USMLE Respiratory

215/216. A 32-year-old male is hospitalized with severe respiratory disease following aspiration pneumonia. Inhaled nitric oxide is administered and he is placed in a prone position to improve oxygenation. Values obtained after the administration of nitric oxide are Mean pulmonary capillary oxygen content = 19 mL/dL Arterial oxygen content = 18 mL/dL Mixed venous oxygen content = 14 mL/dL Cardiac output = 6 L/min

215. Which of the following is the patient's shunt fraction (the ratio of shunted to total pulmonary blood flow)? b. 20% 216. The patient's oxygen consumption is what? e. 240 mL/min

178. In the maximal expiratory flow-volume curves below, Curve A would be typical of which of the following clinical presentations?

a. A 75-year-old man who has smoked two packs of cigarettes per day for 60 years. His breath sounds are decreased bilaterally, and his chest x-ray shows flattening of the diaphragm

194. A 68-year-old male with chronic obstructive pulmonary disease entered the Emergency Department complaining of shortness of breath. His respirations were 35 per minute and labored. He had a productive cough and rales were heard over all lung fields. The patient had a rather ashen complexion and his nail beds gave clear evidence of cyanosis. An arterial blood sample was obtained and a chest x-ray was ordered. The patient was then placed on an O2 mask delivering 40% O2. One-half hour later, the physician was called to the bedside by the nurse who found the patient unresponsive. The patient's complexion had changed to a flushed pink with no trace of cyanosis. His respirations were quiet at a rate of 6 per minute and a tidal volume of 300 mL. Repeat arterial blood gases showed that his arterial PCO2 had increased from 55 to 70 mmHg, and his PaO2 increased from 55 to 70 mmHg. Oxygen therapy most likely resulted in which of the following?

a. Alveolar hypoventilation

224. A 36-year-old man visits his doctor because his wife has long complained of his snoring, but recently observed that his breathing stops for a couple of minutes at a time while he is sleeping. He undergoes polysomnography and ventilatory response testing to ascertain the extent and cause of his sleep apnea. The activity of the central chemoreceptors is stimulated by which of the following?

a. An increase in the PCO2 of blood flowing through the brain

167. A 68-year-old woman with pulmonary fibrosis, who presents with a complaint of increasing dyspnea while performing activities of daily living, is referred for pulmonary function testing. Which of the following laboratory values is consistent with her diagnosis?

a. Decreased diffusing capacity of the lung

230. A 49-year-old coal miner presents with dyspnea, a nonproductive cough, and decreased exercise tolerance. Lung function tests reveal: total lung capacity = 3.34 L (56% of predicted), residual volume = 0.88 L (54% of predicted), and forced vital capacity = 1.38 L (30% of predicted). His arterial PO2 is 68 mmHg. Which of the following values will be approximately normal?

a. FEV1/FVC ratio

212. When the respiratory muscles are relaxed, the lungs are at which of the following?

a. Functional residual capacity (FRC)

179. A 30-year-old female patient is admitted to the Emergency Department with dyspnea, tachycardia, confusion, and other signs of hypoxia. The following laboratory data were obtained while the patient was breathing room air. PaO2 = 67 mmHg PaCO2 = 60 mmHg pH = 7.27 [HCO3 - ] = 26 mEq/L [Hb] = 15 g% SaO2 = 90% PvO2 = 30 mmHg SvO2 = 55% V˙ O2 = 350 mL/min CaO2-CvO2 = 7 mL O2/100 mL Which of the following is the most appropriate classification of the patient's hypoxia?

a. Hypoxic hypoxia (hypoxemia)

201. The diagram below illustrates the intrapleural pressure generated by a patient during a forced expiration. The equal pressure point will move closer to the mouth and the forced expiratory volume will increase if there is an increase in which of the following?

a. Inspired lung volume

196. A 42-week gestation infant is delivered by cesarean section. Which of the following occurs with the baby's first diaphragmatic respiration?

a. PaO2 increases

221. A 72-year-old woman presents to her physician with dyspnea. Pulmonary function tests revealed an increase, rather than a decrease, in the diffusing capacity of the lung. Which of the following conditions best accounts for an increase in the diffusing capacity?

a. Polycythemia

227. Which of the following conditions is most likely to produce the change from the normal maximum flow-volume curve illustrated below?

a. Sarcoidosis

186. During a pulmonary function test, a patient first generated Curve #1. Subsequent to administration of a bronchodilator, she generated Curve #2. The increased flow in Curve #2 versus Curve #1 is a result of which of the following?

a. Stimulation of b2-adrenergic receptors in bronchial smooth muscle

171. A 6 feet 3 inches tall, 140-lb, 20-year-old male was watching television when he felt pain in his shoulder blades, shortness of breath, and fatigue. His father noticed how pale he was and took him to the Emergency Department, where a chest X-ray revealed a 55% pneumothorax of the right lung due to rupture of a bleb on the surface of the lung. Which of the following is true?

a. The intrapleural pressure in the affected area is equal to atmospheric pressure

209. A 57-year-old female presents with dyspnea on exertion. Pulmonary function studies with plethysmography demonstrate an increase in the work of breathing, and the oxygen consumption is higher-than-normal at rest. Which of the following will decrease the oxygen consumption of the respiratory muscles?

b. A decrease in airway resistance

202. A healthy, 24-year-old man is prescribed sustained-release bupropion (Zyban) for smoking cessation. Twenty-one days after therapy he presents to his family physician with intermittent fever and a generalized rash, at which point the bupropion therapy is discontinued. A month later he develops a dry, intermittent cough and dyspnea. Which of the following pulmonary function test results is consistent with a diagnosis of allergic bronchospasm?

b. A decreased FEV1/FVC

204. A patient presents with a chief complaint of fatigue. He had an increase in heart rate and respiratory rate. The history also revealed symptoms of chills and spiking fever. The right lower lobe was dull to percussion. Vocal fremitus was increased over the right lower lobe and bronchovesicular breathing was present in the region, as well. Ventilation-perfusion (V ˙/Q˙) abnormalities occurring in a patient with lobar pneumonia will generally cause a decrease in which of the following?

b. Arterial carbon dioxide tension

231. Airway resistance is lowest in which of the following?

b. At total lung capacity

213. The diagram below illustrates the change in intrapleural pressure during a single tidal breath.

b. B

234. An 18-year-old girl presents to her primary care physician with an increased frequency of asthma exacerbations over the previous year. At the time of her visit, her physical examination and flow-volume loop are normal. At which point on the flow-volume loop pictured below will airflow remain constant despite an increased respiratory effort?

b. B

185. A woman found comatose in her house is life-flighted to the nearest regional medical center. Blood gases reveal a normal PaO2 but a lower than normal arterial O2 saturation. Which of the following conditions is most consistent with the findings?

b. Carbon monoxide poisoning

207. A patient presents with signs of hypoxia. Arterial blood gases reveal that the PaO2 is normal but the arterial O2 saturation is reduced. Which of the following conditions is the most likely cause of the hypoxia?

b. Carbon monoxide poisoning

191. A patient with congestive heart failure (CHF) develops increasing shortness of breath in the recumbent position. A chest x-ray reveals cardiomegaly, horizontal lines perpendicular to the lateral lung surface indicative of increased opacity in the pulmonary septa, and lung consolidation. Pulmonary edema in CHF is promoted by which of the following?

b. Increased pulmonary capillary hydrostatic pressure

223. A 68-year-old patient with shortness of breath is referred for pulmonary function testing, including lung volumes, flow-volume curves, and lung compliance. Which one of the following statements best characterizes pulmonary compliance?

b. It is inversely related to the elastic recoil properties of the lung

189. Noninvasive color Doppler ultrasound studies are ordered on a term infant and a preterm infant of 28-weeks gestation. Which of the following is likely to have a lower value in the preterm infant?

b. Pulmonary blood flow

172. An 18-year-old girl with a 9-year history of wheezing on exertion is referred for pulmonary function tests. The diagram below represents the spirometry tracing of a forced vital capacity. Her total lung capacity was 110% of predicted. Which of the following values will most likely be above normal?

b. Residual volume

168. A 24-year-old woman collapsed in a New York City subway station. An autopsy showed that a blood clot had traveled to her lung and caused her death. The medical examiner ultimately ruled that the blood clot was caused by the use of a birth control patch. Which of the following occurs if the blood flow to an alveolus is totally obstructed by a pulmonary thromboembolism?

b. The PO2 of the alveolus will be equal to that in the inspired air

226. A 28-year-old on oral contraceptives develops tachypnea and reports dyspnea. A ventilation/perfusion scan is ordered to check for pulmonary thromboemboli. Which of the following best explains why, as she takes in a normal inspiration, more air goes to the alveoli at the base of the lung than to the alveoli at the apex of the lung?

b. The alveoli at the base of the lung are more compliant

200. A 68-year-old man who has chronic obstructive pulmonary disease (COPD) presents to his pulmonologist with fatigue, dyspnea at rest, and peripheral edema. His blood gases on room air are PaO2 = 60 mmHg, PaCO2 = 60 mmHg, and pH = 7.36. His alveolar-arterial (A-a) O2 gradient, at a barometric pressure of 760 mmHg and a respiratory exchange ratio (R) of 0.8, is approximately what?

c. 15 mmHg

169. A 150-lb patient scheduled for abdominal surgery is sent for pre-op evaluation and testing. His chest x-ray is normal, and pulmonary function results on room air show: Tidal volume = 600 mL Respiratory rate = 12/min Vital capacity = 5000 mL PaO2 = 90 mmHg PaCO2 = 40 mmHg PECO2 = 28 mmHg The volume of the patient's physiological dead space, determined by applying Bohr's equation, equals which of the following?

c. 180 mL

199. A 56-year-old man presents to the Emergency Department with severe abdominal pain and a temperature of 103°F. The patient is in severe respiratory distress. Moderate amounts of pulmonary edema fluid are aspirated during suctioning. The patient is placed on a ventilator with an FIO2 of 0.5 and an arterial blood gas sample reveals a PO2 of 160 mmHg and a PCO2 of 40 mmHg. His alveolar oxygen tension, at a barometric pressure of 747 mmHg and a respiratory exchange ratio (R) of 0.8, is approximately what?

c. 300 mmHg

184. A candidate for cardiac transplantation undergoes cardiac catheterization. Hemodynamic findings include: Pulmonary Artery Pressure = 35 mmHg Cardiac Output = 4 L/min Left Atrial Pressure = 15 mmHg Which of the following is his pulmonary vascular resistance?

c. 5 mmHg/L/min

165. A group of third year medical students accompanied a medical mission team to Peru. After arriving at the airport in Bolivia, they hiked to a remote mountain village in the Andes. At this elevation of 18,000 ft, the barometric pressure was 380 mmHg, resulting in a PO2 of the dry inspired air of what?

c. 80 mmHg

233. A patient with Wegener's glomerulonephritis presents with sinusitis and hemoptysis. His chest radiograph shows several large cavitary pulmonary nodules, consistent with ventilation-perfusion imbalance with low V ˙ /Q˙ units. Which of the following will be greater than normal in a patient with a low V ˙ /Q˙ ratio?

c. A-a gradient

208. The wife of a recently married 24-year-old medical student reports that even though her husband doesn't snore, he stops breathing for periods of 1 to 2 minutes while he is sleeping. His physician refers him for a polysomnography study and pulmonary function testing, including ventilatory response curves. The tests confirm the apneic episodes during sleep and show depressed ventilatory responsiveness of both the peripheral and central chemoreceptors. Peripheral and central chemoreceptors both contribute to the increased ventilation that occurs as a result of which of the following?

c. An increase in arterial carbon dioxide tension

228. An increase in cardiac output and skeletal muscle blood flow during exercise causes which of the following?

c. Diffusing capacity of the lungs to increase

188. Diagnostic pulmonary function screening tests are ordered on a patient with a persistent cough. The patient is instructed to take in a maximal inspiration and then to exhale the breath as hard and fast as he can to generate a maximal expiratory flow-volume (MEFV) curve. As a result, the patient generates Curve C shown below. The patient's MEFV curve is consistent with which of the following sets of values for the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1)?

c. FVC 3.1L, FVC 48%, FEV1 2.8, FEV1 pred 50%

177. A 27-year-old man develops adult respiratory distress syndrome (ARDS) after near-drowning. Conventional mechanical ventilation on 100% O2 together with inhaled nitric oxide do not provide sufficient oxygenation. Porcine surfactant is instilled via fiberoptic bronchoscope, and the PaCO2, fraction of inspired oxygen (FIO2), and shunting improve impressively. The improvements in respiratory function occurred because surfactant increased which of the following?

c. Lung compliance

174. A medical student waiting to do her first patient interview at the Clinical Skills Center becomes very anxious and increases her rate of alveolar ventilation. If her rate of CO2 production remains constant, which of the following will decrease?

c. PaCO2

218. A hospitalized patient is found semicomatose. Arterial blood gases reveal hypercapnia. Which of the following is the most likely cause of the high arterial PCO2?

c. Profound hypoxia

211. A 48-year-old coal miner complains of shortness of breath and a productive cough. The history reveals that he has smoked 1 to 2 packs of cigarettes per day since he was 16 years old. Pulmonary function studies are ordered including an esophageal balloon study to measure intrapleural pressures. Normally, intrapleural pressure is negative throughout a tidal inspiration and expiration because of which of the following?

c. The intact pleura causes the lungs and chest wall to recoil away from each other throughout a tidal breath

166. A 28-year-old man is admitted to the Emergency Department with multiple fractures suffered in a car accident. Arterial blood gases are ordered while the patient is breathing room air. After obtaining the arterial blood sample, the blood-gas technician draws room air into the syringe before measuring the blood-gas values. As a result, which of the following is true?

c. The measured PaO2 will be higher and the measured PaCO2 will be lower than the patient's actual blood gas values

182. A patient with right lower lobar pneumonia exhibits increasing respiratory distress. The patient is intubated, placed on a mechanical ventilator, and positioned on his left side. The dependent lung has a lower:

c. V/Q ratio

205. A patient with congestive heart failure, orthopnea, and paroxysmal nocturnal dyspnea is referred for pulmonary function testing in the supine and upright positions. Which of the following is higher at the apex of the lung than at the base when a person is upright?

c. V/Q ratio

173. A 125-lb, 40-year-old woman with a history of nasal polyps and aspirin sensitivity since childhood presents to the Emergency Department with status asthmaticus and hypercapnic respiratory failure. She requires immediate intubation and is placed on a mechanical ventilator on an FIO2 of 40%, a control rate of 15 breaths/min, and a tidal volume of 500 mL. Which of the following is her approximate alveolar ventilation?

d. 5625 mL/min

175. A 36-year-old man with a history of AIDS and Pneumocystis infection presents to the Emergency Department with severe respiratory distress. The patient is placed on a ventilator at a rate of 16, tidal volume of 600 mL, and FIO2 of 1.0. An arterial blood sample taken 20 minutes later reveals a Po2 of 350 mmHg, a Pco2 of 36 mmHg, and a pH of 7.32. At a barometric pressure of 757 mmHg, and assuming a normal respiratory exchange ratio (R) of 0.8, the patient's alveolar oxygen tension is approximately which of the following?

d. 665 mmHg

183. A subject training for a triathlon reaches a workload while running that exceeds his anaerobic threshold. As a result, which of the following is increased?

d. Alveolar ventilation

220. A healthy 32-year-old woman undergoes pulmonary exercise stress testing prior to starting a training regimen in preparation for her first marathon. Normally, during moderate aerobic exercise, which of the following occurs?

d. Alveolar ventilation increases

214. Which of the following is higher at total lung capacity than it is at residual volume?

d. Anatomical dead space

217. A 37-year-old woman is admitted to the hospital with severe kyphoscoliosis. Over time, this anatomical distortion results in respiratory muscle weakness. Which of the following physiological variables will most likely be above normal in this patient?

d. Arterial carbon dioxide tension

192. A patient with emphysema is referred for his annual pulmonary function testing to assess the progression of his disease. As a result of alveolarseptal departitioning in emphysema, there is a decrease in which of the following?

d. Diffusing capacity

195. A scientist doing experiments with sodium cyanide started experiencing headache, dizziness, clumsiness, decreased visual acuity, and nausea. The medical student doing research in the laboratory was not certain if this was unusual behavior for the professor, but thought it best to take him to the Emergency Department to be evaluated for possible hypoxia. Blood values obtained on the professor while he was breathing room air were as follows: Hb: 16 g% SaO2: 97.5% PaO2: 102 mmHg PvO2: 65 mmHg PaCO2: 27 mmHg SvO2: 90% pH: 7.57 Cardiac Output: 5.6 L/min [HCO3 - ]: 23 mEq/L The professor's hypoxia is most likely the result of which of the following?

d. Impaired oxygen utilization

232. A spirometer can be used to measure directly which of the following?

d. Inspiratory capacity

198. An 18-year-old college student living in a dormitory contracts meningitis, which causes a centrally mediated increase in his respiratory rate. The basic respiratory rhythm is generated in which of the following regions of the brain?

d. Medulla

206. A 58-year-old factory worker, who has worked in the insulation industry for over 30 years, develops progressive shortness of breath. His wife has tried to get him to go to the doctor, and he finally relents with the appearance of hemoptysis. A chest x-ray is consistent with an alveolitis from asbestos inhalation. Which of the following is the major route for removal of small particles from the alveoli?

d. Phagocytosis

170. A hospitalized patient has tachypnea and significantly labored respirations requiring mechanical ventilation. Based on the pressure-volume curve of the lungs shown as Curve Z in the figure below, which of the following is the most likely diagnosis for the patient?

d. Pulmonary edema

225. A patient complains of paroxysmal episodes of not being able to catch her breath. When no abnormalities are detected with conventional pulmonary function screening, the pulmonologist orders a methacholine challenge test. Which of the following will increase as a result of stimulating cholinergic receptors on the bronchial smooth muscle?

d. Resistive work of breathing

181. A 68-year-old woman convalescing from surgery developed a fever, hypoxemia, and shortness of breath. She was given 100% O2 for 30 minutes, and the lab results were as follows: PaO2 = 95 mmHg PaCO2 = 33 mmHg pH = 7.46 [HCO3 - ] = 22 mEq/L [Hb] = 15 g% SaO2 = 95% 162 The response to 100% O2 reveals that the patient has which of the following?

d. Right-to-left shunting

222. A 49-year-old farmer develops a headache and becomes dizzy after working on a tractor in his barn. His wife suspects carbon monoxide poisoning and brings him to the Emergency Department where he complains of dizziness, lightheadedness, headache, and nausea. The patient's skin is red, he does not appear to be in respiratory distress, and denies dyspnea. Blood levels of carboxyhemoglobin are elevated. Which of the following best explains the absence of respiratory signs and symptoms associated with carbon monoxide poisoning?

e. Arterial oxygen tension is normal

197. A 29-year-old woman is admitted to the hospital because of increasing dyspnea and swelling of both feet. An examination of her chest shows a severe pectus excavatum with only 2 cm of space between the vertebral bodies and the sternum. Pulmonary function tests show FVC and FEV1/FVC values that were 15 and 100%, respectively, of predicted. Which of the following laboratory measurements will most likely be below normal in this patient?

e. Arterial pH

219. Pulmonary vascular resistance decreases if which of the following occurs?

e. Cardiac output is increased

180. A patient with parotid gland cancer has damage to the glossopharyngeal nerve. As a result, which of the following respiratory reflexes will be impaired?

e. Carotid body chemoreceptor reflex

203. A 5-month-old boy is admitted to the hospital for evaluation because of repeated episodes of sleep apnea. During a ventilatory response test, his ventilation did not increase when PaCO2 was increased, but decreased during hyperoxia. Which of the following is the most likely cause of this infant's apnea?

e. Dysfunctional central chemoreceptors

229. Which of the changes in arterial blood gas values was obtained from a patient with an atelectatic left lung causing a large intrapulmonary shunt?

e. E

164. A healthy, 30-year-old woman is referred for a life insurance physical. She has never smoked, and her breath sounds are normal. Her expiratory reserve volume, as depicted in the spirometry tracing below, equals which of the following?

e. E-D

190. A 35-year-old woman with gestational diabetes develops hypertension and preeclampsia, requiring the preterm delivery of her fetus of 30- weeks gestation. The mother is given two doses of betamethasone, 12 mg, intramuscularly, 24 hours apart. Which of the following is the purpose of the antenatal steroid therapy?

e. Increase the lecithin/sphingomyelin ratio in the amniotic fluid

193. A Swan-Ganz catheter is placed in a post-myocardial infarction (MI) patient in the Medical Intensive Care Unit. The patient is found to have a pulmonary artery wedge pressure of 25 mmHg, which is indicative of which of the following?

e. Increased net fluid movement out of the pulmonary capillaries

176. A sedentary individual goes to her physician's office for a cardiopulmonary exercise stress test evaluation prior to starting a weight-loss exercise regimen. Physiological changes that occur during deep inspirations as lung volume approaches total lung capacity include which of the following?

e. Pulmonary vascular resistance increases

210. An 18-year-old male is thrown from his motorcycle and suffers a complete transection of the brainstem above the pons. As a result, which of the following will most likely occur?

e. The limbic system will no longer be able to exert any control over ventilation

187. An asthmatic patient experiences an acute exacerbation, which causes her breathing to become labored and faster. As a result, which of the following changes in airflow is expected?

e. The pressure gradient required for airflow will increase