3.5 Lung Cancer, Interstitial & Suppurative Lung Disease, Sleep Apnoea & Respiratory Failure

Lung Cancer, Interstitial & Suppurative Lung Disease, Sleep Apnoea & Respiratory Failure

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Lung Cancer

Lung cancer is the leading cause of cancer death in the UK; about 70% of cases are linked to smoking.

NICE NG12 Recognition and Referral

• Suspected cancer pathway referral if the chest X-ray suggests lung cancer, or the person is aged 40 or over with unexplained haemoptysis.
• Urgent chest X-ray (within 2 weeks) for people aged 40 or over with 2 or more unexplained symptoms, or 1 or more if they have ever smoked: cough, fatigue, shortness of breath, chest pain, weight loss, appetite loss.
• Consider an urgent chest X-ray for people aged 40 or over with persistent or recurrent chest infection, finger clubbing, supraclavicular or persistent cervical lymphadenopathy, chest signs consistent with lung cancer, or thrombocytosis.
• NHS England's lung cancer screening programme (formerly Targeted Lung Health Checks) invites people aged about 55–74 with a history of smoking for risk assessment and low-dose CT.

Types and Clues

Other features: Pancoast tumour at the lung apex (shoulder pain, wasting of hand muscles, Horner's syndrome), superior vena cava obstruction, recurrent laryngeal nerve palsy (hoarseness), hypertrophic pulmonary osteoarthropathy.

Investigation: contrast CT of the chest and upper abdomen, then PET-CT and tissue diagnosis (CT-guided biopsy, bronchoscopy or EBUS-guided node sampling). Treatment of early non-small cell cancer is surgery (lobectomy) or stereotactic radiotherapy if unfit; advanced disease uses immunotherapy, targeted drugs and chemotherapy.

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Interstitial Lung Disease (ILD)

• Idiopathic pulmonary fibrosis (IPF): usually men over 60 with progressive breathlessness, dry cough, fine bibasal end-inspiratory ("Velcro") crackles and clubbing. Spirometry is restrictive (reduced FVC, normal or high FEV1/FVC) with reduced gas transfer (TLCO). High-resolution CT shows basal, subpleural reticulation and honeycombing (usual interstitial pneumonia pattern). Antifibrotics (pirfenidone, nintedanib) slow decline in eligible patients; corticosteroids are not used; pulmonary rehabilitation, oxygen and palliative care support.
• Other causes: drugs (amiodarone, methotrexate, nitrofurantoin, bleomycin), connective tissue disease (rheumatoid arthritis, systemic sclerosis), hypersensitivity pneumonitis (bird fancier's or farmer's lung; mainly upper zones; remove exposure), and occupational dust (asbestosis in the lower zones; silicosis and coal workers' pneumoconiosis in the upper zones).
• Asbestos also causes benign pleural plaques and mesothelioma (a prescribed industrial disease and a reason for coroner referral after death).

Sarcoidosis

Multisystem non-caseating granulomas, common in young adults and people of African-Caribbean origin. Features include bilateral hilar lymphadenopathy, ILD, erythema nodosum, uveitis, skin plaques (lupus pernio), hypercalcaemia and raised serum ACE. Löfgren's syndrome (erythema nodosum, bilateral hilar lymphadenopathy, arthralgia, fever) has an excellent prognosis. Many cases resolve; corticosteroids are used for organ-threatening disease (eyes, heart, nervous system, hypercalcaemia, progressive lung disease).

Bronchiectasis

Permanent bronchial dilatation with chronic productive cough and recurrent infections. Causes include previous severe infection (including TB), cystic fibrosis, immunodeficiency, allergic bronchopulmonary aspergillosis and primary ciliary dyskinesia. HRCT shows dilated airways (the "signet ring" sign). Management: airway clearance physiotherapy, sputum culture-guided antibiotics for exacerbations (usually 14 days; Pseudomonas is common), and long-term macrolides for frequent exacerbations.

Cystic Fibrosis (CF)

Autosomal recessive mutation of the CFTR chloride channel (F508del is the commonest variant). It is detected by newborn blood spot screening (immunoreactive trypsinogen) and confirmed by a sweat chloride of 60 mmol/L or more. Features: recurrent chest infections, bronchiectasis, pancreatic insufficiency (steatorrhoea, needing enzyme replacement), meconium ileus, CF-related diabetes and male infertility. CFTR modulators (elexacaftor/tezacaftor/ivacaftor) have transformed outcomes.

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Obstructive Sleep Apnoea (OSA)

Recurrent upper airway collapse during sleep causing snoring, witnessed apnoeas and excessive daytime sleepiness (assessed with the Epworth Sleepiness Scale; STOP-BANG for screening). Risks: obesity, large neck, retrognathia, alcohol and sedatives. Diagnosis is by home sleep study (apnoea-hypopnoea index). CPAP is offered for moderate or severe OSA (and for mild OSA with symptoms affecting quality of life), alongside weight loss (NICE NG202). Drivers with OSA causing excessive sleepiness must not drive until symptoms are controlled and must tell the DVLA.

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Respiratory Failure & Arterial Blood Gases

A Systematic ABG Approach

1. pH (normal 7.35–7.45): acidaemia or alkalaemia?
2. PaCO2 (normal 4.7–6.0 kPa): a high PaCO2 with low pH is respiratory acidosis.
3. Bicarbonate (normal 22–26 mmol/L): a low bicarbonate with low pH is metabolic acidosis.
4. Compensation: a chronic respiratory acidosis has a raised bicarbonate (as in stable COPD).
5. Anion gap = Na⁺ − (Cl⁻ + HCO₃⁻), normally about 8–12 mmol/L. A raised anion gap suggests ketoacidosis, lactic acidosis, renal failure or toxins (methanol, ethylene glycol, salicylates); a normal anion gap (hyperchloraemic) acidosis suggests diarrhoea, renal tubular acidosis or large volumes of 0.9% saline.
6. Oxygenation in the context of the inspired oxygen.