Pulmonary Circulation and Pulmonary Edema DR KAMRAN AFZAL

OBJECTIVES1. Describe regional differences in pulmonary

blood flow in an upright person

2. Define zones I, II, and III in the lung, with respect to pulmonary vascular pressure and alveolar pressure

3. Describe the major functions of the bronchial circulation

4. Discuss pulmonary edema

5. Identify Clinical Correlations

Distribution of blood circulation1. 280 billion capillaries, supplying 300 million alveoli2. Total volume of blood in all vessels

1. man: 5.4 l (70-80 ml / kg)2. woman: 4.5 l (65-70 ml / kg)

3. Distribution: 1. Heart 7%2. Pulmonary circulation 9-10%3. Systemic circulation 84%

1. from that veins 75%2. large arteries 15%3. small arteries 3%4. capilaries: 7%

DOUBLE CIRCULATION

Double circulation is made possible because of heart

advantage

1.all body organs with oxygenated blood at high pressure

2. at low pressure to the lungs as they are spongy tissue

Gravity and Distance:

– Distance above or below the heart (arterial ,venous) – Distance between Apex and Base

Pulmonary Blood Pressures

Pulmonary Capillary dynamics1. Starling forces (ultra filtration)

1. Capillary hydrostatic P = 7 mmHg.2. Interstitial hydrostatic P = -8 mmHg.3. Plasma colloid osmotic P = 28 mmHg.4. Interstitial colloid osmotic P = 14 mm

2. Filtration forces = 15 mmHg.

3. Reabsorption forces = 14 mmHg.

4. Net forces favoring filtration = 1 mmHg.

5. Excess fluid removed by lymphatics

3 Zones3 Zones

.

1. 23 mm Hg pressure difference between top and bottom

2. At top, 15 mm Hg < than the PAP at the level of the heart

3. At the bottom, 8 mm Hg greater than the PAP at the level of the heart.

Gravity and Blood Flow

Regional Pulmonary Blood Flow Depends Upon Position Relative to the Heart

Main PA 15 mmHg

Apex 2 mmHg

Base 25 mmHg

Gravity, Alveolar Pressure, and Blood Flow

1. Typically no zone 1 in normal healthy person

zone 2 (intermittent flow) at the apices.

zone 3 (continuous flow) in all the lower areas.

2. Large zone 1 in positive pressure ventilation

3. In normal lungs, Zone 2 begins 10 cm above the mid-level of the heart to the top of the lungs.

Effect of hydrostatic P on regional pulmonary flowFrom apex to base capillary P (gravity)

1. Zone 1: 2. no flow3. alveolar air pressure (PALV) is

higher than arterial pressure during any part of cardiac cycle.

4. Zone 2:5. intermittent flow6. systolic arterial pressure higher than

alveolar air pressure, but diastolic arterial pressure below alveolar air pressure.

7. Zone 3:8. continuous flow9. pulmonary arterial pressure (Ppc)

remain higher than alveolar air pressure at all times.

1. The ratio of V/Q in lung at rest 0.8 (4.2 L/min ventilation divided by 5.5 L/min blood flow).

2. When the ventilation (Va) is zero, yet there is still perfusion (Q) of the alveolus, the Va/Q is zero.

3. at the other extreme, when there is adequate ventilation, but zero perfusion, the ratio Va/Q is infinity.

4. At a ratio of either zero or infinity, there is no exchange of gases through the respiratory membrane of the affected alveoli

Lung blood flow rises towards bases and also during Exercise

1.- at rest, the blood flow is very low

at the top of the lungs; most of the

flow is through the bottom of the

lung.

2.-During exercise, flow ↑(4-7) fold.

- Top of lung ↑ by 700 to 800%,

the - =bottom by 200 to 300%.

reason for these differences is PAP

↑ during exercise to convert the lung

apices from a zone 2 to a zone 3

pattern .

Double circulationin the respiratory system

1. Bronchial Circulation 2. Pulmonary Circulation

1. Bronchial -1. Arises from L Ventricle.(systemic - oxygenated).2. 1-2% of left ventricular output.3. Supplies the supporting tissues of the lungs, including

the connective tissue, septa, and bronchi.

• Venous return from the bronchial by 2 routes.1. bronchial drainage is into azygous (1/2) 2. 2.pulmonary veins (1/2) (short circuit

• Pulmonary Circulation Arises from• Right Ventricle. • Receives 100% of blood flow.

Special features of bronchial circulation

1. LV output > (1=2%) than RV output & some deO2 blood into O2ated pulmonary venous blood + L atria

2.Does not supply beyond terminal respiratory units (respiratory bronchioles, alveolar ducts, and alveoli)

3.Bronchial arterial pressure is =same as Aortic pressure, and bronchial vascular resistance is > than resistance in the

pulmonary circulation

4.Only capable of undergoing angiogenesis,(new vessels).

Definition:

• Pulmonary edema is a condition characterized by fluid accumulation in the lungs caused by back pressure in the lung veins. This results from malfunctioning of the heart.

Causes:

• Pulmonary edema is a complication of a myocardial infarction (heart attack), mitral or aortic valve disease, cardiomyopathy, or other disorders characterized by cardiac dysfunction.

Pathophysiology:

• Fluid backs up into the veins of the lungs. Increased pressure in these veins forces fluid out of the vein and into the air spaces (alveoli). This interferes with the exchange of oxygen and carbon dioxide in the alveoli.

Symptoms:

• Extreme shortness of breath, severe difficult breathing

• Feeling of "air hunger" or "drowning" • "Grunting" sounds with breathing • Inability to lie down • Rales• Wheezing • Anxiety

Symptoms:

• Restlessness

• Cough

• Excessive sweating

• Pale skin

• Nasal flaring

• Coughing up blood

• Breathing, absent temporarily

Signs:

• Listening to the chest with a stethoscope (auscultation) may show crackles in the lungs or abnormal heart sounds.

• A chest x-ray may show fluid in the lung space.

• An echocardiogram may be performed in addition to (or instead of) a chest x-ray.

Tests:

Blood oxygen levels (low) A chest X-ray may reveal the following: Fluid in or around the lung space Enlarged heart

Tests:

An ultrasound of the heart (echocardiogram) may reveal the following:

Weak heart muscle Leaking or narrow heart valves Fluid surrounding the heart

Treatment:

• This is a medical emergency! Do not delay treatment. Hospitalization and immediate treatment are required.

• Oxygen is given, by a mask or through endotracheal tube using mechanical ventilation.

Expectations (Prognosis):

• Pulmonary edema is a life-threatening condition. It is often curable with urgent treatment and subsequent control of the underlying disorder.

Complications:   

• Long-term dependence on a breathing machine (ventilator)