Respiratory System

• Functions of the Respiratory System

  • Breathing
  • Exchange of gases
  • Oxygenation of blood
  • Removal of Carbon Dioxide
  • Acid-Base Balance
  • Defense against pathogens and irritants
  • Temperature and humidity regulation
  • Vocalization and speech production

  
• Respiration


  1. Pulmonary ventilation

  2. External respiration

  3. Respiratory gas transport

  4. Internal respiration
• Bronchodilation


  Widening of the bronchial airways
• Bronchoconstriction


  Narrowing of the bronchial airways

  
• Asthma


  • Chronic inflammatory disorder of bronchial airways
  • Results in airway obstruction in response to external stimuli

  
• Characters of airways in asthmatic patients

  • Airway hyper-reactivity/responsiveness
  • Inflammation
  • Swelling
  • Thick mucus production
  • Bronchospasm (constriction of the bronchial muscles)

  
• Symptoms of asthma


  • Acute bronchoconstriction
  • Shortness of breath
  • Chest tightness
  • Wheezing
  • Rapid respiration
  • Cough
• Causes of asthma


  • Infection
  • Emotional conditions
  • Stress
  • Exercise
  • Pets
  • Seasonal changes
  • Some drugs as aspirin, β blockers
• Aetiology of asthma


  • Airway hyperresponsiveness
  • Bronchoconstriction

  
• Pathophysiology of asthma


  • Extrinsic (allergen is thought to be the cause, common in children)
  • Intrinsic (symptoms triggered by non-allergenic factors, common in adults)
• COPD (Chronic Obstructive Pulmonary Disease)

  • Chronic irreversible airflow obstruction
  • Lung damage and inflammation of the air sacs (alveoli)
  • Smoking is a high risk factor

  
• Treatment for COPD


  • Inhaled bronchodilators
  • Inhaled glucocorticoids
  • Oxygen therapy
• Pathophysiology of COPD


  • Mucus hypersecretion, ciliary dysfunction and complications
  • Airflow limitations and hyperinflation
  • Gas exchange abnormalities
  • Pulmonary hypertension and cor pulmonale
  • Systemic effects

  
• Aetiology of COPD

  • Smoking
  • Inflammation
  • Proteinase and antiproteinase imbalance
  • Oxidative stress
• Causative agents for URTI

  • Colds and flu - rhinovirus, coronavirus, parainfluenza virus, influenza virus, adenovirus
  • Influenza (aka true influenza) - Influenza A, B and rarely C
  • Pharyngitis (aka sore throat) - EBV, Streptococcus pyogenes, Lancefield group A ß-hemolytic streptococcus
  • Epiglotittis - Hib, pneumococci, streptococci, staphylococci

  
• Causative agents for LRTI

  • Pneumonia - CAP: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Klebsiella pneumoniae, Mycoplasma pneumoniae
  • Pneumonia - HAP: Pseudomonas aeruginosa, Escherichia coli, MRSA, Klebsiella pneumoniae

  
• Severe Acute Respiratory Syndrome (SARS)


  • Causative agent: SARS Cov
  • Causes pneumonitis, presenting with flu-like prodrome
  • Progresses to dyspnea, dry cough, and adult respiratory distress syndrome
• Cystic fibrosis


  • Inherited, autosomal recessive disease
  • Defect in transport of ions in and out of the cell
  • Changes in consistency and chemical composition of exocrine secretions
  • In the lungs, manifestations include production of a very sticky, tenacious mucus

  
• Drugs for Allergic Rhinitis

  • Antihistamines: Diphenhydramine, Chlorpheniramine, Cetirizine, Azelastine
  • Corticosteroids: Beclamethasone, Budesonide, Fluticasone
  • Alpha agonists: Oxymetazoline, Phenylephrine, Psuedoephedrine
  • Cromolyn
• Drugs for Asthma


  • ß2-adrenergic agonist: SABA (Salbutamol, Terbutaline), LABA (Formoterol, Salmeterol)
  • Corticosteroids: Beclamethasone, Budesonide, Fluticasone
  • Leukotriene modifiers: Montelukast, Zafirlukast, Zilueton
  • Cromolyn
  • Cholinergic antagonists: Ipratropium, Tiotropium
  • Theophylline
  • Omalizumab
• Drugs for COPD


  • Bronchodilators: ß2 agonist, Cholinergic antagonists
  • Corticosteroids: Beclamethasone, Budesonide, Fluticasone
  • Roflumilast
• Drugs for URTI


  • Give antibiotics to all patients suspected with streptococcal infection and do not investigate unless symptoms persist
  • Give antibiotics to all patients suspected with streptococcal infection but stop them if a throat swab is negative
  • Wait for throat swab culture results before starting antibiotics
• Drugs for LRTI


  • Bronchitis 2˚ to COPD: Doxycycline, Amoxicillin, Co-amoxiclav, Clarithromycin, Cefixime
  • CAP: Benzylpenicillin, Amoxicillin, Erythromycin, ß-lactam + macrolide
  • HAP: Co-amoxiclav, Ureidopenicillin + aminoglycoside, Cephalosporin + aminoglycoside, Meropenem, Linezolid, Ceftazidime, Temocillin
• Treatment for SARS is largely supportive
• Drugs for cystic fibrosis

  • Staphylococcus-colonized: flucloxacillin, erythromycin
  • Pseudomonas-colonized: oral ciprofloxacin, nebulized colistin
  • Chronically colonized: prophylactic IV ß-lactam/aminoglycoside combination
  • Treatment failure: meropenem, quinolones
  • Burkholderia cepacia - may be resistant to all available antibiotic therapies, combination therapy is used