Secondary Spontaneous Pneumothorax

Pneumothorax that arises as a complication of existing lung disease. It is more dangerous than primary pneumothorax because lung reserve is poor, so even a small air collection can cause respiratory failure.

• Incidence is about 2 to 6 per 100,000 per year, peaking at 60 to 65 years. COPD with emphysema causes about 70% (higher risk when FEV1 is less than 1 L).
• Other causes: cystic fibrosis (lifetime risk about 6 to 8%, more in severe adult disease), tuberculosis (cavities and fibrosis, about 1 to 3% of cases), necrotising pneumonia (Staphylococcus aureus, Klebsiella), Pneumocystis pneumonia in HIV (cysts and pneumatoceles, up to about 5 to 10% of cases), lung cancer, interstitial lung disease (idiopathic pulmonary fibrosis, sarcoidosis, lymphangioleiomyomatosis, Langerhans cell histiocytosis), connective tissue disease (rheumatoid arthritis, systemic sclerosis, Marfan and Ehlers-Danlos syndromes), catamenial thoracic endometriosis, cannabis related bullae and positive pressure ventilation.
• Hospital mortality is about 5 to 15% in COPD (higher with hypercapnia, bilateral pneumothorax, age over 65, and HIV). Recurrence is about 40 to 50% over 5 years.

• Breathlessness out of proportion to the size of the pneumothorax, chest pain, cough, hypoxaemia and sometimes hypercapnia. Signs may be masked by hyperinflation. Subcutaneous emphysema suggests a large leak.
• Differential diagnosis: acute exacerbation of COPD, large bulla, pulmonary embolism, pneumonia, heart failure, myocardial infarction, empyema, oesophageal rupture, pericarditis and skin fold on X-ray.
• Complications: respiratory failure, tension pneumothorax, persistent air leak (about 20 to 30% beyond 5 days), bronchopleural fistula, empyema, haemopneumothorax, pneumomediastinum, recurrence, and death.

• Erect chest X-ray; CT chest to distinguish pneumothorax from bullae and to assess the underlying disease before drain insertion into a bulla.
• Pulse oximetry and arterial blood gas for all; ECG; full blood count; creatinine; HIV test; CD4 count if positive; sputum Xpert MTB/RIF and culture; serum LDH and beta-D-glucan for Pneumocystis pneumonia; sputum culture in cystic fibrosis.
• Spirometry once recovered, and a search for the cause (alpha-1 antitrypsin level, immunology screen, cancer workup).

• Admit all patients for at least 24 hours, with oxygen to SpO2 88 to 92% when carbon dioxide retention is possible and 94 to 98% otherwise. Do not give high flow oxygen to a patient with COPD and retention without monitoring blood gases.
• Choose the method by size and symptoms:
  • Rim 1 to 2 cm, minimal breathlessness, age under 50: needle aspiration up to 2.5 L (16 to 18 gauge cannula), followed by observation and repeat X-ray.
  • Rim more than 2 cm, or breathless, or aspiration fails: chest drain, small bore 10 to 14 French (large bore 24 to 28 French if the patient is ventilated or the leak is large), connected to an underwater seal, without suction at first. Apply suction at 10 to 20 cmH2O if the lung has not re-expanded within 48 hours.
  • Small pneumothorax (less than 1 cm): admit and give oxygen, with repeat X-ray at 24 hours.
  • Tension pneumothorax: needle decompression with a 14 gauge cannula at the fifth intercostal space in front of the mid-axillary line (or second space mid-clavicular line), then a drain.
• Persistent air leak or failure to re-expand at 48 hours: refer to thoracic surgery on day 2 to 3 (sooner than in primary pneumothorax).
  • Video assisted thoracoscopic stapling of blebs or bullae with pleurodesis (mechanical abrasion or talc 2 to 5 g poudrage) for fit patients; recurrence 2 to 5% after surgery versus 40 to 50% without it.
  • Patients unfit for surgery: talc slurry 4 to 5 g in 50 mL saline through the drain after intrapleural lidocaine 3 mg/kg (maximum 250 mg) and systemic analgesia; bronchoscopic one way endobronchial valves; autologous blood patch 1 to 2 mL/kg through the drain (evidence is limited).
  • Offer definitive pleurodesis after the first episode in most patients, because a recurrence may be fatal.
• Treat the underlying disease at once:
  • COPD: salbutamol 2.5 to 5 mg and ipratropium 500 micrograms nebulised every 4 to 6 hours (air driven nebulisers with supplemental oxygen by nasal cannulae), prednisolone 30 to 40 mg daily for 5 days, and antibiotics for purulent sputum (amoxicillin 500 mg to 1 g three times daily, or doxycycline 200 mg then 100 mg daily, or co-amoxiclav 625 mg three times daily for 5 days).
  • Tuberculosis: rifampicin 10 mg/kg (maximum 600 mg), isoniazid 5 mg/kg (maximum 300 mg), pyrazinamide 25 mg/kg (maximum 2 g) and ethambutol 15 mg/kg (maximum 1.2 g) daily for 2 months, then rifampicin and isoniazid daily for 4 months, with pyridoxine 25 to 50 mg daily.
  • Pneumocystis pneumonia: co-trimoxazole 120 mg/kg/day in 3 to 4 divided doses for 21 days, with prednisolone 40 mg twice daily for 5 days, 40 mg daily for 5 days, then 20 mg daily for 11 days when PaO2 is less than 9.3 kPa; start antiretroviral therapy within 2 weeks.
  • Cystic fibrosis: IV antibiotics for infection, airway clearance, and specialist centre care; talc pleurodesis can complicate later transplantation, so involve the transplant team.
  • Necrotising pneumonia: IV antibiotics (ceftriaxone 2 g daily with flucloxacillin 2 g every 6 hours, or vancomycin 15 to 20 mg/kg every 8 to 12 hours when methicillin resistant Staphylococcus aureus is likely).
  • Lymphangioleiomyomatosis: sirolimus 1 to 2 mg daily (trough 5 to 15 ng/mL) after pleurodesis; catamenial disease: surgery then goserelin 3.6 mg SC every 28 days for 6 months (evidence is limited).
• Ventilated patients: place a drain before positive pressure ventilation when a pneumothorax is present, use low tidal volumes (6 mL/kg), and avoid non-invasive ventilation unless the lung is drained.
• Analgesia and prophylaxis: paracetamol 1 g four times daily, morphine 2.5 mg IV titrated with care in hypercapnia, enoxaparin 40 mg SC daily, omeprazole 20 mg daily if on steroids.
• Special groups:
  • HIV: treat the cause (Pneumocystis pneumonia, tuberculosis), start antiretroviral therapy, and expect a higher recurrence rate.
  • Elderly: assess frailty and goals of care before surgery; chemical pleurodesis through the drain is an option.
  • Pregnancy: lymphangioleiomyomatosis and catamenial disease are important causes; multidisciplinary delivery planning.
  • Renal impairment: avoid NSAIDs; adjust antibiotic doses.
• Red flags: SpO2 less than 90%, pH less than 7.35, PaCO2 greater than 6 kPa, hypotension, bilateral disease, leak beyond 48 hours, expanding subcutaneous emphysema.
• Follow up: daily review until the drain is out, chest X-ray after drain removal and at 2 weeks, clinic review at 4 to 6 weeks; stop smoking; vaccinate (influenza, pneumococcal conjugate, COVID-19); advise against diving and avoid flying until cleared.