Pulmonary circulation€¦ · Pulmonary circulation Physiological anatomy: the Pul Artery is 5cm...

Pulmonary circulation Physiological anatomy: the Pul Artery is 5cm length and thin (1/3 of aorta ) , while

the branches are short and have more diameter so it will have a large compliance (7 ml/mmHg).

pulmonary veins are thin & short. bronchial arteries originate from the systemic circulation

(carry 1-2% of C.O -oxygenated blood-) then empty into pulmonary veins then to the left atrium so the left ventricle pumps 1-2% more than the right ventricle.

rich lymphatic drainage to the right thoracic duct to

prevent edema

Pressures in the pulmonary system:

1- Right ventricle: 25-1 mmHg

2- Pulm. Artery: 25-8 mmHg

3- Pulm. cap. : 8 mmHg

4- Left atrium & major veins: 2 mmHg

5- Pulmonary wedge pressure about 5mm hg.

Increase in congestive heart failure

Blood volume of the lungs: :

450 ml ( 9% of total blood volume)

70 ml are found in the capillaries

Blood volume of the lungs -Lungs as blood reservoir

if the person is bleeding or blowing air out hardly the volume can reach 200 ml.

if the person has left heart failure or mitral valve stenosis or regurgitation the volume can reach 900 ml shift from systemic

Circulation.

MEASUREMENT OF PULMONARY

BLOOD FLOW

Fick Principle

VO2 = Oxygen Consumption CaO2 = Arterial Content

CvO2 = Venous Content

VO2=Q(CaO2-CvO2

)

Q = Blood flow

MEASUREMENT OF PULMONARY BLOOD

FLOW

VO2 = 250 ml/min

CaO2 = 20 ml O2/100 ml blood

CvO2 = 15 ml O2/100 ml blood

VO2=Q(CaO2-CvO2

)

Q = 250 ml O2/min = 250 ml O2 * 100 ml blood

(20-15) ml O2/100 ml blood min 5 ml O2

Q = 5000 ml blood /min

Blood flow

Effect of alveolar [O2]:

when [O2] decreases below 70% of normal alveolar epithelial cells secrete vasoconstrictors adjacent blood vessels constrict blood flows to better aerated alveoli (extreme low [O2] 5x resistance)

Effect of hydrostatic pressure:

in normal upright adult there’s a difference between the lowest and highest points of the lung

the gradient is 23 mmHg (15 mmHg above the heart & 8 mmHg below it)

Regional pulmonary blood flow : 1-Zone 1: No blood flow (capill. pr. < alveol, pr.) 2-Zone 2: Intermittent blood flow 3-Zone 3: Continuous blood flow. (capill. pr. > alveol. pr.) in normal lungs zone 1 cannot be found, zone 2 is in the

apex of the lung and zone 3 represents the base.

Regional pulmonary blood flow :

arterial pressure in pulmonary artery is 25-8 mmHg at apex systolic 25-15= 10 mmHg

during diastole 8-15 mmHg= -7?

(Hydrostatic pressure difference is 15 mmHg between the level of the heart and the lung apex)

if the person is lying down or exercising only zone 3 can be seen.

C. Increase flow to the top by about 700-800% and

200-300% in the lower part because during exercise convert apices from zone 2 to zone 3

PULMONARY CIRCULATION IN LEFT SIDE HEART FAILURE

When the left atrial pressure increase more than 7mmhg will cause increase of pulmonary arterial pressure which will increase the load on right ventricle.

Pulmonary capillary dynamics: 7 mmHg cap. Pressure. blood passes through the capillary in 0.8sec increasing the C.O lowers the time to 0.3sec Capillary fluid exchange dynamics: outward forces= 7+14+8 = 29 mmHg inward forces = 28 mmHg mean filtration pr. = 1 mmHg “handled by lymph”

lungs Systemic cir.

Capillary pressure 7 mmHg 17 mmHg

Interst. Osm. Pr. 14 mmHg 8 mmHg

Interst. Neg. pr. -8 mmHg -3 mmHg

Pulmonary Capillary Dynamics Outward Forces

Pulmonary capillary pressure 7 mmHg

Interstitial osmotic pressure 14 mmHg

Negative interstitial pressure 8 mmHg

Total 29 mmHg

Inward Forces

Plasma osmotic pressure 28 mmHg

Net filtration pressure 1 mmHg

Negative interstitial pressure keeps alveoli dry

Pulmonary Capillary Dynamics

Hydrostatic

Osmotic

+7 -8

28 14

+1

Lymphatic pump

0

-8 surface tension

Net

hydrostatic pressure

-5

Pulmonary edema Alveoli are always dry except for a small amount of fluid

secreted by alveolar cells on the alveolar surface. When interstitial pressure becomes (+) water will fill the alveoli Causes: 1- Left-sided heart failure ↑ venous+cap. pr 2-Damage to the pulmonary capillary membrane caused by : a- infections (pneumonia) b- breathing chlorine gas or sulfur dioxide gas.

Safety factors 21 mmHg in acute states

35 mmHg in chronic cases ( Lymph expand)

Left Atrial Pressure

Edem

a F

orm

atio

n

Heart Failure and Pulmonary Edema

25 0

Pulmonary Edema

Causes of pulmonary edema

left heart failure

damage to pulmonary blood cap membrane, as

In pneumonia or breathing chlorine gas or sulfur dioxide gas

Safety factor

negative interstitial pressure

lymphatic pumping

decreased interstitial osmotic pressure

PLEURAL EFFUSION Pleural effusion (edema) : Collection of large free fluid

in the pleural space

1-Blockage of lymphatic drainage from pleural space

2- Cardiac failure (increase peripheral and pulmonary cap pressure)

3- Decrease plasma colloid osmotic pressure

4- Infection or inflammation of the surface of pleural

cavity