Chapter·PhysiologyGas exchange

Alveolar-arterial oxygen gradientDownloads

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1

A 32-year-old female with Crohn's disease diagnosed in her early 20s comes to your office for a follow-up appointment. She is complaining of headaches and fatigue. Which of the following arterial blood gas findings might you expect?

AHigh PaO2, normal O2 saturation (SaO2), normal O2 content (CaO2)

BLow PaO2, low O2 saturation (SaO2), low O2 content (CaO2)

CNormal PaO2, normal O2 saturation (SaO2), normal O2 content (CaO2)

DNormal PaO2, normal O2 saturation (SaO2), low O2 content (CaO2)

ELow PaO2, normal O2 saturation (SaO2), normal O2 content (CaO2)

2

Four days after undergoing an elective total hip replacement, a 65-year-old woman develops a DVT that embolizes to the lung. Along with tachypnea, tachycardia, and cough, the patient would most likely present with a PaO2 of what?

A120 mmHg

B100 mmHg

C85 mmHg

D110 mmHg

E60 mmHg

3

A 17-year-old boy presents to the emergency department of a hospital located in the town of Recuay (which is situated at 3,400 meters above mean sea level [MAMSL]) in the Ancash Region (Peru), 48 hours after returning from a 21-day stay in Lima (the capital city of Peru at 0 MAMSL). The patient has no previous medical history. His current complaints include cough, dyspnea at rest, hemoptysis, chest pain, and vomiting. His vital signs include: blood pressure 90/60 mm Hg; heart rate 149/min; respiratory rate 37/min; temperature 36.5°C (97.7°F); and O2 saturation 71%. Physical examination reveals polypnea, perioral cyanosis, intercostal retractions, and diffuse pulmonary crackles. His laboratory results are as follows: Hemoglobin 19.2 g/dL Hematocrit 60% Leukocytes 13,000 (Bands: 12%, Seg: 78%, Eos: 0%, Bas: 0%, Mon: 6%) Urea 25 mg/dL Creatinine 0.96 mg/dL A chest X-ray is shown. Which of the following statements is true and most likely regarding this patient’s condition?

AThe pulmonary vasculature relaxes in response to hypoxia

BMarked increase in pressure gradient can lead to tissue hypoxia

CHypoxic stimulation of the peripheral chemoreceptors results in increased minute ventilation

DFollowing a rapid and sustained increase in altitude, decreased sympathetic activity transiently increases cardiac output, blood pressure, heart rate, and venous tone

EThe net change in response to hypoxia results in decreased cerebral blood flow

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