How To Failed Lungs Defense Mechanism

How To Failed Lungs Defense Mechanism

The lungs are bacteria free in normal condition because presence of high defense mechanism such as-
  1.  Nasopharyngeal filtering action
  2. Mucociliary action of the lower respiratory airways
  3. The presence of alveolar macrophages and immunoglobulins. 


Failure of these defense mechanism in certain conditions and may developed pneumonia -
1. Altered consciousness : The oropharyngeal contents may be aspirated and causing unconsciousness such as in -

  • Coma
  • Cranial Trauma
  • Seizures
  • Cerebrovascular accidents
  • Drugs overdose
  • Alcoholism

2. Depressed cough and glottic reflexes : In this condition aspirated gastric contents in to the lungs such as in -

  • Old age
  • Traumatic pain or Thoracoabdominal surgery
  • Neuromuscular disease
  • Weakness due to malnutrition
  • Kyphoscoliosis
  • Severe Obstructive Pulmonary Disease
  • Endotracheal intubation
  • Tracheostomy

3. Impaired mucociliary transport : The normal protection offered by mucus covered ciliated epithelium in the airways from the larynx to terminal bronchioles. It is impaired or destroyed in many conditions i.e.

  • Cigarette smoking
  • Viral respiratory infections
  • Immotile cilia syndrome
  • Inhalation of hot or corrosive gases
  • Old age
4. Impaired alveolar macrophage function : Alveolar macrophages function are impaired in such conditions that cause pneumonia -
  • Cigarette smoking
  • Hypoxia
  • Starvation
  • Anaemia
  • Pulmonary Oedema
  • Viral respiratory infections
5. Endobronchial obstruction : Endobronchial obstruction may cause pneumonia that may occurs in such conditions -
  • Tumour
  • Foreign body
  • Cystic fibrosis
  • Chronic bronchitis
6. Immunocompromised conditions : Disorders of lymphocytes including congenital and acquired immunodeficiencies -


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