Pulmonary circulation

1. PULMONARY CIRCULATION

2. Three Types Pulmonary artery Bronchial artery Lymphatic circulation

3. Pulmonary Arterial Circulation

4. Bronchial Arteries Two left and one right From descending aorta Contributes to a physiological shunt

5. General Characters Thin walled , distensible , large compliance Low pressure , low resistance , high capacitance system Pul capillaries are larger and have more anastamosis Helps in gas exchange Serves as a filter Metabolic functuions Serves as a blood reservoir

6. Cont’d PVR falls with increased pulmonary arterial pressure Occurs because of two reasons Recruitment Increased capillary distension Importance :- prevents pulmonary edema reduces velocity

7. Pulmonary Blood Flow Vessels contain 600 ml of blood at rest Increases and decreases according to posture and pathological conditions

8. Pressures in pulmonary system Pressure Pulmonary system Systemic vasculature Ventricular pressure RV- 25 (systolic) LV- 120 systolic Pulmonary artery 25 sys 8 diastolic 120 sys 80 dias MAP 15 mm/hg 100 Pulse pressure 17 40 atrial pressure LA – 5 RA - 0 Pressure gradient Pp= MAP- MVP = 15-5 =5 100

9. Pulmonary Capillary Pressure Mean value is 10 mmHg Is less than colloid osmotic pressure 25mmHg So a net suction force of 15mmHg is keeping the alveoli dry However if hydrostatic pressure raises more than 25mmHg then pulmonary edema ensures

10. Pulmonary Capillary Wedge Pressure Is measured to give the LAP Direct measurement of LAP is difficult So indirect measurement is done LAP corresponds to PCWP Measures by swans gans catheter Catheter is wedged in the tip of the small branch of pulmonary artery Stops flow of blood in that

11. Swans Gans Catheter

12. Regional Distribution Of Pulmonary Blood Same as the CO or LV output Effect of gravity :- in supine position MAP is same allover the lungs so uniform perfusion Gravity changes the hydrostatic pressure Zero reference plane is at the level of RA Which is approximately at the middle of the lung or hilum

13. In a 30cm height lung In the middle pressure is 15mmHg In the apex its 11 mmHg less ie 4mmHg In the base its 26mmHg At Standing Position

14. Perfusion Zones Of Lungs Depends upon three pressure PA - alveolar pressure Pa – pulmonary arterial pressure Pv – pulmonary venous pressure Divided into three zones in erect posture – 1, 2, 3

15. Zone 1 Area of zero perfusion Does not exist in normal lungs Occurs when Pul arterial pressure becomes less than alveolar pressure Pulmonary capillaries become collapsed Flow becomes zero Ex- pulmonary embolism , shock , obstructive lung diseases ,

16. Zone 2 Region of intermittent blood flow This occurs during systole when the pul arterial pressure raises more than PA In normal lungs this zone occurs from apex to hilum of the lungs Systolic pa pressure is 25 and diastolic is 8

17. In a 30cm height lung In the middle pressure is 15mmHg In the apex its 11 mmHg less ie 4mmHg In the base its 26mmHg At Standing Position

18. Zone 3 This zone has continues high blood flow Here pa is greater than PA during the entire cardiac cycle this region occurs in from the middle zone of lungs to bottom

19. Effect of exercise Blood flow increases 4- 7 times Near base its 2-3 times In apex its 8 times So whole lungs becomes zone 3 Possible because of two reasons Recruitment Distensibility Ability of lungs to accommodate large blood serve two purpose Reduces rt heart work and prevents pulmonary edema

20. Pulmonary Capillary Dynamics Pulmonary transit time 4sec Net filtration pressure Net outward forces :- Interstitial oncotic pressure = 14mmHg Intersttial hydrostatic pressure = -8 Capillary hydroststic pressure = 7 Total = 29mmHg Net inward pressure:- Plasma oncotic pressure = 28mmHg NFP = 29-28= 1

21. Regulation Neural regulation is not very effective Chemical control is major regulatory mechanism

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