Metabolism and blood flow Flashcards
What is the pressures in the pulmonary capillaries?
25/8mmHg normally
What are some dz states that can alter this pulmonary capillary pressure?
CHF
Emphysema
What are the alveolar pressures?
Pulmonary capillary pressure
What the alveolar pressures during inspiration and exhalation?
Sub atmospheric during inspiration
- about 2 atm’s during exhalation
How does the change in alveolar pressures affects pulmonary capillaries?
Increase pressure during exhalation causes pulmonary capillaries to close
- during inspiration these capillaries distend due to low alveolar pressures
What are a couple examples that close pulmonary capillaires? Where typically?
Positive ventilation
Tension pneumo
- both at the apex
What are some ways to decrease pulmonary resistance?
- Increased recruitment of caps
- Distention
Caused by increase pulmonary arterial pressure
What are some ways to increase pulmonary capillary resistance?
- Increase alveolar pressure via exhalation
- NE and Serotonin
What affect does Ach have on pulmonary resistance?
Decreases it
What is the MOA of Ach?
Increases the activity of Nitric oxide synthase
What does an increase in nitric oxide synthase lead to?
Increase in NO
- Leads to increase cGMP by increasing activity of Guanylate cyclase
What does an increase in cGMP lead to?
- Increase in K+ channel activation
- increase in myosin light chain phosphatase.
What does the activation of K+ channels lead to?
Increase efflux of potassium.
- Leads to hyper polarization and thus smooth muscle relaxation
How does the pulmonary vasculature have such a small resistance compared to systemic?
- Much shorter
2. More capillaries leading to larger radius
What is the typical pulmonary resistance?
2mmHg/L/Min
What is the equation for pulmonary blood flow?
Vo2/(Cao2-Cvo2)
What is the blood flow distribution for zone 1?
PA>Part>Pvein
When is zone 1 like this?
during positive pressure ventilation
- apex of lung
- physiologic dead space –> no ventilation
What is the blood flow distribution for zone 2?
Part>PA>Pvein
What is the blood flow distribution for zone 3?
Parr>Pvein>PA
What determines the blood flow in zone 2?
Arterial pressure- alveolar pressure
- towards apex of lung
What determines the blood flow in zone 3? What does this resemble?
arterial pressure- venous pressure
- normal systemic circulation
- base and midline of lungs
Does doubling the atmospheric pressure on the capillaries affect flow, for instance while scuba diving?
No- relatively all pressure change is the same
What is the reason and MOA of hypoxic pulmonary vasoconstriction?
Shunting to perfuse areas that are being better ventilated
- Shut down of K+ channels which leads to hyperpolarizatoin of cell
- leads to contraction of smooth muscle
