M14-15

• Oxygen is needed to sustain life
• Blood is oxygenated through the mechanisms of

  1. Ventilation

  2. Perfusion

  3. Transport of respiratory gases
• Neural and chemical regulators

  • Control the rate and depth of respiration in response to changing tissue oxygen demands
• The cardiovascular system


  • Provides the transport mechanisms to distribute oxygen to cells and tissues of the body
• The exchange of respiratory gases occurs between


  The environment and the blood
• Respiration


  The exchange of oxygen and carbon dioxide during cellular metabolism
• The airways of the lung transfer oxygen from

  The atmosphere to the alveoli, where the oxygen is exchanged for carbon dioxide
• Through the alveolar capillary membrane

  Oxygen transfers to the blood, and carbon dioxide transfers from the blood to the alveoli
• Gases move into and out of the lungs through

  Pressure changes
• The diaphragm and external intercostal muscles


  Contract to create a negative pleural pressure and increase the size of the thorax for inspiration
• Work of breathing


  The effort required to expand and contract the lungs
• Work of breathing


  • Inspiration
  • Expiration
  • Surfactant
  • Atelectasis
  • Compliance and airway resistance
• Lung volumes


  • Tidal
  • Residual
  • Forced vital capacity
• Ventilation


  The process of moving gases into and out of the lungs
• Perfusion


  The ability of the cardiovascular system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs
• Diffusion


  Exchange of respiratory gases in the alveoli and capillaries
• Pulmonary circulation


  Moves blood to and from the alveolar capillary membrane for gas exchange
• Diffusion is the process for the exchange of respiratory gases in


  The alveoli of the lungs and the capillaries of the body tissues
• Oxygen transport system


  • Consists of the lungs and cardiovascular system
• Carbon dioxide, a product of cellular metabolism, diffuses into


  Red blood cells and is rapidly hydrated into carbonic acid (H2CO3)
• The carbonic acid then dissociates into

  Hydrogen (H) and bicarbonate (HCO3-) ions
• Hemoglobin


  • Buffers the hydrogen ion, the (HCO3-) diffuses into the plasma
• Neural regulation


  1. Central nervous system controls the respiratory rate, depth, and rhythm

  2. Cerebral cortex regulates the voluntary control of respiration
• Chemical regulation


  1. Maintains the rate and depth of respirations based on changes in the blood concentrations of CO2 and O2, and in hydrogen ion concentration (pH)

  2. Chemoreceptors sense changes in the chemical content and stimulate neural regulators to adjust
• Cardiovascular Physiology


  • Involves delivery of deoxygenated blood (blood high in carbon dioxide and low in oxygen) to the right side of the heart and then to the lungs, where it is oxygenated
  • Oxygenated blood (blood high in oxygen and low in carbon dioxide) then travels from the lungs to the left side of the heart and the tissues
• Right ventricle


  Pumps deoxygenated blood through systemic circulation
• As blood passes through the circulatory system

  There is an exchange of respiratory gases, nutrients, and waste products between the blood and the tissues
• Myocardial pump


  • Two atria and two ventricles
  • As the myocardium stretches, the strength of the subsequent contraction increases (Starling's law)
• Myocardial blood flow


  1. Unidirectional through four valves

  2. S1: mitral and tricuspid close

  3. S2: aortic and pulmonic close
• Coronary artery circulation


  • Coronary arteries supply the myocardium with nutrients and remove wastes
• Systemic circulation


  • Arteries and veins deliver nutrients and oxygen and remove waste products
• Cardiac output


  Amount of blood ejected from the left ventricle each minute
• Stroke volume


  Amount of blood ejected from the left ventricle with each contraction
• Preload


  End-diastolic pressure
• Afterload


  Resistance to left ventricular ejection
• Conduction System

  • Transmits electrical impulses
  • Generates impulses needed to initiate the electrical chain of events for a normal heartbeat
• Normal sinus rhythm (NSR)

  • Originates at SA node, follows normal sequence through conduction system
  • P wave
  • PR interval
  • QRS complex
  • QT interval
• Factors Affecting Oxygenation

  • Physiological factors
  • Decreased oxygen-carrying capacity
  • Hypovolemia
  • Decreased inspired oxygen concentration
  • Increased metabolic rate
  • Conditions affecting chest wall movement
  • Pregnancy, obesity, neuromuscular disease, musculoskeletal abnormalities, trauma, neuromuscular disease, CNS alterations
  • Influences of chronic diseases
• Hypoventilation


  Alveolar ventilation inadequate to meet the body's oxygen demand or to eliminate sufficient carbon dioxide
• Hyperventilation


  Ventilation in excess of that required to eliminate carbon dioxide produced by cellular metabolism