Exam #3: Pulmonary Circulation Flashcards
How do pulmonary arteries structurally compare to the systemic arteries?
1) Shorter
2) More compliant
3) Thinner walled
This allows them to accomodate the entire cardiac output
What is the bronchial circulation?
Circulation to the lung parenchyma itself
- Bronchial arteries provide oxygenated systemic blood to the lungs
- Bronchial veins carry 1/3 of the bronchial circulation back to the RA
- Remaining 2/3 goes to the LA via the pulmonary veins, which is responsible for the “physiological shunt” of blood
What is the effect of bronchial circulation?
Physiological shunting of blood & drop in partial pressure of oxygen in systemic circulation compared to alveolar oxygen
What is hypoxic pulmonary vasoconstriction (HPV)?
- Decreased alevolar Po2 i.e. alveolar hypoxia (<70 mmHg) causes local vasoconstriction, which is the OPPOSITE of what happens in systemic circulation
- Blood redistribution to better aerated alveoli i.e. serves to match ventilation & perfusion by redirecting perfusion to better oxygenated alveoli
What causes HPV?
Airway obstruction Failure of ventilation Acute lung damage High altitude COPD
What is the long term effect of HPV?
Pulmonary arterial hypertension (PAH)
What are the effects of gravity on the distribution of pulmonary blood flow? What is the clinical significance?
- Blood flow is greater in the bases of the lungs than the apex in the standing individual.
- Clinically, this is why you look for evidence of edema at the bases of the lungs
Describe the structure of the pulmonary capillaries.
Thin walled
Leaky to protein
Low pressure
Form a sheet of flow
Summarize the pulmonary capillary & interstitial fluid dynamics.
1) Normal outward forces are greater than inward forces, which provides a filtration pressure out of the pulmonary capillaries into the interstitial space
2) Pulmonary lymphatic pressure is negative relative to interstitial, which results in the recycling of fluid
What causes an increased in interstitial hydrostatic pressure?
Edema
What conditions will increase intravascular hydrostatic pressure?
Increased blood volume
Poor heart function
What will decrease capillary osmotic pressure?
CKD
Liver disease
What conditions will change capillary permeability?
Drug toxicity
Infection
Autoimmune disease
What is the ventilation- perfusion relationship?
Matching ventilation (V) to perfusion (Q) is essential for ideal gas exchange
What is the average normal for V/Q?
0.8