40 Questions
What percentage of the cardiac output does bronchial circulation account for?
2%
Why might new vessels branch from the bronchial veins?
As a response to pulmonary circulation blockage
What is the average diameter of pulmonary capillaries?
~6 um
How long does it take for a red blood cell to travel through the pulmonary capillaries at resting cardiac output?
4-5 seconds
What is the primary function of the pulmonary circulation?
Gas exchange
In which zone of the lung does continuous blood flow normally occur?
Zone 3
Which parameter is used to estimate left ventricular preload?
Pulmonary capillary wedge pressure
In Zone 1 of the lung, what is the typical state regarding blood flow?
No blood flow
Which technique is used to measure total pulmonary blood flow (cardiac output)?
Thermal dilution technique with Swan-Ganz catheter
Where is pulmonary capillary wedge pressure (PCWP) typically measured to estimate left ventricular preload?
In Zone 3
What is a major determinant of Pulmonary Vascular Resistance (PVR)?
Transmural pressure difference
How does the thin walls of pulmonary vessels affect Pulmonary Vascular Resistance (PVR)?
Allows PVR to be influenced by varying pressures
How does the distribution of resistance in the pulmonary circulation compare to systemic circulation?
Pulmonary circulation has 1/3 resistance in each vessel type: distributing, exchange, and collecting
What happens to Pulmonary Vascular Resistance (PVR) due to vasoconstriction in response to hypoxia?
PVR increases
In the pulmonary circulation, what is the typical drop in pressure from the Pulmonary Artery (PA) to the left atrium?
~10 mmHg
What happens to the extra-alveolar vessel resistance to blood flow at high lung volumes?
Decreases
How does pulmonary vascular resistance (PVR) change as cardiac output increases?
Decreases
What effect does distention have on the diameter of blood vessels?
Increases the diameter
How are alveolar and extraalveolar vessels related in terms of resistance?
They are in series and their resistances are additive
What happens to the resistance to pulmonary blood flow with an increase in mean pulmonary artery pressure?
Decreases
Where is the hilar region located in relation to the apex and base of the lungs?
15cm below apex/15cm above base
What is the pulmonary arterial blood pressure at the apex of the lung if the pulmonary arterial pressure is 25/8 and a 15cm column of blood exerts a pressure of 11mmHg at its base?
14 mmHg
According to Starling’s forces, where is the first place pulmonary edema occurs based on the interaction of pressures in the lung?
Base of the lung
Why does more blood flow occur in the lower regions of the lung compared to the upper regions?
Higher extravascular pressure in lower regions
What is the total pulmonary blood flow conceptually influenced by in terms of pulmonary artery pressure, pulmonary vein pressure, and alveolar pressure?
Interaction of all three pressures
How does negative-pressure (eupnea) breathing affect LV filling and stroke volume?
Decreases LV filling and stroke volume
What happens to pulmonary blood flow during positive pressure ventilation (PPV)?
Pulmonary blood flow decreases
How does positive pressure ventilation affect the afterload of the right ventricle (RV)?
Increases the afterload of RV by increasing PVR
How do positive alveolar pressures and decreased venous return affect Zone 1 in the lungs?
Increase Zone 1
How does positive pressure ventilation (PPV), especially with PEEP, affect low ventilation-perfusion ratios (shunt)?
May decrease or prevent low ventilation-perfusion ratios (shunt)
What is the primary determinant of pulmonary vascular resistance?
Pulmonary artery pressure
How does increased cardiac output affect pulmonary vessels?
Decreases pulmonary vascular resistance
In which zone of the lung do the effects of gravity have the greatest impact on pulmonary blood flow?
Zone 3
What is the major contributor to regional distribution of pulmonary blood flow in the lungs?
Gravity
How does hypoxic pulmonary vasoconstriction impact pulmonary blood flow?
Decreases pulmonary blood flow
Which condition is most likely to cause an increase in total pulmonary blood flow?
Positive pressure breathing
What is the main factor influencing distention and recruitment of vessels in pulmonary circulation?
Gravity
How does the location of vessels affect their resistance in the pulmonary circulation?
Vessels near the apex have higher resistance
What effect does mechanical ventilation have on pulmonary blood flow?
Decreases total pulmonary blood flow
Which factor is NOT a determinant of pulmonary vascular resistance?
Bronchial circulation
This quiz explores the effects of mechanical ventilation, specifically positive pressure ventilation (PPV), on pulmonary blood flow. Topics include changes in intrapleural pressure, venous return, left ventricular filling, stroke volume, cardiac output, RV preload, and right atrial pressure.
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