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Chapter 14

Chapter 14. Dr. D. Washington. Cardiac Output. I. Definition: C.O. (L/min)= heart rate X stroke volume or(ml/min) (beats/min)(ml/beat) II. Cardiac Index (C.O./m 2 body surface) III. Regulation of cardiac output A. Rate of Venous return (limiting factor) 1. Peripheral resistance

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Chapter 14

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  1. Chapter 14 Dr. D. Washington

  2. Cardiac Output I. Definition: C.O. (L/min)= heart rate X stroke volume or(ml/min) (beats/min)(ml/beat) II. Cardiac Index (C.O./m2 body surface) III. Regulation of cardiac output A. Rate of Venous return (limiting factor) 1. Peripheral resistance 2. Mean systemic pressure (filling) 3. Right atrial pressure therefore V.R. = mean systemic pressure - Rt. atrial. P total peripheral resistance

  3. Cardiac Output B. Pumping Effectiveness (permissive regulator) 1. Starling’s Law 2. Starling’s Curve 3. Sympathetic & Drug Actions a. Chronotropic Affects (heart rate) b. Inotropic Affects (strength of contraction) positive inotropic ‘’ ‘’ ‘’ negative inotropic ‘’ ‘’ ‘’ 4. Relative terms a. End diastolic vol (pres) 120 ml/ventricle b. End systolic vol ‘’ 40 ‘’ ‘’ c. Stroke volume 80 ml/beat

  4. Starling’s Curve systole intensity of contraction diastole Filling pressure (myocardial fiber length)

  5. Control of Cardiac Output

  6. End-diastolic volume Venous return Negative Intrathoracic pressure Blood Volume Venous pressure Breathing Urine Tissue-fluid Venoconstriction Skeletal volume volume muscle pump Sympathetic Nerve stimulation

  7. Measurement of Cardiac Output I. Direct or Invasive a. Fick method B. Indicator Dilution method II. Indirect or Non-invasive a. Echocardiography b. Computed Tomography c. Radionuclide Imaging

  8. Cardiac Output A. Fick Method C.O. = O2 consumption = 250 ml/min Arterial Blood = 190 ml/L Venous Blood = 140 ml/L C.O. = 250 ml/min = 5 L/min O2 consumption (ml/min) [AO2] - [VO2] ml/min

  9. Cardiac Output Fick Method Lungs O2 consumption = 250 ml/min O2 = 140 ml/L Rt heart O2 = 190 ml/L Lt heart Cardiac Output = 5,000 ml/min

  10. Other Techniques Currently Used to Measure Cardiac Output Radionuclide (gamma camera) Echocardiography Computed Tomography

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