CCP Cardiopulmonary Physiology & Pathophysiology 2 — Questions and Answers
Question 1: Which parameter best describes the relationship between pulmonary capillary wedge pressure and left ventricular preload?
- PCWP directly reflects right ventricular end-diastolic volume
- PCWP approximates left atrial pressure and thus left ventricular preload (Correct answer)
- PCWP measures pulmonary vascular resistance exclusively
- PCWP reflects right atrial pressure when the mitral valve is open
Correct answer: PCWP approximates left atrial pressure and thus left ventricular preload
Pulmonary capillary wedge pressure approximates left atrial pressure, providing an indirect measure of left ventricular preload.
Question 2: During cardiopulmonary bypass, a patient develops significant metabolic acidosis. Which compensatory mechanism would the perfusionist expect?
- Decreased respiratory rate to retain CO2
- Renal bicarbonate retention without any respiratory change
- Increased ventilation to blow off CO2 and raise pH (Correct answer)
- Decreased cardiac output to reduce acid production
Correct answer: Increased ventilation to blow off CO2 and raise pH
Respiratory compensation for metabolic acidosis involves hyperventilation to reduce PaCO2 and raise blood pH.
Question 3: What is the primary determinant of pulmonary vascular resistance in a patient with hypoxic pulmonary vasoconstriction?
- Elevated PaCO2 causing alkalosis
- Alveolar hypoxia triggering smooth muscle contraction (Correct answer)
- Increased pulmonary venous pressure from left heart failure
- High cardiac output overwhelming pulmonary vessels
Correct answer: Alveolar hypoxia triggering smooth muscle contraction
Alveolar hypoxia triggers smooth muscle contraction in pulmonary arterioles, the hallmark mechanism of hypoxic pulmonary vasoconstriction.
Question 4: A perfusionist notes the arterial waveform shows pulsus paradoxus. Which condition is most consistent with this finding?
- Aortic regurgitation
- Cardiac tamponade (Correct answer)
- Mitral stenosis
- Hypertrophic cardiomyopathy
Correct answer: Cardiac tamponade
Cardiac tamponade causes pulsus paradoxus due to pericardial pressure limiting right heart filling and exaggerating inspiratory BP drop.
Question 5: Which factor has the greatest impact on myocardial oxygen consumption during cardiac surgery?
- Heart rate and wall tension (preload/afterload) (Correct answer)
- Coronary perfusion pressure alone
- Ambient temperature of the operating room
- Arterial oxygen saturation at the time of incision
Correct answer: Heart rate and wall tension (preload/afterload)
Myocardial oxygen consumption is primarily determined by heart rate, wall stress (related to preload and afterload), and contractility.
Question 6: In a patient with severe mitral regurgitation on bypass, which hemodynamic change would the perfusionist most likely observe before bypass?
- Elevated systemic vascular resistance with low cardiac output
- Reduced pulmonary artery pressure with high SVR
- Elevated left atrial pressure and pulmonary hypertension (Correct answer)
- Low left ventricular end-diastolic pressure with high SVR
Correct answer: Elevated left atrial pressure and pulmonary hypertension
Severe mitral regurgitation causes volume overload of the left atrium, elevating left atrial pressure and subsequently causing pulmonary hypertension.
Question 7: What is the physiologic significance of the Bohr effect during cardiopulmonary bypass?
- Increased temperature shifts the oxyhemoglobin curve left, increasing O2 release
- Decreased pH shifts the oxyhemoglobin curve right, facilitating O2 unloading to tissues (Correct answer)
- Elevated CO2 shifts the oxyhemoglobin curve left, impairing O2 delivery
- Increased 2,3-DPG during bypass shifts curve left, reducing O2 release
Correct answer: Decreased pH shifts the oxyhemoglobin curve right, facilitating O2 unloading to tissues
The Bohr effect describes how decreased pH (acidosis) shifts the oxyhemoglobin dissociation curve rightward, reducing hemoglobin's O2 affinity and facilitating tissue O2 delivery.
CCP Cardiopulmonary Physiology & Pathophysiology 2
Which parameter best describes the relationship between pulmonary capillary wedge pressure and left ventricular preload?