Pulmonary Circulation Flashcards
(61 cards)
PAPs
25/10 mean 15
Where do pulmonary vessels branch of into?
Alveolar vessels- closely related to acini, can become compressed with high PEEP
Extra alveolar- Larger and thicker, do not compress with high PEEP,
Vascular resistance / lung volume graph
āJā shape, high resistance at low volumes, low resistance at medium volumes, high resistance at high volumes
How are alveolar dimensions controlled?
Not by autonomic or hormone control
Alveolar capillaries contribute to 40% resistance
Alveolar arterioles contribute to 50% of resistance (compared to 75% of SVR)
How is blood flow directed to the lungs?
With increased CO, lungs RECRUIT mainly
Recuit- opens more vessels as any muscle does during work out
Also distend to a smaller amount
Functional Capillary volume
70ml (1ml/kg) at rest
200ml maximal volume during exercise
How fast does gas exchange occur?
.25 seconds, but stays in network for .75 seconds
How much blood is in the lungs
500 ml- 50% of weight of lungs
More than any other organ
Capacitance resevoir of lungs
can alter from 50% to 200% of resting volume
Prevents change in blood return to RV from affected LV filling pressures of 2-3 cardiac cycles
Chief mechanism of fall in PVR during exercise
Recruitment
Distension
Internal vessel pressure rises and opens capillary beds
Elevated LA pressure extends capillary beds (mitral regurg, LV failure)
Leads to lung congestions and ultimately HF
Seen at high vascular pressures
Pleural pressure during inspiration
Volumes in RV and LV
More negative than -5mm H2)
Lower pressure allows for more venous return to right heart
Higher RV pressure
LV ejects less blood
Pleural pressure on expiration
Pleural pressure less negative than -5mm H2O
Higher pressures decrease venous return
Less RV ejection pressure
What increases PVR?
Higher and lower lung volumes
How do extra alveolar and alveoli react during breathing?
Extra alveolar dilate on inspiration
Alveolar compress during inspirating
How does mechanical ventilation effect alveolar pressure?
Increases alveolar pressure- can decrease CO or increase VQ mistmatch
- Increase amount of ZONE 2
- Increase in resistance to ZONE 2
Where does bronchial blood circulation return to?
RA via azygos vein
Conducting airways to terminal bronchioles, & pleura, interlobar spaces, pulmonary arteries and veins
1-2% of cardiac output
The rest of the bronchial blood exits lung by small anastomeses with pulmonary veins to contribute to normal venous mixture (R to L shunt)
How much fluid do the lymphatic system remove?
20 ml/hr
Hydrostatic forces (slightly negative) are responsible
VO2 at rest
Oxygen consumption/ minute
300 ml/min
CO= O2 Consumption (VO2)/ AV O2 differences
Fick principle
One method of determining CO, blood flow thru lungs
Indicator dilution principles
Dye injected into venous circulation
Diluted concentration measured on arterial side
Thermodilution technique also commonly used to measure CO
Blood flow at different levels
Top lung- low
Middle lung- higher
Bottom lung- Peaks but drops at very bottom
Pressure gradient from gravity on systemic BP
0.74mm Hg/cm
In supine position- arterial pressure is higher in feet than in head
