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Respiratory System Conditions and Diseases
Lung disease has huge implications. Respiratory tract infections are common, and smoking air pollution, and environmental chemicals have led to huge increases in COPD rates. Lung cancer is the biggest malignant killer. Lungs are also secondarily affected in almost every dying patient, through pulmonary edema, atelectasis, or pneumonia.
- obstructive
diseases - restrictive
diseases - acute lung
conditions - infectious/inflammatory
diseases - other lung
conditions
Obstructive diseases
Obstructive diseases are characterized by airflow limitations on lung function tests. Obstructions can result from airway narrowing or loss of elastic recoil. Important obstructive diseases include:
- asthma
- chronic obstructive pulmonary disease (COPD)
- bronchiectasis
- cystic fibrosis
Restrictive Diseases
Restrictive, or diffuse interstitial diseases, are characterized by diffuse and usually chronic involvement of alveolar connective tissue. Important restrictive diseases include:
- environmental lung diseases ~25%
- sarcoidosis ~20%
- idiopathic pulmonary fibrosis (aka usual interstitial pneumonia)~15%
- collagen vascular disease (scleroderma, SLE, ankylosing spondylitis) ~10%
- acute respiratory distress syndrome
The array of restrictive pathologies all cause dyspnea, tachypnea, end-inspiratory crackles, and eventual cyanosis, without wheezing. Diffusing capacity, lung volume, and compliance all decrease.
Chest X rays show diffuse infiltration by small nodules, irregular lines, or ground glass shadows. Pulmonary hypertension and cor pulmonale may result. Advanced destruction leads to honeycomb lung.
Oxygen diffusion capacity and compliance decrease.
Alveolitis appears to be the earliest manifestation of all restrictive diseases, with most types of leukocytes accumulating in the interstitial and alveolar spaces. Interstitial or granulomatous inflammation can occur.
Pulmonary function tests can be used to distinguish these patterns.
Acute Lung Conditions
Infectious Diseases of the Respiratory System
Infections are important causes and complications of respiratory disease. 100 million respiratory infections/year (Glass R, JAMA 2003) Coughs, colds, and antibiotics
upper airway tract infections |
lower airway tract infections |
Defense against respiratory infections include:
- Nasal clearance, the glottal and laryngeal reflex, or tracheobrochial clearance reflex.
- Respiratory secretions and mucociliary clearance operate within the lower airways.
- Within the lungs, surfactant, alveolar clearance and the immunologic response.
Particulate trapping occurs throughout the respiratory system. Particles of various sizes are trapped in various locales:
- > 10 μm: nose and upper airways
- 3 to 10 μm: trachea and bronchi
- 1 to 5 μm: terminal airways and alveoli
- < 1 μm: in and out freely
Common bacterial pathogens:
- Streptococcus pneumoniae (most common)
- Haemophilus influenzae (most common in patients with COPD)
- Moraxella catarrhalis
- Mycoplasma pneumoniae
- Chlamydaphyla pneumoniae
- Legionella pneumophila
- Staphylococcus aureus (very virulent)
- Bordetella pertussis
- Gram negatives/anaerobes
Common viral pathogens:
- resipratory syncytial virus (RSV)
- parainfluenza virus - common childhood RTI; can cause croup
- adenovirus - responsible for 5-10% of pediatric RTIs
- rhinovirus - cause of common cold
- influenza A
Other Lung Conditions and Disorders
lung cancer
congenital lung problems
agenesis or hypoplasia
trachial or bronchial malformations
vascular anomalies
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