Interstitial Lung Disease

ILD refers to a wide group of diseases which primarily affect the connective tissue fibrous framework of the lung.

Presentation

1. ILD may be found incidentally with fibrotic changes seen on CXR
2. Often patients have a non-specific presentation with
   • Progressive breathlessness with the 4Cs – cough (which is dry), cyanosis, clubbing (both in advanced disease) and crackles (classically fine ‘velcro’)
   • Hypoxaemia
   • Raised inflammatory markers
   • Diffuse CXR shadowing

Aetiology

1. Idiopathic Interstitial Pneumonias (IIPs)
   • IIPs are a group of diffuse lung diseases of unknown cause in which the underlying pathological process is one of varying degrees of inflammation and fibrosis
   • The most common forms present with a chronic or insidious onset, i.e. Idiopathic Pulmonary Fibrosis (IPF) or Non-Specific Interstitial Pneumonia (NSIP)
   • There are also forms which present more acutely, e.g. Acute Interstitial Pneumonia (AIP), or are smoking-related e.g. Respiratory Bronchiolitis Interstitial Lung Disease (RB-ILD), Desquamative Interstitial Pneumonia (DIP)
2. Connective Tissue Disease
   • Rheumatoid arthritis
   • Scleroderma
   • Sjogren’s disease
   • Polymyositis/dermatomyositis
3. Exposure-related/Toxins
   • Occupational, e.g. farmer’s lung (hypersensitivity pneumonitis), asbestosis
   • Environmental
   • Recreational, e.g. pigeon-fancier’s lung (hypersensitivity pneumonitis)
   • Drugs, e.g. methotrexate, amoidarone, nitrofurantoin
     For more information see Pneumotox
   • Sarcoidosis
   • Beryliosis
4. Rare
   • Vasculitis/diffuse alveolar haemorrhage (DAH)
   • Langerhans cell histiocytosis (LCH)
   • Eosinophilic pneumonias
   • Neurofibromatosis
   • Lymphangioleiomyomatosis (LAM)

Idiopathic Pulmonary Fibrosis

1. Typically develops over months to years
2. Typical patient is elderly, male and an ex-smoker
3. HRCT pattern shows changes of fibrosis with traction bronchiectasis, pleural thickening and honeycomb patterns in a subpleural or basal distribution. In IPF there is minimal inflammatory ground glass shadowing.
4. Prognosis is poor with average survival 3-5 years from diagnosis, even with treatment
5. Nintedanib and pirfenidone are anti-fibrotic drugs licensed in IPF to slow decline in lung function and reduce risk of acute exacerbations

Workup of Suspected ILD

1. Take a good history including extrapulmonary symptoms, occupational/recreational exposure, smoking and medication.
2. Look for evidence of an underlying cause on examination –  skin/joint/eye disease
3. Assess for differential diagnosis of breathlessness and crepitations – e.g. heart failure or bronchiectasis
4. Bloods – ESR and CRP, FBC, autoantibodies (ANA, ANCA), serum precipitins and BBV testing
5. Imaging – CTPA with HRCT slices ideal first line as deterioration often precipitated by PE
6. Urine dipstick and microscopy
7. Sputum with extended AFB culture
8. Pulmonary function testing (when recovered from acute infection/reason for deterioration)
9. Consider bronchoscopy and BAL for atypical infections, Transbronchial, Cryobiopsy or surgical lung biopsy depending upon ILD Multi-disciplinary outcome.
10. Echo to assess cardiac function (pulmonary oedema) and determine if cor pulmonale

Exacerbations of ILD

1. An exacerbation is defined as an acute, unexplained, worsening of symptoms
2. The cause is often unclear or idiopathic
3. Usually exacerbations of ILD develop sub-acutely in <30 days
4. HRCT shows extensive ground glass inflammatory changes and/or consolidation on top of chronic changes
5. Disease exacerbations are a common cause of death in patients with mild-moderate or apparently stable ILD
6. Inpatient mortality is >60%. Mortality within 6 months of discharge is >90%.

Acute Management

1. Empirical high dose steroids – 1000mg methylprednisolone IV for 3 days acutely
2. Low threshold for treating infection – consider atypical infections, e.g. PCP, especially if on immunosuppressants
3. Oxygen therapy to target SpO₂ 94-98%
4. Consider ceiling of care and appropriateness of escalation to CCU for HFNO
5. Benefits of HFNO include the ability to deliver up to 95% oxygen with humidification and a CPAP effect to improve delivery. Patients often tolerate HFNO well. HFNO is contraindicated if hypercapnic respiratory failure
6. Mechanical ventilation is associated with near 100% mortality in IPF but may occasionally be recommended by the respiratory team.
7. Refer to respiratory team for MDT discussion

Initiation of HFNO

1. Start flow at 30l/min and increase as needed to max 60l/min
2. Adjust O₂ flow meter to achieve 40% oxygen and increase/decrease as needed to achieved prescribed O₂ saturation
3. If SpO₂ not reaching target ensure O₂ is at maximum (95%) and increase flow to maximum 60 litres
4. If no improvement, consider returning to non-re-breather mask+/- wall nasal cannulae

If SpO₂ within target and patient improving

1. Consider weaning O₂ while maintaining target SpO₂
2. Once O₂ weaned to 40% or less, gradually wean flow by 5-10 litres at a time
3. Discontinue HFNO and commence venturi mask or nasal cannulae when patient remains stable and target SpO₂ is maintained on 30% O₂ and a flow of 30l/min and when sputum clearance is no longer an issue

Long-term management

1. This is largely supportive, e.g. stop smoking, avoid further exposure to drugs/toxins, and home oxygen when required.
2. After MDT consideration, patients may be started on anti-fibrotic drugs or referred for lung transplant.
3. Long-term steroids are not routinely used.
4. Management of comorbidities, GERD, Pulmonary Hypertension, Pulmonary Rehabilitation.
5. Early anticipatory care planning and, when required, palliative care involvement are important for all patients.
6. Early Referral for Lung Transplantation to tertiary Care centre if patient fulfil the criteria for it.

Prognosis

1. Median survival for IPF/CFA is about 3 years from diagnosis
2. Acute exacerbation with respiratory failure has in hospital mortality:50%
3. 5YS post transplant is around 50%

Links

• Lederer, DJ, Martinez F.J., Idiopathic Pulmonary Fibrosis. NEJM. 2018; 378: 1811-1823 – Search on

Knowledge Network

Content by Emily Turner. Updated by Wasib Shah.