Pulmonary circulation and V/Q ratio Flashcards
(29 cards)
What is the typical length of the pulmonary artery?
5 cm
What are characteristics of the pulmonary artery?
Thin-walled
High compliance
Can accommodate 2/3 of SV of RV
Constrict in response to hypoxia
What are the SBP, DBP, and MAP of the pulmonary A?
SBP - 25 mmHg
DBP - 8 mmHg
MAP - 15 mmHg
What is the average pulmonary capillary pressure?
7 mmHg
What is the average pressure of the pulmonary veins and L atrium?
2 mmHg, range of 1-5 mmHg
What is the comparison of pulmonary circulatory pressure and systemic pressures?
Pulmonary is 1/6 of systemic, same as RV to LV
What does regional pulmonary blood flow depend on?
The position relative to the heart
Base has more blood flow than apex while standing
What are the characteristics of zone 1?
No blood flow
Alveolar pressure is higher than arterial pressure throughout every part of the cardiac cycle
Pathological and when breathing against PEEP
What are the characteristics of zone 2?
Pulsatile flow
Systolic arterial pressure is higher than alveolar pressure, but diastolic is lower
What are the characteristics of zone 3?
Continuous flow
Pulmonary arterial pressure is always higher than alveolar pressure
When will pulmonary pressure increase in left sided heart failure?
When L atrial pressure rises by more than 7-8 mmHg
What things can cause pleural effusion?
Blockage of lymphatics
Cardiac failure
Diminished capillary oncotic pressure
Damage to the capillary walls
What is the effect of hypoxia on PVR?
SyNS increases PVR in the presence of hypoxia after smooth muscle remodeling
What are stimuli that can cause active changes in PVR?
Alveolar hypoxia
Motor innervation
Circulating vasoactive substance
How does exercise effect PVR?
Not much change because of the vessels distensibility and recruitment of additional vessels
At what lung volume is the lowest PVR?
At FRC
What are the functions of pulmonary circulation?
Gas exchange
Blood filter
Blood reservoir
Metabolism
What is the effect of inspiration of circulation?
Decreased flow in alveolar vessels
Increased flow in extra-alveolar vessels
Decreased LA and LV pressures
Decreased SBP
What is always a sign of inadequate alveolar ventilation?
Increased PaCO2
What is the ideal V/Q ratio?
1.0
What is the V/Q ratio at rest?
0.8
What is ventilation at rest?
4.2 L/min
What is perfusion at rest?
5.5 L/min
What is the V/Q ratio when ventilation is adequate but there is no perfusion?
Infinity
