Restrictive Pulmonary Disorders & Related Conditions

Restrictive Pulmonary Disorders – Overview

• Restrictive pattern = ↓ lung expansion → ↓ total lung capacity (TLC), vital capacity (VC), functional residual capacity (FRC)
• Common examples
  • Interstitial lung disease (ILD) – idiopathic pulmonary fibrosis (IPF)
  • Sarcoidosis – autoimmune, systemic
  • Obesity & obesity-hypoventilation syndrome (Pickwickian)
  • Viral epidemics/pandemics: SARS, MERS, COVID-19

Lung Parenchyma Disorders

Fibrotic Interstitial Lung Diseases

Diffuse Interstitial Lung Disease (DILD)

• Thickening & fibrosis of alveolar interstitium → classic restrictive defect

Sarcoidosis

• Acute or chronic, systemic, unknown cause; presumed immunologic
• Non-caseating granulomas in multiple organs

Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis)

• Etiology: inhaled organic antigens (moldy hay, bird droppings, etc.)
• Immunologic inflammation of alveoli & bronchioles
• Occupational & predominantly in non-smokers

Occupational Lung Diseases

• Inhalation of toxic gases / foreign particles
• Pneumoconiosis = ILD caused by inorganic dusts (silica, coal, asbestos, etc.)

Atelectatic Disorders

Acute (Adult) Respiratory Distress Syndrome – ARDS

• Etiology: diffuse alveolar–capillary damage → non-cardiogenic pulmonary edema, widespread atelectasis, fluffy alveolar infiltrates
• Pathogenesis
  • Direct (aspiration, pneumonia, inhalation injury) or indirect (sepsis, trauma, pancreatitis) injury → inflammatory cascade → ↑ permeability
• Hallmark: refractory hypoxemia due to intrapulmonary shunt
• Clinical: precipitating event with low circulating volume, severe dyspnea
• Diagnosis: hypoxemia unresponsive to ↑ FiO_2; CXR = bilateral infiltrates; ABG, cultures, PFTs, biopsy
• Treatment: supportive; mechanical ventilation with PEEP, supplemental O_2

Infant Respiratory Distress Syndrome – IRDS

• Etiology: hemorrhagic edema, patchy atelectasis, hyaline membranes
• Pathogenesis: deficient surfactant → ↑ surface tension, ↓ compliance
• Hallmark: refractory hypoxemia identical to ARDS
• Clinical: nasal flaring, expiratory grunting, intercostal retractions, rapid shallow breaths
• Diagnosis: CXR “white-out”, severe hypoxemia & acidosis on ABG
• Treatment: mechanical ventilation with PEEP/CPAP, O_2, exogenous surfactant

Pleural Space Disorders

Pneumothorax

• Air in pleural space
• Types / Pathogenesis
  • Primary: rupture of apical subpleural blebs
  • Secondary: complication of underlying lung disease (COPD, cystic fibrosis)
  • Tension: air under pressure; mediastinal shift → emergency
• Clinical: tachycardia, sudden unilateral chest pain, dyspnea, ↓/absent breath sounds, hyper-resonance
• Diagnosis: CXR, ECG, ABG
• Treatment
  • < 15\%–25\% collapse: symptomatic
  • > 15\%–25\%: chest tube + water seal/suction, 100\% O_2

Pleural Effusion / Empyema

• Pathologic collection of fluid/pus in pleural cavity due to another disease
• Empyema = infected pleural fluid
• Manifestations vary with size/type (transudate, exudate, chylous, hemorrhagic)
• Diagnosis: thoracentesis (diagnostic & therapeutic), CXR, CT, US
• Treatment: manage underlying cause, drain fluid, antibiotics if infected

Neuromuscular, Chest Wall & Obesity Disorders

Neuromuscular Disorders – Weak Respiratory Muscles → Ventilatory Failure

• Poliomyelitis – viral destruction of spinal/brainstem motor neurons
• Amyotrophic Lateral Sclerosis (ALS) – progressive UMN & LMN degeneration
• Muscular Dystrophies – X-linked (Duchenne), skeletal & respiratory muscle weakness
• Guillain–Barré Syndrome (GBS)
  • Acute demyelinating polyneuropathy, immune-mediated
  • Ascending symmetric weakness → possible respiratory failure
• Myasthenia Gravis (MG)
  • Autoimmune ACh receptor blockade
  • Fatigable weakness ↑ with exercise, ↓ with rest; can involve respiratory muscles

Chest Wall Deformities

• Kyphoscoliosis – idiopathic / congenital / neuromuscular; ↓ chest compliance
• Ankylosing Spondylitis – HLA-B27 (+); chronic ligamento-osseous inflammation & fusion
• Flail Chest – ≥2 fractures in ≥2 adjacent ribs → paradoxical movement (inward inspiration / outward expiration)

Obesity & Obesity-Hypoventilation

• Etiology: BMI > 30\;kg·m^{-2}; majority due to chronic caloric surplus > expenditure
• Minor proportion: single-gene mutations ( 4\%–6\% ), endocrine (hypothyroid, corticosteroids), hypothalamic lesions
• Pathogenesis: ↑ chest/abdominal mass → ↓ ventilatory drive & mechanics
• Clinical – Pickwickian syndrome: daytime somnolence, severe hypoxemia, hypercapnia, polycythemia, cor pulmonale; also ED, SOB, headaches, enuresis
• Diagnosis: physical exam, BMI, comorbidities
• Treatment: weight-loss program (family involvement), aerobic exercise, supplemental O_2, bariatric surgery

Infection or Inflammation of the Lung

Pneumonia

• Etiology: infection of alveoli & interstitium by
  • Aspiration (normal flora / gastric) 20\%–35\%
  • Inhalation of contaminants (viral, Mycoplasma)
  • Hematogenous spread
• Categories: community vs hospital acquired; bacterial (Gram+ / Gram−), atypical, viral, fungal
• Pathogenesis
  • Community bacterial: impaired defenses → alveolar exudate
  • Viral: interstitial inflammation without exudate
• Clinical
  • Bacterial: fever, chills, productive cough with purulent sputum, crackles, bronchial breath sounds, CXR infiltrates
  • Legionella: systemic (fever, diarrhea, abd pain) + pneumonia from contaminated water
  • Viral: URTI prodrome, wheezing, rales
  • Fungal (Pneumocystis) – opportunistic in HIV
• Diagnosis: CXR, sputum gram stain/culture, blood cultures, WBC
• Treatment: empiric → culture-guided antibiotics; repeat CXR at 6–8 weeks post-therapy

Severe Acute Respiratory Syndromes

SARS (2003)

• Coronavirus; severe pneumonia; limited U.S. cases (n=8)

MERS (2012, Saudi Arabia)

• Related coronavirus; sporadic outbreaks

SARS-CoV-2 (COVID-19, 2019-present)

• Transmission: close contact, airborne droplets
• Two pulmonary phenotypes
  • L-type: low elastance (near-normal compliance)
  • H-type: high elastance (stiff lungs)
• Three stages
  1. Flu-like: fever, myalgia, cough, dyspnea
  2. Pulmonary inflammation & coagulopathy → ↑ inflammatory markers, progression to ARDS
  3. Multiorgan fibrosis – alveolar, cardiac, renal, hepatic, GI

Pulmonary Tuberculosis (TB)

• Etiology: Mycobacterium tuberculosis inhaled/ingested; high risk in immunosuppressed (HIV)
• Pathogenesis
  • Spread via lymph & blood → macrophage ingestion → granuloma formation
  • Dormancy; fibrotic/calcified Ghon tubercles = hallmark
• Clinical: low-grade fever, night sweats, fatigue, weight loss; later purulent productive cough
• Diagnosis
  • Sputum culture for acid-fast bacillus (definitive)
  • Positive PPD, Quantiferon, radiographic nodules
• Treatment
  • Multi-drug regimen 6–9 mo, specialist referral
  • Major failure cause = non-adherence

NGN Case Study – Guillain–Barré Syndrome (GBS)

• 45-yr-old post-viral illness with ascending weakness → ICU
• Priority problems to prevent
  • Respiratory failure (weak respiratory muscles)
  • Dysrhythmia & hypotension (autonomic dysfunction)
  • Hyperthermia (loss of sweating / thermoregulation)
• GI bleeding, depression, anorexia may occur but not primary priorities

Key Numerical / Statistical References

• BMI obesity cutoff: \ge 30\;kg·m^{-2}
• Obesity due to single-gene mutations: 4\%–6\%
• Pneumothorax management thresholds: 15\%–25\% lung collapse
• Pneumonia aspiration source: 20\%–35\% of cases
• TB drug therapy duration: 6–9 months

Clinical Hallmarks & Signatures

• ARDS/IRDS: refractory hypoxemia to supplemental O_2
• Sarcoidosis: non-caseating granulomas; HLA-B27 negative (unlike ankylosing spondylitis)
• Flail chest: paradoxical motion
• Ghon tubercle: calcified granuloma in TB
• Pickwickian syndrome: obesity hypoventilation triad (obesity + daytime hypercapnia + sleep-related hypoventilation)

Connections & Implications

• Many restrictive disorders converge on decreased lung compliance and ventilation–perfusion mismatch → chronic hypoxemia, pulmonary hypertension, cor pulmonale.
• Viral pandemics (SARS-CoV-2) reinforce need for public health, rapid vaccine development, and ventilatory management strategies similar to ARDS protocols.
• Obesity epidemic intersects with respiratory pathophysiology (obesity-hypoventilation) highlighting lifestyle, socioeconomic, and endocrine contributors.
• Neuromuscular etiologies (GBS, MG, ALS) demonstrate significance of systemic diseases on pulmonary function and necessity for interdisciplinary management (neurology, pulmonology, critical care).