Oxygenation

• Physiology of the Respiratory System

  The study of the normal functioning of the respiratory system

  
• Divisions of the Respiratory System

  • Upper respiratory system (mouth, nose, pharynx, larynx)
  • Lower Respiratory System (trachea, lungs, bronchi, bronchioles, alveoli, pulmonary capillary network, pleural membranes)

  
• Pulmonary Ventilation


  1. Inspiration (inhalation)

  2. Expiration (exhalation)
• Factors for adequate ventilation

  • Clear airways
  • Intact central nervous system and respiratory center
  • Intact thoracic cavity capable of expanding and contracting
  • Adequate pulmonary compliance and recoil

  
• Tidal volume


  Approximately 500 mL of air inspired and expired with each breath in adults
• Lung compliance


  The expansibility or stretchability of lung tissue, tends to decrease with aging
• Lung recoil


  The continual tendency of the lungs to collapse away from the chest wall, necessary for normal expiration
• Surfactant


  A lipoprotein produced by specialized alveolar cells, acts like a detergent reducing surface tension of alveolar fluid
• Alveolar Gas Exchange


  1. Diffusion of oxygen from alveoli into pulmonary blood vessels

  2. Diffusion of carbon dioxide from blood into alveoli
• Transport of Oxygen and Carbon Dioxide

  1. Oxygen transported from lungs to tissues

  2. Carbon dioxide transported from tissues to lungs
• Hemoglobin


  Normally, most oxygen (97%) combines loosely with hemoglobin in red blood cells and is carried to tissues
• Systemic Diffusion


  Diffusion of oxygen and carbon dioxide between capillaries and tissues/cells
• Carbonic acid and carbon dioxide levels

  • When blood levels fall, rate and depth of respiration decrease
  • When blood levels rise, rate and depth of respiration increase
• PaCO2


  Partial pressure of dissolved CO2 in arterial blood, normal range is 35-45 mmHg

  
• Age-related changes affecting respiratory system

  • Chest wall and airways become more rigid and less elastic
  • Decreased amount of exchanged air
  • Decreased cough reflex and cilia action
  • Drier and more fragile mucous membranes
  • Decreased immune system efficiency
  • Increased risk of gastroesophageal reflux disease
• High altitude, heat, cold, air pollution

  Affect oxygenation
• People at high altitudes

  Have increased respiratory and cardiac rates
• Healthy people exposed to air pollution

  May experience stinging of eyes, headache, dizziness, coughing
• Physical exercise or activity

  Increases rate and depth of respirations, increases oxygen supply
• Sedentary people lack alveolar expansion and deep breathing patterns, less able to respond to respiratory stressors
• Certain occupations predispose to lung disease (asbestosis, anthracosis, organic dust disease)
• Diseases of the respiratory system

  Can adversely affect blood oxygenation
• Benzodiazepines and opioids


  Can decrease rate and depth of respirations, require careful monitoring especially in older clients
• Stress and stressors


  Can affect oxygenation, may cause hyperventilation
• Epinephrine released during stress

  Causes bronchodilation, increasing blood flow and oxygen delivery
• Partial airway obstruction


  Indicated by low-pitched snoring sound during inhalation
• Complete airway obstruction


  Indicated by extreme inspiratory effort with no chest movement and inability to cough or speak
• Lower airway obstruction


  May be indicated by stridor, a harsh high-pitched sound during inspiration
• Breathing patterns


  • Eupnea (normal, quiet, rhythmic, effortless)
  • Tachypnea (rapid respirations)
  • Bradypnea (abnormally slow respiratory rate)
  • Apnea (absence of breathing)
• Hypoventilation


  Inadequate alveolar ventilation, may lead to hypercarbia or hypoxemia
• Cheyne-Stokes respirations


  Marked rhythmic waxing and waning of respirations with periods of apnea
• Biot's (cluster) respirations


  Shallow breaths interrupted by apnea, seen in CNS disorders
• Orthopnea


  Inability to breathe easily unless sitting upright or standing
• Dyspnea


  Difficulty breathing or feeling short of breath
• Hypoxemia


  Reduced oxygen levels in the blood, can lead to tissue hypoxia and cellular injury/death
• Cyanosis


  Bluish discoloration of skin, nails, mucous membranes due to reduced hemoglobin-oxygen saturation
• The cerebral cortex can tolerate hypoxia for only 3 to 5 minutes before permanent damage occurs