Blood supply of lungs

dr.prapulla chandra

• Blood supply of lung includes-

BRONCHIAL CIRCULATION- comprising of bronchial arteries and veins

PULMONARY CIRCULATION- comprising of pulmonary arteries and veins

Differences

• Bronchial arteries supplies oxygenated blood pumped from the left ventricle- systemic circulation relatively smaller diameter, high pressure

• Pulmonary arteries supplies deoxygenated blood pumped from the right ventricle . This circulation relatively larger diameter, low pressure

DEVELOPMENT

• By the completion of 16th week intrauterine life, the preacinar structures of bronchi, pulmonary vessels, bronchial arteries are developed

• Pulmonary trunk developed from 6th primitive branchial arch

• Vessels developed from mesenchymal tissue

Fetal and neonatal circulation

• Before birth, lungs receive about 10 to 15 percent of right ventricle output

• In comparison to adult circulation, fetal circulation has

More vascular resistance High initial tone Greater vascular reactivity Reactive hyperemia• PGs, endothelins and NO plays an important role in

regulating fetal circulation.

• After first breath there is marked drop in PVR Due to: Increased Po2 Expansion of the lungs

Bronchial circulation• It is a part of systemic circulation• It contains 1-2 percent of cardiac output

BRONCHIAL ARTERIES Origin• The left BA (superior & inferior) usually arise directly from the

thoracic aorta at the level of T5&T6 vertebra • The origin of the right bronchial artery is variable; in order of

frequency, it may arise from• right posterior intercostal artery (usually the 3rd), • a common trunk shared with the left superior bronchial artery, or • directly from the aorta.

2 Left bronchial artery

1 Right bronchial artery

Bronchial artery branching pattern Cauldwell et al - four patterns:

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Type I Type II Type III Type IV

Cauldwell EW, Siekert RG, Lininger RE, Anson BJ.The bronchial arteries: an anatomic study of 105 human cadavers. Surg Gynecol Obstet 1948; 86:395–412.

Type I • Incidence: 40.6% • Left: 2• Right: 1 {intercostobronchial

trunk (ICBT)}

12

Single rt.branch

Lt. 2 br.arties

Sup.left bronchial

artert

Inf.Left bronchial

artery.

Right bronchial

artery.

Type II• Incidence: 21.3%• Left:

1 left Bronchial Artery• Right: 1intercostobronchial

trunk

13

Single Lft.bron.art

Single.Rt.ICBT

Type III • Incidence: 20.6%• Left: 2• Right : 2

(1intercostobronchial trunk & 1 Right bronchial artery)

14

Left sup.& Left Inf .bronchial artery.

Right ICBT

Right Bronchial artery

.

Type IV• Incidence: 9.7% • Left: 1• Right: 2

(one intercostobronchial trunk and one bronchial artery)

15

Single Left artery

Rt.ICBT

Rt.Bron.art.

• Normal BA measure < 1.5 mm in diameter at their origin and 0.5 mm at their point of entry into a BPS

• BA >2 mm at CT is most likely abnormal , upto 8mm in hypertrophied

Distribution to lung• The br. A supply blood to the bronchi and connective

tissue of the lungs. They end at the level of the respiratory bronchioles. They anastomose with the branches of the pulmonary arteries, and together, they supply the visceral pleura of the lung

Functions• It has features of nutrient circulation• they supply the lungs with oxygenated blood • It also participates in air conditioning of the inspired

air.

Bronchial veins• There is typically a single bronchial vein at

each hilum, formed from the superficial bronchial veins with deep bronchial veins, draining into the pulmonary veins.

Deep bronchial veins• The deep bronchial veins form from intrabronchial

venous plexuses. These vein drains either directly into the left atrium or into thepulmonary vein. Within the lung there are significant anastmoses with the intrapulmonary pulmonary veins.

• Superficial bronchial veins• The superficial bronchial veins consist of a subpleural

venous network which receive tributaries from extra-pulmonary bronchi, hilar lymph nodes and the vaso vasorum of the hilar pulmonary vessels and unite to form a single bronchial vein at each hilum.

• on the right, they drain into the azygos vein. On the left they drain into the left superior intercostal vein, accessory hemiazygos vein or left brachiocephalic vein. At the hilum they communicate with the pulmonary veins.

VENOUS DRAINAGE

• The bronchial circulation proliferates beyond the

limits in the following conditions: Pulmonary atresia bronchiectasis lung abscess lung cancer•In chronic MS, Haemoptysis occurs from bronchial

veins

Pulmonary Pulmonary circulationcirculation

PULMONARY CIRCULATION

Pulmonary arteryArises from the infundibulum of the right ventricle

at pulmonary valve and runs posteriorly slightly upwards and divide below the aortic arch in to right and left

Right pulmonary artery runs laterally under aortic arch and posterior to ascending aorta and superior venacava before dividing at the hilum into upper, middle and lower branches ,to supply upper, middle and lower lobes respectively

• Left pulmonary artery runs laterally, upwards and

posteriorly,anterior to descending aorta and connected to ligamentum arteriosum.

• It divides into upper and lower branches; they supply upper and lower lobes

• Sub divides in a variable pattern on both sides

• Counting from peripheral small arteries to the main

pulmonary trunk, there are 17 orders of branching on both sides.

• Pulmonary arteries breaking up to pulmonary capillaries that form network around the alveolus.

• Media of the vessels consists of elastic fibrils(5 or 6layers) with smooth muscle fibers, collagen and mucopolysaccharide ground substance.

Pulmonary artery distribution

Alveolar wall

Lung capillaries

Lung capillaries

Alveolus

Pulmonary veins

• Four in number two on each side They commence in a capillary network upon the

walls of the air sacs, where they are continuous with capillary ramifications of the pulmonary artery and joining together form a single trunk for each lobule

• On right side two in number - because middle lobe

vein joined with upper lobe vein• On left side two in number• These four veins perforate the fibrous layer of the

pericardium and opens separately in to upper and back of the left atrium

• Pulmonary artery—de-oxygenated• Pulmonary veins—only veins which carry oxygenated

blood

Functions of the pulmonary circulation• Respiratory and non-respiratory• Respiratory- gas exchange• Non-respiratory

•Blood filter•Blood reservoir•Metabolic•Nutrient

Gas exchange

The pulmonary artery branches rapidly give rise to nearly 300 million capillaries

Gas exchange between alveolar gases and blood occur within the lung capillaries by simple diffusion.

Oxygen diffuses from the alveolus to pulmonary capillary blood, ,Co2 diffuses in the reverse direction, as determined by their concentration gradient

Blood filter

• Micro vessels are so numerous, that effectively serves as a filter to entrap the foreign materials present in the blood

• This filter mechanism prevent entry of potentially harmful particles in to systemic circulation

• Entrapped materials can be removed by enzymatic process, macrophages or absorption into lymphatic system

Reservoir of blood for left ventricle

• Pulmonary circulation is very compliant and accommodate about 500 ml of blood in an adult

• This can serve as a reservoir for left ventricle particularly during times when output exceeds venous return

• The cardiac output can increase rapidly by drawing upon pulmonary blood volume without depending on instantaneous increase in venous return

Metabolic function of the pulmonary circulation

• Uptake or metabolic conversion of vasoactive substances into circulation done by endothelial cells.

• Conversion of Angiotensin I to angiotensin II

Neurohumoral function of lung

Angiotensinogen

ANGIOTENSIN I

ANGIOTENSIN II

RENIN

CONVERTING ENZYME

PERIPHERAL VASOCONSTRICTION

ALDOSTERONE SECRETION

INCREASED BLOOD PRESSURE

Pulmonary vascular resistance

• Normal pulmonary circulation is a low resistance, high compliant vascular bed

• Calculated by using• R=P.PA-P.LA/QT• Normal value of R for pulmonary circulation is 0.1 mm

hg/L/minIn humans residing at high altitude, will have high PVR,

because muscular media of the small pulmonary arteries and arterioles becomes thicker.

Pulmonary vascular pressures

• Pulmonary pressure drop along the length of pulmonary vascular tree

• Since pulmonary capillary pressure can’t be measured directly, they are generally estimated to be intermediate between the mean pulmonary arterial and pulmonary wedge pressures

• Pulmonary capillary flow recorded by using Body plethysmograph Nitrous oxide methodAverage pul. Art. Pressure is about 10-12 mm Hg(1/8 th

of systemic circulation)During systole 20-30 mm of Hgdiastole 5 to 10mm of HgAgeing associated with slight increase in pulmonary

arterial pressure

LEFT ATRIAL AND PULMONARY WEDGE PRESSURE • In intact, unanaesthetized humans, the mean left

atrial pressure is about 5 to 10 mm Hg.• It is measured by advancing a cardiac catheter

through the right side of the heart and pulmonary arterial tree until it impacts in a small precapillary vessel

Pulmonary blood volume

• It is about 10 percent of total systemic circulation• Measured by using indicator dilution principle• 70 kg human male contains approximately 400-500

ml

• This value is useful for 1.Determination of the mechanical behavior of lung. 2.Provides preload for the left ventricle, acts as a

reservoir3.As a supply of Hb for alveolar-capillary gas exchange4.As a source of water and macromolecules that

engage in alveolar-capillary exchange5.As a potential mechanism for increasing pulmonary

capillary pressures and promoting pulmonary edema.

Pulmonary blood volume Increases in -IV infusion -immersing the body in water -by inflation of an antigravity suit -by negative pressure breathing -systemic vasoconstriction -lying down position

• Decreases -when person stands - After a large venesection -during positive-pressure breathing -valsalva maneuver -systemic vasodilatation

Pulmonary vasomotor

control

•The initial vascular tone of pulmonary circulation is attributed to balance between vasodilation and vasoconstriction caused by various mediators.

•Vasodialtion caused by prostacyclins, nitric oxide

•Constriction by endothelins..

Under normal conditions

hypoxia

Role of nerves in pulmonary vasomotor control• Sympathetic innervation to pulmonary circulation

includes alpha adrenergic receptors -predominate-(eg:NE)- constrictor beta adrenergic receptors-(eg:isoproterenol)- dilator• Cholinergic activity does not appear to be implicated

Acute hypoxia

• Pressor effect of acute hypoxia on the pulmonary circulation was given by Euler and Liljestrand

• This pressor effect redirects blood flow to better ventilated portion

• Acute hypoxia increases pulmonary arterial pressure, does not affect left atrial pressure, and little increase in cardiac output

• The pressor effect starts within seconds, generally

reaches peak by 3 min, and attenuates gradually as hypoxia continues

• Acidosis augments pressor response• This effect Is predominantly at pre-capillary level

(i.e.: small muscular art. and arterioles)

Hypoxic pulmonary vasoconstriction

PO2 = 100 mmHg

100

40

40 100

100

40

40

PO2

hypoxia

Chronic hypoxia• Ex. High altitude• It causes remodeling of small pulmonary arteries and

arterioles leading to high PVR,due to muscular media thickening.

•Acute hypercapnia -Little response is seen if the pH is maintained

at near normal level Acidosis causes pulmonary vasoconstriction, where

as alkalosis causes vasodilatation.

other vasoactive substances

• Vasodilators Ach Bradykinin Isoprenaline• Vasoconstrictors Catecholamine Angiotensin II Histamine Serotonin

Effect of gravity

• In upright lung blood flow increases steadily from top to bottom

Gravity determines highest blood flow at lung base

0 cm

End expiration

+10 cm

-10 cm

Pa > Ppa >Ppv

(cmH2O)Ppa >Pa >Ppv

Ppa > Ppv >Pa

Palv = 0

HEMOPTYSISCOMMON CAUSES:•Tuberculosis ( active or inactive)•Bronchiectasis (including cystic fibrosis)•Bronchogenic Carcinoma•Mycetoma ( aspergillloma /Fungal ball)•Lung abcess•Mitral stenosis•Pulmonary Contusion or trauma

Tuberculosis

MECHANISMS•Active tubercular pneumonitis- bronchiolar erosion•Rupture of Rasmussen’s aneurysm (pulmonary. artery)•Healed calcified lymphnode - eroding through bronchial arteries into airway (expectoration of broncholith)

BRONCHIECTASIS

• Pathologically it is destruction of the cartilaginous support of bronchial wall and bronchial dilatation owing to parenchymal retraction from alveolar fibrosis

ANATOMICAL CHANGES:• Bronchial artery hypertrophy• Expansion of peribronchial & sub mucosal

bronchiolar arteriolar plexus• Augmentation of anastomoses with the pulmonary

arterial bed

MYCETOMA

MECHANISMS:• Mechanical trauma of the vascular granulation

tissue by the movement of the fungal ball in the cavity

• Vascular injury from aspergillus associated endotoxin

• Aspergillus related proteolytic activity• Vascular damage from a type 3 hypersensitivity

reaction

Abnormal pulmonary vascular

communications

Systemic artery-pulmonary vascular communications• May be congenital or acquired• Acquired is most common• Haemodynamically presents as left to right shunt

between coronary,intercostal or internal mammary and pulmonary circulation

• There will be continuous murmur over the site of communication

• It maybe a complication of intrathoracic neoplasm or chronic inflammatory conditions.

Systemic artery–pulmonary artery shunt

Congenital Pulmonary Arteriovenous Malformation (PAVM)• AKA pulmonary a-v fistulae = pulmonary a-v aneurysm = cavernous angiomas of the lung

• Defined as abnormal vascular communications between pulmonary arteries and veins that lead veno-arterial shunting

There is a close association b/w PAVM and hereditary hemorrhagic telangiectasia (osler weber rendu syndrome),an autosomal dominant condition in 50-60% of cases and

the reverse in 5-15% cases

It has been shown that a gene located on chr 9q3 is strongly associated with the presence of two conditions

• Divided into simple or complex• Simple PAVMs consist of segmental artery joining

thin-walled aneurysmal sac drained by single vein (majority of cases)

• Complex PAVMs involves arterial supply from 2 different segmental arteries (only small percentage)

• Can have multiple lesions(20-30%), • bilateral disease(10%)• More than half found in lower lung fields• Sizes vary typically 1-5 cm and can exceed 10cm

• Most commonly found in lower lobes adjacent to visceral pleura

• Presenting features: dyspnea and epistaxis Cyanosis and clubbing Extra cardiac murmur• Treatment is by excision

ANOMALOUS SYSTEMIC PULMONARY PERFUSION

• Usually from descending thoracic aorta, also from ascending aorta, innominate, subclavian etc

• Asymptomatic but may present with recurrent hemoptysis in some cases

CXR shows normal or increased vascular markings in the vicinity of anomalous vessels

Aortograhy is diagnostic

Treatment consists of surgical ligation, embolisation or even lung resection to control hemoptysis.

ANOMALOUS ORIGIN OF LEFT PULMONARY ARTERY

• The left pulmonary artery arises in anomalous fashion from right pulmonary artery

• To reach left lung, it loops around right main bronchus like a sling and runs b/w trachea and esophagus to enter left hilum with consequent dyspnoea and dysphagia

ANOMALOUS PULMONARY VENOUS DRAINAGE

As a result of persistant communication b/w embryonic system of cardinal veins and pulmonary venous plexus, pulmonary veins drain systemically into ivc.

PULMONARY ARTERY STENOSIS

• Charaterised by coarctation of pulmonary arteries with poststenotic dilatation

BAUM and his colleagues divided the patients into two groups

TYPE1: Main pulmonary artery affected; associated with CVS anomalies TYPE2: Peripheral branch involved

CXR may show poststenotic dilatation of affected pulmonary artery branches, oligemia and signs of PAH or cor pulmonale

Diagnosis confirmed by pulmonary angiography

ABSENT UNILATERAL PULMONARY ARTERY

• Failure of development of either right or left side of primitive sixth branchial arch so that no communication exists b/w main pulmonary artery trunk and the lung on affected side, which receives its blood supply systemically most frequently bronchial vessels.

Usually associated with CHD

Associated with pulmonary artery hypertension

Diagnosis by CXR, VP-scan, pulmonary arteriography

Treatment usually not possible, although reconstructive anastomotic surgery and recanalisation possible in some.

SINGLE LEFT PULMONARY ARTERY

ABSENCE OF MAIN PULMONARY ARTERY

The pulmonary artery trunk may be completely absent as a result of agenesis of primitive sixth branchial arch or of developmental failure of septum dividing truncus arteriosus

L-R shunt exists, the lungs being supplied by bronchial or other systemic aberrant vessels

Poor prognosis, most patients being stillborn or dying in infancy with pulmonary hypertension.

Pulmonary hypertension•Mean pulmonary artery pressure >25mm Hg at rest or >30 mm Hg with exercise

•Anatomical changes Intimal atheromas Medial hypertrophy Remodeling of muscular arteries

Pulmonary thromboembolism

• The condition in which blood clot (thrombus or multiple thrombi) migrate from the systemic circulation to pulmonary vasculature.

• Most of the clots arise from “ deep veins” of lower & upper extremity

• Increases right vent. overload - RHF• Increase in intrapulm. shunting , V/Q mismatch • Pulm. infarct in 20% of cases in patients with cardiac or

pulmonary disease

Pulmonary embolism (1)Pulmonary embolism (1)

Pulmonary embolism (2)Pulmonary embolism (2)

Pulmonary vasculitis PRIMARY• Large: Giant cell

arteritis,Takayasu arteritis

• Medium:PAN,Kawasaki• Small:WG,CSS,HSP,Micr

oscopic polyangitis

SECONDARY

• Infection• Necrotizing sarcoid

granulomatosis• DRUGS(propyl

thiouracil,D-pencillamine,sulfasalazine,minocycline)

THANK YOU

Next seminar on 06-03-2015 SOLITARY PULMONARY NODULE by Dr. deepika