OXYGENATION NOTES

• Oxygenation


  1. Ventilation

  2. Perfusion

  3. Diffusion
• Most cells in the body obtain their energy from chemical reactions involving oxygen and the elimination of carbon dioxide
• Conditions or diseases which change the structure and function of the respiratory system can alter respiration

  • Atelectasis
  • COPD-emphysema
  • Pneumonia
  • MSKL abnormalities (kyphosis)
  • Rib fracture (trauma)
• Conditions or diseases which can alter perfusion

  • Pregnancy
  • Obesity
  • Peripheral vascular disease (PVD)
  • Pulmonary edema
  • Pulmonary embolism
  • Anemia
  • Pneumonia
• Ventilation


  • Process of moving gases into and out of the lungs
  • Major inspiratory muscle of respiration is the diaphragm
• Perfusion


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


  • Responsible for moving the molecules from one area to another (O2 and CO2 exchange)
• For a healthy individual, breathing is quiet and requires minimal effort
• Inspiration


  1. Active process, stimulated by chemical receptors in the aorta

  2. Pressure is decreased in comparison to atmospheric pressure
• Expiration


  1. Passive process, requiring elastic recoil of lungs, requiring little or no muscle work

  2. Pressure is increased in comparison to atmospheric pressure
• Elastic recoil


  Produced by elastic fibers in the lung tissue and by surface tension in the fluid lining the alveoli
• Surfactant is a chemical produced in the lungs to maintain the surface tension in the alveoli and keeps them from collapsing
• Advanced COPD patients lack elastic recoil of the lungs and alveoli, therefore the work of breathing is increased
• Other patients with pulmonary diseases have decreased surfactant production, which in turn may develop atelectasis
• Atelectasis


  Collapse of alveoli, preventing normal gas exchange
• Accessory muscles


  • Can increase lung volume during inspiration
  • Patients with COPD, especially emphysema use these muscles to increase lung volume
• One observes elevation of the patient's clavicle during inspiration
• Compliance


  Ability of lungs to expand and distend in response to increased intra-alveolar pressure
• Compliance is decreased in diseases such as pulmonary edema, interstitial, and pleural fibrosis. Also during fractured ribs (kyphosis)
• Airway resistance


  Pressure difference between the mouth and alveoli in the relation to the rate of flow of inspired gas
• Airway resistance can be increased by an airway obstruction. Small airway disease: asthma and tracheal edema
• Decreased lung compliance, increases airway resistance
• Active expiration, or the use of accessory muscles increases the work of breathing
• Spirometry


  Used to measure volume of air entering or leaving the lungs
• Spirometry can tell health states such as: pregnancy, exercise, obesity, or obstructive and restrictive conditions of the lungs
• What affects pressures and volumes within the lungs: amount of surfactant, degree of compliance, and strength of respiratory muscles
• Pulmonary Circulation


  • Moves blood to and from alveolocapillary membrane in order for gas exchange to occur
  • Serves as a reservoir for blood so that the lung can increase its blood volume without large increases in pulmonary artery or venous pressure
  • Acts as a filter, removing small thrombi before they can reach vital organs
• Pulmonary circulation pathway


  • Pulmonary artery
  • Pulmonary arterioles
  • Pulmonary capillaries (blood comes in contact with alveolocapillary membrane and gas exchange occurs)
  • Pulmonary venules
  • Pulmonary veins
• Oxygen transport system


  Consists of the lungs and the cardiovascular system
• Delivery of oxygen depends on the amount entering the lungs (ventilation), blood flow to the lungs and tissues (perfusion), rate of diffusion, and oxygen carrying capacity
• Carbon dioxide diffuses into red blood cells and rapidly hydrated into carbonic acid
• Factors Affecting Oxygenation


  • Anemia - decreases oxygen-carrying capacity of blood
  • Toxic inhalant - decreases oxygen-carrying capacity of blood
  • Airway obstruction - limits delivery of inspired oxygen to alveoli
  • High altitude - atmospheric oxygen concentration is lower and inspiratory oxygen concentration decreases
  • Fever - increases metabolic rate and tissue oxygen demand
  • Decrease chest wall motion - prevents lowering of diaphragm, reducing volume of air inspired
• Hyperventilation


  State of ventilation in excess of that required to eliminate the normal venous carbon dioxide produced by cellular metabolism. Increased ventilation, therefore eliminates more CO2.
• Causes of hyperventilation


  • Anxiety, infections, drugs or an acid-base imbalance
  • Hypoxia associated with pulmonary embolus or shock
  • Fever (increase body temperature, increases metabolic rate, therefore increasing carbon dioxide production)
  • Chemically induced (salicylate poisoning, amphetamines)
• Signs and symptoms of hyperventilation

  • Leads to less O2 reaching tissues and hypoxia
  • Dizzy
  • Shortness of breath (SOB)
  • Lightheaded
• Hypoventilation


  When alveolar ventilation is inadequate to meet the body's oxygen demand or to eliminate sufficient carbon dioxide. If untreated, this can lead to a rapid decline of health status, leading to convulsion, unconsciousness and death. Inadequate ventilation, therefore retains more CO2) (too much CO2 means more acidic)
• Causes of hypoventilation


  • Severe atelectasis (collapse of the alveoli)
  • COPD (inappropriate administration of excessive oxygen)
  • Alkalosis
  • Excessive oxygen is administered, therefore stimulus to breathe is negated
• Signs and symptoms of hypoventilation

  • Mental status changes
  • Lead to changes in Level Of Consciousness (LOC)
  • Convulsions
  • Sleepiness
  • Dysrhythmias
  • Potential cardiac arrest
• Treatments for hypoventilation


  • Improving tissue oxygenation
  • Restoring ventilatory function
  • Treating underlying case
  • Achieving acid-base balance
• Hypoxia


  Inadequate tissue oxygenation at the cellular level. Can result from deficiency in oxygen delivery or oxygen utilization at the cellular level. Inadequate tissue oxygenation.