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Pulmonary Circulation Pulmonary Circulation Dr. Walid Daoud Dr. Walid Daoud MBBCh, MSc, MD, FCCP MBBCh, MSc, MD, FCCP Director of Chest Department Director of Chest Department , , Shifa Hospital, Shifa Hospital, A. A. Professor of Chest Medicine Professor of Chest Medicine

Pulmonary Circulation Dr. Walid Daoud MBBCh, MSc, MD, FCCP Director of Chest Department, Shifa Hospital, A. Professor of Chest Medicine

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Pulmonary CirculationPulmonary Circulation

Dr. Walid DaoudDr. Walid DaoudMBBCh, MSc, MD, FCCPMBBCh, MSc, MD, FCCP

Director of Chest DepartmentDirector of Chest Department , ,

Shifa Hospital, Shifa Hospital, A. Professor of Chest MedicineA. Professor of Chest Medicine

Types of circulationTypes of circulation

11 . .Systemic (bronchial): Systemic (bronchial): High pressure, low flow circulationHigh pressure, low flow circulation

22 . .PulmonaryPulmonary::

Low pressure, high flow circulationLow pressure, high flow circulation

Pulmonary circulatory systemPulmonary circulatory system____________________________________________________________________________

11 . .Pulmonary vesselsPulmonary vessels::

- - Pulmonary artery is thin with large diameter, Pulmonary artery is thin with large diameter, distensible and large compliance distensible and large compliance

22 . .Bronchial vesselsBronchial vessels::

Forms 1-2% of total cardiac outputForms 1-2% of total cardiac output..

33 . .LymphaticsLymphatics . .

Pressures in pulmonary circulationPressures in pulmonary circulation ____________________________________________________________________________

11 . .Pressure pulse curve in RVPressure pulse curve in RV::

Systolic P in RV = 25 mmHgSystolic P in RV = 25 mmHg

Diastolic P in RV = 0-1 mmHgDiastolic P in RV = 0-1 mmHg

22 . .Pressures in pulmonary arteryPressures in pulmonary artery::

Systolic P = 25 mmHgSystolic P = 25 mmHg

Diastolic P = 8 mmHgDiastolic P = 8 mmHg

Mean pulmonary arterial P = 15 mmHgMean pulmonary arterial P = 15 mmHg

33 . .Pulmonary capillary pressure Pulmonary capillary pressure = 7 mmHg= 7 mmHg

44 . .Left atrial P Left atrial P =1-5 mmHg, =1-5 mmHg, PCWP PCWP = 5 mmHg= 5 mmHg

Blood volume of the lungsBlood volume of the lungs ____________________________________________________________________________

11 . .Lung serve as a blood reservoirLung serve as a blood reservoir::

Blood volume in lung is 450 ml or 90% ofBlood volume in lung is 450 ml or 90% of

total blood volume and 70 ml of this intotal blood volume and 70 ml of this in

pulmonary capillaries. Loss of blood causespulmonary capillaries. Loss of blood causes

shift of blood from pulmonary to systemicshift of blood from pulmonary to systemic

circulationcirculation

22 . .Left heart failure may shift blood fromLeft heart failure may shift blood from

systemic to pulmonary circulationsystemic to pulmonary circulation::

Blood flow through lungs & its distributionBlood flow through lungs & its distribution ____________________________________________________________________________

Blood flow is the cardiac outputBlood flow is the cardiac output

Dilatation of pulmonary vessels increases blood Dilatation of pulmonary vessels increases blood flow and constriction decreases blood flowflow and constriction decreases blood flow

Decreased alveolar O2 below 70% produces Decreased alveolar O2 below 70% produces constriction of pulmonary vessels and increase constriction of pulmonary vessels and increase vascular resistance and reduces local blood flow. vascular resistance and reduces local blood flow. This leads to shift of blood from poorly ventilated This leads to shift of blood from poorly ventilated to better areated alveolito better areated alveoli

This is opposite effects observed in systemic This is opposite effects observed in systemic circulationcirculation . .

Effects of hydrostatic pressure gradients in Effects of hydrostatic pressure gradients in the lungs on regional pulmonary blood flow the lungs on regional pulmonary blood flow____________________________________________________________________________

Lung apex is more ventilated and less perfusedLung apex is more ventilated and less perfused

Lung base is less ventilated and more perfusedLung base is less ventilated and more perfused

Zones of pulmonary blood flowZones of pulmonary blood flow::

Zone 1: no blood flow during all cardiac cycleZone 1: no blood flow during all cardiac cycle

Alveolar P > Capillary PAlveolar P > Capillary P

Zone 2: Intermittent blood flow at lung apexZone 2: Intermittent blood flow at lung apex

Capillary P > Alveolar P only during systoleCapillary P > Alveolar P only during systole

Zone 3: continuous blood flow at lung baseZone 3: continuous blood flow at lung base

Capillary P > Alveolar P during all cardiac cycleCapillary P > Alveolar P during all cardiac cycle

Effects of hydrostatic pressure gradients in Effects of hydrostatic pressure gradients in the lungs on regional pulmonary blood flow the lungs on regional pulmonary blood flow____________________________________________________________________________

Normally, lungs have only zone 2 and 3Normally, lungs have only zone 2 and 3

In upright position, pulm P at apex is 15 mmHg In upright position, pulm P at apex is 15 mmHg less than P at level of heart (25 mmHg) so less than P at level of heart (25 mmHg) so the apical systolic P is 10 mmHg greater than the apical systolic P is 10 mmHg greater than zero alveolar P. so blood flows through apical zero alveolar P. so blood flows through apical pulm cap. During cardiac diastole, diastolic P pulm cap. During cardiac diastole, diastolic P at level of heart is 8 mmHg is not enough to at level of heart is 8 mmHg is not enough to push blood up the 15 mmHg hydrostatic push blood up the 15 mmHg hydrostatic pressure gradient to cause diastolic blood pressure gradient to cause diastolic blood flow so blood flow at apex is intermittentflow so blood flow at apex is intermittent..

Effects of hydrostatic pressure gradients in Effects of hydrostatic pressure gradients in the lungs on regional pulmonary blood flow the lungs on regional pulmonary blood flow____________________________________________________________________________

In the lower region of lung from 10 cm above In the lower region of lung from 10 cm above level of heart, pulm art P during both systole level of heart, pulm art P during both systole and diastole is greater than zero alveolar P and diastole is greater than zero alveolar P so there is continuous flow through alveolar so there is continuous flow through alveolar capillaries (zone 3)capillaries (zone 3)..

In lying position blood flow is zone 3 in whole In lying position blood flow is zone 3 in whole lung including apexlung including apex..

Zone 1 blood flow occurs abnormallyZone 1 blood flow occurs abnormally____________________________________________________________________________

Zone 1 means no blood flow and occurs when Zone 1 means no blood flow and occurs when pulm systolic P is too low or alveolar P too pulm systolic P is too low or alveolar P too high to allow flow, as in the followinghigh to allow flow, as in the following::

11..Breathing positive pressure in upright position Breathing positive pressure in upright position when alveolar pressure at 10 mmHg when alveolar pressure at 10 mmHg..

22..Severe blood loss in upright position whereSevere blood loss in upright position where

pulm systolic P is lowpulm systolic P is low..

Effect of exercise on pulm blood flowEffect of exercise on pulm blood flow____________________________________________________________________________

Blood flow increases in all parts of the lung, the Blood flow increases in all parts of the lung, the increase in flow 700-800% at top of the lungincrease in flow 700-800% at top of the lung

Increase in flow 200-300% at lung baseIncrease in flow 200-300% at lung base

The increase in pulm art P during exercise The increase in pulm art P during exercise converts zone 2 into zone 3 pattern of flowconverts zone 2 into zone 3 pattern of flow..

Severe increase in cardiac output is not Severe increase in cardiac output is not associated with large increase in pulmonary associated with large increase in pulmonary artery pressure and increase in pulm flow due artery pressure and increase in pulm flow due to increase no. of open capillaries, dilatation to increase no. of open capillaries, dilatation

of capilllaries and increase pulm art Pof capilllaries and increase pulm art P . .

Effect of left sided heart failure on Effect of left sided heart failure on pulmonary circulationpulmonary circulation ____________________________________________________________________________

Normally left atrial P 1-5 mmHgNormally left atrial P 1-5 mmHg

When the left heart fails, the left atrial pressure When the left heart fails, the left atrial pressure increases (up to 40-50 mmHg) and this increases (up to 40-50 mmHg) and this increases the pulmonary artery pressure and increases the pulmonary artery pressure and capillary pressure and pulmonary edema capillary pressure and pulmonary edema resultsresults..

Pulmonary capillary dynamicsPulmonary capillary dynamics ____________________________________________________________________________

Pulmonary capillary pressure 7 mmHgPulmonary capillary pressure 7 mmHg

Mean pulmonary capillary pressure 15 mmHgMean pulmonary capillary pressure 15 mmHg

Transit time 0.8 sec and when cardiac output Transit time 0.8 sec and when cardiac output increases as in exercise transit time isincreases as in exercise transit time is

decreased to 0.3 secdecreased to 0.3 sec..

So in only a fraction of second blood pass So in only a fraction of second blood pass through alveolar capillaries and becomes through alveolar capillaries and becomes

oxygenated with removal of carbon dioxideoxygenated with removal of carbon dioxide . .

Capillary exchange of fluid in lungs and Capillary exchange of fluid in lungs and pulmonary interstitial fluid dynamicspulmonary interstitial fluid dynamics ____________________________________________________________________________

THANK YOUTHANK YOU