School of Medicine SUNYAB PGY452 Respiratory Lectures March 12 2015 Daniel D Swartz Ph D Lecture 4 Ventilation and Perfusion Reading Assignment Berne Levy chapter 22 pages 444 458 Alveolar Ventilation and Dead Space IC 4L IRV 3L Wgt 200 lbs f 10 BPM VA Regional Distribution of Lung Volume Base of the lung Higher pleural pressure Lower volume Higher compliance Fig 22 2 B L Expired or minute Ventilation VT x f Chap 22 pg 444 Ventilation Equations where n f Chap 22 pg 447 Physiological Dead Space 1 Physiologic Dead Space wasted ventilation 2 Shunt wasted blood flow Physiologic dead space Alveolar Dead Space Q Pulmonary embolism Ventilation Shunt 1 Physiologic Dead Space wasted ventilation 2 Shunt wasted blood flow Blocked airway VA Shun t Dead Space wasted Ventilation Total Dead Space VD Clinical Measurement of Dead Space Ratio 1 Minute Deadspace Ventilation VD VD X VE VT pg 448 2 VD VT Paco2 PECO2 Paco2 Bohr Dead space Equation Physiologic Dead Space Fowler s Method Anatomical Dead Space Ventilation Perfusion Ratio Each alveolus is supplied with both airflow ventilation and blood flow perfusion However these are not evenly distributed to each alveolus throughout the lungV A Q Ventilation Perfusion Ratio Perfusion 1 reoxygenate blood and dispense CO2 2 fluid balance in lung 3 distribute metabolic products to and from the lungs Q VA Pulmonary capillaries hold 75 ml at rest and recruit additional capillaries up to 150 200 ml Fig 29 4 Ventilation Perfusion VA Pulmonary arteries are less muscular and more compliant than systemic arteries allows for lower resistance and lower pressure Q Fig 22 5 B L Factors that affect blood flow Perfusion through the lung Flow P PVR 1 Pulmonary vascular resistance PVR 2 Gravity 3 Alveolar pressure 4 Arterial to venous pressure gradient P Blood Pressures in the Systemic vs Pulmonary Circulations Pulmonary vessels Less muscular and more compliant lower pressure Lower pressure gradient More dilated Favors a left to right shunt Q 6 L Min Pulmonary Blood Flow 1 PVR 2 Gravity 3 Alveolar Pressure 4 Arterial to Venous Pressure Gradient Q 6 L Min Fig 22 6 B L Pulmonary Vascular Resistance PVR Systemic Vascular Resistance 10 15 mmHg L min Increase pulmonary blood flow Exercise recruits pulmonary capillaries no rise in pressure and easily increase diameter with little rise in pressure compared to systemic capillaries Chap 22 pg 451 Zones of Differential Perfusion Zone 1 0 74mmHg cm above heart blood flow ventilation perfusion Zone 2 waterfall effect PA PV Zone 3 Increased transmural pressure distends vessels pressure inside vessels Fig 22 8 B L Normal A and Abnormal B Perfusion Scans of the Lung Ventilation Perfusion Relationships Ventilation Perf usion Ratio regulates gas exchange 3 4 x 18 x Fig 22 10 B L Effect of Gravity on Pulmonary Blood Flow VENTILATION PERFUSION RELATIONSHIP P PL 5 cm H Wg t 40 20 Pressure cm H O cm H2O Q VA 05 Q 2 1 Q 10 3 V A Q Q VA 2O VA Q 15 FLOW in Liters Minute Q 2O P PL 2 5 cm H 2 2O Volume TLC 50 0 RV P PL 10 cm H Bottom of lung Top of lung VA Q Recruit and increase diameter 100 Ventilation Perfusion Ratio in Different Lung Units Blocked airflow 1 Tumor 2 Infection 3 Airway constriction 4 Mucous 4 Inhaled object peanut 0 ml min 1 ml min Physiologic shunt pores 1 ml min VA Q 0 1 0 1 ml min Alveolar Dead Space 1 ml min Blocked blood flow Pulmonary embolism 1 Prolonged bed rest 2 Travel long distance 3 Estrogen birth control pills pregnancy 4 obesity Q 0 ml min VA Q 1 1 1 VA Q 1 0 Normal Ventilation Perfusion in the Lung Fig 22 11 B L Right to Left Anatomic Shunt Right to Left Anatomic Shunt A Normal carotid and bronchial circ B Abnormal atrial septal defect Fig 22 12 B L
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