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CRNA (NCE) practice questions

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Question 1Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which neurotransmitter is released from the presynaptic terminal at the neuromuscular junction?

  1. Acetylcholine Correct answer.
  2. gamma-Aminobutyric acid
  3. Dopamine
  4. Norepinephrine

Explanation

Somatic motor neurons are cholinergic: the arriving action potential opens voltage-gated calcium channels, calcium enters the terminal, and acetylcholine vesicles fuse with the membrane. The released acetylcholine then binds postjunctional receptors to depolarize the muscle fiber.

Question 2Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Binding of acetylcholine to which receptor generates the end-plate potential that initiates muscle contraction?

  1. Nicotinic acetylcholine receptor Correct answer.
  2. Beta-2 adrenergic receptor
  3. GABA-A receptor
  4. Muscarinic acetylcholine M2 receptor

Explanation

The motor end plate carries muscle-type nicotinic acetylcholine receptors, which are ligand-gated cation channels. Channel opening permits sodium influx, producing the depolarizing end-plate potential that triggers muscle action potentials.

Question 3Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which lung volume cannot be measured with simple spirometry?

  1. Residual volume Correct answer.
  2. Expiratory reserve volume
  3. Inspiratory reserve volume
  4. Tidal volume

Explanation

Spirometry tracks only gas that moves into and out of the mouth, so any volume exchanged with the atmosphere is measurable. Residual volume stays in the thorax after maximal exhalation and must be obtained indirectly by helium dilution, nitrogen washout, or body plethysmography.

Question 4Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which factor is the principal determinant of systemic vascular resistance?

  1. Aortic compliance
  2. Arteriolar radius Correct answer.
  3. Capillary cross-sectional area
  4. Venous capacitance

Explanation

By the Poiseuille relationship, resistance varies inversely with the fourth power of vessel radius, so small changes in caliber cause large changes in resistance. Arterioles have the greatest combined resistance and are the main site of sympathetic control of systemic vascular resistance.

Question 5Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which hormone is stored and released by the posterior pituitary?

  1. Adrenocorticotropic hormone
  2. Thyroid-stimulating hormone
  3. Oxytocin Correct answer.
  4. Prolactin

Explanation

The posterior pituitary releases oxytocin and vasopressin, both synthesized in hypothalamic neurons and transported down axons for storage. The anterior pituitary produces and secretes the other hormones listed.

Question 6Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

In blood, the largest fraction of carbon dioxide is carried in which form?

  1. Bicarbonate Correct answer.
  2. Carbonic acid
  3. Dissolved carbon dioxide
  4. Carbaminohemoglobin

Explanation

Carbonic anhydrase in erythrocytes converts carbon dioxide and water to carbonic acid, which dissociates to bicarbonate and hydrogen ion; bicarbonate then leaves the cell in exchange for chloride. Roughly 70 percent of carbon dioxide travels as plasma bicarbonate, far more than the dissolved and carbamino fractions.

Question 7Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Closure of which structures generates the first heart sound?

  1. Closure of the aortic and pulmonic valves
  2. Closure of the mitral and tricuspid valves Correct answer.
  3. Rapid ventricular filling
  4. Opening of the mitral and tricuspid valves during the rapid filling phase

Explanation

As ventricular pressure rises above atrial pressure at the start of systole, the mitral and tricuspid leaflets snap shut and produce the first heart sound. Semilunar valve closure generates the second sound, and valve opening is normally silent.

Question 8Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which enzyme terminates acetylcholine action in the synaptic cleft of the neuromuscular junction?

  1. Choline acetyltransferase
  2. Monoamine oxidase
  3. Acetylcholinesterase Correct answer.
  4. Catechol-O-methyltransferase

Explanation

Acetylcholinesterase anchored in the synaptic basal lamina hydrolyzes acetylcholine to choline and acetate, promptly ending the end-plate potential. The choline is then recaptured by the nerve terminal for resynthesis.

Question 9Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Succinylcholine produces muscle paralysis through which mechanism?

  1. Persistent depolarization of the motor end plate Correct answer.
  2. Blockade of voltage-gated sodium channels in the motor axon
  3. Inhibition of presynaptic acetylcholine release
  4. Competitive antagonism at the postjunctional nicotinic receptor

Explanation

Succinylcholine is a depolarizing blocker: it binds nicotinic receptors and holds the end plate depolarized, so the surrounding muscle membrane accommodates and becomes unexcitable. Because it is not degraded at the receptor, paralysis persists until plasma butyrylcholinesterase hydrolyzes the drug.

Question 10Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which volatile anesthetic has the lowest blood-gas partition coefficient?

  1. Desflurane Correct answer.
  2. Halothane
  3. Isoflurane
  4. Sevoflurane

Explanation

The blood-gas partition coefficient expresses solubility in blood relative to gas; a lower value means less agent must be dissolved before the alveolar and arterial partial pressures rise. Desflurane, at about 0.42, is the least blood-soluble of the volatile agents and therefore has the fastest induction and emergence.

Question 11Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

In a region of alveolar hypoxia, which compensatory response reduces ventilation-perfusion mismatch?

  1. Systemic arteriolar vasodilation
  2. Hypoxic pulmonary vasoconstriction Correct answer.
  3. Increased surfactant secretion
  4. Bronchial smooth muscle relaxation

Explanation

Alveolar hypoxia constricts the adjacent pulmonary arterioles, diverting blood away from poorly ventilated lung units toward better-ventilated regions. This hypoxic pulmonary vasoconstriction is the lung's main mechanism for limiting shunt and preserving arterial oxygenation.

Question 12Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which change shifts the oxyhemoglobin dissociation curve to the right?

  1. Alkalosis
  2. Decreased arterial carbon dioxide tension due to hyperventilation
  3. Decreased body temperature
  4. Increased erythrocyte 2,3-diphosphoglycerate Correct answer.

Explanation

A rightward shift reduces hemoglobin affinity for oxygen and favors unloading at the tissues. It is produced by increased 2,3-diphosphoglycerate, acidosis, hypercapnia, and hyperthermia, all of which stabilize the deoxygenated conformation of hemoglobin.

Question 13Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Sodium is reabsorbed by the Na-K-2Cl cotransporter in a nephron segment that is impermeable to water. Which segment is this?

  1. Proximal convoluted tubule
  2. Thick ascending limb Correct answer.
  3. Descending limb of the loop of Henle
  4. Distal convoluted tubule

Explanation

The thick ascending limb reabsorbs sodium, potassium, and chloride via the Na-K-2Cl cotransporter while remaining water impermeable, so tubular fluid becomes dilute. This diluting segment is also the site of action of loop diuretics.

Question 14Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Ketamine produces amnesia and hypnosis primarily through which action?

  1. Antagonism of NMDA glutamate receptors Correct answer.
  2. Agonism at alpha-2 adrenergic receptors
  3. Potentiation of GABA-A receptor currents
  4. Agonism at mu opioid receptors

Explanation

Ketamine is a noncompetitive antagonist at the NMDA subtype of glutamate receptor, which accounts for its dissociative hypnotic state and its analgesic properties. This differs from most intravenous anesthetics, which act chiefly by enhancing GABA-A mediated inhibition.

Question 15Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A local anesthetic infiltrated into infected, acidic tissue often fails to produce an adequate block. Which mechanism best explains this?

  1. Tissue esterases rapidly degrade the drug at low pH
  2. Sodium channels become insensitive to all blockers in acidosis
  3. Less uncharged base is available to cross the nerve membrane Correct answer.
  4. Protein binding of the drug within the nerve membrane is reduced

Explanation

Local anesthetics are weak bases that must cross the lipid membrane in the uncharged form before binding the channel from inside as the charged cation. In acidic tissue the equilibrium shifts toward the charged form, so less drug reaches the binding site and the block is weak.

Question 16Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

An acute rise in mean arterial pressure occurs in a healthy adult. Which reflex response is expected?

  1. No change, because baroreceptors adapt within one cardiac cycle
  2. Bradycardia with venoconstriction and increased cardiac output
  3. Tachycardia with arteriolar vasoconstriction
  4. Bradycardia with arteriolar vasodilation Correct answer.

Explanation

Arterial baroreceptors in the carotid sinus and aortic arch increase their firing as pressure rises, which increases vagal outflow and withdraws sympathetic outflow. The result is bradycardia, reduced contractility, and arteriolar and venous dilation, which lowers pressure back toward the set point.

Question 17Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Malignant hyperthermia is most often caused by a mutation producing which effect?

  1. Decreased sensitivity of the contractile proteins to calcium
  2. Failure of acetylcholine binding at the motor end plate
  3. Uncontrolled calcium release from the sarcoplasmic reticulum Correct answer.
  4. Excessive calcium reuptake into the sarcoplasmic reticulum

Explanation

The classic defect is in the skeletal muscle ryanodine receptor, which releases calcium from the sarcoplasmic reticulum. Triggering agents such as volatile anesthetics and succinylcholine open the abnormal channel, producing sustained calcium efflux, intense muscle contraction, and a hypermetabolic state.

Question 18Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which condition typically produces a metabolic acidosis with a normal anion gap?

  1. Lactic acidosis
  2. Salicylate poisoning
  3. Diabetic ketoacidosis
  4. Diarrhea Correct answer.

Explanation

The anion gap reflects unmeasured anions; a normal gap acidosis results from loss of bicarbonate or retention of acid with chloride as the accompanying anion. Diarrhea causes gastrointestinal bicarbonate loss and a hyperchloremic acidosis without accumulating unmeasured anions.

Question 19Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

The cricothyroid muscle is innervated by which nerve?

  1. Internal branch of the superior laryngeal nerve
  2. Recurrent laryngeal nerve
  3. Hypoglossal nerve
  4. External branch of the superior laryngeal nerve Correct answer.

Explanation

The external branch of the superior laryngeal nerve supplies the cricothyroid, which tenses and lengthens the vocal cords. It runs close to the superior thyroid vessels, placing it at risk during thyroid surgery.

Question 20Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Glycopyrrolate is administered with neostigmine at the end of a case primarily to do which of the following?

  1. Block muscarinic effects such as bradycardia Correct answer.
  2. Prolong the duration of neuromuscular blockade
  3. Reverse residual opioid-induced respiratory depression
  4. Increase the rate of neostigmine metabolism

Explanation

Neostigmine increases acetylcholine at all cholinergic synapses, so muscarinic effects including bradycardia and secretions accompany reversal of blockade. Glycopyrrolate is an antimuscarinic that prevents these effects, and it is used because it does not cross the blood-brain barrier.

Question 21Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which opioid has a context-sensitive half-time that remains essentially constant regardless of how long the infusion has run?

  1. Remifentanil Correct answer.
  2. Fentanyl
  3. Morphine-6-glucuronide
  4. Sufentanil

Explanation

Remifentanil is cleared by nonspecific plasma and tissue esterases, so its offset depends on hydrolysis rather than on redistribution from saturated compartments. As a result, decreasing the infusion produces a rapid decline in effect even after prolonged administration.

Question 22Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Compared with lidocaine, bupivacaine is more potent primarily because of which property?

  1. A larger uncharged fraction at physiologic pH
  2. Greater lipid solubility and protein binding Correct answer.
  3. Slower systemic clearance from plasma
  4. Smaller molecular size allowing faster diffusion

Explanation

Potency within the amide local anesthetics tracks lipid solubility, which governs penetration of the nerve membrane, and protein binding, which keeps drug at the channel site. Bupivacaine ranks higher than lidocaine on both properties, so a smaller mass produces an equivalent block.

Question 23Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A 70-kg patient receives a 100-mg intravenous dose of a drug with a volume of distribution of 0.5 L/kg. Assuming immediate and complete mixing, what plasma concentration results?

  1. 14 mg/L
  2. 0.7 mg/L
  3. 5.7 mg/L
  4. 2.9 mg/L Correct answer.

Explanation

Volume of distribution is 0.5 L/kg multiplied by 70 kg, or 35 L. Dividing the 100-mg dose by 35 L gives approximately 2.9 mg/L as the predicted plasma concentration.

Question 24Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A patient with euvolemic hyponatremia is diagnosed with syndrome of inappropriate antidiuretic hormone. Which laboratory pattern is expected?

  1. Urine osmolarity above 100 mOsm/kg with urine sodium below 20 mmol/L
  2. Urine osmolarity below 100 mOsm/kg with urine sodium below 20 mmol/L
  3. Urine osmolarity above 100 mOsm/kg with urine sodium above 40 mmol/L Correct answer.
  4. Urine osmolarity below 100 mOsm/kg with urine sodium above 40 mmol/L

Explanation

Inappropriate antidiuretic hormone action concentrates the urine despite plasma hypotonicity, so urine osmolarity exceeds 100 mOsm/kg. Volume expansion from water retention also promotes sodium excretion, so urine sodium is generally above 40 mmol/L in the euvolemic patient.

Question 25Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Normal adult cerebrospinal fluid production by the choroid plexus is closest to which rate?

  1. 150 mL/day
  2. 250 mL/day
  3. 500 mL/day Correct answer.
  4. 50 mL/day

Explanation

The choroid plexus produces cerebrospinal fluid at roughly 0.3 to 0.4 mL per minute, which is about 500 mL per day. Because total cerebrospinal fluid volume is only about 150 mL, the entire volume turns over several times daily.

Question 26Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which opioid is most likely to produce chest wall rigidity when administered as a rapid intravenous bolus?

  1. Fentanyl Correct answer.
  2. Morphine
  3. Hydromorphone
  4. Methadone

Explanation

Rapid bolus administration of potent, highly lipophilic opioids such as fentanyl can produce centrally mediated rigidity of the chest wall and vocal cords. The effect is dose- and speed-dependent and is treated or prevented with neuromuscular blockade, opioid antagonism, or slower administration. Less lipophilic opioids given at usual induction doses rarely cause this.

Question 27Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Motor innervation of the diaphragm is provided by which nerve?

  1. Phrenic nerve Correct answer.
  2. Intercostal nerves
  3. Long thoracic nerve
  4. Vagus nerve

Explanation

The phrenic nerve arises from cervical roots C3 through C5 and supplies the sole motor innervation to each hemidiaphragm. Its cervical origin explains why the diaphragm can continue to function after lower cervical or thoracic spinal cord injury. Thoracic spinal levels instead supply the intercostal and abdominal muscles of respiration.

Question 28Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A patient receiving positive-pressure ventilation has an acute rise in intrathoracic pressure. Which hemodynamic change is expected?

  1. Decreased venous return and decreased cardiac output Correct answer.
  2. Increased venous return and increased cardiac output
  3. Increased left atrial preload with a rise in right atrial pressure
  4. No change in right atrial pressure or ventricular filling

Explanation

Raising intrathoracic pressure raises right atrial pressure and reduces the pressure gradient from the systemic veins to the right heart, so venous return falls. With less right ventricular filling, left ventricular output and systemic blood pressure decrease. This mechanism explains the hypotension that can follow high airway pressures or a sudden pneumothorax.

Question 29Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A patient with a gastric outlet obstruction has repeated large-volume emesis. Which acid-base and electrolyte pattern is most likely?

  1. Metabolic alkalosis with hyperkalemia and hyperchloremia
  2. Metabolic acidosis with hypokalemia and hypochloremia
  3. Respiratory alkalosis with hypochloremia and hypokalemia
  4. Metabolic alkalosis with hypokalemia and hypochloremia Correct answer.

Explanation

Gastric fluid is rich in hydrochloric acid, so repeated vomiting removes hydrogen and chloride ions and generates a hypochloremic metabolic alkalosis. Volume depletion activates the renin-angiotensin-aldosterone axis, promoting renal potassium and hydrogen excretion. The combination produces hypokalemia with paradoxical aciduria.

Question 30Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

Which nondepolarizing neuromuscular blocker is degraded by Hofmann elimination, making its duration largely independent of hepatic and renal function?

  1. Vecuronium
  2. Rocuronium
  3. Cisatracurium Correct answer.
  4. Pancuronium

Explanation

Cisatracurium undergoes Hofmann elimination, a spontaneous degradation in plasma that depends on pH and temperature rather than on liver or kidney function; it is also ester-hydrolyzed to a minor degree. This makes its duration reliable in organ failure, though hypothermia and acidosis slow the process. The aminosteroid agents depend mainly on hepatic uptake and biliary or renal excretion.

Question 31Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

In a healthy awake adult, which factor most strongly influences cerebral blood flow?

  1. Arterial carbon dioxide tension Correct answer.
  2. Arterial oxygen tension
  3. Hemoglobin concentration
  4. Mean arterial pressure within the autoregulatory range

Explanation

Carbon dioxide is the most potent direct regulator of cerebral arteriolar tone, with hypercapnia producing vasodilation and hypocapnia producing vasoconstriction. Cerebral blood flow changes by roughly 2 to 4 percent for each 1 mmHg change in arterial carbon dioxide tension. Arterial oxygen tension and mean arterial pressure matter mainly outside their normal ranges.

Question 32Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A drug is cleared by the liver with a high extraction ratio. If hepatic blood flow falls by half while intrinsic clearance is unchanged, which pair of changes is expected?

  1. Systemic clearance falls and oral bioavailability decreases Correct answer.
  2. Systemic clearance falls and oral bioavailability increases
  3. Systemic clearance increases and oral bioavailability decreases
  4. Systemic clearance is unchanged and oral bioavailability is unchanged

Explanation

For a high-extraction drug, hepatic clearance is flow-limited, so systemic clearance tracks hepatic blood flow and falls when flow falls. Extraction fraction equals intrinsic clearance divided by the sum of intrinsic clearance and flow, so a lower flow raises extraction and leaves less drug escaping first-pass metabolism. Oral bioavailability therefore decreases as well.

Question 33Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A patient has a large left-to-right intracardiac shunt through a ventricular septal defect. Which best explains why systemic arterial oxygenation is largely preserved?

  1. Compensatory hyperventilation restores arterial oxygen content
  2. The shunt fraction is too small relative to pulmonary blood flow to matter
  3. Bronchial circulation absorbs the additional pulmonary blood flow
  4. Shunted blood is already oxygenated before it enters the systemic circulation Correct answer.

Explanation

In a left-to-right shunt, oxygenated blood from the left heart recirculates through the pulmonary circuit and returns to the systemic circulation without mixing with desaturated blood. Arterial oxygen content therefore stays near normal, although the pulmonary circulation is volume overloaded. Systemic hypoxemia from shunting requires a right-to-left pathway that bypasses the lungs.

Question 34Basic Sciences (Anatomy, Physiology, Pathophysiology, Pharmacology)

A patient has a plasma antidiuretic hormone concentration that is markedly elevated and a urine osmolality of 1200 mOsm/kg. At which nephron site does the hormone produce the water permeability change responsible for this concentrated urine?

  1. Descending limb of the loop of Henle
  2. Collecting duct Correct answer.
  3. Proximal convoluted tubule
  4. Thick ascending limb of the loop of Henle

Explanation

Antidiuretic hormone binds V2 receptors on principal cells of the collecting duct, raising intracellular cAMP and triggering insertion of aquaporin-2 water channels into the apical membrane. Water then moves down the medullary osmotic gradient into the hypertonic interstitium, concentrating the urine. Water movement in the proximal tubule and descending limb is constitutive and not regulated by ADH.

Question 35Anesthesia Equipment, Instrumentation, and Technology

Pulse oximetry estimates arterial oxygen saturation by applying which principle?

  1. Raman scattering of laser light
  2. Beer-Lambert law Correct answer.
  3. Doppler shift of ultrasound
  4. Fick principle with inert gas

Explanation

Pulse oximetry compares light absorption at two wavelengths using the Beer-Lambert law. The pulsatile component represents arterial blood, while the nonpulsatile component is subtracted as baseline.

Question 36Anesthesia Equipment, Instrumentation, and Technology

What cuff pressure is recommended for an adult endotracheal tube to minimize mucosal ischemia?

  1. 5 to 10 cm H2O
  2. 60 to 70 cm H2O
  3. 40 to 50 cm H2O
  4. 20 to 30 cm H2O Correct answer.

Explanation

Endotracheal tube cuff pressure should be maintained at 20 to 30 cm H2O. Pressures above 30 cm H2O can exceed tracheal capillary perfusion pressure and cause mucosal ischemia.

Question 37Anesthesia Equipment, Instrumentation, and Technology

An oscillometric blood pressure monitor determines blood pressure by detecting:

  1. pulse wave velocity in the radial artery
  2. cuff pressure oscillations Correct answer.
  3. Korotkoff sounds with a microphone
  4. Doppler frequency shifts in the brachial artery

Explanation

Oscillometric monitors inflate the cuff and detect pressure oscillations produced by arterial pulsation. The point of maximal oscillation corresponds to mean arterial pressure, and systolic and diastolic values are derived.

Question 38Anesthesia Equipment, Instrumentation, and Technology

The primary function of a PEEP valve in a breathing circuit is to:

  1. limit peak inspiratory pressure
  2. measure exhaled tidal volume
  3. prevent rebreathing of carbon dioxide
  4. hold positive end-expiratory pressure Correct answer.

Explanation

A PEEP valve adds resistance during exhalation, maintaining positive end-expiratory pressure. This helps keep alveoli open and improves oxygenation.

Question 39Anesthesia Equipment, Instrumentation, and Technology

The main advantage of ultrasound guidance for peripheral nerve blockade is:

  1. replacement for sterile technique
  2. direct needle and spread visualization Correct answer.
  3. guaranteed block success
  4. elimination of local anesthetic toxicity

Explanation

Ultrasound allows real-time visualization of the needle tip, nerve structures, and local anesthetic spread. This can improve safety and block quality but does not guarantee success.

Question 40Anesthesia Equipment, Instrumentation, and Technology

Forced-air warming blankets primarily transfer heat by:

  1. radiation
  2. convection Correct answer.
  3. conduction
  4. evaporation

Explanation

Forced-air warmers blow warmed air over the patient's skin, transferring heat primarily by convection. Conduction and radiation contribute less.

Question 41Anesthesia Equipment, Instrumentation, and Technology

A Miller laryngoscope blade is best described as:

  1. a curved blade that sits in the vallecula
  2. a blade with a built-in camera
  3. a blade used only for nasal intubation
  4. a straight blade that lifts the epiglottis Correct answer.

Explanation

The Miller blade is a straight blade that is placed beneath the epiglottis and lifts it to expose the glottis. The Macintosh blade is curved and sits in the vallecula.

Question 42Anesthesia Equipment, Instrumentation, and Technology

In the United States, an oxygen cylinder is color-coded:

  1. brown
  2. gray
  3. black
  4. green Correct answer.

Explanation

In the US color-coding system, oxygen cylinders are green. Nitrous oxide is blue, carbon dioxide is gray, and medical air is yellow.

Question 43Anesthesia Equipment, Instrumentation, and Technology

On a normal capnogram, phase III (the plateau) represents:

  1. inspiratory baseline
  2. dead-space gas
  3. alveolar gas Correct answer.
  4. cardiac oscillations

Explanation

Phase III is the alveolar plateau, representing gas that has equilibrated with alveolar CO2. Phase I is inspired dead-space gas and phase II is the transition.

Question 44Anesthesia Equipment, Instrumentation, and Technology

A variable-bypass vaporizer controls anesthetic concentration by:

  1. heating liquid agent to a fixed boiling point
  2. injecting liquid agent directly into the circuit
  3. splitting flow around the vaporizing chamber Correct answer.
  4. measuring agent concentration with a galvanic cell

Explanation

In a variable-bypass vaporizer, fresh gas is divided between the vaporizing chamber and a bypass channel. The ratio determines the final agent concentration.

Question 45Anesthesia Equipment, Instrumentation, and Technology

The reaction of carbon dioxide with soda lime produces:

  1. calcium carbonate and water Correct answer.
  2. carbon monoxide and hydrogen
  3. sodium chloride and oxygen
  4. calcium hydroxide and nitrogen

Explanation

Soda lime absorbs CO2 through a reaction with calcium hydroxide, forming calcium carbonate and water. The reaction is exothermic.

Question 46Anesthesia Equipment, Instrumentation, and Technology

The anesthesia waste-gas scavenging system is designed to:

  1. humidify inspired gases
  2. recycle exhaled anesthetic agent
  3. filter bacteria from the circuit
  4. vent excess circuit gas outdoors Correct answer.

Explanation

The scavenging system collects excess anesthetic gas from the breathing circuit and vents it outside or to a waste-gas system. It protects operating room personnel from occupational exposure.

Question 47Anesthesia Equipment, Instrumentation, and Technology

The oxygen failure safety device on an anesthesia machine is designed to:

  1. increase oxygen flow to compensate for a leak
  2. stop nitrous oxide when oxygen pressure falls Correct answer.
  3. open the pressure-limiting valve automatically
  4. sound an alarm only when the pipeline disconnects

Explanation

The oxygen failure safety device responds to low oxygen supply pressure by shutting off or reducing nitrous oxide flow. It does not measure actual inspired oxygen concentration.

Question 48Anesthesia Equipment, Instrumentation, and Technology

In pressure-controlled ventilation, which variable is set by the clinician?

  1. tidal volume
  2. inspiratory pressure Correct answer.
  3. expiratory time only
  4. peak flow rate

Explanation

Pressure-controlled ventilation sets a target inspiratory pressure; tidal volume then depends on compliance and resistance. Volume-controlled ventilation sets tidal volume directly.

Question 49Anesthesia Equipment, Instrumentation, and Technology

A slow, undulating baseline on the ECG that varies with the respiratory cycle is most often caused by:

  1. a loose electrode
  2. electrocautery interference
  3. 60-Hz electrical interference
  4. respiratory variation Correct answer.

Explanation

Respiratory variation causes the cardiac electrical axis and electrode contact to change with breathing, producing a slow undulating baseline. Electrocautery and 60-Hz interference cause high-frequency noise.

Question 50Anesthesia Equipment, Instrumentation, and Technology

A train-of-four ratio greater than 0.9 after neuromuscular blockade indicates:

  1. cuff leak
  2. adequate recovery Correct answer.
  3. deep blockade
  4. need for more relaxant

Explanation

A train-of-four ratio above 0.9 indicates adequate recovery from nondepolarizing neuromuscular blockade. Ratios below 0.9 suggest residual blockade.