Critical Illness and Rare Pulmonary Conditions

Acute Respiratory Distress Syndrome (ARDS)

Definition

•    Non-cardiogenic pulmonary oedema due to increased alveolar-capillary permeability

Berlin criteria

•    Timing: within 1 week of insult

•    CXR: bilateral opacities not fully explained by effusions or collapse

•    Origin of oedema: not due to cardiac failure/fluid overload

•    Oxygenation: PaO₂/FiO₂ <300 mmHg (with PEEP ≥5 cm H₂O)

Common triggers

•    Sepsis (most common)

•    Massive transfusion

•    Aspiration

•    Severe trauma

•    Pancreatitis

Management

•    Lung-protective ventilation: low tidal volume (~6 mL/kg), limit plateau pressures

•    Conservative fluid management

•    Prone positioning in severe cases

•    ECMO (last resort)

Alveolar Haemorrhage Syndromes

Triad

•    Haemoptysis

•    Anaemia (acute drop)

•    Diffuse pulmonary infiltrates (bilateral)

Causes

•    Granulomatosis with polyangiitis (GPA)

•    Goodpasture’s syndrome (anti-GBM antibodies)

•    SLE

•    Other vasculitides (e.g., microscopic polyangiitis)

Diagnosis

•    Bronchoalveolar lavage: bloody fluid that remains persistently haemorrhagic on sequential aliquots

•    Immunology: anti-GBM, ANCA

Management

•    High-dose steroids ± plasma exchange (Goodpasture's)

•    Immunosuppression (cyclophosphamide)

Pulmonary Lymphangioleiomyomatosis (LAM)

Features

•    Rare cystic lung disease affecting young women (childbearing age)

•    Linked to tuberous sclerosis complex (TSC)

Clinical

•    Progressive dyspnoea

•    Recurrent pneumothoraces

•    Chylous pleural effusions

Imaging

•    Diffuse thin-walled cysts (HRCT)

Management

•    Sirolimus (mTOR inhibitor)

•    Avoid oestrogen

•    Lung transplantation in advanced cases

Pulmonary Alveolar Proteinosis

Pathophysiology

•    Impaired surfactant clearance by alveolar macrophages → alveolar filling

Clinical

•    Progressive dyspnoea

•    Cough with "milky" sputum

Imaging

•    HRCT: "Crazy paving" pattern (ground-glass opacities + interlobular septal thickening)

Diagnosis

•    Bronchoalveolar lavage: opaque, milky fluid; foamy macrophages with periodic acid–Schiff (PAS)-positive material

Management

•    Whole lung lavage (mainstay)

•    GM-CSF therapy in some cases

Extra Revision Pearls

•    ARDS → non-cardiogenic, PaO₂/FiO₂ <300, bilateral infiltrates

•    Key ARDS causes: sepsis, aspiration, pancreatitis, transfusions (TRALI)

•    Goodpasture’s clue → haematuria + pulmonary haemorrhage

•    LAM → young woman, recurrent pneumothorax, tuberous sclerosis

•    Alveolar proteinosis clue → "crazy paving" + milky lavage fluid

•    ECMO consideration in severe refractory ARDS

•    Avoid excessive fluid loading in ARDS — conservative strategy improves outcomes