Physics Exam 3
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Questions and Answers

What is the result of the Joule-Thompson Effect on a gas?

  • Volume increase of the gas
  • Pressure increase of the gas
  • Temperature increase of the gas
  • Expansion of gas causes cooling (correct)

    • What is the primary reason why tubing becomes extremely hot during compression?

  • Work done to compress the gas
  • Friction generated during compression
  • Adiabatic compression of the gas (correct)
  • Heat exchange with the surroundings

    • When is an anesthesia machine typically in a semi-open circuit mode?

  • During maintenance of anesthesia
  • During delivery of precise inspired gas concentrations
  • During controlled ventilation
  • During induction and emergence (correct)

    • What is the purpose of inspiratory and expiratory valves in an anesthetic breathing circuit?

    <p>To prevent rebreathing from mechanical deadspace</p> Signup and view all the answers

    What is the primary purpose of the Diameter Index Safety System (DISS) in anesthesia machines?

    <p>To ensure the correct gas is connected to the correct outlet via the specific threaded connections for each type of gas</p> Signup and view all the answers

    What is the purpose of the Pin Index Safety System?

    <p>To prevent mounting of the wrong cylinder by using specific holes in the tank</p> Signup and view all the answers

    What is the primary advantage of using a low flow system?

    <p>It saves volatile and retains heat and moisture</p> Signup and view all the answers

    What is the purpose of the sidestream sampler in a circle system?

    <p>Last chance to prevent administration of hypoxic gas mixture</p> Signup and view all the answers

    What is the effect of inhaling dry gases without heat and humidity?

    <p>It increases mucus viscosity and promotes ciliary dysfunction</p> Signup and view all the answers

    What is the effect of a stuck closed inspiratory or expiratory valve?

    <p>It increases the risk of airway obstruction</p> Signup and view all the answers

    What is the primary purpose of the Mapleson breathing systems?

    <p>To provide a semi-open system for pediatrics and transport</p> Signup and view all the answers

    What is the effect of a desiccated CO2 absorber on sevoflurane?

    <p>It breaks down sevoflurane into Compound A</p> Signup and view all the answers

    Match each system to its classification

    <p>Open = No rebreathing and no reservoir Semi-open = No rebreathing with a reservoir Semi-closed = Partial rebreathing with a reservoir Closed = Complete rebreathing with a reservoir</p> Signup and view all the answers

    In closed breathing systems, the amount of gas consumed by the patient should match what metric?

    <p>Amount of gas added to the circuit</p> Signup and view all the answers

    What are examples of open breathing systems?

    <p>Insufflation</p> Signup and view all the answers

    What type of breathing system is a non-rebreather?

    <p>Semi-open circuit - no rebreathing with a reservoir</p> Signup and view all the answers

    What allows rebreathing of exhaled gas in semi-closed and closed breathing systems?

    <p>Carbon dioxide absorbent</p> Signup and view all the answers

    What are two ways to address rebreathing of CO2?

    <p>Replace the CO2 absorbent</p> Signup and view all the answers

    In a semi-open circle system, what is the relationship between FGF (Fresh Gas Flow) and minute ventilation?

    <p>FGF &gt; Minute ventilation</p> Signup and view all the answers

    In a semi-closed circle system, what is the relationship between FGF (fresh gas flow) and minute ventilation?

    <p>FGF &lt; Minute ventilation</p> Signup and view all the answers

    A circle system with a very low FGF and APL closed is what type of breathing system?

    <p>Closed - FGF only replaces gas consumed by the pt (APL is closed)</p> Signup and view all the answers

    What is the result of a malfunction of either unidirectional valve in a circle system? (select 2)

    <p>Hypercarbia</p> Signup and view all the answers

    What is the role of the APL in a circle system? (select 2)

    <p>To direct gas into the scavenger when circuit pressure reaches a certain limit</p> Signup and view all the answers

    How do you convert a closed or semi-closed circuit into a semi-open one?

    <p>By increasing the FGF</p> Signup and view all the answers

    Which Mapelson circuit is best for spontaneous ventilation?

    <p>Mapelson A</p> Signup and view all the answers

    Which Mapelson circuit is best and worst for controlled ventilation?

    <p>Mapelson A - worst</p> Signup and view all the answers

    What is unique about Mapelson breathing systems?

    <p>They lack CO2 absorbers because CO2 is lowered by the addition of fresh gas and elimination through the APL</p> Signup and view all the answers

    Which Mapelson circuit is best and worst for spontaneous ventilation?

    <p>Mapelson A is best, Mapelson B is worst</p> Signup and view all the answers

    What is the Bain system and how does it deliver fresh gas?

    <p>The Bain system is a type of anesthetic breathing circuit that delivers fresh gas through a concentric tube inside the corrugated tubing, allowing for a humidification, but it makes it easier to be kinked</p> Signup and view all the answers

    When is an anesthesia machine in semi-closed mode?

    <p>During maintenance of anesthesia</p> Signup and view all the answers

    What is a benefit of rebreathing?

    <p>Increase heat and humidity while decreasing costs</p> Signup and view all the answers

    Where is mechanical dead space located in circle systems?

    <p>Y-piece and endotracheal tube</p> Signup and view all the answers

    What are the effects of lower FGF?

    <p>Increased humidity in the system and slower reduction in body temperature</p> Signup and view all the answers

    Full E cylinder of O2 volume of 4.8 L at 14.7psi

    <p>True</p> Signup and view all the answers

    What is the main difference between the pressure of oxygen cylinders and nitrous oxide cylinders?

    <p>Pressure of oxygen accurate reflects gas remaining while the pressure of nitrous oxide will fall only once all the liquid N2O has evaporated</p> Signup and view all the answers

    What action can you take if the inspiratory or expiratory valves are stuck open?

    <p>Convert the system to a semi-open one by increasing FGF &gt; MV to wash out CO2</p> Signup and view all the answers

    What actions can you take if the inspiratory/expiratory valves are stuck closed?

    <p>Take patient off the ventilator and bag ventilate them</p> Signup and view all the answers

    In the bag/vent selector switch in a circle system, when are the reservoir bag and APL valve used?

    <p>During manual/spontaneous ventilation</p> Signup and view all the answers

    In the bag/vent selector switch in a circle system, when are the vent and pressure relief valve used?

    <p>During mechanical ventilation</p> Signup and view all the answers

    What is the function of the APL (Adjustable Pressure Limiting) valve in an anesthesia circuit?

    <p>To determine how much gas remains in the circuit and how much is directed towards the scavenger</p> Signup and view all the answers

    What is a byproduct of desflurane, enflurane, and isoflurane as a result of prolonged high gas flows, high temperatures, high concentrations of agents, and use of barium hydroxide lime?

    <p>CO</p> Signup and view all the answers

    What is the function of a scavenger in an anesthetic system?

    <p>To remove excess gas from the breathing circuit and minimize environmental exposure to waste anesthetic gases</p> Signup and view all the answers

    What plays a role in the scavenger system during spontaneous ventilation?

    <p>APL</p> Signup and view all the answers

    What plays a role in the scavenger system during mechanical ventilation?

    <p>Ventilator spill valve</p> Signup and view all the answers

    What are the key negative consequences of uneven gas removal from the scavenger system?

    <p>Too much gas removal results in negative pressure in the circuit</p> Signup and view all the answers

    What is the main difference between active and passive scavenging systems?

    <p>Active systems use suction to remove gas while passive systems rely on positive pressure from FGF to remove gas</p> Signup and view all the answers

    What is true about open scavenging interface?

    <p>It can only be used with active systems and works by releasing waste gas to the environment or pulling room air into the system</p> Signup and view all the answers

    What is the primary purpose of pressure relief valves in closed scavenging interfaces?

    <p>To communicate with the atmosphere</p> Signup and view all the answers

    What is the purpose of sodium hydroxide in sodium lime?

    <p>To neutralize carbonic acid</p> Signup and view all the answers

    What is the purpose of using 4-8 mesh granules with soda lime?

    <p>To balance surface area and airflow resistance</p> Signup and view all the answers

    What are the reactions that work to remove CO2 from a breathing circuit?

    <p>All of the above</p> Signup and view all the answers

    Match the correct dye with its color on exhaustion

    <p>Ethyl violet white when fresh = purple on exhaustion Phenolphthalein white when fresh = pink on exhaustion Clayton yellow red when fresh = yellow on exhaustion Ethyl orange orange when fresh = yellow on exhaustion</p> Signup and view all the answers

    Mimosa Z red when fresh and white on exhaustion

    <p>True</p> Signup and view all the answers

    What are the ideal width and lengths for blood pressure cuffs?

    <p>40% of the arm circumference, 2/3 or 80% the length of the arm</p> Signup and view all the answers

    In doppler BP, only the ____ can be measured

    <p>SBP</p> Signup and view all the answers

    What is the difference in light absorption between oxygenated and deoxygenated hemoglobin?

    <p>Oxygenated hemoglobin absorbs more infrared light, and deoxygenated hemoglobin absorbs more red light.</p> Signup and view all the answers

    Which of the following relationships describe how pulse oximetry works?

    <p>Lambert's relationship: light absorption to the thickness of the absorbing layer, Beer's relationship: light absorbed and amount of solute</p> Signup and view all the answers

    What Spo2 measurements does methyhemoglobin result in?

    <p>Overestimation with a plateau</p> Signup and view all the answers

    Bilirubin causes falsely high SPO2

    <p>False</p> Signup and view all the answers

    Methylene blue and indocyanine green, nail polish underestimates SPO2 (i.e. falsely low)

    <p>True</p> Signup and view all the answers

    When does SPO2 tend to be falsely overestimated?

    <p>At low SPO2 &lt;80%</p> Signup and view all the answers

    What is the primary cause of the penumbra effect when using a pulse oximeter?

    <p>Different path lengths of red and infrared light causing light to be shunted</p> Signup and view all the answers

    What is the result of the penumbra effect on SpO2?

    <p>Falsely high if SPO2 &lt;85%</p> Signup and view all the answers

    What curve shifts may change the patient's PaO2 without changes in SPO2?

    <p>Oxyhemoglobin dissociation</p> Signup and view all the answers

    What is the implication of severe anemia with Hct<25% on SPO2 readings?

    <p>It results in decreased reliability when SPO2 is low.</p> Signup and view all the answers

    What happens to the reliability of SPO2 readings when Hct is less than 10%?

    <p>Reliability decreases at all levels</p> Signup and view all the answers

    • ETCO2 (expired) < alveolar CO2 (at alveoli)

    <p>True</p> Signup and view all the answers

    The mass spectroscopy and Raman spectroscopy are able to measure O2, CO2, N2O, and volatile agents

    <p>True</p> Signup and view all the answers

    What does it indicate when ETCO2 doesn't come down and stays persistently elevated?

    <p>An incompetent expiratory valve</p> Signup and view all the answers

    What is indicated by the loss of leveling at the bottom of the waveform during the inspiration phase?

    <p>Incompetent inspiratory valve</p> Signup and view all the answers

    What is the purpose of using EEG and EMG in anesthesia?

    <p>To calculate the level of consciousness and sedation</p> Signup and view all the answers

    What is the bispectral index (BIS) goal for sedation and general anesthesia?

    <p>40-60 for GA</p> Signup and view all the answers

    What is Zone 3 in an MRI environment?

    <p>A strictly restricted area immediately outside of the MRI room where interaction between ferromagnetic objects and MRI can result in serious injury or death</p> Signup and view all the answers

    What is Zone 4 in an MRI facility?

    <p>MRI scanner magnet room</p> Signup and view all the answers

    What does pulse pressure variation during inspiration and expiration rely on?

    <p>Frank-Starling curve to determine fluid responsiveness</p> Signup and view all the answers

    In atrial fibrillation, what would you expect to observe on CVP?

    <p>Absence of a wave and prominent c wave</p> Signup and view all the answers

    What occurs when the right atrium (RA) contracts against a closed tricuspid valve during right ventricle (RV) systole?

    <p>Cannon waves in CVP</p> Signup and view all the answers

    What are the three components of the fire triad?

    <p>Oxidizer, ignition source, and fuel</p> Signup and view all the answers

    What is macro shock?

    <p>A type of electrocution where electricity enters through the skin and flows through a substantial portion of the body, only a fraction actually going through the heart</p> Signup and view all the answers

    What is a key difference between electricity conducted directly to the heart via microshock and other forms of electric shock?

    <p>It is more concentrated and can cause fibrillation at smaller levels of current</p> Signup and view all the answers

    What is the main difference between AC and DC?

    <p>AC uses less amperage to move electricity long distances and DC moves electricity short distances</p> Signup and view all the answers

    If electricity is like water, what is the voltage equivalent to?

    <p>Pressure</p> Signup and view all the answers

    If electricity is like water, what is the current equivalent to?

    <p>Flow rate</p> Signup and view all the answers

    What is the definition of inductance?

    <p>The tendency of a AC circuits to resist changes in the current flowing through it by generating a magnetic field.</p> Signup and view all the answers

    What is a capacitor and what type of medical device uses this technology?

    <p>A capacitor is a device that stores electrical energy, and a defibrillator uses this technology</p> Signup and view all the answers

    What is the relationship between impedance and conductivity?

    <p>Impedance is inversely proportional to conductivity</p> Signup and view all the answers

    Impedance = resistance

    <p>True</p> Signup and view all the answers

    What is reactance a measure of in an AC circuit?

    <p>The opposition to a change in current due to the inductor or capacitor</p> Signup and view all the answers

    In inductive reactance, changes in ____ are resisted by generating a magnetic field

    <p>Current</p> Signup and view all the answers

    What happens in capacitive reactance?

    <p>Capacitors resist changes by storing energy</p> Signup and view all the answers

    What is the purpose of the isolation transformer in the OR?

    <p>To convert grounded power to ungrounded power</p> Signup and view all the answers

    What is the purpose of ensuring the OR is ungrounded?

    <p>All of the above</p> Signup and view all the answers

    What is the function of a Line Isolation Monitor (LIM)?

    <p>To continuously test the impedance of the two isolated power wires to determine impedance to the ground</p> Signup and view all the answers

    What is the relationship between impedance and isolation in a circuit?

    <p>The lower the impedance, the poorer the isolation, resulting in an alarm</p> Signup and view all the answers

    What is a consequence of capacitance in AC operated equipment?

    <p>Small leakage currents that degrade the isolated power system</p> Signup and view all the answers

    What happens when a ground fault is detected in a GFCI?

    <p>It trips and cuts off power</p> Signup and view all the answers

    Match each characteristic to the proper Mapelson circuit

    <p>A = APL close to pt B = Both APL and FGF close to pt C = No corrugated tubing D = FGF close to pt</p> Signup and view all the answers

    What are the characteristics of Mapelson E and F circuits?

    <p>Mapelson E has no APL or reservoir</p> Signup and view all the answers

    660 nanometers (nm) in the red part of the visible spectrum and 940 nm in the infrared part

    <p>True</p> Signup and view all the answers

    Study Notes

    Physics of Gases

    • Work done to compress a gas requires energy, which is manifested as heat.
    • Adiabatic process: no exchange of heat with surroundings, but temperature of the gas rises.
    • Gay-Lussac's gas law: as pressure increases, temperature increases with a constant volume.
    • Tubing can become extremely hot during compression, and any particles or dirt can combust.
    • "Crack" cylinder before use to remove any particles that may be in the connector.

    Joule-Thompson Effect (Joule-Kelvin Effect)

    • Expansion of gas causes cooling.
    • Examples of compressed gases expanding in anesthesia:
      • Nitrous oxide tanks have gas and liquid; as gas is pulled off the top, the liquid continuously expands to gas.
      • Will fall rapidly as residual gas flows from the cylinder.

    Medical Compressed Gases

    • Common medical compressed gases:
      • Oxygen (O2)
      • Nitrous oxide (N2O)
      • Medical air
      • Entonox (50/50 nitrous and oxygen)
      • Heliox
      • Xenon
    • Importance of checking labels to verify what gas is inside a tank, as colors differ and tanks are reusable.

    Cylinder Information

    • Cylinder markings:
      • Material of the tank
      • Maximum filling pressure (psig)
      • Serial number and inspection date
    • Checked for leaks and structural integrity with overpressure test every 10 years.
    • Types of cylinders:
      • E cylinder: nominal value of 4.8L at 14.7psi, max fill 1900psig holds 660L
      • H cylinder: nominal value of 43.6L at 14.7psi, max fill 2200psig holds 6900L

    Pin Index Safety System

    • Prevents mounting of the wrong cylinder using pins placed complementary to specific holes in the tank.
    • Each gas has a unique pin configuration.

    Quick Couplers

    • Each has a specific pin configuration for individual gases.
    • Attached hose should be color-coded for specific gas.

    Diameter Index Safety System (DISS)

    • Threaded connections with specific diameters for each gas.
    • Required on all anesthesia machine gas inlets.
    • Prevents cross-connection of gases.
    • Standardized.

    Safety Precautions

    • Gas cylinders should never be left standing upright and unsecured.
    • Risk of breaking at the neck if they fall over and release intense pressure.

    Liquid Oxygen

    • Stored in liquid form at large facilities with "unlimited" volume.
    • Requires specific technology and equipment.
    • Liquid O2 stored at -160°C, pressure inside storage vessel ~85 psig.
    • Insulated with vacuum to maintain temperature.
    • Oxygen gas pulled from top of container, heated, then passed through pressure regulator to bring to pipeline pressure (50 psi).

    Medical Vacuum and Nitrogen

    • Medical vacuum used for Bovie smoke and exhaled air and volatiles.
    • Nitrogen in OR used for air tools.

    Breathing Circuits

    • Types of breathing circuits:
      • Open: no reservoir, no rebreathing
      • Semi-open: reservoir, no rebreathing
      • Semi-closed: reservoir, partial rebreathing
      • Closed: reservoir, complete rebreathing
    • Rebreathing prevented by inspiratory and expiratory valves in the circuit.
    • CO2 removed from breathing circuit using Y-piece.

    Mapleson Breathing Systems

    • Semi-open circuits used for pediatrics and transport.
    • Inhaled and exhaled gases travel through the same tubing.
    • Requires high FGF to wash out CO2, no scrubber, and risks rebreathing and hypercarbia if gas flows are too low.
    • Typical fresh gas flows: 20-25Lpm or 2.5x MV.
    • Circle system only takes 1-2Lpm.

    CO2 Removal Methods

    • Chemical absorption
    • Washout by fresh gas
    • Separation of exhaled gas from fresh gas
    • Use of T-piece without reservoir

    Soda Lime

    • Most common CO2 absorbent
    • Composition: 80% calcium hydroxide, 15% water, 4% sodium hydroxide, 1% potassium hydroxide (activator), silica
    • Irregular shape to increase surface area
    • Optimal size: 4-8 mesh
    • Should be shaken before use to prevent air channeling, and turned off when not in use to prevent desiccation.

    HMEF (Heat and Moisture Exchange Filter)

    • Hydrophobic filter that precipitates water vapor on the filter.
    • May also offer some bacterial and viral filtration, but not adequate for infectious patients.

    Scavenger System

    • Removes waste gases from the system via APL valve or vent pressure relief valve.
    • Has adjustment knob to control vacuum pressure.
    • Points of exit for waste gas in circle system:
      • APL valve
      • Reservoir bag
      • Ventilator relief valve
    • If suction is too high, pulls air from patient breath, causing low TV and hypoxia.
    • If suction is too low, gas backs up, causing increased pressure to the patient and barotrauma.

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