Interstitial and occupational lung disease

1Definition

Interstitial lung disease (ILD) is a group of disorders that inflame and scar (fibrose) the lung tissue between the air sacs (the interstitium). The lungs become stiff and small, and oxygen passes poorly into the blood.

Occupational lung disease is lung disease caused by breathing in dusts, fibres, fumes or organic material at work.

2Classification

3Causes and risk factors

• Years of exposure to dusts at work without masks or ventilation: cotton mills (S18), stone quarries, mines, construction, agriculture (S21 farmer).
• Smoking, older age and male sex for IPF; family history; autoimmune disease; some drugs (amiodarone, methotrexate); radiotherapy.

4Pathophysiology to impairments

1. Repeated injury causes inflammation and scarring of the interstitium.
2. Stiff lungs need more effort to inflate: lung volumes and compliance fall (restriction), so breathing becomes rapid and shallow.
3. Thickened alveolar walls slow oxygen transfer (low DLCO). During exercise, blood moves through the lungs faster, so there is even less time to pick up oxygen: marked exertional desaturation.
4. Low oxygen narrows lung vessels: pulmonary hypertension and right heart failure.
5. Breathlessness causes inactivity and muscle weakness; a dry cough is often troublesome.

5Clinical features

• Progressive breathlessness on exertion; dry cough; fatigue; weight loss.
• Fine, "Velcro-like" crackles at the lung bases at the end of inspiration; clubbing (especially IPF); cyanosis late.
• Rapid, shallow breathing; reduced chest expansion; SpO₂ that falls sharply on walking.
• Signs of the cause: joint disease, skin changes, work history.

6Investigations

Three spirometric findings in restrictive disease (3 marks in S19)

1. FVC reduced (and FEV1 reduced in proportion).
2. FEV1/FVC normal or high (0.70 or more, often above 0.80).
3. Total lung capacity reduced on lung volume testing, with low DLCO in ILD.

See the spirometry curve on the COPD page: restriction lowers the plateau, obstruction slows the rise.

• HRCT: reticular lines, honeycombing, ground-glass areas, traction bronchiectasis (S21: "heterogeneous opacities").
• Chest X-ray: small lungs, reticular or nodular shadows; silicosis shows upper-zone nodules and "eggshell" calcified nodes.
• 6MWT with SpO₂: distance and the lowest SpO₂ (key for rehab and oxygen prescription).
• ABG, echo (pulmonary hypertension), autoimmune blood tests.

7Medical management

• Remove exposure: leave or change the dusty job; masks and dust control.
• Antifibrotic drugs (nintedanib, pirfenidone) slow decline in IPF and other progressive fibrosis.
• Steroids or immunosuppressants for inflammatory types (hypersensitivity pneumonitis, connective tissue disease).
• Oxygen: long-term if resting oxygen is low; ambulatory oxygen for marked exertional desaturation.
• Pulmonary rehabilitation: strong recommendation for ILD (ATS 2023).
• Vaccinations, smoking cessation, treatment of reflux and cough; lung transplant in selected patients; palliative care in advanced disease.

8Complications

• Respiratory failure; pulmonary hypertension and cor pulmonale.
• Acute exacerbations (sudden worsening, often fatal in IPF); infections; pneumothorax.
• Lung cancer (higher with IPF, asbestosis and silicosis); TB (higher with silicosis).
• Deconditioning, anxiety, depression.

9PT assessment

• Work history (type and years of exposure, masks), smoking, symptoms (mMRC), cough.
• Breathing pattern, chest expansion, crackles, clubbing.
• SpO₂ at rest and during a 6MWT; heart rate; Borg breathlessness.
• Muscle strength; function in ADL and work.
• Outcome measures: 6MWT distance and lowest SpO₂, mMRC, St George's Respiratory Questionnaire (IPF version), King's Brief ILD questionnaire.

10PT diagnosis by ICF

Worked example from a real paper (S18, 15 marks)

"A 40 year old female, working in cotton mill since past 15 years was admitted for complaint of grade II dyspnoea with diagnosis of ILD. Discuss ICF. Write physiotherapy goals and management for the same."

11Problem list and goals (3 marks in S17)

• Short-term: safe exercise with SpO₂ kept at about 88% or more (with oxygen if needed); breathing control and pacing during ADL; cough control strategies.
• Long-term: better exercise tolerance (6MWT) and quality of life; independent home exercise; energy conservation; avoidance of further dust exposure; return to suitable work.

12PT management

Pulmonary rehabilitation for ILD (7 marks in S21)

• Aerobic training: walking or cycling 3–5 days a week, 20–30 minutes, at moderate breathlessness (Borg 3–4); use interval training (short bouts with rests) if SpO₂ drops quickly.
• Oxygen during exercise: titrate to keep SpO₂ at about 88–90% or more; many ILD patients need it.
• Resistance training of legs and arms 2–3 days a week.
• Breathing control and recovery positions (forward lean); pacing; energy conservation.
• Cough control: sip water, swallow, nose breathing, suppression techniques for a dry cough.
• Thoracic mobility and posture exercises; inspiratory muscle training may help.
• Education: disease, oxygen safety (no smoking or flames near oxygen), when to seek help, workplace protection.

13Precautions and stop criteria

• Stop or reduce if SpO₂ falls below about 85% despite oxygen, or with chest pain, dizziness or severe breathlessness.
• Pulmonary hypertension: avoid sudden heavy exertion, breath-holding and heavy lifting; watch for syncope.
• Steroid use: bone fragility.
• Oxygen safety around flames and smoking.

14Education and prevention

• Avoid the dust that caused the disease; ask about job transfer; wear a fitted respirator mask if exposure continues.
• Stop smoking.
• Keep active every day within safe SpO₂ limits.
• Get vaccinated; report fever or sudden worsening breathlessness early.
• Silicosis: screening for TB.

15Prognosis

Varies by type: IPF progresses over a few years even with treatment; some hypersensitivity and inflammatory types improve if exposure stops and treatment starts early. Pulmonary rehabilitation improves exercise capacity, breathlessness and quality of life.

16Exam corner

• S18 Q4(b), 15 marksThe worked example in section 10.
• S21 Q2(d), 7 marksPhysiotherapy for a 43-year-old male farmer with ILD, heterogeneous opacities in the right lung, mMRC grade 2, dry cough and generalised weakness.
• 3-mark questionsGoals of management in restrictive lung disease (S17). Three spirometric findings in restrictive lung disease (S19).

Technique cards for this topic: oxygen therapy, exercise testing, ABG, dyspnoea and energy conservation, pulmonary rehabilitation.

Keywords to underline

restrictive pattern FEV1/FVC normal or high low TLC and DLCO exertional desaturation oxygen during exercise interval training remove exposure byssinosis silicosis