and alveolar gas
Phase 3: plateau, light upstroke, longest phase, end of expiration
Phase 4: rapid decline, beginning of inspiration
68
Which phase in the capnography is PEtCO2 measured?
At the end of phase 3, at the end of the plateau, alveolar gas is sampled, normal is 30-40 mmHg
69
How does the capnography change in someone with an obstructive disorder?
Slow rise in phase 2, little to no phase 3
70
What does esophageal intubation look like on the capnography?
Peak at first, then hardly any CO2 readings (this is why we look for a few good breaths before determining it was a successful intubation)
71
What does rebreathing look like on capnography? What are some examples of why this might happen?
Value remains above 0 or baseline
| Ex: equipment dead space, exhausted CO2 absorber, inadequate fresh gas flows
72
What does capnography look like when neuromuscular blockade starts to wear off?
curare cleft (little notch during phase 3) or little spikes during phase 1
73
What do cardiac oscillations look like in capnography?
Little vibrations during phase 4, harmless
74
What are the two common absorbents used in CO2 scrubber?
Soda Lime and Amsorb Plus (calcium hydroxide lime)
| Note: Litholyme (lithium hydroxide) is new, not clinically used yet though
75
What is soda lime composed of?
```
80% calcium hydroxide
15% water (water reacts with CO2)
4% sodium hydroxide
1%potassium hydroxide
0.2% silica (makes granule harder)
```
76
How much CO2 does soda lime absorb per 100g? How much time will this take in an average person?
26L of CO2 per 100g of absorbent
| So, if a normal person releases 12L/hour, 100g works for about 2 hours
77
How does the reaction work with the soda lime and CO2 absorber?
CO2 combines with water to form carbonic acid. Carbonic acid reacts with the hydroxides to form sodium/potassium/calcium carbonate plus water plus heat
78
What is calcium hydroxide lime (Amsorb) composed of?
80% calcium hydroxide
16% water
1-4% calcium chloride
Calcium sulfate adds hardness
79
How much CO2 does calcium hydroxide lime absorb per 100g?
10L of CO2 per 100g of calcium hydroxide lime
80
When should the CO2 absorbent be replaced?
When 50-70% of the absorbent turns ethyl violet
| Note: this will turn back to white if left for a period of time (overnight)
81
What size are the CO2 absorbent granules? What should the harness number be?
4-8 mesh, this was determined to be the best size because it creates enough surface area without creating too much resistance (Note: when exhaled air passes through the CO2 absorber this is called "channeling")
The hardness number should be over 75, tested by crushing
82
Why is it important to keep flows over 2L? (note: this was only tested in monkeys, so protocols don't require this)
When granules come into contact with anesthetic agest (like sevoflurane), it can degrade to compound A which is nephrotoxic
83
What happens if CO2 dries out (flow left on overnight or use of very high flows for example)?
Granules dry out and carbon monoxide can build up and poison the patient, it can also build up heat and produce a fire
84
What are some recommendations for safe use of CO2 absorbent?
Turn off flow when machine is not in use, change absorbent regularly or when color change indicates exhaustion, change all absorbent (not just one canister), and change if uncertain of state of hydration (FGF), low flows preserve humidity in granules
85
What do these colors correspond with? Green, blue, yellow, black, brown?
```
Green: oxygen
Blue: nitrous oxide
Yellow: air
Black: nitrogen
Brown: helium
```
86
How much does a full E-cylinder of oxygen hold? Air cylinder? Nitrous oxide cylinder? What is different about determining how much nitrous oxide is left?
E-cylinder of oxygen holds 2000-2200 psi (625-700L)
Air holds 1900-2000 psi (625L)
Nitrous oxide holds 745 psi (1590L), stored as liquid, so pressure does NOT indicate how much is left, weight does!
87
What regulatory agency specifies the purity of medical gases in the United States Pharmacopoeia?
FDA
88
What regulatory agency establishes the requirements for manufacturing, filling, qualification, transportation, storage, handling, maintenance, re-qualification, and disposition of medical gas cylinders and containers?
DOT (dept of transportation)
89
What is displayed on the the cylinders? (DOT regulated)
Permanent markings on the shoulder of the cylinder, labeling on the shoulder (not covering any permanent markings), and tags (show if the cylinder is full, in use, or empty)
90
What safety system is used by the medical gas pipelines?
DISS (diameter index safety system), provides non-interchangeable connections for the gas lines consisting of a body, nipple, and nut, this is required for every anesthesia machine
91
What is vaporization and what three things does it depend on?
Vaporization is conversion of liquid to gas
| Dependent on vapor pressure, temperature, and amount of carrier gas used
92
How is vapor pressure created?
Gas molecules bombard the surface of the liquid and the walls of the container creating vapor pressure
93
At 20 degrees C, what are the volatile agents vapor pressures? (Halothane, Isoflurane, Desflurane, Enflurane, Sevoflurane)?
```
Halothane: 244 mmHg
Isoflurane: 240 mmHg
Desflurane: 669 mmHg
Enflurane: 172 mmHg
Sevoflurane: 160 mmHg
```
94
What is latent heat of vaporization?
The number of calories it takes to change one gram of liquid into vapor without temp change (this energy comes from the liquid)
95
What is specific heat?
The number of calories required to increase the temperature of one gram of a substance by one degree C (this is true for solid, liquid, or gas)
96
What is thermal conductivity?
A measure of speed with which heat flows through a substance (the higher the thermal conductivity, the better the substance conducts heat)
97
When does the boiling point of a substance occur?
When vapor pressure = barometric pressure
98
What are the three components of a vaporizer?
They must be..
1. agent specific (bc they all have dif vapor pressures)
2. temperature compensated
3. variable bypass
99
What is the variable bypass portion of the vaporizer?
A portion of the gas flow will pass into the vaporizing chamber to become saturated with vapor, this rejoins the gas flow for dilution to the concentration that is delivered
100
How does increased and decreased altitude effect barometric pressure? How does this effect the concentration of vaporizers?
Increased altitude decreases barometric pressure
Decreased altitude increases barometric pressure
With lower pressures (in increased altitude), concentration of agents increases and become more potent keeping the same partial pressure
EXCEPT for Desflurane bc it is in the Tec-6 at 2 atms.. it is opposite, you need increased conc at increased altitude
101
Why does desflurane need a Tec 6 vaporizer?
The heating chamber changes the agent to 2 atmopheres so it doesn't as readily change to liquid
102
How does the copper kettle work?
"measured flow, bubble through"
A flowmeter for the kettle sends gas through the vaporizer and the flow is directed town toward the liquid (bubble through), requires lots of flow and lots of calculations, wastes vaporizers
103
List some potential hazards of vaporizers.
Wrong agent poured in vaporizer (high-low-high, low-high-low)
Contamination, Tipping, Overfilling
Admin of more than one vapor (we have lock out system for this)
Leaks (check during low pressure system check)
Pumping effect (some back flow can occur when using pipeline)
104
What is the molecular theory of matter?
Matter is made of molecules that exist as solid, liquid, and gas
105
What is the kinetic theory of matter?
Molecules are in constant, random motion and have a degree of attraction to each other (van der waal forces)
106
What is a critical temperature?
The temperature above which a gas can't be liquid, regardless of how much pressure is applied
A gas can't be liquified if the ambient temp is GREATER than the critical temp. However, a gas CAN be liquified if enough pressure is applied at ambient temp BELOW critical temp
107
What is oxygen's critical temp? What is nitrous oxide's critical temp?
Oxygen's is -119 degrees C
Nitrous oxide's is 39 degrees C
Room temp is 20 degrees C
Significance: Nitrous oxide's critical temp is above room temp so it is liquid at room temperature
108
According to Avagadro, how many molecules in 1 mole?
| At STP, how many liters in 1 mole?
6. 02x10^23 molecules
| 22. 4 L
109
Boyle's Law? What is constant?
V = 1/P ... Volume and pressure are inversely related
| Constant temperature
110
List applications of Boyle's Law.
Reservoir bag: applying pressure (squeezing the bag) causes volume to decrease
Spontaneous breathing: as pressure decreases (becomes negative), volume in the lung increases
Bellows: as pressure increases, volume in bellows decrease
111
What is Charles Law? What remains constant?
Volume and temperature are directly proportional
| Pressure remains constant
112
What is the application to Charles' Law?
Balloons burst on hot days, because as temp goes up, volume goes up
113
What is Gay-Lussac's Law? What remains constant?
Temperature and pressure have a directly proportional relationship
Volume remains constant
114
What is an application of Gay-Lussac's Law?
If a full cylinder is moved from inside to the hot temperature outside, the pressure in the cylinder can increase (causing it to shoot off)
115
What is Dalton's Law? What is the application?
Total pressure of a gas mixture is the SUM of the partial pressures
Ptotal= P1 + P2 + P3 ...
Application: Air is composed of 21% oxygen, 79% nitrogen, so then since total atmospheric pressure is 760, we can calculate how much of that belongs to each gas. We can also calculate how much anesthetic gases are delivered.
116
What is Fick's Law?
Rate of diffusion is...
DIRECTLY proportional to concentration gradient, surface area, solubility
INVERSELY proportional to thickness of the membrane and molecular weight
Vgas = (area x solubility x partial pressure difference) / (molecular weight x distance)
117
What are the applications of Fick's Law?
Second gas effect: one anesthetic increases uptake of the next given anesthetic
Diffusion hypoxia: diffusion across the alveolar-capillary membrane
ETT cuff expands with nitrous oxide use
Placental transfer of drugs and oxygen
118
What is Graham's Law?
Gas diffusion rate is inversely proportional to the square root of its molecular weight
119
What is Henry's Law?
The amount of gas dissolved in a liquid is DIRECTLY proportional to the partial pressure of the gas in contact with the solution
120
What is the application of Henry's Law?
Gives us the two important constants: 0.003 mL O2 per mmHg partial pressure and 0.067 mL CO2 per mmHg partial pressure (per 100mL blood)
Using these constants, we can do FiO2 x 5 then multiply this answer by the constant
121
What is adiabatic cooling?
Change in temperature of matter without gain or loss of heat (using pressure or volume)
When a nitrous oxide cylinder is opened, frost can form on the outlet due to cooling
122
What is the Joule- Thompson effect?
Expansion of a gas causes cooling
| As gas leaves a cylinder, the expansion cools the surrounding air causing condensation on the cylinder
123
What is Poiseuille's Law?
Flow is...
DIRECTLY proportional to pressure gradient and radius^4 of the tube
INVERSELY proportional to length of the tube and viscosity of the fluid
Q = (pi x r^4 x change in pressure) / (8 x n x L)
124
What is the practical application of Poiseuille's Law?
IV flow, airway, blood flow (polycythemia), thorpe tubes (flowmeters- at low flows, the float is tubular)
125
What is Reynold's number?
Reynold's number = (density x diameter x velocity) / viscocity
Reynold's greater than 2000 means turbulent flow
126
What were Bernouli's theory and Venturi's application?
Bernoulii related pressure and velocity. A narrow diameter decreased wall pressure which increased speed and a wide diameter increased wall pressure which decreased speed
Venturi Oxygen Masks was an application to this theory, gives high flows at FiO2 of 25-40%
Other applications: jet ventilation and nebulizers
127
What is Beer's and Lambert's Law?
Beer: absorption of radiation by a given thickness of a solution of a given concentration is the same as 2x the thickness of a solution of 1/2 the concentration
Lambert: Each layer of equal thickness absorbs an equal fraction of radiation that passes through it
128
What is the clinical application of Beer's Law?
Pulse ox:
Oxygenated emits light at 940 nm, infrared light
Deoxygenated hemoglobin emits light at 660 nm, red light
129
What are the errors in pulse oximetry readings?
How do the following change the readings: carboxyhemogloblin, methgb, Hgb F, HgbS, polycythemia, methylene, isosulfan blue, indocyanine green, indigo carminine, and blue nail polish
Carboxyhemoglobin: flase high
Methgb: if sats over 85, flase low, if sats less than 85, false high
HgbF, HgbS, polycythemia: no effect
Methylene, isosulfan blue: false low
Indocyanine green, indigo carmine, blue nail polish: false low
130
What is LaPlace's Law?
Pressure gradient across a tube/sphere/cylinder is T=Pr
| tension = pressure x radius
131
What are the clinical applications of LaPlace's Law?
Alveoli need surfactant to stay open
Aneurysm due to increased wall tension
A dilated ventricle has increased tension on the wall, so increased end diastolic pressure
132
What is Ohm's Law?
V = IR (voltage = current flow x resistance)
| In medical terms.. Flow = change in pressure / resistance
133
What are the applications of Ohm's Law?
Transducers, thermistors, blood flow circulation
134
2% lidocaine is how many g/mL?
2g/100mL, so 20mg/mL
135
1:10,000 epi means 1 gram in 10,000 mL, what is that per mL?
100 mcg/mL
136
What are some vent alarms?
Low pressure (drop in peak pressure)
Sub atmospheric pressure (pressure of less than -10 cmH2O)
Sustained pressure (15 cmH2O for over 10 sec)
High peak airway pressure (excess pressure in system at over 60 cm H20)
Low oxygen supply
Ventilator setting (vent's inability to deliver the desired MV)
137
What is final position after you're done checking the machine?
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Vaporizers and flowmeters off
APL valve OPEN
Selector switch to "bag"
Suction ready
Breathing system ready to use
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138
How do you check the high pressure system?
Unplug oxygen pipeline from anesthesia machine
Open oxygen cylinder and verify it is at least half full (1000 psi), close cylinder
O2 flush until it reads 0 psi
Turn on anesthesia machine and listen for fail-safe alarm
Reconnect pipeline, make sure pipeline reads 50 psi
139
What emergency ventilation equipment do you have in the room?
Ambu bag and mask
suction
jet ventilator
plan B airways equipment - LMA
