Deck 20: Cardiac Output, Venous Return, and Their Regulation

Question 1

A 60-year-old woman in the intensive care unit has a large arteriovenous fistula. Her cardiac output is 10 L/min, oxygen consumption is 250 mL/min, and pulmonary vein oxygen concentration is 180 ml/L. What is the pulmonary artery oxygen concentration (in ml/L)?

A)145
B)155
C)165
D)185
E)205

Answer 1

B

Question 2

In which of the following conditions would you expect a decreased resistance to venous return?

A)Anemia
B)Increased venous resistance
C)Increased arteriolar resistance
D)Increased sympathetic output
E)Obstruction of veins

Answer 2

A

Question 3

Which of the following is normally associated with an increased cardiac output?

A)Cardiac tamponade
B)Increased venous compliance
C)Moderate anemia
D)Severe aortic stenosis
E)Surgically opening the chest

Answer 3

C

Question 4

A 40-year-old woman is hospitalized with severe anemia. This patient has a cardiac output of 12.5 L/min, oxygen consumption is 250 mL/min, and pulmonary artery oxygen concentration of 160 ml/L. What is the pulmonary vein oxygen concentration (in ml/L)?

A)140
B)150
C)160
D)180
E)200

Question 5

Which of the following statements about resistance to venous return (RVR) is true?

A)An increase in venous resistance causes an increase in RVR
B)Increased parasympathetic stimulation causes an increase in RVR
C)An increase in RVR causes an increase in venous return
D)Sympathetic inhibition causes an increase in RVR
E)Changes in arterial resistance have a greater effect on RVR than do equal changes in venous resistance

Question 6

Which of the following will usually increase the plateau level of the cardiac output curve?

A)Myocarditis
B)Severe cardiac tamponade
C)Decreased parasympathetic stimulation of the heart
D)Myocardial infarction
E)Mitral stenosis

Question 7

Which of the following conditions is normally associated with an increased mean systemic filling pressure?

A)Decreased blood volume
B)Increased venous compliance
C)Increased arterial compliance
D)Congestive heart failure
E)Hypothyroidism

Question 8

A patient with a resting cardiac output of 4 L/min is exercised maximally, increasing cardiac output to 8 L/min. What is the cardiac reserve?

A)250%
B)200%
C)150%
D)100%
E)50%

Question 9

Which of the following normally causes the cardiac output curve to shift to the right along the right atrial pressure axis?

A)Changing intrapleural pressure to -6 mm Hg
B)Increasing mean systemic filling pressure
C)Taking a patient off a mechanical ventilator and allowing normal respiration
D)Surgically opening the chest
E)Breathing against a negative pressure

Question 10

Which of the following will elevate the plateau of the cardiac output curve?

A)Surgically opening the thoracic cage
B)Placing a patient on a mechanical ventilator
C)Cardiac tamponade
D)Decreasing parasympathetic stimulation of the heart
E)Decreasing sympathetic stimulation of the heart

Question 11

For the cardiac output curve defined by the solid line and the venous return curve defined by the dashed line (with equilibrium at point B), what is the resistance to venous return in units of mm Hg/L/min?

A)1.70
B)1.40
C)1.23
D)0.65
E)0.35

Question 12

For the following cardiac output and venous return curves defined by the dashed lines (with the equilibrium at B), which of the following is true?

A)Mean systemic filling pressure is 7 mm Hg
B)Right atrial pressure is 0 mm Hg
C)Resistance to venous return is 1.4 mm Hg/L/min
D)Pulmonary arterial flow is approximately 7 L/min
E)Resistance to venous return is 2.8 mm Hg/L/min