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ABA ADVANCED Exam practice questions

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Question 1Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A 5 L E-cylinder contains oxygen at a gauge pressure of 130 bar. At a flow of 10 L/min, approximately how long will the cylinder last?

  1. 43 minutes
  2. 22 minutes
  3. 130 minutes
  4. 65 minutes Correct answer.

Explanation

Boyle's law gives the volume of gas available at atmospheric pressure: 5 L × 130 bar = 650 L. Dividing 650 L by a consumption of 10 L/min yields 65 minutes. The gauge pressure is not the remaining volume, so the cylinder must first be converted to ambient-pressure gas.

Question 2Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Pulse oximetry is based on which physical principle?

  1. Detection of exhaled CO2 by infrared absorption
  2. Impedance change across the chest wall
  3. Differential red and infrared light absorption by hemoglobin Correct answer.
  4. Doppler shift from pulsatile arterial blood flow

Explanation

Pulse oximetry exploits the different absorption spectra of oxyhemoglobin and deoxyhemoglobin at red and infrared wavelengths. The pulsatile component isolates arterial blood from venous and tissue signals. The ratio of absorbances is converted to saturation.

Question 3Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

In the US medical gas cylinder color code, which color identifies an oxygen cylinder?

  1. Blue
  2. Green Correct answer.
  3. Yellow
  4. Gray

Explanation

In the US color code, oxygen cylinders are green, nitrous oxide cylinders are blue, and air cylinders are yellow. Carbon dioxide is gray, so color alone must be confirmed by the cylinder label.

Question 4Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which statement best describes a Thorpe tube flowmeter?

  1. Rotameter that may be used at any angle
  2. Thermal mass meter independent of density
  3. Variable-orifice meter kept vertical Correct answer.
  4. Fixed-orifice meter that measures pressure

Explanation

A Thorpe tube is a variable-orifice flowmeter: the float rises as flow increases, enlarging the annular orifice. It is calibrated for a specific gas and must be vertical to keep the float weight and gas force balanced.

Question 5Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Capnography is best described as which of the following?

  1. Arterial CO2 measured by blood gas
  2. Continuous CO2 waveform display over time Correct answer.
  3. Exhaled oxygen concentration measurement
  4. Single numeric end-tidal CO2 value

Explanation

Capnography is the continuous graphic display of CO2 concentration over time, whereas capnometry is a single numeric measurement. The waveform allows recognition of obstruction, disconnection, and other ventilation abnormalities.

Question 6Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the primary function of a heat and moisture exchanger in a breathing circuit?

  1. Adds water vapor only during inspiration
  2. Removes carbon dioxide from fresh gas
  3. Retains heat and moisture from exhaled gas Correct answer.
  4. Measures tidal volume during ventilation

Explanation

A heat and moisture exchanger captures exhaled heat and water vapor and returns them during the next inspiration. It reduces humidity loss without adding external water.

Question 7Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the purpose of the anesthesia scavenging system?

  1. Measures anesthetic concentration in the circuit
  2. Collects and removes waste anesthetic gases Correct answer.
  3. Provides positive pressure during exhalation
  4. Humidifies fresh gas before delivery

Explanation

The scavenging system collects waste anesthetic gas from the breathing circuit and ventilator and vents it outside the work area. It protects staff from chronic exposure.

Question 8Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What energy range is typical for the first shock from a biphasic defibrillator in an adult?

  1. 0.5 to 2 J
  2. 120 to 200 J Correct answer.
  3. 360 J
  4. 5 to 20 J

Explanation

Biphasic defibrillators typically deliver 120 to 200 J for adult defibrillation, with the exact energy specified by the manufacturer. Monophasic devices generally use up to 360 J.

Question 9Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A capnogram shows a slurred, shark-fin-shaped phase II upstroke. What does this most likely indicate?

  1. Esophageal intubation with gastric insufflation
  2. Circuit disconnection with loss of waveform
  3. Bronchospasm with uneven alveolar emptying Correct answer.
  4. Hyperventilation lowering end-tidal CO2

Explanation

A prolonged phase II upstroke produces a shark-fin appearance because obstructed alveoli empty slowly and unevenly. This pattern is characteristic of bronchospasm or other expiratory obstruction.

Question 10Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

At the same volumetric flow, which gas is most likely to produce turbulent flow because of its physical properties?

  1. Oxygen because its viscosity is lower
  2. Nitrous oxide because its density is higher Correct answer.
  3. Helium because its density is lower
  4. Air because its density is lower

Explanation

Reynolds number rises with gas density, velocity, and diameter and falls with viscosity. At the same flow, the denser gas reaches turbulent flow first.

Question 11Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

How does a variable-bypass vaporizer control the delivered anesthetic concentration?

  1. It measures agent concentration by infrared absorption
  2. It uses a fixed orifice to control fresh gas flow
  3. It splits gas between bypass and vaporizing chamber Correct answer.
  4. It injects liquid agent directly into the circuit

Explanation

In a variable-bypass vaporizer, fresh gas splits into a bypass path and a vaporizing chamber; the split determines the final agent concentration. Each vaporizer is calibrated for one agent because saturated vapor pressure and boiling point differ.

Question 12Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which statement about oscillometric noninvasive blood pressure measurement is correct?

  1. Cuff pressure is held constant during measurement
  2. Korotkoff sounds are detected by a microphone
  3. The first oscillation corresponds to diastolic pressure
  4. Peak oscillations correspond to mean arterial pressure Correct answer.

Explanation

Oscillometric devices detect pressure oscillations in the cuff as it deflates. The largest oscillations occur near mean arterial pressure, and systolic and diastolic values are derived algorithmically.

Question 13Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

According to Poiseuille's law, how does laminar resistance change if the radius of a tube is halved?

  1. 8-fold
  2. 16-fold Correct answer.
  3. 4-fold
  4. 2-fold

Explanation

Poiseuille's law states that laminar resistance is inversely proportional to the fourth power of radius. Halving the radius therefore increases resistance by 2^4, or 16-fold.

Question 14Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

How is train-of-four neuromuscular monitoring performed?

  1. Double-burst stimuli separated by 750 ms
  2. Single tetanic stimulus at 100 Hz
  3. Four stimuli at 50 Hz with first-to-fourth ratio
  4. Four stimuli at 2 Hz with fourth-to-first ratio Correct answer.

Explanation

Train-of-four uses four supramaximal stimuli at 2 Hz, and the ratio of the fourth twitch to the first quantifies neuromuscular block. A ratio above 0.9 generally indicates adequate recovery.

Question 15Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

How does Doppler ultrasound estimate blood flow velocity?

  1. It estimates velocity from Doppler frequency shift Correct answer.
  2. It uses ionizing radiation to image vessels
  3. It measures blood velocity from resistance changes
  4. It relies on infrared absorption by hemoglobin

Explanation

Doppler ultrasound detects the frequency shift of sound reflected from moving red cells. The shift is proportional to blood velocity, allowing estimation of flow.

Question 16Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which statement about a galvanic oxygen analyzer is correct?

  1. It consumes oxygen and needs periodic replacement Correct answer.
  2. It requires a high-voltage excitation source
  3. It measures oxygen by infrared absorption
  4. It uses paramagnetic properties of oxygen

Explanation

A galvanic oxygen cell generates a current proportional to oxygen partial pressure as oxygen is consumed at the cathode. The electrolyte and anode are depleted over time, so the cell requires periodic replacement.

Question 17Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the function of a pressure regulator on an anesthesia machine?

  1. It reduces cylinder pressure to a constant level Correct answer.
  2. It blends two gases in a fixed ratio
  3. It measures flow by a variable orifice
  4. It increases gas pressure for pipeline delivery

Explanation

A pressure regulator reduces the high, variable cylinder pressure to a constant lower pressure suitable for the machine. This protects downstream components and stabilizes flow.

Question 18Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the recommended intracuff pressure for an endotracheal tube?

  1. 5 to 10 cmH2O
  2. 20 to 30 cmH2O Correct answer.
  3. 80 to 100 cmH2O
  4. 50 to 70 cmH2O

Explanation

Endotracheal tube cuff pressure should be kept at 20 to 30 cmH2O to seal the airway without exceeding mucosal capillary pressure. Higher pressures can cause tracheal mucosal ischemia.

Question 19Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Why can a poorly applied electrosurgical return electrode cause a burn?

  1. High-frequency current causes tetanic contraction
  2. The return electrode carries no current during use
  3. Poor return-electrode contact raises current density Correct answer.
  4. Bipolar diathermy requires a return electrode

Explanation

Return-electrode burns occur when contact is poor because current concentrates at a small area, raising current density. Bipolar diathermy does not require a return electrode because current flows between the two tips.

Question 20Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the operating principle of a mass spectrometer used for gas analysis?

  1. It measures gas concentration by thermal conductivity
  2. It requires disposable electrochemical sensors
  3. It separates ions by mass-to-charge ratio Correct answer.
  4. It uses one infrared wavelength for all gases

Explanation

A mass spectrometer ionizes gas molecules and separates the ions by mass-to-charge ratio, allowing simultaneous measurement of multiple gases. It is used in some research and multiplexed monitoring systems.

Question 21Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Cerebral near-infrared spectroscopy (NIRS) provides which type of information?

  1. It uses ionizing radiation to image the brain
  2. It measures cerebral blood flow in mL/min
  3. It measures arterial saturation in the retina
  4. It reflects mainly venous cerebral oxygen saturation Correct answer.

Explanation

Cerebral oximetry uses near-infrared light to estimate regional hemoglobin oxygen saturation in the frontal cortex. Because most cerebral blood volume is venous, the reading is weighted toward venous saturation.

Question 22Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Approximately what intracardiac current can precipitate ventricular fibrillation, defining the microshock threshold?

  1. 10 amperes
  2. 1 milliampere
  3. 100 milliamperes
  4. 100 microamperes Correct answer.

Explanation

Microshock refers to current applied directly to the myocardium, where as little as 100 microamperes can precipitate ventricular fibrillation. This is far below the macroshock threshold for intact skin.

Question 23Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

How do volatile anesthetics affect somatosensory evoked potentials (SSEPs) at clinical concentrations?

  1. Volatile anesthetics have no effect at clinical doses
  2. SSEPs monitor only motor pathway integrity
  3. SSEPs are unaffected by temperature
  4. Volatile anesthetics reduce amplitude and prolong latency Correct answer.

Explanation

Volatile anesthetics depress cortical and spinal evoked responses, reducing amplitude and prolonging latency. This must be considered when interpreting SSEP monitoring during surgery.

Question 24Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

During high-flow ventilation through a narrow endotracheal tube, turbulent resistance predominates. Which change most reduces this resistance?

  1. Adding helium to the inspired mixture Correct answer.
  2. Increasing the viscosity of the carrier gas
  3. Increasing the density of the carrier gas
  4. Doubling the length of the endotracheal tube

Explanation

In turbulent flow, resistance is proportional to gas density. Helium has a much lower density than nitrogen or oxygen, so a helium-oxygen mixture reduces turbulent resistance through a narrow tube.

Question 25Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A nitrous oxide cylinder is partly empty but still contains liquid. What happens to the cylinder pressure as gas is withdrawn?

  1. Pressure equals atmospheric when half full
  2. Pressure stays constant while liquid and vapor coexist Correct answer.
  3. Pressure rises steadily as the cylinder empties
  4. Pressure falls linearly as gas is withdrawn

Explanation

Nitrous oxide is stored as a liquid-vapor mixture, and its pressure remains constant at the saturated vapor pressure as long as liquid remains. The pressure gauge therefore does not indicate the remaining volume until the liquid is gone.

Question 26Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

The pin-index safety system prevents misconnection of a cylinder to an anesthesia machine yoke. Which pin configuration is assigned to oxygen?

  1. 2 and 5 Correct answer.
  2. 3 and 5
  3. 1 and 6
  4. 1 and 5

Explanation

The pin-index safety system uses two pins on the cylinder yoke that must fit matching holes in the cylinder valve. Oxygen is assigned pin positions 2 and 5; nitrous oxide uses 3 and 5, carbon dioxide uses 1 and 6, and medical air uses 1 and 5.

Question 27Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Pulse oximetry estimates arterial oxygen saturation by exploiting which principle?

  1. Differential absorption of red and infrared light in pulsatile tissue Correct answer.
  2. Absorption of infrared light by carbon dioxide molecules in the breathing circuit
  3. Detection of backscattered ultrasound from flowing erythrocytes
  4. Direct measurement of oxygen partial pressure with a Clark electrode

Explanation

Pulse oximetry applies the Beer-Lambert law at two wavelengths, red and infrared. The pulsatile component is assumed to arise from arterial blood, while the nonpulsatile component is subtracted as background. The resulting ratio is mapped to arterial saturation.

Question 28Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A sidestream capnograph sampling line becomes partially occluded with water. What is the most likely effect on the displayed waveform?

  1. The waveform will be delayed and attenuated, with a prolonged rise time Correct answer.
  2. The capnogram will show a sudden drop to zero during each inspiration
  3. The displayed waveform will show a prolonged phase III upstroke but normal EtCO2
  4. The end-tidal value will be falsely low and the waveform will be flattened

Explanation

Partial obstruction reduces sample flow, so gas takes longer to reach the analyzer and mixing blurs the waveform. This produces delay, attenuation, and a prolonged rise time rather than a simple calibration offset. Water trapping can also cause a falsely low or unstable reading.

Question 29Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A full oxygen E-cylinder at room temperature reads approximately what pressure?

  1. 1900-2200 psi Correct answer.
  2. 750 psi
  3. 500 psi
  4. 1000 psi

Explanation

A full oxygen E-cylinder at 20 degrees Celsius has a pressure of about 2000 psi, or roughly 13,800 kPa. The pressure falls steadily as oxygen is consumed because oxygen remains a gas at room temperature rather than a liquefied gas.

Question 30Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A Bourdon gauge attached to an oxygen cylinder directly measures which variable?

  1. Pressure within the cylinder relative to atmosphere Correct answer.
  2. Flow rate of oxygen leaving the cylinder in liters per minute
  3. Volume of gas remaining in the cylinder at standard temperature and pressure
  4. Mass of oxygen currently contained in the cylinder

Explanation

A Bourdon gauge is a mechanical pressure gauge: a curved tube straightens as internal pressure rises, moving a needle. It indicates cylinder pressure relative to atmosphere, not volume or mass remaining. Volume can only be inferred if temperature and cylinder size are known.

Question 31Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Desflurane requires a heated, pressurized vaporizer because of which property?

  1. Its high saturated vapor pressure at room temperature Correct answer.
  2. Its rapid degradation by carbon dioxide absorbent
  3. Its low molecular weight compared with other volatile agents
  4. Its high solubility in blood and adipose tissue at body temperature

Explanation

Desflurane has a saturated vapor pressure near 670 mmHg at 20 degrees Celsius, close to atmospheric pressure. A conventional variable-bypass vaporizer cannot deliver it predictably at that vapor pressure, so it is heated and pressurized to create a controlled vapor stream.

Question 32Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

What is the primary purpose of a line isolation monitor in an operating room?

  1. To detect hazardous leakage current to ground from isolated equipment Correct answer.
  2. To interrupt the circuit when the leakage current exceeds 5 milliamperes
  3. To measure the resistance of the patient return electrode
  4. To limit the current delivered by the electrosurgical generator during cutting

Explanation

The line isolation monitor continuously measures the impedance between an isolated power circuit and ground. It alarms when the amount of current that could flow to ground through a fault reaches a hazardous level, typically about 2 to 5 mA, but it does not interrupt the circuit.

Question 33Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Cardiac output measured by thermodilution relies on which relationship?

  1. Change in thoracic impedance during the cardiac cycle
  2. Doppler shift of ultrasound in the pulmonary artery
  3. Inverse relation between temperature change and blood flow Correct answer.
  4. Fick principle using oxygen consumption and arteriovenous oxygen difference

Explanation

Thermodilution injects a known volume of cold fluid and measures the downstream temperature change. The area under the temperature-time curve is inversely related to cardiac output, so a larger output washes out the cold bolus faster and produces a smaller area.

Question 34Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which material property underlies the generation of ultrasound by a transducer?

  1. Thermistors change resistance with temperature
  2. Photodiodes emit light when polarized
  3. Piezoelectric crystals deform when an alternating voltage is applied Correct answer.
  4. Ferromagnetic cores change length when exposed to an alternating magnetic field

Explanation

Piezoelectric crystals change shape when a voltage is applied and generate a voltage when deformed. An alternating driving voltage makes them vibrate at high frequency to produce ultrasound, and the same crystal can detect returning echoes.

Question 35Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Infrared capnography identifies carbon dioxide because the molecule does which?

  1. Emits light at a wavelength proportional to its temperature
  2. Absorbs infrared energy at a characteristic wavelength Correct answer.
  3. Changes the refractive index of the sample cell
  4. Scatters infrared light in proportion to its molecular weight

Explanation

Carbon dioxide absorbs infrared light strongly at about 4.3 micrometers. The analyzer measures the reduction in infrared transmission through the sample cell, which is proportional to carbon dioxide concentration after calibration.

Question 36Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Synchronized cardioversion differs from unsynchronized defibrillation in that it does which?

  1. Delivers a lower energy shock through the same adhesive pads and cables
  2. Times the shock to the QRS complex to avoid the vulnerable period Correct answer.
  3. Requires the patient to be conscious and unsedated
  4. Uses a biphasic waveform exclusively in all patients

Explanation

Synchronized cardioversion delivers the shock at the peak of the R wave so it does not fall in the vulnerable period of repolarization. Unsynchronized defibrillation is used for ventricular fibrillation or pulseless ventricular tachycardia, where no reliable QRS is present.

Question 37Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

An arterial line displays a systolic pressure of 160 mmHg, diastolic of 60 mmHg, and mean of 80 mmHg. Which interpretation is most likely?

  1. The system is calibrated at the wrong zero level
  2. The system is overdamped, which flattens the waveform and underestimates systolic pressure
  3. The transducer is positioned at the level of the right atrium
  4. The system is underdamped and ringing, overestimating systolic pressure Correct answer.

Explanation

An underdamped system oscillates after the pressure impulse, producing an exaggerated systolic peak and sometimes a lower diastolic value. The mean pressure is less affected because it reflects the area under the waveform. Overdamping, by contrast, flattens the waveform and underestimates systolic pressure.

Question 38Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which breathing system component absorbs exhaled carbon dioxide in a circle circuit?

  1. Pressure-limiting valve
  2. Soda lime canister Correct answer.
  3. Inspiratory unidirectional valve
  4. Reservoir bag

Explanation

The circle system passes exhaled gas through a carbon dioxide absorber, usually soda lime or barium hydroxide lime. The absorbent chemically binds carbon dioxide so that the gas can be rebreathed while fresh gas replenishes oxygen and anesthetic.

Question 39Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which oxygen analyzer principle depends on the paramagnetic property of oxygen?

  1. A galvanic cell generates a current proportional to the oxygen concentration
  2. A fuel cell consumes oxygen at a platinum cathode
  3. Oxygen displaces a diamagnetic reference gas in a magnetic field Correct answer.
  4. Oxygen absorbs ultraviolet light at 254 nm

Explanation

Oxygen has a strong paramagnetic susceptibility because of unpaired electrons, so it is attracted into a magnetic field. In a paramagnetic analyzer, oxygen displaces a reference gas or changes the force on a suspended dumbbell, and that movement is translated into oxygen concentration.

Question 40Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

In the presence of methemoglobinemia, pulse oximetry typically shows which pattern?

  1. A falsely low saturation that corrects with supplemental oxygen
  2. A saturation that alternates with the respiratory cycle
  3. A saturation that plateaus near 85% despite a normal PaO2 Correct answer.
  4. A normal saturation that falls only during exercise

Explanation

Methemoglobin absorbs red and infrared light similarly, so the ratio-of-ratios algorithm is confounded. The displayed saturation tends to plateau around 85% and does not reliably track the true PaO2 or oxygen saturation. Co-oximetry is needed for accurate measurement.

Question 41Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Why can a cylinder become hot during rapid filling?

  1. Expansion of gas during filling absorbs heat from the cylinder wall
  2. The cylinder metal releases stored heat when pressurized
  3. Liquid oxygen forms and releases latent heat of vaporization
  4. Rapid compression of gas in the cylinder converts work to heat Correct answer.

Explanation

When a cylinder is filled rapidly, gas already inside is compressed and work is converted into heat. If heat cannot dissipate quickly, the cylinder temperature rises; this adiabatic heating is a recognized fire and explosion hazard during rapid filling.

Question 42Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

The oxygen flush valve on an anesthesia machine delivers approximately what flow?

  1. 10-15 L/min
  2. 100-150 L/min
  3. 5-10 L/min
  4. 35-75 L/min Correct answer.

Explanation

The oxygen flush valve bypasses the vaporizer and flowmeters and delivers a high flow of oxygen, typically 35 to 75 L/min, directly to the breathing circuit. It is used to rapidly refill the reservoir bag or to ventilate during an emergency.

Question 43Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

During electrosurgery, the ECG monitor shows a wandering baseline and high-frequency noise. What is the best explanation?

  1. The patient has developed a new ventricular tachycardia
  2. The ECG limb electrodes have been placed in reversed positions
  3. The ECG display gain has been set to an inappropriately low value
  4. Electromagnetic interference from the electrosurgical unit Correct answer.

Explanation

Electrosurgical current generates a strong electromagnetic field and high-frequency electrical noise that can enter ECG leads. This produces baseline wander and spikes that can mimic arrhythmias; the tracing should be interpreted with the interference in mind.

Question 44Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A patient with a permanent pacemaker requires electrosurgery. Which configuration is safest?

  1. Monopolar electrosurgery with the return pad placed on the thigh
  2. Monopolar electrosurgery at the lowest setting with the pad on the chest
  3. Bipolar electrosurgery with closely spaced active and return electrodes Correct answer.
  4. Bipolar electrosurgery with the return pad placed near the pacemaker

Explanation

Bipolar electrosurgery confines current to the small area between the tips, reducing the field that reaches the heart and pacemaker. Monopolar current can travel through the body and interfere with pacing or cause heating at the lead tip. The return pad should be positioned so current does not cross the pacemaker.

Question 45Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

Which central venous pressure waveform finding suggests tricuspid regurgitation?

  1. Prominent a wave
  2. Large v wave Correct answer.
  3. Absent a wave
  4. Cannon a wave

Explanation

The v wave reflects atrial filling against a closed tricuspid valve during ventricular systole. Tricuspid regurgitation adds a systolic regurgitant wave, producing a prominent v wave. Cannon a waves occur with atrioventricular dissociation.

Question 46Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A sudden drop in end-tidal carbon dioxide to near zero during cardiopulmonary resuscitation most likely indicates which problem?

  1. Soda lime exhaustion
  2. Circuit leak
  3. Severe hyperventilation with a respiratory alkalosis
  4. Loss of pulmonary blood flow Correct answer.

Explanation

End-tidal carbon dioxide depends on delivery of carbon dioxide to the lungs by pulmonary blood flow. A sudden fall to near zero during cardiopulmonary resuscitation suggests loss of pulmonary blood flow, such as from esophageal intubation, massive pulmonary embolism, or ineffective compressions.

Question 47Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A pressure monitoring system has a damping coefficient of 0.1. Which waveform effect is expected?

  1. Overshoot and ringing at the resonant frequency Correct answer.
  2. Flattening of the systolic peak and a widened waveform
  3. Loss of the dicrotic notch only
  4. Faithful reproduction of the arterial waveform

Explanation

A damping coefficient near 1 is optimal; values well below 1 indicate an underdamped system. With a coefficient of 0.1, the catheter-transducer system oscillates at its resonant frequency, causing overshoot and ringing that exaggerate systolic pressure.

Question 48Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

The oxygen supply pressure alarm on an anesthesia machine typically sounds when oxygen pressure falls below what level?

  1. About 20 psi
  2. About 30 psi Correct answer.
  3. About 10 psi
  4. About 50 psi

Explanation

The oxygen supply pressure alarm is usually set to activate when oxygen pressure falls to about 30 psi, approximately 200 kPa. This warns of a failing pipeline or cylinder supply before the low-pressure circuit is compromised.

Question 49Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A Thorpe tube flowmeter calibrated for oxygen is used to deliver helium at a given float position. How does the actual helium flow compare with the indicated flow?

  1. Zero because helium is not calibrated
  2. Lower than the indicated flow
  3. Equal to the indicated flow
  4. Higher than the indicated flow Correct answer.

Explanation

A Thorpe tube is calibrated for a specific gas, usually oxygen or air. Helium has a much lower density and viscosity than oxygen, so at a given float position the pressure drop needed to support the float occurs at a higher volumetric flow. The actual helium flow is therefore greater than the indicated flow.

Question 50Basic Sciences Applied to Anesthesiology (physics, equipment, monitoring)

A flexible fiberoptic bronchoscope used for intubation relies on which property?

  1. Magnetic resonance of hydrogen nuclei
  2. Piezoelectric vibration of a quartz crystal in an electric field
  3. Total internal reflection within glass fibers Correct answer.
  4. Photoelectric absorption by hemoglobin

Explanation

Fiberoptic bundles use total internal reflection: light striking the core-cladding boundary above the critical angle is reflected back into the core. This allows light and images to be transmitted along a flexible, bent bundle.