Shields Lecture 5

Question 0

Discuss bronchial bloodflow.

Answer 0

• very small portion (1 to 2%) of the LV output

* provides tracheobronchial tree with arterial blood

Question 1

Identify the tracheobronchial tree blood supply down to the terminal bronchioles.

Answer 1

Bronchial arteries arising from the aorta or intercostal arteries

Question 2

Discuss pulmonary bloodflow

Answer 2

• Entire RV output
• supplies lungs with mixed venous blood
• undergoes gas exchange with air in the pulmonary capillaries

Question 3

Identify the blood supply to the terminal bronchioles

Answer 3

Respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli receive oxygen directly by diffusion from the alveolar air

Question 4

Describe the role of the lungs as a reservoir for blood volume

Answer 4

• 450 mL of total blood volume
• 20 to 30% increase in blood volume in heart failure patients
• increased intrathoracic pressure decreases blood volume
• changes from supine to upright posture decrease blood volume by 27%

Question 5

Compare the pulmonary vascular resistance to systemic vascular resistance

Answer 5

pulmonary vessels:

• much less resistance to bloodflow
• are more distensible and compressible due to lower intravascular pressures
• PVR is 1/10 of SVR

Question 6

Compare the effect afterload on the right ventricle compared to left ventricle

Answer 6

The right ventricle does not pump against high pressures normally so it fails during acute pulmonary hypertension due to being very sensitive to changes in Afterload. The left ventricle has a greater workload, higher metabolic demand and normally pumps against extremely high pressures to perfuse the head. If the left ventricle fails, it bulges into the septum, pushing the septum into the right ventricle and compressing the stroke volume of the right ventricle.

Question 7

Describe the effect of airway pressure on zero order capillaries

Answer 7

If alveoli collapse, pulmonary capillaries collapse and there is little blood flow through them= less shunt

Question 8

Discuss the role of alveolar collapse in pulmonary vascular resistance

Answer 8

As closing capacity exceeds FRC = less PVR

Question 9

Identify the number of first order pulmonary capillaries and their blood volume

Answer 9

300 million

150 mL

Question 10

Define recruitment and distention as they relate to perfusion

Answer 10

Increased blood flow increases mean pulmonary artery pressure, which opposes hydrostatic forces and exceeds critical opening pressure in previously unopened vessels, opening
New parallel Pathways (recruitment) and lowering pulmonary vascular resistance. As perfusion pressure increases, transmural pressure gradient of pulmonary blood vessels increases, causing vessel distention of already opened vessels (widening of vessels). This increases radii and decreases resistance to bloodflow. Distention occurs after recruitment occurs

Question 11

Compare and contrast alveolar effects and extra alveolar effects on capillary size

Answer 11

As lung volume increases, extra alveolar vessels get wider ( diameter increases ) and resistance decreases within those vessels. Intra-alveolar vessels get smaller and tighter as they are elongated. Diameter decreases and resistance increases in those vessels as alveoli expand