Effects of lung disease

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  • Effects of lung disease
    • Measures of lung function
      • Lung disease affects ventilation and gas exchange
      • 1) Tidal volume: volume of air in each breath, usually between 0.4-0.5 dm3
      • 2) Ventilation rate: number of breaths per minute. Healthy person at rest= 15 breaths
      • 3) Forced expiratory volume (FEV): max volume of air that can be breathed out in 1 second
      • 4) Forced vital capacity (FVC): max volume of air it is possible to breathe forcefully out of the lungs after a deep breath in
    • Pulmonary Tuberculosis (TB)
      • 1) Someone becomes infected with TB bacteria, immune system cells build wall around bacteria in lungs. Forms small, hard lumps- tubercles
      • 2) Infected tissue in tubercles dies, gaseous exchange surface damaged, tidal volume decreased
      • 3) TB causes fibrosis, further reduces tidal volume
      • 4) Reduced tidal volume means less air can be inhaled with each breath. In order to get enough oxygen, patients must breathe faster. Ventilation rate increased
      • 5) Common symptoms: persistent cough, coughing up blood/mucus, chest pains, shortness of breath, fatigue
    • Fibrosis
      • 1) Formation of scar tissue in lungs. Can result from infection/ exposure to asbestos/dust
      • 2) Scar tissue thicker and less elastic than normal
      • 3) Lungs less able to expand, can't hold as much air as normal. Tidal volume reduced, as is FVC
      • 4) Reduction in rate of gaseous exchange, diffusion slower across thicker scarred membrane
      • 5) Symptoms of fibrosis include shortness of breath, dry cough, chest pain, fatigue, weakness
      • 6) People with fibrosis have faster ventilation rate than normal to get enough air to lungs to oxygenate blood
    • Asthma
      • 1) Respiratory condition, airways become irritated/ inflamed
      • 2) During asthma attack, smooth muscle lining bronchioles contracts, large amount of mucus produced
      • 3) Causes constriction of airways, making it difficult to breathe properly. Air flow in/out of lungs severely reduced, less O2 enters alveoli, moves into blood. Reduced air flow means FEV severely reduced
      • 4) Symptoms: wheezing, tiight chest, shortness of breath. Can be relieved by drugs which relax the bronchioles/ open up the airways
    • Emphysema
      • 1) Lung disease caused by smoking/long term exposure to air pollution- foreign particles become trapped in alveoli
      • 2) Causes inflammation, attracts phagocytes to area. Phagocytes produce enzyme that breaks down elastin (protein in walls of alveoli)
      • 3) Elastin is elastic- helps alveoli return to normal shape during ventilation
      • 4) Loss of elastin means alveoli can't recoil to expel air as well (remains trapped in alveoli)
      • 5) Leads to destruction of alveoli walls, reduces SA of alveoli, rate of gaseous exchange decreases
      • 6) Symptoms: Shortness of breath, wheezing. Increased ventilation rate, try to increase amount of O2 reaching lungs
  • All conditions reduce rate of gas exchange in alveoli. Less O2 able to diffuse into bloodstream, body cells receive less O2, rate of aerobic respiration reduced. Less energy released, sufferers often feel tired/weak


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