Flashcards in Pulmonary Circulation Deck (30)
What kind of bloods does the pulmonary artery carry?
oxygen deficient blood to the lungs
What kind of blood does the pulmonary vein carry?
oxygen-rich blood to the heart (left artery)
What are the functions of pulmonary circulation?
1. Gas exchange (oxygen and carbon dioxide)
2. filter - can capture/trap emboli into the lung (better than being trapped in the brain)
3. blood reservoir for left ventricle - decrease load on LV
4. nutrient supply - pulmonary circulation and bronchial circulation
What are physiological factors that determine the effect of inhaled drug therapy?
1. aerosal particle size and permeability
2. airway geometry (does the drug get to alveoli)
3. pulmonary circulation (drug absorption)
4. lung clearance mechanisms
5. underlying lung disease
describe pulmonary vessels
1. pulmonary artery 30% the thickness of the aorta
2. flexible and distensible
3. capillaries are numerous with multiple branches and anastomoses - each alveolus sits in a capillary basket
what is the mean systemic pressure in the arteries?
*highest pressure is 120 and goes down to 0 when empty
What is the mean pulmonary pressure ?
*goes up to 25 during systole
what 2 circulations are the lungs perfused by?
1. pulmonary circulation
2. bronchial circulation
what kind of blood do bronchial arteries carry?
provide systemic blood to the lung tissue which arise from the aorta and enter the lungs and supply the lung tissue except the alveoli
What does V stand for?
1. indicates effective minute ventilation of aerated pulmonary alveolar gas exchange surface with oxygenated gas
2. need both alveolar recruitment and adequate respiratory activity
*amount of air that goes to lung
What does Q stand for?
1. flow volume per unit time
2. indicates proportion of cardiac output that perfuses pulmonary circuit
3. commonly extrapolated by determining pulmonary vascular resistance
*amount of blood that goes to the lung. What effects perfusion is the amount of oxygen rather than cardiac output
2. V/Q mismatch
3. worsening hypoxia
4. pulmonary vascular constriction
This leads to respiratory failure, acidosis, circulatory failure
well ventilated alveolus
1. oxygen tension rises
2. endothelial NO synthesis
3. relaxation of pulmonary vessels
Good gas exchange (V + Q are matched)
what is the formula for minute ventilation?
min vent = vol. (ml) air breathed in & out/min
what is the formula for pulmonary ventilation?
pul. vent = Tidal Vol (ml) x resp. rate (breaths/min)
What is alveolar ventilation?
1. more important than pulmonary ventilation
2. the volume of air exchanged between the atmosphere and the alveolar per minute
3. less than pulmonary ventilation due to "anatomic dead space"
What is anatomic dead space?
the volume of air in conducting airways that is not available for gas exchange (~150 ml in adults)
What is the formula for alveolar ventilation?
(TV - dead space) x resp. rate
what happens to alveolar ventilation during deep slow breathing compared to quiet breathing at rest? What happens to pulmonary ventilation?
Alveolar ventilation is highest during deep slow breathing compared to quiet slow breathing at rest because deeper breathing means a larger tidal volume.
pulmonary ventilation remains the same for quite breathing and deep slow breathing
Vessel diameter is influenced by what extra vascular forces?
2. body position
3. lung volume
4. alveolar pressures/intrapleural pressures
5. intravascular pressures
what is the formula for pulmonary vascular resistance?
PVR = Ppulm/Qpulm
PVR = (Ppa - Pla)/ CO
describe flow of blood in zone 1 of the lung
may be absent because there is inadequate pressure to overcome alveolar pressure
describe flow of blood in zone 3 of the lung
continuous and driven by the pressure in the pulmonary arteriole - pulmonary venous pressure
describe flow of blood in zone 2 of the lung
may be pulsatile and driven by the pressure in the pulmonary arterior - alveolar pressure (collapsing the capillaries)
define shunted ventilation
A perfused part of the lung is not adequately ventilated
alveolar deadspace ventilation
a ventilated part of the lung is not adequately perfused
What can cause alveolar deadspace ventilation?
pulmonary embolism, pulmonary hypertension
what can cause shunted ventilation, leading to V and Q mismatch?
pneumonia, pulmonary edema, atelectasis (partial or complete collapse of the lung)
When is PVR (pulmonary vascular resistance) lowest and highest?
Pulmonary vascular resistance is lowest near the FRC (functional residual capacity) and increases at both high and low lung volumes.