CCP Cardiopulmonary Physiology & Pathophysiology 3 — Questions and Answers
Question 1: Which statement best describes the Frank-Starling mechanism as it applies to perfusion management?
- Increased preload always increases cardiac output regardless of ventricular function
- Stroke volume increases with preload up to a point, then plateaus or declines in a failing heart (Correct answer)
- Afterload reduction always overrides the Frank-Starling effect
- Cardiac output is independent of end-diastolic volume during bypass
Correct answer: Stroke volume increases with preload up to a point, then plateaus or declines in a failing heart
The Frank-Starling mechanism states that stroke volume increases with preload within physiologic limits, but a failing ventricle may not augment output with further volume loading.
Question 2: A patient on bypass develops a sudden decrease in mixed venous oxygen saturation (SvO2). Which is the LEAST likely cause?
- Increased metabolic demand due to inadequate anesthesia depth
- Decreased pump flow rate
- Increased arterial oxygen content from higher FiO2 (Correct answer)
- Anemia from excessive hemodilution
Correct answer: Increased arterial oxygen content from higher FiO2
Increased arterial oxygen content (from higher FiO2) would improve SvO2, not decrease it; the other options all reduce oxygen delivery or increase consumption.
Question 3: What is the clinical importance of V/Q mismatch in patients with chronic obstructive pulmonary disease undergoing cardiac surgery?
- V/Q mismatch causes metabolic alkalosis requiring sodium bicarbonate correction
- Areas of low V/Q act as shunt, increasing PaCO2 and decreasing PaO2 (Correct answer)
- V/Q mismatch only affects carbon dioxide elimination, not oxygenation
- High V/Q areas (dead space) primarily cause hypoxemia in COPD
Correct answer: Areas of low V/Q act as shunt, increasing PaCO2 and decreasing PaO2
Low V/Q regions in COPD act like shunt units, allowing deoxygenated blood to pass without gas exchange, raising PaCO2 and lowering PaO2.
Question 4: During hypothermic bypass at 28°C, a perfusionist checks blood gases using the alpha-stat strategy. What is the primary goal of this approach?
- Maintain pH at 7.40 and PaCO2 at 40 mmHg when measured at the patient's actual temperature
- Maintain pH at 7.40 and PaCO2 at 40 mmHg when measured at 37°C regardless of patient temperature (Correct answer)
- Correct blood gases to normal values at 28°C by adding CO2 to the oxygenator
- Maximize cerebral blood flow by allowing pH to fall with hypothermia
Correct answer: Maintain pH at 7.40 and PaCO2 at 40 mmHg when measured at 37°C regardless of patient temperature
Alpha-stat management maintains pH 7.40 and PaCO2 40 mmHg when measured at 37°C (in vitro), allowing physiologic changes to occur naturally with hypothermia.
Question 5: Which cardiac lesion creates the greatest risk of paradoxical embolism during cardiac surgery?
- Aortic stenosis with calcified valve leaflets
- Patent foramen ovale allowing right-to-left shunting (Correct answer)
- Mitral valve prolapse with regurgitant jet
- Tricuspid regurgitation with dilated right atrium
Correct answer: Patent foramen ovale allowing right-to-left shunting
A patent foramen ovale allows venous emboli (air or thrombus) to cross from the right to left atrium and enter the systemic circulation.
Question 6: In a patient with pulmonary hypertension, which intraoperative maneuver would most effectively reduce right ventricular afterload?
- Increasing pump flow rate to raise systemic pressure
- Administering inhaled nitric oxide to selectively dilate pulmonary vasculature (Correct answer)
- Giving systemic vasopressors to increase mean arterial pressure
- Reducing FiO2 to minimize oxygen toxicity
Correct answer: Administering inhaled nitric oxide to selectively dilate pulmonary vasculature
Inhaled nitric oxide selectively dilates pulmonary vasculature, reducing pulmonary vascular resistance and right ventricular afterload without causing systemic hypotension.
Question 7: What does a widened arteriovenous oxygen content difference (CaO2 - CvO2) indicate during cardiopulmonary bypass?
- Adequate oxygen delivery with low metabolic demand
- Excessive oxygen delivery causing hyperoxia
- Inadequate oxygen delivery relative to tissue oxygen consumption (Correct answer)
- Normal oxygen utilization with good cardiac output
Correct answer: Inadequate oxygen delivery relative to tissue oxygen consumption
A widened a-vO2 difference indicates tissues are extracting more oxygen than normal, suggesting oxygen delivery is insufficient relative to metabolic demand.
CCP Cardiopulmonary Physiology & Pathophysiology 3
Which statement best describes the Frank-Starling mechanism as it applies to perfusion management?