Pulmonary circulation Physiological anatomy: the Artery is 5cm thin (1/3 of aorta diameter) , while the branches are short and have more diameter so it will have a large compliance (7 ml/mmHg). pulmonary veins are thin & short. bronchial arteries originate from the systemic circulation (carry 1-2% of C.O -oxygenated blood-) then empty into pulmonary veins then to the left atrium so the left ventricle pumps 1-2% more than the right ventricle. rich lymphatic drainage to the right thoracic duct to prevent edema

Pressures in the pulmonary system: 1- right ventricle: 25-1 mmHg 2- pulm. Artery: 25-8 mmHg 3- pulm. cap. : 8 mmHg 4- left atrium & major veins: 2 mmHg Blood volume of the lungs: :  450 ml ( 9% of total blood volume)  70 ml are found in the capillaries

Blood volume of the lungs if the person is bleeding or blowing air out hardly the volume can reach 200 ml. if the person has left heart failure or mitral valve stenosis or regurgitation the volume can reach 900 ml

MEASUREMENT OF PULMONARY BLOOD FLOW Fick Principle VO2=Q(CaO2-CvO2) VO2 = Oxygen Consumption CaO2 = Arterial Content Q = Blood flow CvO2 = Venous Content

MEASUREMENT OF PULMONARY BLOOD FLOW VO2=Q(CaO2-CvO2) CaO2 = 20 ml O2/100 ml blood VO2 = 250 ml/min CvO2 = 15 ml O2/100 ml blood Q = 250 ml O2/min = 250 ml O2 * 100 ml blood (20-15) ml O2/100 ml blood min 5 ml O2 Q = 5000 ml blood /min

Blood flow Effect of alveolar [O2]:  when [O2] decreases below 70% of normal  alveolar epithelial cells secrete vasoconstrictors  adjacent blood vessels constrict  blood flows to better aerated alveoli (extreme low [O2]  5x resistance) Effect of hydrostatic pressure:  in normal upright adult there’s a difference between the lowest and highest points of the lung the gradient is 23 mmHg (15 mmHg above the heart & 8 mmHg below it)

Regional pulmonary blood flow : 1-Zone 1: No blood flow (capill. pr. < alveol, pr.) 2-Zone 2: Intermittent blood flow 3-Zone 3: Continuous blood flow. (capill. pr. > alveol. pr.) in normal lungs zone 1 cannot be found, zone 2 is in the apex of the lung and zone 3 represents the base.

Regional pulmonary blood flow :  arterial pressure in pulmonary artery is 25-8 mmHg at apex systolic 25-15= 10 mmHg during diastole 8-15 mmHg= -7? (Hydrostatic pressure difference is 15 mmHg between the level of the heart and the lung apex)  if the person is lying down or exercising only zone 3 can be seen.

Pulmonary capillary dynamics:  7 mmHg cap. Pressure.  blood passes through the capillary in 0.8sec  increasing the C.O lowers the time to 0.3sec Capillary fluid exchange dynamics:  outward forces= 7+14+8 = 29 mmHg  inward forces = 28 mmHg  mean filtration pr. = 1 mmHg “handled by lymph” lungs Systemic cir. Capillary pressure 7 mmHg 17 mmHg Interst. Osm. Pr. 14 mmHg 8 mmHg Interst. Neg. pr. -8 mmHg -3 mmHg

Pulmonary Capillary Dynamics Outward Forces Pulmonary capillary pressure 7 mmHg Interstitial osmotic pressure 14 mmHg Negative interstitial pressure 8 mmHg Total 29 mmHg Inward Forces Plasma osmotic pressure 28 mmHg Net filtration pressure 1 mmHg Negative interstitial pressure keeps alveoli dry

Pulmonary Capillary Dynamics Hydrostatic +7 -8 -8 surface tension hydrostatic pressure Osmotic 28 14 Net +1 -5 Lymphatic pump

Pulmonary edema Alveoli are always dry except for a small amount of fluid secreted by alveolar cells on the alveolar surface. When interstitial pressure becomes (+) water will fill the alveoli Causes: 1- Left-sided heart failure ↑ venous+cap. pr 2-Damage to the pulmonary capillary membrane caused by : a- infections b- breathing chlorine gas or sulfur dioxide gas. Safety factors 21 mmHg in acute states 35 mmHg in chronic cases

Heart Failure and Pulmonary Edema Edema Formation 25 Left Atrial Pressure

Pulmonary Edema Causes of pulmonary edema Safety factor left heart failure damage to pulmonary blood cap membrane, as In pneumonia or breathing chlorine gas or sulfur dioxide gas Safety factor negative interstitial pressure lymphatic pumping decreased interstitial osmotic pressure

Pleural effusion (edema) : Collection of large free fluid in the pleural space 1-Blockage of lymphatic drainage from pleural space 2- Cardiac failure (increase cap pressure) 3- Decrease plasma colloid osmotic pressure 4- Infection or inflammation of the surface of pleural cavity