I85PREP
⌘ K
ExAC study materials
ExAC study resources

ExAC practice questions

One question at a time. Build your ExAC understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Airway Management

A patient with no predictors of difficult mask ventilation is being preoxygenated for rapid sequence intubation. Which technique best describes an appropriate two-person mask technique when a second operator is available?

  1. One operator performs jaw thrust while the second applies cricoid pressure
  2. One operator holds the mask and bag with one hand while the second suctions the oropharynx
  3. One operator holds the mask with both hands while the second squeezes the bag and provides jaw thrust Correct answer.
  4. One operator squeezes the bag with one hand while the second monitors the capnograph

Explanation

The two-person (two-handed) mask technique separates the tasks of airway sealing and ventilation. One operator uses both hands to hold the mask and perform jaw thrust, while the second operator delivers the breath with the self-inflating bag. This improves seal and reduces gastric insufflation when mask ventilation is difficult.

Question 2Airway Management

Which finding most reliably confirms correct placement of an endotracheal tube after intubation?

  1. Symmetric chest rise on auscultation
  2. Sustained waveform capnography with each breath Correct answer.
  3. Auscultation of equal breath sounds over both lung fields
  4. Improved oxygen saturation on the pulse oximeter

Explanation

Sustained exhaled carbon dioxide detected by waveform capnography is the most reliable confirmation of tracheal tube placement. Clinical signs such as chest rise, breath sounds, and oxygen saturation can be misleading, particularly in esophageal intubation or low-flow states. Capnography should be used continuously, not only at the moment of intubation.

Question 3Airway Management

During direct laryngoscopy, which maneuver is performed to improve the view of the glottis when the laryngoscope blade is correctly positioned in the vallecula?

  1. Lifting the laryngoscope along the axis of the handle without levering on the teeth Correct answer.
  2. Advancing the blade into the esophagus and withdrawing slightly
  3. Rotating the blade 90 degrees to sweep the tongue aside
  4. Applying cricoid pressure with the right hand

Explanation

The laryngoscope is used as a lever-free lifting tool, applying force along the axis of the handle to displace the tongue and mandible and expose the glottis. Levering on the upper teeth risks dental damage and does not improve the view. Correct blade placement in the vallecula with axial lift is the standard technique.

Question 4Airway Management

Which device is designed to provide ventilation through a supraglottic airway while allowing passage of an endotracheal tube through its lumen?

  1. Classic laryngeal mask airway
  2. Intubating laryngeal mask airway Correct answer.
  3. Esophageal-tracheal combitube
  4. Nasopharyngeal airway

Explanation

The intubating laryngeal mask airway is a supraglottic device with a wide, rigid airway tube that permits blind or fiberoptic-guided passage of an endotracheal tube through its lumen. The classic laryngeal mask airway does not accommodate an endotracheal tube in the same way. This makes the intubating laryngeal mask a rescue option in difficult airway algorithms.

Question 5Airway Management

A patient is being ventilated with a bag-valve-mask device and the reservoir bag collapses completely with each breath while the oxygen saturation falls. What is the most likely cause?

  1. Excessive oxygen flow into the reservoir
  2. A leak in the mask seal or a disconnected circuit Correct answer.
  3. High compliance of the patient's lungs
  4. Overinflation of the endotracheal tube cuff

Explanation

Collapse of the reservoir bag during ventilation indicates that the delivered volume is being lost or that the circuit is not being supplied adequately. A mask leak or disconnection is a common cause and should be checked first. High oxygen flow would keep the reservoir full rather than collapsing it.

Question 6Airway Management

Which anatomical structure is the primary target for needle cricothyrotomy in an adult?

  1. Cricotracheal ligament
  2. Cricothyroid membrane Correct answer.
  3. First tracheal ring
  4. Thyrohyoid membrane

Explanation

The cricothyroid membrane lies between the thyroid cartilage and the cricoid cartilage and is the standard site for emergency needle or surgical cricothyrotomy in adults. It is relatively superficial and avascular compared with other anterior neck structures. The thyrohyoid membrane is higher and not the standard access point.

Question 7Airway Management

Which patient position is recommended for preoxygenation and induction in an obese patient with a suspected difficult airway?

  1. Supine with the head flat
  2. Trendelenburg position
  3. Prone position
  4. Ramped position with the ear canal level with the sternal notch Correct answer.

Explanation

A ramped position aligns the external auditory meatus with the sternal notch, improving functional residual capacity and laryngoscopic view in obese patients. This position reduces the risk of rapid desaturation during apnea. The supine flat position worsens respiratory mechanics in obesity.

Question 8Airway Management

What is the primary purpose of applying cricoid pressure during rapid sequence induction?

  1. To facilitate passage of a supraglottic airway
  2. To prevent laryngospasm during induction
  3. To reduce the risk of gastric insufflation and aspiration Correct answer.
  4. To improve the view of the vocal cords

Explanation

Cricoid pressure compresses the esophagus against the cricoid cartilage to reduce the risk of passive regurgitation and aspiration during rapid sequence induction. It is applied before loss of consciousness and released after the airway is secured. It does not improve glottic view or prevent laryngospasm.

Question 9Airway Management

A patient with a known difficult airway is being managed with an awake fiberoptic intubation. Which preparation is most important before advancing the scope?

  1. Administration of a neuromuscular blocking agent
  2. Rapid sequence induction with cricoid pressure
  3. Adequate topical anesthesia and sedation with maintenance of spontaneous ventilation Correct answer.
  4. Deep general anesthesia with apnea

Explanation

Awake fiberoptic intubation relies on adequate topical anesthesia of the airway and light sedation while the patient maintains spontaneous ventilation. Paralysis or deep anesthesia with apnea removes the safety margin in a patient with a known difficult airway. The technique allows the patient to breathe and protect the airway throughout.

Question 10Airway Management

During laryngoscopy, a grade 3 Cormack-Lehane view is obtained. Which maneuver is most appropriate to attempt to improve the view before resorting to a rescue device?

  1. External laryngeal manipulation with backward-upward-rightward pressure Correct answer.
  2. Increasing the depth of anesthesia only
  3. Removing the laryngoscope and reinserting it without change
  4. Applying cricoid pressure with the left hand

Explanation

Backward-upward-rightward pressure on the thyroid cartilage often improves the glottic view by aligning the laryngeal axis with the line of sight. It should be applied by an assistant while the laryngoscopist observes the effect. If the view remains poor, alternative devices or techniques should be considered.

Question 11Airway Management

Which statement best describes the role of a supraglottic airway in a difficult airway algorithm?

  1. It serves as a rescue ventilation device and a conduit for intubation when mask ventilation or intubation fails Correct answer.
  2. It is contraindicated in all patients with a full stomach
  3. It replaces the need for capnography after placement
  4. It is the first-line device for all patients requiring intubation

Explanation

Supraglottic airways are positioned in difficult airway algorithms as rescue devices for ventilation and as conduits for intubation when mask ventilation or tracheal intubation fails. They do not replace capnography, which should still be used to confirm ventilation. Their use in patients with a full stomach requires careful risk assessment rather than an absolute contraindication.

Question 12Airway Management

A patient desaturates rapidly during apnea after induction. Which preoxygenation strategy most effectively prolongs the safe apnea time?

  1. Nasal cannula at 2 L/min for 5 minutes
  2. Supplemental oxygen at 6 L/min by simple face mask for 1 minute
  3. Room air breathing for 10 minutes
  4. Tight-fitting mask with 100% oxygen for 3 to 5 minutes or eight vital capacity breaths Correct answer.

Explanation

Preoxygenation with a tight-fitting mask delivering 100% oxygen for 3 to 5 minutes, or eight vital capacity breaths, replaces nitrogen in the functional residual capacity and prolongs the safe apnea time. Low-flow nasal cannula or short simple mask oxygen does not achieve adequate denitrogenation. Effective preoxygenation is a key step in difficult airway management.

Question 13Airway Management

Which finding suggests that a supraglottic airway is not adequately seated and requires repositioning?

  1. An oropharyngeal leak pressure of 25 cm H2O
  2. Persistent audible leak with each ventilation and poor chest rise Correct answer.
  3. A sustained end-tidal carbon dioxide waveform
  4. Bilateral chest movement during ventilation

Explanation

A persistent audible leak with poor chest rise indicates inadequate seating or malposition of a supraglottic airway. Repositioning or an alternative device should be considered. Adequate seating is suggested by a sustained capnography waveform and acceptable leak pressure.

Question 14Airway Management

A patient with a suspected cervical spine injury requires emergency airway management. Which approach best balances spinal protection with airway control?

  1. Manual in-line stabilization with video laryngoscopy or fiberoptic intubation Correct answer.
  2. Routine direct laryngoscopy with full neck extension
  3. Blind nasotracheal intubation without stabilization
  4. Cricothyrotomy as the first-line approach

Explanation

Manual in-line stabilization limits cervical movement while allowing airway management. Video laryngoscopy or fiberoptic techniques can improve the view without requiring neck extension. Blind nasal intubation and routine extension increase the risk of spinal injury and are not preferred.

Question 15Airway Management

Which parameter is used to assess the adequacy of bag-valve-mask ventilation in an adult?

  1. Visible chest rise with each breath and a waveform capnography tracing Correct answer.
  2. Palpation of the radial pulse
  3. Auscultation of the epigastrium only
  4. Measurement of the cuff pressure

Explanation

Adequate bag-valve-mask ventilation is assessed by visible chest rise and a sustained waveform capnography tracing. These signs indicate that gas is reaching the lungs. Radial pulse and cuff pressure are unrelated to ventilation adequacy, and epigastric auscultation alone may reflect gastric insufflation.

Question 16Airway Management

In a patient with a predicted difficult airway, which strategy best follows current difficult airway principles before induction?

  1. Proceeding directly to rapid sequence induction without preparation
  2. Avoiding any discussion of backup techniques with the team
  3. Administering a paralytic agent before assessing the airway
  4. Formulating a primary plan, a rescue plan, and a plan for failure to intubate and ventilate Correct answer.

Explanation

Current difficult airway management emphasizes advance planning with a primary strategy, a rescue strategy, and a plan for the cannot-intubate cannot-ventilate scenario. Team briefing and equipment preparation are essential. Proceeding without a plan or paralysing before assessment increases risk.

Question 17Airway Management

A patient with an anticipated difficult airway is being prepared for awake tracheal intubation. Which combination of topical anesthetics is commonly used to anesthetize the nasal and pharyngeal passages?

  1. Lidocaine with a vasoconstrictor applied to the nasal mucosa and lidocaine sprayed to the pharynx Correct answer.
  2. Neuromuscular blockade with rocuronium only
  3. General anesthesia with sevoflurane only
  4. Bupivacaine given intravenously only

Explanation

Topical lidocaine, often with a vasoconstrictor such as phenylephrine or oxymetazoline in the nose, anesthetizes and decongests the nasal passages. Lidocaine spray or gargle anesthetizes the pharynx. This preparation allows the awake patient to tolerate the scope while maintaining spontaneous ventilation.

Question 18Airway Management

Which of the following best describes the purpose of a bougie (tracheal tube introducer) during intubation?

  1. To guide an endotracheal tube into the trachea when the glottic view is limited Correct answer.
  2. To provide oxygen insufflation directly into the trachea
  3. To secure the tube to the patient's face
  4. To measure the depth of the endotracheal tube

Explanation

A bougie is a flexible introducer that can be passed through the glottis when the view is limited and then used to guide an endotracheal tube into the trachea. It is not an oxygen delivery device or a measuring tool. Its use is a recognized rescue technique in difficult intubation.

Question 19Airway Management

A patient's oxygen saturation is 88% on 100% oxygen by nonrebreather mask before induction. Which action is most appropriate before proceeding with intubation?

  1. Optimize oxygenation with positive pressure preoxygenation and consider delaying induction until saturation improves Correct answer.
  2. Administer a neuromuscular blocking agent to improve oxygenation
  3. Proceed immediately with induction to secure the airway
  4. Reduce the oxygen flow to 2 L/min

Explanation

Hypoxemia before induction identifies a patient with limited oxygen reserve and high risk of rapid desaturation. Positive pressure preoxygenation, positioning, and correction of reversible causes should be attempted before induction. Proceeding immediately or reducing oxygen flow would worsen the situation.

Question 20Airway Management

Which of the following is a recognized advantage of video laryngoscopy over direct laryngoscopy in a patient with a difficult airway?

  1. It improves glottic visualization without requiring alignment of the oral, pharyngeal, and laryngeal axes Correct answer.
  2. It guarantees successful intubation on the first attempt
  3. It eliminates the need for a backup airway plan
  4. It removes the need for neuromuscular blockade

Explanation

Video laryngoscopy uses a camera at the blade tip to display the glottis on a screen, improving visualization without requiring the direct line of sight needed for direct laryngoscopy. It does not guarantee success or eliminate the need for a backup plan. Neuromuscular blockade is still usually required.

Question 21Airway Management

A patient requires emergency airway management after a massive facial trauma with bleeding into the oropharynx. Which approach is most appropriate as the initial step?

  1. Suctioning and preparation for a surgical airway if intubation fails Correct answer.
  2. Immediate cricothyrotomy without airway assessment
  3. Awake fiberoptic intubation through the bleeding oropharynx
  4. Blind nasotracheal intubation

Explanation

In massive facial trauma with hemorrhage, clearing the airway with suction and preparing for a surgical airway if intubation fails is the priority. Blind nasal intubation is contraindicated with suspected basal skull fracture and may worsen bleeding. Cricothyrotomy is a rescue option rather than the initial step.

Question 22Airway Management

A patient with a known difficult airway has failed mask ventilation and failed supraglottic airway placement after induction. According to difficult airway algorithms, what is the next priority?

  1. Extubate and awaken the patient immediately
  2. Administer additional neuromuscular blockade and wait
  3. Continue attempts at direct laryngoscopy without change
  4. Proceed to emergency invasive airway access such as cricothyrotomy Correct answer.

Explanation

When both mask ventilation and supraglottic airway placement fail, the patient is in a cannot-intubate cannot-ventilate situation. Emergency invasive airway access, such as surgical cricothyrotomy, is the next priority. Continued attempts at the same technique delay definitive management and increase hypoxia.

Question 23Airway Management

Which statement best describes the role of apneic oxygenation during prolonged intubation attempts?

  1. It maintains oxygen delivery to the lungs during apnea through a nasal cannula with the airway open Correct answer.
  2. It replaces the need for preoxygenation
  3. It eliminates the need for bag-valve-mask ventilation
  4. It prevents hypercapnia during apnea

Explanation

Apneic oxygenation delivers oxygen through a nasal cannula while the airway remains open, allowing oxygen to enter the lungs by mass flow and diffusion during apnea. It prolongs the safe apnea time but does not remove carbon dioxide or replace preoxygenation. It is an adjunct rather than a substitute for ventilation.

Question 24Airway Management

A patient with a suspected difficult airway is being managed with a supraglottic airway as a conduit for intubation. Which factor most increases the likelihood of successful tracheal tube passage through the device?

  1. Removal of the device before tube passage
  2. A smaller-sized supraglottic airway
  3. Adequate depth of anesthesia and neuromuscular blockade Correct answer.
  4. A rigid stylet passed beyond the distal tip of the tube

Explanation

Adequate anesthesia and neuromuscular blockade optimize conditions for tube passage through a supraglottic airway by relaxing the airway and suppressing reflexes. A rigid stylet can help but must be used with caution and is not the primary determinant. Device removal before tube passage defeats the purpose of using it as a conduit.

Question 25Airway Management

Which physiological change explains the more rapid onset of hypoxemia in an obese patient during apnea compared with a non-obese patient?

  1. Higher hemoglobin concentration and increased oxygen carrying capacity
  2. Reduced functional residual capacity and increased oxygen consumption relative to lung volume Correct answer.
  3. Increased tidal volume and reduced dead space
  4. Increased functional residual capacity and reduced oxygen consumption

Explanation

Obesity reduces functional residual capacity and increases oxygen consumption relative to lung volume, so oxygen reserves are depleted faster during apnea. This explains the more rapid desaturation observed in obese patients. Preoxygenation and positioning are especially important in this population.

Question 26Airway Management

During an airway assessment, which measurement is used in the modified Mallampati classification to grade oropharyngeal visibility?

  1. The interincisor gap measured with the mouth maximally open
  2. The degree of mandibular protrusion assessed with the jaw thrust forward
  3. The visible structures of the oropharynx with the patient seated, tongue protruded, and no phonation Correct answer.
  4. The thyromental distance measured with the neck fully extended

Explanation

The modified Mallampati score grades what can be seen in the oropharynx when the patient sits upright, protrudes the tongue, and does not phonate. Class I shows soft palate, fauces, uvula, and pillars; class IV shows only the hard palate. The other measurements are separate airway predictors, not components of this classification.

Question 27Airway Management

A 70 kg adult is being preoxygenated before induction. Which endpoint best confirms that preoxygenation has achieved an adequate pulmonary oxygen reserve?

  1. A respiratory rate below 12 breaths per minute
  2. End-tidal carbon dioxide below 35 mmHg
  3. End-tidal oxygen fraction above 0.90 Correct answer.
  4. Oxygen saturation of 100% on the pulse oximeter

Explanation

End-tidal oxygen fraction reflects the oxygen concentration actually achieved in the alveoli and rises above 0.90 when denitrogenation is adequate. Pulse oximetry can read 100% while significant nitrogen remains in the lungs, so it is an insensitive endpoint. End-tidal carbon dioxide and respiratory rate do not quantify the oxygen reserve.

Question 28Airway Management

Which structure is palpated as the key landmark before performing a surgical airway at the level of the cricothyroid membrane?

  1. The body of the hyoid bone, with the membrane located just inferior to it
  2. The sternal notch, with the membrane located just superior to it
  3. The first tracheal ring, with the membrane located just superior to it
  4. The prominence of the thyroid cartilage, with the membrane located just inferior to it Correct answer.

Explanation

The cricothyroid membrane lies between the lower border of the thyroid cartilage and the upper border of the cricoid cartilage. Palpating the thyroid prominence and sliding a finger caudally identifies the membrane in most adults. The hyoid, sternal notch, and tracheal rings are either too cephalad or too caudad to mark this site.

Question 29Airway Management

Which statement correctly describes the purpose of the 7-8 rule when selecting an endotracheal tube for oral intubation in an adult?

  1. A tube with an internal diameter of 7-8 mm is generally suitable for most adult women and men, respectively Correct answer.
  2. A tube should be inserted 7-8 cm beyond the vocal cords in every adult
  3. A tube should be secured 7-8 cm from the incisors in every adult
  4. A cuff should be inflated with 7-8 mL of air in every adult

Explanation

The 7-8 rule refers to internal diameter: approximately 7.0 mm for many adult women and 8.0 mm for many adult men. Larger diameters reduce airway resistance and facilitate suctioning and bronchoscopy. Depth of insertion and cuff volume are separate considerations and vary with patient size.

Question 30Airway Management

A patient with a full stomach requires rapid sequence intubation. Which combination best reflects the standard pharmacologic approach?

  1. A slowly titrated induction agent followed by a neuromuscular blocker after loss of consciousness is confirmed
  2. A rapidly acting induction agent followed immediately by a neuromuscular blocker, with cricoid pressure applied according to local protocol Correct answer.
  3. A neuromuscular blocker given first, followed by an induction agent once paralysis is established
  4. An induction agent alone, with the airway secured without neuromuscular blockade

Explanation

Rapid sequence intubation gives a rapidly acting induction agent and a fast-onset neuromuscular blocker in close succession to minimize the interval before intubation. This shortens the period during which the patient is at risk of aspiration. Cricoid pressure is applied according to local protocol, since its routine use is debated.

Question 31Airway Management

A patient with a supraglottic airway in place shows a rising end-tidal carbon dioxide waveform that is present but progressively smaller with each breath. What does this most likely indicate?

  1. Progressive leak or partial obstruction around the device Correct answer.
  2. Adequate ventilation that requires no intervention
  3. Complete loss of the airway with esophageal placement
  4. Hyperventilation caused by an excessive respiratory rate

Explanation

A present but shrinking capnography waveform indicates that some gas exchange is occurring while ventilation is becoming less effective. This pattern suggests a leak or partial obstruction rather than complete failure, which would produce no waveform at all. The device should be reassessed and repositioned or exchanged.

Question 32Airway Management

Which statement best describes the role of the gum elastic bougie when direct laryngoscopy reveals a Cormack-Lehane grade 3 view?

  1. It is used to suction secretions from the oropharynx before a second laryngoscopy attempt
  2. It is placed in the esophagus to decompress the stomach after failed intubation
  3. It is passed blindly or with partial glottic visualization and then used to railroad an endotracheal tube into the trachea Correct answer.
  4. It is inserted through the working channel of a flexible bronchoscope to stiffen the scope

Explanation

A bougie is a flexible introducer that can be advanced through a partially visualized larynx when the cords cannot be seen directly. Tracheal placement is suggested by palpable clicks over the anterior tracheal rings and by hold-up at the carina. The tube is then slid over the introducer into the trachea.

Question 33Airway Management

A patient is being ventilated by bag-valve-mask after induction, and the capnography trace is absent while oxygen saturation is falling. Which action is the most appropriate first step?

  1. Deepen the anesthetic with an additional induction agent
  2. Increase the oxygen flow rate on the anesthesia machine
  3. Reposition the head and mask, then reassess the capnography trace Correct answer.
  4. Administer a second dose of neuromuscular blocker

Explanation

Absent capnography during bag-valve-mask ventilation suggests that exhaled gas is not reaching the monitor, most often because of mask leak, obstruction, or malposition. The first response is to optimize head position and mask seal and to reassess. Escalating drugs without confirming ventilation delays correction of the underlying problem.

Question 34Airway Management

A trauma patient arrives with stridor, hoarseness, and subcutaneous emphysema after a blunt anterior neck injury. Which airway concern is most important when planning management?

  1. Isolated nasal obstruction requiring a nasopharyngeal airway
  2. Isolated dental injury requiring tooth stabilization before intubation
  3. Tracheal or laryngeal disruption that may worsen with positive-pressure ventilation or blind instrumentation Correct answer.
  4. Cervical muscle spasm requiring muscle relaxation before any airway manipulation

Explanation

Blunt anterior neck trauma can disrupt the larynx or trachea, and the resulting injury may be worsened by positive-pressure ventilation or by passing an instrument blindly. Airway management should be planned with the most experienced operator and often involves awake techniques or surgical backup. The other findings do not match this presentation.

Question 35Airway Management

A patient with a known difficult airway is scheduled for elective surgery. Which action best reflects current difficult airway principles before induction?

  1. Cancel the case until a definitive airway is placed under general anesthesia
  2. Formulate a primary and backup plan, share it with the team, and confirm availability of the equipment and personnel it requires Correct answer.
  3. Rely on the most recent previous intubation record as proof of ease
  4. Proceed with routine induction and address difficulty only if it arises

Explanation

Difficult airway management requires an explicit strategy with a primary plan and clearly defined backup options. The plan must be communicated to the team, and the required equipment and skilled personnel must be immediately available. Previous success does not guarantee future ease, and delaying planning until difficulty occurs is unsafe.

Question 36Airway Management

Which statement best explains why a supraglottic airway may fail to seal in a patient with a large body habitus and reduced neck mobility?

  1. The device cuff cannot be inflated in patients with a body mass index above 30
  2. The device requires a laryngoscope for insertion in all patients with reduced neck mobility
  3. The device is contraindicated whenever the patient has any degree of neck stiffness
  4. The device tip may fail to seat in the upper esophagus because of altered pharyngeal anatomy and positioning Correct answer.

Explanation

A supraglottic airway depends on correct positioning of its tip and cuff within the pharynx to create a seal. Altered anatomy and restricted positioning can prevent proper seating and lead to leak or obstruction. Cuff inflation is not prohibited by body habitus, and the device is not universally contraindicated.

Question 37Airway Management

A patient requires awake tracheal intubation because of a predicted difficult airway. Which finding best confirms that topical anesthesia of the airway is adequate before the scope is advanced?

  1. The patient tolerates passage of the scope past the vocal cords without coughing or gagging Correct answer.
  2. The patient reports a metallic taste after lidocaine nebulization
  3. The patient's oxygen saturation remains above 94% on room air
  4. The patient's heart rate decreases by more than 20 beats per minute

Explanation

Adequate topical anesthesia is demonstrated by tolerance of instrumentation, especially passage beyond the vocal cords without coughing or gagging. Nebulized lidocaine produces variable systemic absorption and taste is not a reliable endpoint. Oxygen saturation and heart rate changes do not measure mucosal anesthesia.

Question 38Airway Management

Which statement best describes the principle behind apneic oxygenation during a prolonged intubation attempt?

  1. Carbon dioxide is actively removed by the oxygen delivery device
  2. Oxygen continues to move into the alveoli by mass flow while carbon dioxide is eliminated slowly, extending the safe apnea time Correct answer.
  3. Oxygen is delivered only by intermittent bag-valve-mask breaths between attempts
  4. Oxygen saturation is maintained solely by increasing the fraction of inspired oxygen on the ventilator

Explanation

During apnea, oxygen continues to be taken up from the alveoli while carbon dioxide accumulates slowly because of the body's large stores. Supplying oxygen to the pharynx during laryngoscopy exploits this gradient and prolongs the time before desaturation. It does not eliminate carbon dioxide or replace ventilation.

Question 39Airway Management

A patient with a supraglottic airway in place cannot be ventilated, and the device is being considered as a conduit for tracheal intubation. Which condition must be met for this approach to be reasonable?

  1. The device cuff must remain fully deflated during the attempt
  2. The patient must be able to open the mouth more than 3 cm
  3. The device must be a second-generation model with a gastric channel regardless of seating
  4. The device must be correctly seated and allow passage of a bronchoscope or tube through it into the trachea Correct answer.

Explanation

Using a supraglottic airway as an intubation conduit requires that the device be properly positioned and that its lumen permit passage of a bronchoscope or tube toward the larynx. If ventilation through the device fails, the device is not functioning as a conduit and other rescue options should be pursued. Gastric channels and mouth opening are relevant considerations but not the defining requirement.

Question 40Airway Management

A patient with a known difficult airway has failed mask ventilation and failed supraglottic airway placement after induction, and pulse oximetry is falling. Which action best follows difficult airway principles?

  1. Proceed promptly to a front-of-neck airway while continuing attempts at oxygenation Correct answer.
  2. Continue supraglottic airway attempts until saturation reaches 70%
  3. Repeat laryngoscopy with the same blade and technique several more times
  4. Give additional neuromuscular blocker and wait for improved conditions

Explanation

When ventilation cannot be established by mask or supraglottic airway and oxygenation is deteriorating, the situation meets the criteria for a cannot-intubate-cannot-oxygenate emergency. The priority is prompt establishment of a front-of-neck airway while oxygenation efforts continue. Repeating failed techniques or delaying intervention increases the risk of hypoxic injury.

Question 41Respiration and Ventilation

A patient's arterial blood gas shows a PaO2 of 60 mmHg and a PaCO2 of 55 mmHg while breathing room air at sea level. Which primary respiratory problem does this combination most directly indicate?

  1. Diffusion-limited oxygen transfer with normal ventilation
  2. Right-to-left intracardiac shunting with normal alveolar gas
  3. Compensated metabolic alkalosis
  4. Alveolar hypoventilation with impaired oxygenation Correct answer.

Explanation

An elevated PaCO2 indicates alveolar hypoventilation, and the low PaO2 on room air reflects impaired gas exchange accompanying it. Together they point to a ventilatory failure pattern rather than a purely metabolic problem.

Question 42Respiration and Ventilation

Which lung volume can be measured by spirometry alone, without plethysmography or gas dilution techniques?

  1. Residual volume
  2. Inspiratory capacity Correct answer.
  3. Total lung capacity
  4. Functional residual capacity

Explanation

Inspiratory capacity is the sum of tidal volume and inspiratory reserve volume, both of which are directly measured by spirometry. The other listed volumes all require an additional measurement of residual volume or thoracic gas volume.

Question 43Respiration and Ventilation

During quiet tidal breathing, which muscle is the principal generator of the pressure change that drives inspiratory airflow?

  1. Sternocleidomastoid
  2. External intercostal muscles
  3. Diaphragm Correct answer.
  4. Abdominal muscles

Explanation

The diaphragm descends during inspiration, enlarging the thoracic cavity and generating most of the negative intrathoracic pressure in quiet breathing. The other muscles listed contribute mainly during forced or accessory breathing.

Question 44Respiration and Ventilation

According to the oxyhemoglobin dissociation curve, which change shifts the curve to the right and favors oxygen unloading at the tissues?

  1. A fall in PaCO2
  2. A fall in temperature
  3. A rise in pH
  4. A rise in 2,3-diphosphoglycerate Correct answer.

Explanation

Increased 2,3-DPG reduces hemoglobin oxygen affinity, shifting the curve right and enhancing tissue oxygen delivery. The Bohr effect also shifts the curve right when CO2 or hydrogen ions increase.

Question 45Respiration and Ventilation

A patient has a ventilation-perfusion ratio of zero in a region of lung. What does this ratio indicate about that lung unit?

  1. High ventilation relative to perfusion
  2. Dead-space ventilation without perfusion
  3. Balanced ventilation and perfusion
  4. Shunt perfusion without ventilation Correct answer.

Explanation

A V/Q ratio of zero means perfusion is present while ventilation is absent, which defines a true shunt. Blood passing such a unit remains unoxygenated and mixes with systemic arterial blood.

Question 46Respiration and Ventilation

Which structure is the primary site of airway resistance in the normal respiratory system?

  1. Respiratory bronchioles
  2. Terminal bronchioles
  3. Medium-sized bronchi Correct answer.
  4. Alveolar ducts

Explanation

Although individual small airways have high resistance per unit length, their enormous combined cross-sectional area makes medium-sized bronchi the dominant contributor to total airway resistance. This is why resistance falls as generations increase distally.

Question 47Respiration and Ventilation

Which of the following best describes the primary function of surfactant in the alveolus?

  1. Increasing mucus viscosity to trap particles
  2. Reducing surface tension and stabilizing alveolar size Correct answer.
  3. Increasing alveolar surface tension to promote collapse
  4. Promoting fluid secretion into the alveolar space

Explanation

Surfactant lowers alveolar surface tension, which reduces the collapsing pressure described by Laplace's law and prevents small alveoli from emptying into larger ones. This stabilizes alveoli and reduces the work of breathing.

Question 48Respiration and Ventilation

A patient hyperventilates voluntarily for several minutes. Which arterial blood gas change is expected?

  1. Decreased PaO2 and decreased pH
  2. Decreased PaCO2 and increased pH Correct answer.
  3. Increased PaCO2 and increased pH
  4. Increased PaCO2 and decreased pH

Explanation

Hyperventilation increases alveolar ventilation and washes out CO2, lowering PaCO2. The resulting reduction in carbonic acid raises blood pH, producing respiratory alkalosis.

Question 49Respiration and Ventilation

During forced expiration in a healthy subject, which change in pleural pressure is expected compared with quiet expiration?

  1. Pleural pressure equals alveolar pressure
  2. Pleural pressure becomes more negative
  3. Pleural pressure remains unchanged
  4. Pleural pressure becomes more positive Correct answer.

Explanation

Forced expiration requires contraction of abdominal and internal intercostal muscles, which raises intrathoracic and pleural pressure above atmospheric. Quiet expiration is largely passive, with pleural pressure remaining negative.

Question 50Respiration and Ventilation

A patient's arterial PCO2 rises from 40 to 60 mmHg with no change in metabolic rate. What best explains the effect on alveolar ventilation?

  1. Alveolar ventilation has approximately halved Correct answer.
  2. Alveolar ventilation has approximately doubled
  3. Alveolar ventilation is unchanged
  4. Alveolar ventilation has increased fourfold

Explanation

At steady state, PaCO2 is inversely proportional to alveolar ventilation when CO2 production is constant. Raising PaCO2 by 50 percent therefore implies alveolar ventilation has fallen by roughly one-third to one-half depending on the exact baseline assumptions.