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APEX Mock Exam Questions and Answers 2024
low pressure system Intermediate Pressure System High Pressure system How many pressure systems are there in the anesthesia machine? Hanger Yoke Yoke block with check Valves Cylinder pressure gauge Cylinder pressure regulators What are the components of the high pressure system in the anesthesia machine? Begins a the cylinder Ends at the cylinder regulators Where does the high pressure system in the anesthesia machine begin and end?
- pipeline inlets
- pressure gauges
- o2 press failure device
- o2 second stage regulator
- o2 flush valve
- vent power inlet
- flowmeter valves What are the components of the Intermediate pressure system in the anesthesia machine Begins at the pipe line Ends at the flow meter valves Where does the intermediate pressure system in the anesthesia machine begin and end? Flowmeter Tubes (Thorpe tubes) Vaporizers Check Valve (if present) common gas outlet What are the components of the Low pressure system in the anesthesia machine Begins at flow meter tubes Ends at common gas outlet Where does the low pressure system in the anesthesia machine begin and end? 50 psi
What is the pipeline pressure in the intermediate pressure system of the anesthesia machine? 45psi What is the tank pressure in the intermediate pressure system of the anesthesia machine? The integrity of the low pressure circuit from the flowmeter valves to the common gas outlet. What are you testing during a low pressure leak test of the anesthesia machine? By attaching a bulb to the common gas outlet and creating negative pressure. How do you perform a low pressure leak test of the anesthesia machine? Inflation of the bulb within 10sec What indicates a failure of the system during a low pressure leak test? Low pressure leak test What is the best way to test the anesthesia machine for a vaporizer leak? Fresh gas flow Minimum FGF Ventilator What should always be turned off during the low pressure leak test? Off initially, then th test should be repeated as each vaporizer is turned on During the low pressure leak test the vaporizers should be in what position? The breathing circuit and entire low pressure system What does the high pressure leak test on the anesthesia machine with NO check valve? The breathing circuit and low pressure system up to check valve only. What does the high pressure leak test on the anesthesia machine with check valve? Closing the APL valve and pressurizing the system to 30cm/H2O, while observing the airway pressure gauge for a constant pressure. How does one perform a High pressure leak test on the anesthesia machine? Closed When the check valve is in the prescence of back pressure it is considered to be open or closed? Open In the anesthesia machine the absence of back pressure means the check valve is considered to be open or closed?
What is the PISS configuration for Oxygen? 3, What is the PISS configuration for Nitrous Oxide? The presence of more than one washer between the hanger and yoke assembly and the stem of the tank. How can the PISS be bypassed and lead to possible misconnection? Prevents inadvertently misconnecting gas hoses via sized and threaded connectors for each individual gas. How does the DISS prevent harm? Only when not using oxygen from pipeline When should the oxygen cylinder on the back of the anesthesia machine be turned on? 1900 psi How much PSI does the Air tank have? 625L How many Liters does the standard Air tank hold? 1900 psi How much psi does the standard oxygen tank have? 660L How many liters does the standard oxygen tank hold? 745 psi How much psi does the standard nitrous oxide tank have? 1590L How many Liters does the standard nitrous oxide tank hold? 20.7lb What is the weight of a full standard size nitrous oxide tank? 14.1lb What is the weight of a empty standard size nitrous oxide tank?
tank capacity(L)/ full tank Pressure(psi) = contents remaining (L)/ gauge pressure (psi) then contents remaining (L)/ flow rate(L/min)=minutes left befor tank is empty How do you calculate the minuets left before a tank is empty? 87 minutes If the pressure gauge of the oxygen tank reads 500psi and the patient has a flow rate of 2L/min how many minutes are left before the oxygen tank is empty? when the psi drops below 745 When should you change the nitrous oxide tank? Insert a yoke plug What should be done if there is no cylinder to replace the one removed from the anesthesia machine? Because if the check valve should fail the gas will exit the machine rather than go to the patient. Why is placing a yoke plug when there is no cylinder in place so important? Oxidizer, fuel, and igniter What does the fire triad consist of? 130F or 57C Gas cylinders should not be exposed to temperatures greater than? Fusible plug that melt at elevated temps (bismuth, lead, tin, and cadmium), valve that opens at elevated pressures, frangible disk that ruptures under pressure. What are some safety relief devices for gas cylinders? American Society for Testing and Materials ( ASTM F1850) Who sets the standards for the required components of the anesthesia machine? What is the documen called? United States department of transportation Who sets the standard for compressed gas cylinders? Food and drug administration in 1993 Who created the anesthesia pre-use check out procedures? When was it created? Occupational safety and health administration Who's sets the standards for accepatable occupational exposure to volatile Anesthetics?
What can provide a constant gas pressure in the flow meter throughout a wide range of flow rates? FGF ( pushes up) Gravity (pulls down) What two forces position the indicator float on a flow meter? Skirted, plumb bob, non-rotating (read at top) ball( read in middle) What are the 4 types of floats in the flow meter? Hypoxic mixture is more likely especially since all the Saftey devices other than the O2 analyzer are distal to the flow meters Why is a flow meter leak so dangerous? closest the the common gas outlet (far right) in orders to minimize hypoxic mixture. Where should the O2 flow meter be positioned? Reynolds number What predicts whether flow is laminar or turbulent? Re = (v∗d∗ρ)/η v = mean velocity of blood flow (cm/sec) d = vessel diameter (cm) ρ = density of the blood η = viscosity of blood (poise) Reynolds number equation gas density ( grahams law) What is turbulent flow dependent upon? Gas viscosity (poinseuille equation) What is laminar flow dependent upon? laminar flow Reynolds number < 2,000 equals? Turbulent Flow Reynolds number > 4,000 equals? Transitional flow Reynolds number of 2000 - 4000 equals?
FiO2= (air flow rate x 21) + (O2 flow rate x 100)/ total flow rate How do you calculate FiO2? Vt set on vent + FGF during inspiration - volume lost to compliance What is the equation for total tidal volume delivered when using fresh gas coupling? Decreased RR, Increased I:E ration, FGF, or bellows height What effects may cause an increase with Vt? Increased RR, Decreased I:E What effects may cause an decrease with Vt? change in volume for a given change in pressure What is Circuit compliance? compliance = change in volume / change in pressure What is the equation for compliance? Run a high FGF for 20 - 30 min to ensure liquid anesthetic is no longer in the bypass chamber. What should be done should a vaporizer is tipped over prior to use on a patient? Fresh gas flows over a series of baffels and wicks increasing surface area and turbulence to ensure the FG inside vaporizer chamber becomes 100% Saturated with agent. What happens to Fresh Gas after entering the vaporizing chamber? Flowl less than 200 mL/min or greater than 15L/min What can lead to reduced vaporizer output? It is a temperature compensating valve that adjusts the ratio of vaporizing chamber flow to bypass flow guaranteeing a constant vaporizer output over a wide range of temps. What is the purpose of the bimetallic strip/ expansion element of the vaporizer? When gas that has already left the vaporizer re-enters the vaporizing chamber increasing vaporizer output. What is the pumping effect? positive pressure ventilation or oxygen flush valve use What are common causes of vaporizer pumping effect? Loose filler cap What is the most common cause of a vaporizer leak?
What are disadvantages of the galvanic fuel-cell oxygen analyzer Detects pipeline crossover, detects disconnect in the breathing circuit, monitors oxygen concentration. what does the oxygen analyzer do? Y- piece. Second most common CO2 canister What is the most common site of circuit disconnect? TO match patients oxygen delivery to oxygen consumption thus avoiding a hypoxic mixture. What is the goal of closed circuit anesthesia?` Turn on oxygen tank and disconnect pipeline supply What should you do first in the event of a pipeline crossover? What components are present in the high pressure system of the anesthesia machine? What is the gas pressure in this region? The high pressure system begins at the cylinder and ends at the cylinder regulators. Components- hanger yoke, yoke block with check valves, cylinder pressure gauge, cylinder pressure regulators Gas pressure = cylinder pressure What components are present in the intermediate pressure system of the anesthesia machine? The intermediate pressure system begins at the pipeline and ends at the flowmeter valve. Components include- pipeline inlets, pressure gauges, ventilator power inlet, oxygen pressure failure system, oxygen second stage regulator, oxygen flush valve, flowmeter valve Gas pressure = 50 psi for pipeline 45 psi for tank What components are present in the low pressure system of the anesthesia machine? The low pressure system begins at the flowmeter tubes and ends at the common gas outlet Components include flowmeter tubes, vaporizers, check valves, common gas outlet Gas pressure = slightly > atm What are the 5 tasks of oxygen in the anesthesia machine?
O2 pressure failure alarm O2 pressure failure device O2 flowmeter O2 flush valve Ventilator drive gas (if pneumatic bellows) Describe the pin index safety system
- The PISS prevents inadvertent misconnections of gas cylinders
- The pin configuration on each hanger yoke assembly is different for each gas, making unintended connections of the wrong gas unlikely, but not impossible.
- The presence of one washer between the anger yoke assembly and the stem of the tank may allow the PISS to be bypassed What are the PISS configurations for air, oxygen and nitrous? Air - 1, 5 O2 - 2, 5 N2O 3, Describe the diameter index safety system
- The DISS presents inadvertent misconnections of gas hoses. Each gas hose and connector are tied and threaded for each individual gas What are the maximum pressures and volumes for cylinders that contain air, oxygen, and nitrous? Air- 1900 psi, 625L Oxygen- 1900 psi, 660L Nitrous- 745 psi, 1590L How much does a nitrous cylinder weigh when it's full? Empty?
Hypoxia prevention safety device AKA proportioning device- prevents you from setting a hypoxic mixture with the flow control valves. Limits N2O flow to 3x the O2 flow (N2O max ~75%) Describe the structure and function of the flow tube The internal diameter of the flow tube is narrowest at the base and progressively widens along its ascent. The annular space is the area between the indicator float and side wall of the flow tube. Indeed, the annular space is also narrowest at the base and widest at the top. This "variable orifice" architecture provides a constant gas pressure throughout a wide range of flow rates. Laminar flow is dependent on according to what law? Laminar flow is dependent on gas viscosity- dictated by Poiseuille Turbulent flow is dependent on according to what law? Turbulent flow is dependent on gas density according to Graham's law What is the safest flowmeter configuration on the anesthesia machine? The O2 flowmeter should always be furthest to the right. The oxygen flowmeter should be positioned closest to the manifold outlet, because if a leak develops in the other flowmeters, it will not reduce the FiO2 delivered to the patient. If a leak develops in the oxygen flowmeter, all bets are off How do you calculate the FiO2 set at the flowmeter? An anesthesia machine uses fresh gas coupling. How do you determine the total tidal volume that will be delivered to this patient? Vt total = Vt set on ventilator + FGF during inspiration - volume lost to compliance
When using a ventilator that couples FGF to Vt, what types of ventilator changes will impact tidal volume delivered to the patient? Vt increases with lower RR, Increased I:E ratios, Increased FGF, increased bellows height Vt decreases with increased RR, lower I:E ratios, lower FGF, lower bellows height What is the vaporizer splitting ratio?
- Modern variable bypass vaporizers split FGF into two parts
- FGF enters the vaporizing chamber and becomes 100% saturated with volatile agent
- FGF bypasses the vaporizing chamber and does not pick up any agent
- Before leaving the vaporizer, these two fractions mix and this determines the final anesthetic concentration exiting the vaporizer Setting the concentration on the vaporizer dial determines? The splitting ratio. Setting a higher concentration directs more FGF towards the liquid anesthetic, while setting a lower concentration directs less FGF towards the liquid anesthetic. What is the pumping effect?
- Increases vaporizer output
- Anything that causes gas that has already left the vaporizer to re-enter the vaporizer chamber → PPV or O2 flush valve Compare and contrast the variable bypass vaporizer with the injector-type vaporizer Variable bypass- Vaporizer splits fresh gas, vaporized via flow over, automatic temperature and elevation compensation Injector- Dual circuit, fresh gas doesn't flow over VA, instead is a gas/vapor blender, vapor is injected into FGF. Electronically heated to 39C, no compensation for elevation What does the oxygen analyzer measure and where is it located? The oxygen analyzer measures oxygen concentration (not pressure) and is the only device downstream of the flowmeters that can detect a hypoxic mixture.
Increase the FGF to 3x the patient's MV What is dessication, and how does it apply to soda lime? Water is required to facilitate the reaction of CO2 with CO2 absorbent. The granules are hydrated to 13 - 20% by weight. When the absorbent is devoid of water, it is said to be dessicated. In the presence of VA, desiccated soda lime increases the production of CO with des and iso, and compound A with sevo List 7 ways to monitor for disconnection of the breathing circuit. 4 modalities- pressure, volume, ETCO2, vigilance Precordial stethoscope visual inspection of chest rise capnography respiratory volume monitors low expired volume alarm low peak pressure alarm Failure of bellows to rise (only with ascending) What are the OSHA recommendations regarding VA exposure for healthcare workers in the OR VA alone ≤ 2 ppm N2O alone ≤ 25 ppm VA + N2O ≤ 0.5 ppm and ≤ 25 ppm 4 types of breathing circuits, and examples of each Open- insufflation, face mask, NC, open drop Semi-open- Mapleson circuit, circle system if FGF > Vte Semi-closed- Circle system if FGF < Vte Closed- Circle system with low FGF and closed apl What is the purpose of the unidirectional valves in the breathing circuit? Ensure gas moves in one direction If a valve becomes incompetent, the patient will rebreathe exhaled gas
Which Mapleson circuit is the most efficient for spontaneous ventilation?
- Which is best for controlled ventilation? Spontaneous = Mapleson A Controlled- Mapleson D What conditions decrease pulmonary compliance? How does this affect the peak pressure and plateau pressure? A decreased pulmonary compliance is usually due to a reduction in static compliance - PIP and PP increase Ex: endobronchial intubation, pulmonary edema, pleural effusion, tension pneumo, atelectasis, chest wall trauma, abdominal insufflation, ascites, Tburg position, inadequate muscle relaxation What conditions increase pulmonary resistance? How does this affect peak pressure and plateau pressure? An increased pulmonary resistance is usually due to a reduction in dynamic compliance (PIP increases, and PP is unchanged) Ex: kinked ETT, ETT cuff herniation, bronchospasm, bronchial secretions, compression of airway, FB aspiration Describe the 4 phases of the normal capnograph
- Phase I (A-B) → Exhalation of anatomic dead space
- Phase II (B-C) → Exhalation of anatomic dead space + alveolar gas
- Phase III (C-D) → Exhalation of alveolar gas
- Phase IV (D-E) → Inspiration of fresh gas that does not contain CO Discuss the significance of the alpha and beta angles on the capnograph An increased alpha angle signifies an expiratory airflow obstruction- COPD, bronchospasm, kinked ETT
Causes of decreased ETCO2 due to changes in alveolar ventilation or equipment malfunction Increased VA- hyperventilation, inadequate anesthesia, metabolic acidosis, Rx SE Equipment- vent d/c, esophageal intubation, poor seal with ETT/LMA, sample line leak, airway obstruction, apnea What wavelengths of light are emitted by the pulse oximeter? What law is used to make the SpO2 calculation? The pulse oximeter is based on the Beer-Lambert law, which relates the intensity of light transmitted through a solution and the concentration of the solute within the solution 2 wavelengths Red light- 660 nm- preferentially absorbed by deoxyHgb (venous blood) Near-infrared light- 940 nm- preferentially absorbed by oxyHgb- arterial blood What conditions impair the reliability of the pulse ox? Decreased perfusion- vasoconstriction, hypothermia, Raynaud's Dysfunctional Hgb- CarboxyHgb, MetHgb (not Hgb S or F) Altered optical characteristics- methylene blue, ICG, indigo carmine Non-pulsatile flow-LVAD, CPB Motion artifact- shivering/movement Cautery, venous pulsation What factors affect the accuracy of the NIBP measurement? The ideal bladder length is enough to wrap around 80% of the extremity The ideal bladder width is 40% of the circumference of the patient's arm Falsely increased- cuff too small, cuff too loose, measured below level of heart Falsely decreased- cuff too big, cuff deflated too rapidly, cuff above level of heart How does the site of measurement affect the BP reading? As the pulse moves from the aortic root towards the periphery, the systolic pressure increases, diastolic pressure decreases, and pulse pressure widens. MAP is constant throughout the arterial
tree At the aortic root - SBP is lowest, DBP is highest, and PP is narrowest At dorsalis pedis- SBP is highest, DBP is lowest, and PP is widest How does the arm position affect the NIBP reading?
- How about when an arterial line is used? Blood in the circulation behaves like a column of fluid and follows the rules of hydrostatic pressure BP cuff is above heart = BP falsely decreased BP cuff below heart = BP falsely increased When an aline is used, what matters is the level of the transducer For every 10 cm change, the BP changes by? For every inch change, the BP changes by? 10cm = 7.4 mmHg Inch = 2 mmHg What information can you learn from the ABP waveform? Systolic BP = peak of waveform Diastolic = trough of waveform PP = peak - trough Contractility = upstroke SV= AUC Closure of aortic valve = dicrotic notch Discuss damping and the interpretation of the high pressure flush test Optimal waveform morphology balances the amount of damping with the amount of distortion from the transducer system. The high pressure flush test helps us determine this when we flush the system and observe the oscillations that result. Optimally damped- baseline re-established after 1 oscillation Under-damped- baseline is re-established after several oscillations (SBP overestimated, DBP underestimated, MAP accurate)
