Respiratory Disorders
Introduction
·
The respiratory system ensures the exchange of
gases—oxygen intake and carbon dioxide elimination—essential for cellular
metabolism and survival.
·
Any disruption in this process leads to
respiratory disorders, which may affect airways, alveoli, interstitium, or the
pleura.
·
Respiratory disorders can be acute or chronic,
infectious or non-infectious, and may cause significant morbidity and
mortality.
·
Key pathological mechanisms include airway
obstruction, parenchymal inflammation or destruction, impaired
gas exchange, and respiratory muscle fatigue.
·
Understanding common respiratory disorders is
essential for prevention, early diagnosis, and management.
Chronic Obstructive Pulmonary Disease
(COPD)
Definition
A chronic, progressive, and largely irreversible
airflow limitation characterized by chronic bronchitis and emphysema,
often associated with long-term exposure to noxious particles (e.g., cigarette
smoke).
Etiology / Risk Factors
- Smoking
(primary risk factor)
- Occupational
dust and chemicals
- Air
pollution
- Alpha-1
antitrypsin deficiency (genetic)
- Aging
Pathophysiology
- Chronic
bronchitis: inflammation of bronchi → mucus
hypersecretion → airway narrowing.
- Emphysema:
destruction of alveolar walls → reduced surface area for gas exchange.
- Progressive
airflow limitation → hypoxia and hypercapnia.
Clinical Features
- Chronic
productive cough (especially in morning)
- Dyspnea
on exertion → later at rest
- Wheezing,
chest tightness
- Cyanosis
("blue bloater") or barrel chest ("pink puffer")
- Fatigue,
weight loss
Diagnosis
- Spirometry:
↓ FEV1/FVC ratio (<70%)
- Chest
X-ray: hyperinflated lungs, flattened diaphragm
- ABG:
hypoxemia, hypercapnia
- Blood
test: alpha-1 antitrypsin levels (if young, non-smoker)
Complications
- Pulmonary
hypertension
- Cor
pulmonale (right heart failure)
- Respiratory
failure
Management
- Smoking
cessation (most important)
- Bronchodilators
(β2-agonists, anticholinergics)
- Inhaled
corticosteroids
- Oxygen
therapy (long-term in hypoxemia)
- Pulmonary
rehabilitation, breathing exercises
- In
severe cases: lung volume reduction surgery or transplantation
Pneumonia
Definition
An acute infection of the lung parenchyma (alveoli,
interstitium) caused by bacteria, viruses, fungi, or aspiration.
Types
- Community-acquired
pneumonia (CAP)
- Hospital-acquired
pneumonia (HAP)
- Aspiration
pneumonia
- Opportunistic
pneumonia (immunocompromised patients)
Common Etiological Agents
- Bacterial:
Streptococcus pneumoniae, Klebsiella, Staphylococcus
aureus, Pseudomonas
- Viral:
Influenza, RSV, SARS-CoV-2
- Fungal:
Pneumocystis jirovecii, Histoplasma
Pathophysiology
- Microorganisms
reach alveoli → inflammation → alveolar filling with exudate → impaired
oxygen diffusion.
Clinical Features
- Fever,
chills
- Productive
cough (purulent or rust-colored sputum)
- Dyspnea,
pleuritic chest pain
- Crackles,
bronchial breath sounds
- Fatigue,
confusion (elderly)
Diagnosis
- Chest
X-ray: lobar or patchy consolidation
- Sputum
culture, blood culture
- CBC:
leukocytosis
- Pulse
oximetry / ABG
Complications
- Lung
abscess
- Pleural
effusion, empyema
- Sepsis,
septic shock
Management
- Antibiotics
(empirical, then culture-guided)
- Antivirals
(if viral cause suspected, e.g., influenza)
- Oxygen
therapy, fluids, analgesics
- Vaccination
for prevention (Pneumococcal, Influenza)
Tuberculosis (TB)
Definition
A chronic infectious disease caused by Mycobacterium
tuberculosis, primarily affecting the lungs but can involve other organs.
Risk Factors
- Close
contact with TB patients
- HIV
infection, immunosuppression
- Malnutrition,
diabetes
- Overcrowding,
poverty
Pathophysiology
- Inhalation
of droplet nuclei → bacilli reach alveoli → engulfed by macrophages →
granuloma formation (Ghon complex).
- Reactivation
TB occurs when immunity is low.
Clinical Features
- Chronic
cough (>2 weeks), hemoptysis
- Night
sweats, fever, weight loss, fatigue
- Chest
pain, breathlessness
Diagnosis
- Sputum
smear (Ziehl-Neelsen stain, AFB test)
- Culture
(Löwenstein–Jensen medium)
- GeneXpert
/ PCR
- Chest
X-ray: cavitary lesions, infiltrates
- Mantoux
test (screening)
Complications
- Miliary
TB
- Pleural
effusion, empyema
- Fibrosis,
bronchiectasis
- MDR-TB
(drug resistance)
Management
- First-line
anti-TB drugs (6-month regimen):
2 months HRZE (Isoniazid, Rifampicin, Pyrazinamide, Ethambutol) + 4 months HR (Isoniazid, Rifampicin) - DOTS
(Directly Observed Treatment, Short-course)
- MDR-TB:
second-line drugs (e.g., fluoroquinolones, aminoglycosides)
Lung Infections (Other than TB &
Pneumonia)
Includes viral, fungal, parasitic, and atypical
bacterial infections.
Examples
- Viral:
Influenza, RSV, COVID-19
- Fungal:
Aspergillosis, Histoplasmosis, Cryptococcus
- Atypical
bacteria: Mycoplasma pneumoniae, Chlamydia pneumoniae
Features
- Fever,
cough, malaise
- Wheezing,
dyspnea
- Sometimes
hemoptysis (fungal infections)
Diagnosis
- Sputum
culture, viral PCR
- Chest
imaging (cavitations, nodules, diffuse infiltrates)
- Serology
(fungal infections)
Management
- Antivirals
(oseltamivir for influenza)
- Antifungals
(amphotericin B, voriconazole)
- Supportive
oxygen, fluids, antibiotics (for secondary infections)
Acute Respiratory Distress Syndrome (ARDS)
Definition
A severe, life-threatening condition with diffuse
alveolar damage leading to non-cardiogenic pulmonary edema and acute
hypoxemic respiratory failure.
Causes
- Sepsis
(most common)
- Trauma,
burns
- Aspiration,
pneumonia
- Pancreatitis
- COVID-19
Pathophysiology
- Injury
to alveolar-capillary membrane → increased permeability → fluid leakage
into alveoli → decreased surfactant → stiff lungs → refractory hypoxemia.
Clinical Features
- Acute
onset severe dyspnea
- Hypoxemia
unresponsive to oxygen therapy
- Diffuse
crackles, cyanosis
- Respiratory
distress, tachypnea
Diagnosis
- CXR:
bilateral “white-out” infiltrates
- ABG:
severe hypoxemia (PaO2/FiO2 < 200)
- Rule
out cardiogenic pulmonary edema (normal cardiac function)
Management
- Mechanical
ventilation with low tidal volume
- PEEP
(positive end-expiratory pressure)
- Treat
underlying cause (sepsis, trauma, pneumonia)
- Prone
positioning, ECMO (in refractory cases)
Respiratory Failure
Definition
Failure of the lungs to maintain adequate oxygenation
(PaO2 < 60 mmHg) and/or CO2 elimination (PaCO2 > 50 mmHg).
Types
- Type
I (Hypoxemic): ↓ PaO2 (ARDS, pneumonia, pulmonary
edema)
- Type
II (Hypercapnic): ↑ PaCO2 (COPD, drug overdose,
neuromuscular disorders)
Clinical Features
- Dyspnea,
cyanosis
- Restlessness,
confusion, headache
- Tachypnea
or bradypnea (in severe cases)
- Signs
of underlying cause
Diagnosis
- ABG
analysis
- Pulse
oximetry
- CXR
/ CT for underlying disease
Management
- Oxygen
therapy (careful in COPD)
- Mechanical
ventilation if severe
- Treat
underlying cause (infection, obstruction, drug overdose)
- Bronchodilators,
corticosteroids (if obstructive)
Asthma
Definition
A chronic inflammatory disorder of the airways
characterized by reversible airflow obstruction and bronchial
hyperresponsiveness.
Triggers
- Allergens
(dust, pollen, animal dander)
- Exercise,
cold air
- Respiratory
infections
- Drugs
(aspirin, beta-blockers)
- Occupational
irritants
Pathophysiology
- Exposure
to trigger → immune response → mast cell degranulation → histamine,
leukotrienes → bronchoconstriction + airway inflammation + mucus
production.
Clinical Features
- Episodic
wheezing, breathlessness
- Cough,
especially at night or early morning
- Chest
tightness
- Prolonged
expiration
- In
severe attack: silent chest, cyanosis (status asthmaticus)
Diagnosis
- Spirometry:
reversible ↓ FEV1/FVC, improved after bronchodilator
- Peak
expiratory flow rate monitoring
- Allergy
tests (IgE, skin prick)
Complications
- Status
asthmaticus (life-threatening)
- Respiratory
failure
- Chronic
airway remodeling
Management
- Acute
attack: short-acting β2-agonist
(salbutamol), oxygen
- Long-term
control:
- Inhaled
corticosteroids (first-line)
- Long-acting
β2-agonists (LABA)
- Leukotriene
receptor antagonists
- Avoidance
of triggers
- Patient
education and inhaler technique training
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