40 Questions
What is a major determinant of Pulmonary Vascular Resistance (PVR)?
Transmural pressure difference
What allows for less resistance to flow in the pulmonary circulation compared to systemic circulation?
Transmural pressure difference
What type of pressure drop is observed in the pulmonary circulation from the pulmonary artery to the left atrium?
~ 10 mmHg
What plays a major role in determining Pulmonary Vascular Resistance (PVR) besides active smooth muscle contraction?
Passive factors
How does Pulmonary Vascular Resistance (PVR) compare to Systemic Vascular Resistance (SVR)?
PVR is 1/10 of SVR
In which zone of the lung does capillary pressure never exceed alveolar pressure?
Zone 1
What characterizes Zone 2 of the lung in terms of blood flow?
Intermittent blood flow
How is pulmonary capillary wedge pressure (PCWP) estimated?
Similar to left atrial pressure
What does a Swan-Ganz catheter balloon tip floated into the pulmonary artery estimate?
Pulmonary capillary wedge pressure (PCWP)
During exercise, which lung zone experiences continuous blood flow?
Zone 3
What is the primary function of pulmonary circulation?
Gas exchange
How many pulmonary capillaries supply the alveoli in the lungs?
280 billion
Where do lung structures distal to terminal bronchioles receive oxygen from?
Alveolar air
What is the average diameter of pulmonary capillaries?
~6 um
In the absence of pulmonary circulation, what can serve as collateral circulation for gas exchange in the airways?
Bronchial veins
What is the purpose of Hypoxic Pulmonary Vasoconstriction (HPV)?
To divert blood away from poorly ventilated alveoli
What happens when the PO2 of alveoli decreases in the context of Hypoxic Pulmonary Vasoconstriction?
Smooth muscle in arterioles contracts causing vasoconstriction
What does Hypoxic Pulmonary Vasoconstriction aim to mitigate?
Shunt
How does Hypoxic Pulmonary Vasoconstriction affect the resistance to blood flow in hypoventilated alveoli?
Increases resistance to blood flow
What is the volume and distributive aspect of pulmonary circulation when lying down?
Increased blood flow per unit volume in gravity-dependent lung regions
What is the term for the phenomenon where blood flow is directed away from poorly ventilated areas of the lung to well-ventilated regions?
Hypoxic pulmonary vasoconstriction
In pulmonary circulation, what is the main determinant of arterial pressure?
The cardiac output from the left ventricle
How does increased cardiac output affect pulmonary vessels?
Decreases pulmonary vascular resistance
What is the term for the condition where fluid accumulates in the lungs impairing gas exchange?
Pulmonary edema
How does the position of vessels in the lung affect their resistance?
Vessels closer to the pleura have lower resistance
What happens to the alveolar capillary walls when blood volume inside increases?
They distend
At high lung volumes, which of the following statements is true regarding pulmonary vascular resistance?
Alveolar vessel resistance increases
What happens to pulmonary vascular resistance with increased cardiac output?
Pulmonary vascular resistance decreases
How does recruitment affect pulmonary vascular resistance?
Opens closed capillaries
During exercise, what contributes to the decrease in pulmonary vascular resistance?
Distention of blood vessels
How does positive pressure ventilation (PPV) affect pulmonary blood flow?
Decreases pulmonary blood flow by reducing right ventricular preload
What is the main effect of PPV on the afterload of the right ventricle?
Increases afterload by elevating PVR
Which condition is likely to be associated with an increase in Zone 1 in the lungs?
Positive alveolar pressures and decreased venous return
What effect does positive pressure ventilation, especially with PEEP, have on low ventilation-perfusion ratios (shunt)?
Decreases low ventilation-perfusion ratios
How does a decrease in blood volume to the left heart impact left ventricular filling and stroke volume?
Decreases left ventricular filling and stroke volume
What happens to intrathoracic pressure during positive pressure ventilation?
Elevates intrathoracic pressure
How does resistance to pulmonary blood vessels change during inspiration?
Increases during inspiration
What is the effect of negative-pressure (eupnea) breathing on LV filling and stroke volume?
Decreases LV filling and stroke volume
How does decreased CO affect total thoracic blood volume?
Decreases total thoracic blood volume
What is the impact of decreased RV filling & SV on RVCO?
Decreases RVCO
Test your knowledge on how lung volume affects pulmonary vascular resistance. Learn about the behavior of alveolar capillary walls at different volumes and the location of alveolar vessels.
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