Respiratory

Question 1

What effect does smoking cessation have on the P50 of hemoglobin if the patient stops smoking the day before surgery?

Answer 1

A rightward shift of hemoglobin P50 can occur within a day of smoking cessation. Patients may have improved oxygen delivery to their tissues if they do not smoke on the day of their operation. The Centers for Medicare & Medicaid Services (CMS) has quality criteria, termed Merit-based Incentive Payment System (MIPS), that look at smoking cessation on the day of surgery.

TrueLearn Insight : A rightward shift decreases hemoglobin’s affinity for oxygen and increases oxygen delivery to tissues. The following factors cause a rightward shift of the P50 of hemoglobin:
• Increased levels of 2,3 DPG (will occur when cigarette smoking is stopped)
• Acidosis (also known as the Bohr effect)
• Increased levels of carbon dioxide
• Increased temperature

A leftward shift increases hemoglobin’s affinity for oxygen and reduces tissue delivery. The following factors cause a leftward shift of the P50 of hemoglobin:
• Hypothermia
• Carbon monoxide
• Fetal hemoglobin (Hgb F)
• Methemoglobin
• Hypophosphatemia (seen in the critically ill)

Question 2

Which of the following benefits of smoking cessation occurs during the first 24-48 hours after smoking has ceased?

Answer 2

Most benefits of smoking cessation occur after 2-3 months (reduced sputum production, improved ciliary function, improved closing volume, and increased FEF25-75%). However, a decrease in carboxyhemoglobin concentrations and the resultant rightward shift of the oxyhemoglobin dissociation curve occur in as little as 48 hours after smoking cessation.

Question 3

A 68-year-old male is admitted to the ICU for severe sepsis. He is intubated and sedated but not paralyzed. Ventilator settings are currently Volume Control SIMV with pressure support. Which of the following waveforms is MOST likely representative of this patients current ventilatory settings?

Answer 3

SIMV and Assist Control ventilation can deliver breaths with or without patient effort and are dependent upon triggering within a set time window (SIMV) or with a specific trigger threshold (pressure or flow with assist control) with waveform analysis noting whether the patient is triggering the breath (negative deflection on pressure curve). The usual curve of either is a pressure control (square wave) or volume control (triangle wave). Pressure support modes can also be used delivering a set pressure to a patient triggered breath with expiratory cycling based upon flow decay and is useful for ventilator weaning.

Question 4

A healthy 32-year-old woman has an arterial blood gas drawn postoperatively which shows a PaO2 of 100 mmHg and hemoglobin of 12 g/dL. Out of the total oxygen in her blood, what percentage of that total is dissolved oxygen?

Answer 4

Arterial oxygen content (CaO2) = (Hgb * 1.36 * SaO2) + (0.003 * PaO2)
Undissolved O2: (12 * 1.36 * 0.95) = 15.5; again, any normal SaO2 will suffice
Dissolved O2: (0.003 * 100) = 0.3
0.3 / (15.5 + 0.3) = 0.019 * 100 = 1.9% of the total number of oxygen molecules is dissolved.

Question 5

A 35-year-old pregnant woman is provided with lumbar epidural analgesia with a continuous infusion of dilute local anesthetic solution for pain control during labor. Which is most likely to INCREASE following the initiation of epidural analgesia?

Answer 5

Epidural anesthesia can increase tidal volumes in a patient who has shallow breathing (splinting) due to labor pain.

Question 6

A 10-year-old is brought to the intensive care unit in status asthmaticus. Her vital signs are SpO2 97%, HR 104 bpm, BP 148/88 mm Hg, and RR 34/min. An ABG is drawn and shows pH 7.48, PaO2 92 mm Hg, and PaCO2 28 mm Hg. Imminent respiratory failure can best be predicted by which of the following changes?

Answer 6

A severe asthma attack is initially associated with a compensatory hyperventilatory response and the initial ABG shows respiratory alkalosis with possibly mild hypoxia. An early sign of respiratory fatigue and possible respiratory failure is a pseudonormalization of the PaCO2.

TrueLearn Insight : In a severe acute asthma attack, the end-tidal CO2 value may not be accurate due to significant airway obstruction and a rapid respiratory rate limits movement of CO2. It is likely that PaCO2 would be underestimated based on ETCO2 levels.

Question 7

As alveoli become smaller, what are the effects on pulmonary surfactant concentration and its ability to influence surface tension?

Answer 7

Pulmonary surfactant more effectively reduces surface tension when it is more concentrated. As alveoli shrink, the surfactant concentration increases which more effectively reduces surface tension. On the other hand, as alveoli become more distended, the surfactant is stretched more thinly which results in a decrease in concentration. Subsequently, the surface tension will increase and favor a reduction in size.

Question 8

Which of the following is TRUE regarding the development of atelectasis in the perioperative period?

Answer 8

Atelectasis development occurs during general anesthesia in almost all patients and is an important cause of hypoxemia. The amount of atelectasis is lowest in non-obese patients who maintain adequate muscle tone and have non-thoracic surgery. Techniques for the prevention of further atelectasis include lower inspired oxygen concentrations, use of positive end-expiratory pressure, and intermittent recruitment maneuvers.

Question 9

A 16-year-old patient is brought to the Emergency Department by her mother after she reportedly swallowed a large amount of an unknown over-the-counter medication in a suicide attempt. The patient is lethargic, tachycardic, febrile, and is complaining of nausea, dizziness, a headache, and ringing in her ears. Which MOST resembles the patient’s ABG drawn at this time?

Answer 9

Key signs of aspirin or salicylate toxicity include tinnitus, altered mental status, and tachypnea. Arterial blood gas generally shows a mixed respiratory alkalosis and metabolic acidosis. Initial treatment includes supportive measures, gastric lavage, and activated charcoal. Additional measures include bicarbonate administration to reduce systemic acidosis and to alkalinize urine for increased aspirin clearance. Hemodialysis should be considered in severe toxicity cases.

Question 10

Which of the following curves in the figure below BEST illustrates the relationship between lung volume and pulmonary vascular resistance in a healthy adult?

Answer 10

Pulmonary vascular resistance (PVR) is affected by lung volumes. It is lowest at functional residual capacity (FRC), while increasing or decreasing lung volumes beyond FRC results in an increase in PVR.

Question 11

A 60-year-old man has undergone an 8-hour open nephrectomy for renal cell carcinoma. His only other past medical history is severe COPD. An arterial blood gas is obtained immediately upon arrival to the Post-anesthesia Care Unit (PACU) and is shown below. Which of the following BEST describes the acid-base disorder for this patient?

pH: 7.25
PaCO2: 80 mm Hg
[HCO3-]: 32 mEq/L

Answer 11

Patients with COPD have a chronic respiratory acidosis characterized by hypercarbia with compensated metabolic alkalosis from renal reabsorption of bicarbonate resulting in a (near) normal pH. The decrease in minute ventilation from administration of opioids results in an acute on chronic respiratory acidosis resulting in a low pH.

Question 12

Which of the following mechanisms is most likely the cause for increased shunt fraction in a patient breathing 100% oxygen concentration compared to a patient breathing a mixture of gas with 30% oxygen concentration?

Answer 12

Pulmonary shunt is increased by increased oxygen concentrations, which leads to blunting of hypoxic pulmonary vasoconstriction and microatelectasis.

Question 13

Which of the following is the MOST common anesthetic complication associated with an anterior mediastinal mass?

Answer 13

Anterior mediastinal masses may cause compression of the tracheobronchial tree. The anesthetic plan should be tailored to the size of the mass and the vital structures being compressed.

Question 14

Which of the following statements about dead space is TRUE?

Answer 14

Dead space ventilation is increased by factors that increase anatomic dead space (e.g. neck extension, bronchodilators) or alveolar dead space (e.g. upright positioning, PPV, decreased cardiac output, many lung pathologies).

Question 15

Which of the following statements concerning the relationship between end-tidal carbon dioxide concentration (ETCO2) and partial pressure of arterial carbon dioxide (PaCO2) is TRUE?

Answer 15

End-tidal CO2 monitoring provides a cheap, noninvasive approximation of PaCO2 since, in ideal conditions, ETCO2 ≈ PACO2 ≈ PaCO2. Normally, PaCO2 is slightly higher than ETCO2 and is a result of dead space ventilation. Acute increases in the gradient between PaCO2 and ETCO2 should raise concern for increased dead space ventilation, most commonly from decreased cardiac output and its associated causes.

Question 16

Which of the following would MOST likely cause this flow-volume loop?

Answer 16

Variable intrathoracic obstruction. The peak expiratory flow is decreased and plateaus early. The inspiratory curve is normal. Black dotted curve shows a normal curve.
Variable extrathoracic obstruction. The peak inspiratory flow is decreased and plateaus early. The expiratory curve is normal. Black dotted curve shows a normal curve.
Fixed upper airway obstruction. Inspiratory and expiratory flows are decreased and plateaued giving the loop a box-like appearance. Black dotted curves show normal curves.
Flow-volume loop of COPD. The expiratory phase quickly peaks and then falls to a lower than normal plateau phase. The inspiratory curve is often normal. Black dotted curve shows a normal curve.

Question 17

A 78-year-old man is admitted to the ICU in respiratory distress with suspected pulmonary edema. He has a history of systolic congestive heart failure with an ejection fraction of 20% seen on echocardiogram 1 month ago. He is tachypneic with a respiratory rate of 40 breaths per minute. His other vitals show a blood pressure of 80/50 mm Hg, SpO2 of 85% on non-rebreather facemask, heart rate of 110 beats per minute, and a temperature of 37.3 degrees Celsius. A pulmonary artery catheter was placed previously and the following hemodynamic variables are obtained:

CVP: 20 mm Hg
PAP: 60/30 mm Hg
PCWP: 25 mm Hg
CI: 1.2 mL/min/m^2

He has no known valvular abnormalities. You decide to intubate him and apply PEEP. Which of the following is MOST likely seen with the application of PEEP in this patient?

Answer 17

This patient likely has an acute on chronic systolic heart failure exacerbation with respiratory failure; therefore intubation is necessary with application of PEEP having the effect of increasing intrathoracic pressure, increasing right ventricular afterload (increase in CVP and PAP), but decreasing left ventricular afterload with resultant improvement of CI and PCWP.
PEEP application raises intrathoracic pressure, right ventricular afterload, decreases preload and can cause hypotension in the normovolemic or hypovolemic patient without heart failure. In patients with systolic heart failure, preload is excessive, thus PEEP preload effects are minimized but afterload is decreased with resultant improvement in cardiac output and a decrease in LVEDP.

Question 18

Which of the following statements concerning the relationship of functional residual capacity and closing capacity is TRUE?

Answer 18

Closing capacity (CC) is the volume remaining in the lungs during expiration when alveoli BEGIN to close (B). Closing capacity is equal to the sum of the residual volume (RV) and the closing volume.
Decreasing FRC relative to CC will lead to increased atelectasis and early alveolar closure.

Question 19

The first (top) capnogram may be seen in which of the following situations? A normal (bottom) capnogram is provided below for reference.

Answer 19

A capnogram from a patient with a single lung transplantation due to chronic obstructive pulmonary disease will show a “double peak” pattern, reflecting the difference in function between the healthy transplanted lung and the diseased native lung. The rapid initial exhalation from the healthy, transplanted lung produces the first peak, while the slower rate of rise of exhaled carbon dioxide from the diseased, obstructed lung produces the second peak.

TrueLearn Insight : Capnography may be used during cardiac arrest to indicate the return of cardiac output and spontaneous circulation if end-tidal carbon dioxide >20-25 mm Hg.

Question 20

A 35-year-old female with a history of nasal polyps and asthma presents for an elective cholecystectomy. Which of the following drugs is MOST likely to cause bronchospasm?

Answer 20

Histamine release drugs, such as morphine and atracurium, increase the risk of bronchospasm in patients with reactive airway disease such as asthma. There is a subset of patients with asthma (who classically also have nasal polyps) who have an exacerbation of symptoms, including bronchospasm, with the use of aspirin or non-steroidal anti-inflammatory drugs.

Question 21

You are caring for a 54-year-old asthmatic patient undergoing repair of a finger amputation. The patient is otherwise healthy and general anesthesia with an endotracheal tube is the primary anesthetic. An hour into the case you notice that exhalation continues until the next breath and the patient suddenly becomes hypotensive. Which of the following would NOT be an appropriate treatment?

Answer 21

Air trapping develops when air remains in alveoli at the end of expiration. Emergent management involves disconnecting the expiratory limb from the ventilator. Ventilator adjustments to reduce air trapping include: increasing expiratory time, reducing respiratory rate, or reducing tidal volume.

Question 22

A 35-year-old severe asthmatic is scheduled for hernia repair. During general anesthesia with a MAC of 1.2 (sevoflurane in 50% oxygen with 50% air), airway pressures suddenly begin to rise and tidal volumes decline by 50%. Severe wheezing is heard on physical exam and acute bronchospasm is suspected. Which of following is the MOST appropriate initial treatment?

Answer 22

During acute bronchospasm under general anesthesia, administration of a selective beta2-agonist such as albuterol is first line therapy.

Question 23

Which of the following is more likely to occur with laryngoscopy and intubation in infants when compared to adults?

Answer 23

The hemodynamic responses to laryngoscopy and intubation can be profound and cause significant morbidity and mortality, especially in at risk patients. Blunting of these responses can be through topicalization, performing airway blocks, providing deep anesthesia or analgesia.

Question 24

Expressed as a percentage of the corresponding values in the normal subjects, which one of the following is decreased the most in obese subjects?

Answer 24

Obesity is characterized by a marked decrease in expiratory reserve volume, leading to a decrease in lung compliance and FRC. Decreased FRC also leads to airway closure and decreased PaO2.

Question 25

An otherwise healthy 35-year-old man is at rest in the postoperative anesthesia recovery unit status post-laparoscopic cholecystectomy. He appears somnolent with tachycardia and hypertension ten minutes after arriving. His PCO2 on arterial blood gases is 80 mm Hg. What is his PAO2 while he is still breathing room air?

Answer 25

PAO2 = FiO2(PB – PH2O) – PCO2 / RQ

PAO2 = 0.21(760 – 47) – 80/0.8 = 50 mm Hg

Question 26

Which of the following would MOST likely cause this flow-volume loop?

Answer 26

The flow-volume loop in a patient with COPD is characterized by an expiratory phase with a quick peak followed by a much lower than normal plateau phase. This is representative of the dynamic, intrapulmonary airway obstruction that occurs with COPD during exhalation. The inspiratory phase is usually normal.

Question 27

Which of the following room air blood gas results is MOST likely representative of an otherwise healthy 30-year-old male with moderate to severe carbon monoxide poisoning?

Answer 27

An ABG from a patient with moderate to severe carbon monoxide (CO) poisoning will most likely show a metabolic acidosis with a normal PaO2 and a falsely elevated SaO2. Pulse oximetry will also be falsely elevated.
On an ABG, the calculated SaO2 value is not directly measured, but instead calculated based on the assumption that all Hgb is normal Hgb. Thus the calculated SaO2 value will be falsely high, often 100%, when moderate to high concentrations of COHgb are present. Arterial blood gas analyzers calculate estimated oxygen saturation (O2 sat) in a blood sample based on empirical equations using pH and PO2 values, as well as the standard oxyhemoglobin dissociation curve for oxygen saturation.

Question 28

A patient who is in the intensive care unit requires emergent surgery for ischemia of the small intestine. The patient has had a prolonged hospital course including acute respiratory distress syndrome. The patient’s ICU team has been employing low tidal volume ventilation.

The patient's current ventilatory settings are:
FiO2:  50%
Tidal volume:  6 mL/kg
Respiratory rate:  12/min
PEEP:  5 cm H2O

Which of the following should be the first step if the patient desaturates to 88% in the operating room?

Answer 28

The use of low tidal volume ventilation has been shown to be protective, especially in the critically ill population. Low tidal volumes in combination with positive end expiratory pressure help decrease injury while maintaining oxygenation.

Question 29

Which of the following pulmonary function test findings is MOST consistent with restrictive lung disease?

Answer 29

A restrictive defect is a proportional decrease in all lung volumes; thus VC, FVC and FEV1 are all reduced but FEV1/FVC remains normal.

Question 30

A 68-year-old smoker with chronic bronchitis has a PaCO2 of 55 mm Hg. The patient’s serum bicarbonate is MOST likely which of the following?

Answer 30

To calculate change in PaCO2:
Change in PaCO2 = patient’s PaCO2 - normal PaCO2 = 55 mm Hg - 40 mm Hg = 15 mm Hg
Therefore, the change in HCO3- = 0.4 x 15 = 6.

Question 31

A 26-year-old female with poorly controlled asthma requires emergent appendectomy. Immediately following intubation and confirmation of endotracheal intubation with bilateral breath sounds and end-tidal CO2, the patient has mild, stable oxygen desaturation to 92% while on 100% oxygen. She now has distant breath sounds and high peak airway pressures. Which of the following is the BEST option in this situation?

Answer 31

In mild-to-moderate bronchospasm when the patient is still able to be ventilated, the first choices for treatment are deepening the anesthetic and administering inhaled beta-agonists. In severe bronchospasm with the inability to ventilated, intravenous epinephrine is indicated.

Question 32

Which of the following BEST distinguishes obstructive sleep apnea from central sleep apnea?

Answer 32

In OSA, upper airway obstruction during sleep leads to episodes of apnea and/or hypopnea despite the continued presence of respiratory efforts. In CSA, episodes of apnea occur because of the failure of central respiratory centers to trigger inspiration.

TrueLearn Insight : Long-standing and/or severe obstructive sleep apnea (OSA) can result in heart failure: OSA -> hypoxia/hypercapnia -> pulmonary hypertension -> right ventricle hypertrophy -> right ventricle failure.

Question 33

A 42-year-old woman is scheduled to undergo a right ankle arthroscopy for tarsal tunnel syndrome. She has no other medical problems and is a non-smoker. Her body mass index is 31 kg/m2. Her preoperative SpO2 in the sitting position is 98% with a heart rate of 82/min and blood pressure of 139/43 mm Hg. Prior to pre-oxygenation and induction of anesthesia, she is positioned supine on the operating room table. A decrease in oxygen saturation to 95% over the next few minutes is noted. Which of the following is MOST likely true regarding supine positioning for functional residual capacity and closing capacity?

Answer 33

Closing capacity (CC) is the sum of the residual volume and closing volume (the volume at which small airways begin to close) and is unchanged by supine positioning. Functional residual capacity (FRC) is decreased in the supine position compared with the upright position, which can result in the CC being higher than FRC, resulting in hypoxemia. Closing capacity is increased with other factors, such as increasing age, chronic obstructive pulmonary disease, congestive heart failure, smoking, and surgery.

TrueLearn Insight : A mnemonic for factors increasing closing capacity is ACLS-S: Age, Chronic bronchitis, Left ventricular failure, Smoking, and Surgery.
A mnemonic for factors that decrease FRC is PANGOS: Pregnancy, Ascites, Neonate, General Anesthesia, Obesity, Supine position.

Question 34

A 42-year-old, 85 kg, 5’9” male (ideal body weight 70 kg) is being ventilated with pressure support ventilation during a melanoma excision. The following settings are programmed into the ventilator: pressure support 10 cm H2O, PEEP 5 cm H2O, inspiratory flow trigger 3 L/min, back-up rate 6 breaths/min. The patient is breathing approximately 12 breaths/min with a spontaneous inspiratory flow of 8 L/min.

Meeting which of the following parameters during inspiration will MOST likely cause the ventilator to stop delivering a breath and allow exhalation to occur?

Answer 34

Pressure support ventilation (PSV) is typically flow cycled and once inspiratory flow falls below a certain threshold (often 25% of initial flow rate), ventilator flow stops and exhalation begins.

Question 35

A patient with profound ascites would MOST LIKELY demonstrate which of the following pulmonary function test patterns?

Answer 35

Tense abdominal ascites elicits an extrinsic restrictive lung disease pattern, which is indicated on pulmonary function testing by a decreased forced vital capacity (FVC) and a reduced functional residual capacity (FRC). The FEV1/FVC ratio and FEF25-75% are generally normal.

Question 36

A 17-year-old female with severe asthma and a history of a difficult airway is scheduled for repair of a broken ankle under general anesthesia. She has refused any form of regional anesthesia. The anesthesiologist has decided to perform an awake fiberoptic intubation. Which option below would be LEAST effective in preventing bronchospasm in this patient?

Answer 36

Instrumentation of the trachea such as with an endotracheal tube can cause bronchospasm, especially in patients with asthma. Pretreatment with inhaled bronchodilators and/or oral steroids as well as topical lidocaine all help attenuate this response to the largest degree.

Question 37

Which of the following statements about functional residual capacity is FALSE?

Answer 37

The greatest decrease in functional residual capacity (FRC) occurs when going from 60° upright to supine (0°) or when being placed in Trendelenburg (head-down) more than -30°. The FRC does not significantly decrease when changing from a supine position to Trendelenburg less than -30°.
Functional residual capacity is the sum of the expiratory reserve volume and residual volume. It is reduced by obesity, in females (10% less than males), and when transitioning from upright to supine, prone, or Trendelenburg position.

Question 38

A 55-year-old female has severe tracheal stenosis which produces a fixed intrathoracic obstruction. Which of the following flow-volume loops would MOST likely be observed? Note a normal loop is shown for reference.

Answer 38

A fixed airway obstruction, whether intrathoracic or extrathoracic, will cause a reduction in flow in both the inspiratory and expiratory limbs of the flow-volume loop. A variable intrathoracic obstruction has relatively normal inspiration pattern, but reduced flow on expiration. A variable extrathoracic obstruction has a relatively normal expiration pattern, but reduced flow on inspiration.

Question 39

A 36-year-old female with a body mass index (BMI) of 47 presents for open gastric bypass surgery. Which ventilator strategy below is MOST appropriate for this patient?

Answer 39

Goals of positive pressure ventilation should be centered around avoiding barotrauma as well as avoiding atelectasis. Tidal volumes of 6-8 mL/kg predicted body weight, a PEEP of >5 cm H2O, and low FiO2 should all be utilized when possible. Recruitment maneuvers after intubation may also assist in reducing atelectasis.

Question 40

What must be present to make the diagnosis of obstructive sleep apnea?

Answer 40

Observed sleep related obstructive breathing events (apneas, hypopneas and respiratory effort related arousals) must be documented to make the diagnosis

Question 41

Following total abdominal hysterectomy under general anesthesia, a 69-year-old obese female is noted to be lethargic in the PACU. Which of the following is the MOST likely explanation for the arterial blood gas results below?

pH: 7.17
PaCO2: 83 mm Hg
PaO2: 59 mm Hg
HCO3: 25 mEq/L
SaO2: 88%

Answer 41

Uncompensated respiratory acidosis can be seen postoperatively due to residual neuromuscular blockade, opioids, residual volatile anesthetic/sedative, obstructive sleep apnea, or laryngospasm.

TrueLearn Insight : If residual neuromuscular blockade is suspected, always ensure that an adequate weight-based dosage of antagonism has been administered (e.g., 0.07 mg/kg neostigmine, up to 5 mg maximum). A ceiling effect limits the maximum dose of neostigmine and excessive dosage can lead to a depolarizing blockade.