w7- circulation

Question 1

what are the influences on pulmonary vasculature

Answer 1

gravity, lung volume, alveolar pressure, alveolar oxygen status, and local vasomotor controls.

Question 2

ID important mediators of PVR

Answer 2

Hypoxia and Ph

local vasomotor mediators

constrictors:

hypoxia, thromboxane A2, endothelin-1, alpha adrenergic

Dialators: normal tone at sea level

nitric oxide, prostacyclin, beta adrenergic

Question 3

are local vasodilators also proliferative or anti-proliferative

Answer 3

anti-proliferative

Question 4

what are the normal conditions in the different lung zones

Answer 4

zone 1

low blood flow and hyrdostatic pressure

low perfusion because the pulmonary arterial pressure cannot overcome the alveolar pressure compressing capillaries. The only time that this pressure surpasses alveolar pressure is if it exceeds residual volume and intrapleural pressure becomes greater than airway in the base diminishing ventillation, whereas the apex is favorable. Similarly in mechanical (positive pressure) ventillation and breath hold

Zone 3

highest hydrostatic pressure due to gravity which leads to more flow through increased distention and rercruitment and thusly reduced PVR

Question 5

what 2 things can lead to ceasation of blood flow in zone 1

Answer 5

reduced blood pressure

increased alveolar pressure

Question 6

decribe the impact of lung volume PVR

Answer 6

PVR is lowest at end-expiration (FRC) and increases as lung volumes move in either direction.

At volumes below FRC compression effects on extra alveolar vessels dominate

At volumes above FRC compression effect on capillary vessels offsets traction effects on extra alveolar vessels

•Extra-alveolar vessels”, vessels whose transmural pressures are determined by pulmonary interstitial pressure rather than alveolar pressure (pulmonarycapillaries).

Question 7

define transmural pressure

Answer 7

pulmonary capillaries luminal pressure-alveolar pressure.

extra-alveolar vessels luminal pressure-pleural pressure.

Question 8

describe how pulmonary edema forms

Answer 8

perivascular and peribronchialspaces and is drained (very efficiently) by the lymphatic vessels in the same spaces

Blood fluids tend to extravasate, that is, leave a capillary at its arterial end to form lymph. Most lymph returns to the capillary by reabsorption at its venous end. Net fluid loss is normal and collects in adjacent lymphatics. Extravasation that exceeds lymphatic capacity to remove it causes edema

At high enough pressure, interstitial edematous fluid may cross into alveolar space and become alveolar edema

•

Question 9

what diseases can cause an increase in P_MV= pressure in microvessel

Answer 9

congestive heart failure, mitral stenosis, MI

Question 10

what diseases can cause an increase in P_PMV= pressure in perimicrovascularspace

decrease?

Answer 10

reduced lymphatic drainage from lymphatigitis and or neoplasm

alveolar overdistention, hypoxia

Question 11

what diseases can cause an increase in

Question 12

what diseases can cause an increase in σ= protein reflection coefficient

Answer 12

hyperoxia, sepsis, inhalation injury, drug toxicity

Question 13

what can cause a decrease in πMV= Protein colloid osmotic (oncotic) pressure in the circulation

Answer 13

hemodulution, hypoalbinurea

Question 14

what can cause a decrease in πPMV= Protein colloid osmotic pressure in the peri-microvascular soace

Answer 14

drowing in fresh water

pulmonary edema

high altitude