The effects of lung disease

• Lung diseases affect both ventilation (breathing) and gas exchange in the lungs - how well the lungs function
• measures of lung function:

  1. tidal volume
  2. ventilation rate
  3. forced expiratory volume1 (FEV1)
  4. forced vital capacity (FVC)
• tidal volume = the volume of air in each breath

  usually between 0.4 dm3 and 0.5 dm3 for adults
• Ventilation rate = the number of breaths per minute

  for a healthy person at rest it's about 15 breaths
• Forced expiratory volume1 = the maximum volume of air that can be breathed out in 1 second
• Forced vital capacity = the maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
• Tuberculosis (TB)


  Pulmonary TB is a lung disease caused by bacteria
• When infected with TB bacteria

  1. Immune system cells build a wall around bacteria in the lungs

  2. Forms small, hard lumps - tubercles

  3. Infected tissue within the tubercles dies

  4. Gaseous exchange surface is damaged
• Tuberculosis


  • Tidal volume decreased
  • Causes fibrosis - further reduces tidal volume
  • Reduced tidal volume means less air can be inhaled with each breath
  • Patients have to breathe faster i.e. ventilation rate increased
• Fibrosis


  The formation of scar tissue in the lungs
• Scar tissue


  • Thicker and less elastic than normal lung tissue
  • Lungs less able to expand and so can't hold as much air as normal
  • Tidal volume is reduced
  • Forced vital capacity (FVC) is reduced
  • Reduction in the rate of gaseous exchange
  • Diffusion is slower across a thicker scarred membrane
• Fibrosis sufferers


  Have a faster ventilation rate than normal to get enough air into their lungs to oxygenate their blood
• Asthma


  A respiratory condition where the airways become inflamed and irritated
• Causes of asthma


  • Vary from case to case
  • Usually due to an allergic reaction to substances such as pollen and dust
• During an asthma attack

  1. Smooth muscle lining the bronchioles contracts

  2. Large amount of mucus produced
• Constriction of the airways

  Makes it difficult for the sufferer to breathe properly
• Reduced airflow


  Less oxygen enters the alveoli and moves into blood
• FEV (Forced Expiratory Volume)


  Severely reduced (i.e. less air can be breathed out in 1 second)
• Drugs (often in inhalers)


  Cause the muscle in the bronchioles to relax, opening the airways
• Drugs can relieve symptoms of asthma
• Emphysema

  • lung disease caused by smoking or long-term exposure to air pollution - foreign particles in the smoke (or air) become trapped in the alveoli
• Emphysema


  Lung disease caused by smoking or long-term exposure to air pollution
• Emphysema


  • Foreign particles in the smoke (or air) become trapped in the alveoli
  • Causes inflammation which attracts phagocytes to the area
  • The phagocytes produce an enzyme that breaks down elastin (a protein found in the walls of the alveoli)
  • Elastin is elastic - it helps the alveoli return to their shape after inhaling and exhaling air
  • Loss of elastin means the alveoli can't recoil to expel air as well (it remains trapped in the alveoli)
  • Also leads to destruction of the alveoli walls which reduces surface area of the alveoli so the rate of gaseous exchange decreases
• Effects of lung disease on gas exchange -

  • TB, fibrosis, asthma and emphysema all reduce the rate of gas exchange in the alveoli
  • less oxygen is able to diffuse into the bloodstream
  • body cells receive less oxygen and the rate of aerobic respiration is reduced
  • means that less energy is reduced an sufferers often feel tired and weak