Pulmonary Circulation & Pulmonary edema Respiratory System Pulmonary Circulation & Pulmonary edema Gass diffusion VA/Q fakeralani2000@yahoo.com

Pulmonary circulation Total B. Volume in the body is about 5-6 L Blood Volume in the Lungs:- - about 9 % of the total B. = 450 ml = 450 ml is present in the lungs - 70 ml is in the capillaries. - 380 is divided about equally between the pulmonary arteries & veins.

Lungs as a B. Reservoir Lungs B Vol. vary from 1/2 to 2X of normal Vol. (Physiological & Pathological) For ex.:- If a person blows out air so hard ( Pr. in the lungs about 250 ml of B. pass from pulmonary circulation into systemic circulation. If a person loss B. from the systemic circulation Hemorrhage partly compensated by shift of B. from the lungs into the systemic vessels.

B. to bronchi, bronchioles & parenchyma B. of Bronchial arterial:- is oxygenated B., originate from systemic circulation. i.e from the Lt Ventricle. Its amount is about 1-2 % of the C.O.. B. of Bronchial vein:- is deoxygenated B. goes with the oxygenated B. Of the lung & enters the Lt atrium, rather than passing back to Rt atrium. (reducing the % of Oxygenation 1-2%) So:- The B. flow through Lt ventricular is about 1-2% > than the Rt ventricular output. - The B. oxygenation is reduced by 1-2 %.

B. Flow & Its Distribution in the Lungs & Amount of pulmonary B. flow/min. = C.O Its distribution in the lungs is affected by:- - Oxygenation:- O2 Conc. < 70% of normal Vasoconstriction vascular resistance 5 X So Sending the B. to the oxygenated area - Hydrostatic Pr.:-

Capi. B. Flow & Effect of alveolar Pr. Capillaries in the alveolar walls:- - Distended by the B. Pr. inside them. - Compressed by alveolar Pr. on their outsides. So - If the alveolar Pr. is > than the capillary B. Pr. the capillaries close & there is no B. flow. In normal lungs, there is 3 possible zones of pulmonary B. flow:-

Zones of Pulmonary B. Flow Zone 1: Minute area = Alveolar Dead space No B. flow during all portions of the cardiac cycle because the local alveolar capillary Pr. never rises > than the alveolar Pr. during the cardiac cycle Zone 2: Apex of the lungs Intermittent B. flow Only during systole Cap. Pr. is > than the alveolar Pr. , So there is flow of B. (Not during Diastole) Zone 3: Lower parts of the lungs Continuous blood flow because the Cap. Pr. is > than alveolar Pr. during the entire cardiac cycle

Zones of Pulmonary B. Flow Normally, the lungs have only zones 2 & 3 B. flow Zone 2 :- (intermittent flow) = at the apices (8-15 cm above heart level). Systolic Pr =25 mmHg / Diastolic Pr =8 mmHg. Zone 3:- (Continuous flow) = (Start from 8 cm above the heart downward) Zone 1:- is present only if there is B.Pr. Or alveolar Pr. (Physiological maneuver / Pathological)

Interstitial colloid Pr Interstitial Colloid Pr Pulmonary Capillary Dynamics Pulmonary Capillary Systemic Capillary Sys. Cap. Pr. Colloid Pr Pul.Cap.Pr Colloid Pr 28 mmHg 17 mmHg 7 mmHg 28 mmHg Interstitial Fluid Pr –8 mmHg Interstitial colloid Pr 7 mmHg Interstitial Pr -8 mmHg Interstitial Colloid Pr 14 mmHg 32-28 =4 29-28 =1 Filtration Pr.

Effect of filtration Pr. Minute quantity of fluid continually flow from pulmonary capillaries into the interstitial place Most of this fluid is reabsorbed back by difference of Pr. Between arterial and venous side The rest is pumped back to the circulation through pulmonary lymphatic.

Effect of the -ve interstitial Pr. “Dryness”: Normally the alveoli are kept dry except for a small amount of fluid that keep them moist. because The -ve Pr. of interstitial space suck fluid from the alveoli through the small openings between these epithelial cells. Interstitial -1 to +1 -8 mmHg Lymph. H2O H2O Cap.

Pulmonary Edema: Any factor that causes filtration of fluid from the capillaries or re-absorption of fluid will cause edema.

The most common clinical causes of edema 1. Pulmonary capillary Pr.: Acute Lt Ventricular failure. Mitral valve disease. 2. Colloid osmotic Pr. Sever Hypoproteinemia. 3. Damage of pulmonary capillary membrane Infection (pneumonia) Inhalation of noxious gas like chorine or sulfur dioxide.

Acute Pulmonary edema: Capillary Pr. > 25 mmHg it will cause rapid sever edema that causes death within < than one hour As it is happen in acute Lt heart failure during which capillary Pr. may be up to 50 mm Hg.

Pulmonary Interstitial edema & Alveolar edema Interstitial fluid Vol. > 50% (100ml) cause rupture of the alveolar epithelial wall & fluid will pour into the alveoli. So In most conditions of interstitial edema there is alveolar edema with the interstitial edema. (except in slight minor conditions)

Pulmonary Edema Kerley lines:- Sign seen on chest X ray with interstitial pulmonary edema. 

Alveolar Edema

Pleural fluid Transudate from the interstitial fluid through - the a porous mesenchymal serous membrane of the pleura. This fluid contains tissue proteins that make pleural fluid a mucoid characteristics (slippage). So facilitate movement of the lungs within the thoracic cage.

Amount of the Pleural Fluid It is only few ml. The extra amount normally pumped away by lymphatic vessels into: 1.  The mediastinum. 2.  The superior surface of diaphragm. 3.  The lateral surface of the parietal pleura. Pleural fluid = Pleural effusion.

Pulmonary Gas Diffusion

Gas Diffusion The key to gas diffusion is the Partial Pr. gradients Both for O2 & CO2 O2 flows downhill :- From Air Alveoli Blood Tissues CO2 flows downhill :- From Tissues Blood Alveoli Air

The key to gas diffusion Partial Pr. Gradients Both for O2 & CO2 159-154 104 95 45 40 40 0.0

Laws that control Gas Diffusion Air is a gas mixture (N2 + O2 + CO2 + Water vapor) Daltons Law & Partial Pr:- - Individual gases in a mixture:- Exert Pr. α to their conc. Air Pr. = Pa. Pr. (N2 + O2 + CO2 + H2O) 760 = 600.7 + 159.1 ± 0.2 ± ? (Water Vapor Pr. is variable)

Partial Pr. of gases in dry Air Standard atmospheric Pr. (at sea level):- Pr. of dry air = 760 mmHg. N2 is 79.04% of air:- PN2 = 600.7 mmHg O2 is 20.93% of air:- PO2 = 159.1 mmHg. CO2 is 0.03%:- PCO2 = 0.2 mmHg. % of gas X 760

Effect of water vapor on Partial Pr. Gases Water Vapor exert a Pr. (like other gases) Water Vapor constitute part of the total gas Pr. in the air As Air enter the respiratory system it will be humidified (Saturated with water)   Water Vapor Pr. is affected much by temperature At room temp. = 20 mm Hg At 37 ºC = 47 mm Hg

Effect Of Water Vapor On Partial Pr. Of Different Gases To calculate the Partial Pr. Of Different Gases in the Presence Of Water Vapor - We Subtract the Water Vapor Pr. from the total Air Pr.  (760 – 47 = 713 mm Hg). - Then we apply the formula:- PN2 = (79/100) X 713 = 564 mm Hg PO2 = (20.96/100) X 713 = 149 mmHg PCO2 = (0.04/100) X 713 = 0.3 mmHg

Partial Pr. of Respiratory Gases Gas Dry Atm. air Humid.air Alveolar air Expired air Air mmHg% mmHg% mmHg% mmHg%   N2 79.04 78.62 597 74.09 563.4 74.9 569.0 74.5 566 O2 20.93 20.84 159 19.67149.3 13.6 104.0 15.7 120 CO2 0.03 0.04 0.3 0.04 0.3 5.3 40.0 3.6 27.0 H2o 0.0 0.50 3.7 6.2 47 6.2 47 6.2 47 Total 100 100 760 100 760 100 760 100 760

Ventilation/Perfusion ratio Prof F.S.Al-Ani fakeralani2000@yahoo.com Respiratory System Ventilation/Perfusion ratio Prof F.S.Al-Ani fakeralani2000@yahoo.com

Ventilation Perfusion Ratio (ֹVA/Q) The relationship between Ventilation & B. flow for the lung without direct indication to the gas exchange characteristics across the respiratory membrane.

of Ventilation & Perfusion. When the ventilation perfusion ratio = 1.0 VA/ Q = 1.0 There is Equal amount of Ventilation & Perfusion.   VA/Q

Distribution of VA/Q Normally: There is a widely different ֹVA/Q ratio in the different parts of the lung Ranging From 0 to ∞ Due to disproportionate Ventilation & Perfusion patterns in the different lung units.

Distribution of VA/Q

Distribution of VA/Q In a normal person in the upright position:- At the Apex:- There capillary B. flow that causes Va/Q (Va/Q is about 2.5 X > the ideal value) This represent the alveolar dead space. At the Base:- The capillary B. flow on the expense of Vent. causes Va/Q to about 0.6 the ideal value This represent the physiological shunt

VA/ Q ratio At the apex of the lung:- At the base of the lung:- Less B. & relatively high ventilation So we have a high V/Q ratio. At the base of the lung:- More B. flows & less air gets there So we have low V/Q ratio. At the middle of the lungs:- Good match of B. to ventilation So a Good V/Q ratio.

(According to VA/ Q ratio) Lungs are divided into 3 compartments   1. Apical lung region: Alveolar Capillary receive adequate ventilation But little or no B. Flow. So VA/ Q = high. 2. Mid lung region : Alveolar Capillary receive normal ventilation & normal B. flow. So (VA/Q = 1) 3. Base of the lungs: Alveolar Capillary receive little or no ventilation but normal B. flow. So ( VA/ Q = low)

Total Alveolar Perfusion The amount of B. that reach the alveoli/min. In normal adult male (70 Kg body weight) the amount of B. that reach the alveoli / min. is about 5 – 5.5 L/min (This represent the C.O.). This total amount of B. does not perfuse the different alveoli equally.

Distribution of pulmonary flow It has been estimated that: 90% of pulmonary capillary B. flow is directed through compartment 2 (Middle region of the lungs) the remaining 10% is split between compartment 1 & 3.

Physiological shunt + Anatomical shunt B. Oxygenation Physiological shunt + Anatomical shunt At Middle of the lungs: There is optimal oxygenation of the B. about 100% saturation of Hb. At base of the lungs: There is bad oxygenation of B. because alveolar B. comes in contact with under-ventilated alveoli bad Saturation of Hb. (Physiological shunt) The B. of base of the lungs as well as the B. from bronchi parenchyma, are mixed (Anatomical shunt) (Physiological shunt + Anatomical shunt) will Hb. saturation of pulmonary arterial to 97%.

Intrapulmonary shunt (Left to Right shunt): Mixing the will oxygenated B. from the will ventilated alveoli with the B. of the under ventilated alveoli + the B. from the parenchyma of the lungs lead to what is called as Intrapulmonary shunt During which:- 2%-3% of the pulmonary B. flow is mixed directly (without oxygenation) with oxygenated arterial B. that comes from the ventilated alveoli.

Total VA/Q Alveolar ventilation:- TV - Dead space (Anat. + Alveolar) X Resp. Rate 350 X 12 = 4200 ml/ min. Alveolar perfusion:- All the C.O. of Rt Side of the heart = 5.5 L/min So The total VA/Q ratio = 4200/5500 = 0.8

Effect of respiratory rate & depth On the rate on alveolar ventilation R. Rate 12 / minute (Normal) 10/minute (Decrease) 30/minute (Increase) Tidal Volume 500 ml 600 ml 200 ml Minute Volume 6 Liter Alveolar Ventilation (500 – 150) X12 = 4200 ml (600 – 150) X10 =4500 ml (200 – 150) X30 = 1500 ml