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1B restrictive lung disease Flashcards

1
Q

What is a restrictive lung disease?

A
  • Lung volumes are small
  • Expansion of lung is restricted
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2
Q

What is lung expansion restricted by in restrictive lung disease?

A
  • Intrinsic lung disease (alterations to lung parenchyma)
    • Interstitial lung disease (ILD)
  • Extrinsic disorders (compress lungs or limit expansion)
    • Pleural
    • Chest wall
    • Neuromuscular (decrease ability of respiratory muscles to inflate/delate the lungs)
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3
Q

What is the lung parenchyma?

A

The alveolar regions of the lung

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4
Q

What is the interstitial space?

A

Space between alveolar epithelium and capillary endothelium

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5
Q

What are the important cellular components of the lung parenchyma?

A
  • Alveolar type 1 epithelial cell
  • Alveolar type 2 epithelial cell
  • Fibroblasts
  • Alveolar macrophages
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6
Q

What do alveolar type 1 epithelial cells do?

A

Gas exchange surface (approx. 70m2)

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7
Q

What do alveolar type 2 epithelial cells do?

A

Surfactant to reduce surface tension, stem cell for repair

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8
Q

What do fibroblasts in the lung parenchyma do?

A

Produce extracellular matrix (ECM) e.g. collagen type 1

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9
Q

What do alveolar macrophages do?

A

Phagocytose foreign material, surfactant

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10
Q

What are the functions of the interstitial space?

A
  • Contains lymphatic vessels, occasional fibroblasts and ECM
  • Structural support to lung
  • very thin (few micrometres thick) to facilitate gas exchange
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11
Q

Which immune cells are closely associated with the lung epithelium?

A

Macrophages

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12
Q

What are interstitial lung diseases?

A

Inflammation or fibrosis in the interstitial space

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13
Q

What subsets of ILDs are there?

A
  • Idiopathic
  • Autoimmune
  • Exposure related
  • With cysts or airspace filling
  • Sarcoidosis
  • Others
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14
Q

What are the clinical presentations of ILD?

A
  • Progressive breathlessness
  • Non-productive cough
  • Limitation in exercise tolerance
  • Symptoms of CTD
  • Occupational and exposure history
  • Medication history (drug induced?)
  • Family history (up to 20% are familial)
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15
Q

What clinical examination findings are there for ILD?

A
  • Low O2 sats (resting or exertion)
  • Fine bilateral inspiratory crackles
  • Digital clubbing

+/- features of connective tissue disease- skin, joints, muscles

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16
Q

What investigations are done for ILD?

A
  • Blood tests (e.g. ANA, RhF, CCP)
  • Pulmonary function tests
  • 6-minute walk test (6MWT)
    • SpO2 ≤ 88% associated with increased risk of death
  • High-resolution CT scan (HRCT)
  • Invasive testing:
    • Bronchoalveolar lavage (BAL)
    • Surgical lung biopsy (2-4% mortality)
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17
Q

Describe the physiology of ILD in the lungs

A
  • Scarring makes the lung stiff so ↓ lung compliance
  • ↓ Lung volumes (TLC, FRC, RV)
  • ↓ FVC
  • ↓ diffusing capacity of lung for carbon monoxide (DLCO)
  • ↓ arterial PO2 – particularly with exercise
  • Normal or ↑ FEV1/ FVC ratio
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18
Q

Describe the pattern of forced expiration

A

FEV1/FVC ratio = 100% → normally 100- a restrictive ratio doesn’t always mean disease, since small sporty people with large airways and little lungs can empty their lungs quickly

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19
Q

What is HRCT?

A

High-resolution CT: essential for ILD diagnosis

  • thin slices and high-frequency reconstruction – gives good resolution at level of secondary pulmonary lobule (smallest functional lung unit identifiable on CT)
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20
Q

What does this HRCT pattern show?

A

Usual interstitial pneumonia

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21
Q

What does this HRCT pattern show?

A

Non-specific interstitial pneumonia

22
Q

What does this HRCT pattern show?

A

Organising pneumonia

23
Q

Why is MDT diagnosis important in ILD?

A

Integration of clinical, radiological +/- pathological information to make a diagnosis

24
Q

How is early ILD managed?

A
  • Pharmacological therapy
    • immunosuppressive drugs, antifibrotics
  • Clinical trials
  • Patient education
  • Vaccination
  • Smoking cessation
  • Treatment of co-morbidities (GORD, obstructive sleep apnoea, pulmonary HTN)
  • Pulmonary rehab
25
Q

How is late ILD managed?

A
  • Supplemental oxygen
  • Lung transplantation
  • Palliative care (symptom management, end-of-life care)
26
Q

What are some key examples of ILD?

A
  • Idiopathic pulmonary fibrosis
  • Hypersensitivity pneumonitis (HP)
  • Systemic sclerosis (SSc); associated ILD
27
Q

What is idiopathic pulmonary fibrosis (IPF)?

A
  • Progressive, scarring lung disease of unknown cause
  • 6,000 new cases diagnosed each year
  • 1% of all deaths in UK
  • Incidence increases with age - most >60yrs
  • More common in men
  • Average decline in forced vital capacity (FVC) = 150 – 200mls / year
28
Q

What is AE-IPF?

A

Acute exacerbations of IPF

  • Occur in 5-15% of patients
  • Median survival 3-4 months
  • In-hospital mortality ~50%
29
Q

What is the prognosis like for IPF?

A

Poor

Median untreated survival is 3-5 years

30
Q

What are the proposed mechanisms of IPF?

A

Predisposing factors:

  • Genetic susceptibility
    • MUC5B, DSP
  • Environmental triggers
    • Smoke, viruses, pollutants, dusts
  • Cellular ageing
    • Telomere attrition, senescence
31
Q

How is IPF initiated?

A

Alveolar epithelial injury

  • Denuded alveolar epithelium seen by electron microscopy1,2
  • Targeted injury to AECIIs in mouse model – ↑ collagen deposition3
  • Re-epithelialization disturbed in IPF4
32
Q

Describe the histopathology of IPF

A
  • honeycomb cyst
  • fibroblastic
33
Q

What are characteristic features of IPF on CT scan?

A
34
Q

Why was there a change in the conventional treatment for IPF?

A

Immunosuppression is harmful in IPF

PANTHER-IPF trial

  • Randomized, double-blind, placebo-controlled trial
  • Combination treatment with prednisone + azathioprine +N-acetylcysteine –> increased risk of death and hospitalisation
  • Led to a change in the conventional treatment for IPF
35
Q

Give examples of antifibrotics and their effect on IPF

A
  • Nintedanib (tyrosine kinase inhibitor)
  • Pirfenidone (pyridine compound)

Antifibrotics slow disease progression in IPF but do not cure

36
Q

What treatment for IPF is in clinical trials?

A

Drugs targeting fibrotic pathways

37
Q

What is hypersensitivity pneumonitis (HP)?

A
  • ILD caused by immune- mediated response in susceptible and sensitised individuals to inhaled environmental antigens
  • Genetic and host factors may explain why only few exposed individuals get HP
  • Involves small airways and parenchyma
38
Q

How is HP classified?

A
  • Acute HP
    • Intermittent, high-level exposure
    • Abrupt symptom onset, flu-like syndrome 4-12 hours after exposure
  • Chronic HP
    • Long-term, low-level exposure
    • Nonfibrotic (purely inflammatory)
    • Fibrotic (associated with high mortality)
39
Q

What is the epidemiology of HP?

A
  • Rare - incidence in UK ~ 1 per 100,0001
  • Mean age onset 50 – 60 yrs
  • M = F
  • Less frequent in smokers
  • Worldwide prevalence varies due to differences in antigen exposure, agricultural, industrial practices etc.
  • 3- fold ↑ risk of death compared to general population1
40
Q

What is HP driven by?

A

Immunological dysregulation

  • Antigen exposure and processing by the innate immune system
  • Inflammatory response mediated by T-helper cells and antigen-specific immunoglobulin (Ig) G antibodies
  • Accumulation of lymphocytes and formation of granulomas
41
Q

What are some environmental antigens for HP?

A
  • African Grey Parrots (exposure to droppings)
  • (Mouldy) Hay
42
Q

What is the diagnosis of HP like?

A
  • Detailed exposure history – antigen not identified in ~50%1
  • Inspiratory ‘squeaks’ on auscultation - caused by the coexisting bronchiolitis
  • Specific circulating IgG antibodies (serum precipitins) to potential antigens
  • HRCT
  • Bronchoalveolar lavage (BAL) lymphocyte count >30%2
43
Q

What is the treatment for HP?

A
  • Complete antigen removal/avoidance is crucial
  • Corticosteroids often used
  • Immunosuppressants e.g. mycophenolate mofetil (MMF) and azathioprine used but poor evidence base
  • Progressive, fibrotic HP – Nintedanib (antifibrotic)1
44
Q

What is systemic sclerosis associated (SSc) ILD?

A

Autoimmune connective tissue disease characterised by immune dysregulation and progressive fibrosis that affects skin, with variable internal organ involvement

  • Slow indolent course vs. rapid progression
45
Q

What is the epidemiology of SSc ILD?

A
  • Rare: 10-50 cases per 1mill per year
  • Affects young, middle-aged women
  • Develops in 30-40% and is most common cause of death- 10year mortality of 40%
  • Male, older age, smoker, >20% extent on HRCT, FVC <70% –> worse survival
46
Q

What are the clinical features of SSC?

A
47
Q

How are SSc clinical features classified?

A

Based on skin involvement

  • Limited cutaneous SSc (pulmonary HTN more common)
  • Diffuse cutaneous SSc (ILD more common)
48
Q

What autoantibodies are in SSc?

A
  • Anti-centromere
  • Anti-Scl-70: associated with increased with ILD
49
Q

Describe the pathogenesis of SSc-ILD

A
50
Q

What are HRCT patterns in SSc-ILD?

A

Non-specific interstitial pneumonia (NSIP) pattern is the most common pattern

51
Q

What is the management of SSc-ILD?

A
  • Determined by disease extent on HRCT and lung function trajectory (monitor every 3 – 6 months)
  • Corticosteroid use is controversial and risk of renal crisis with high doses (>10mg/day)
  • Immunosuppressives – cyclophosphamide, mycophenolate mofetil (MMF)1
  • Progressive fibrotic phenotype– Nintedanib (antifibrotic)2

cardioresp (15 decks)

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