Pneumothorax - secondary
Description
- Pneumothorax occurring in a lung with pre-existing disease
- The distinction from primary matters because the patient has no respiratory reserve - the same volume of air causes far more compromise, resolves more slowly, and recurs more often
Primary vs secondary
| Primary (PSP) | Secondary (SSP) | |
|---|---|---|
| Lung | Normal | Diseased |
| Typical patient | Tall thin young male smoker | Older, COPD, smoker |
| Symptoms | Often mild | Marked dyspnoea out of proportion to size |
| Mortality | ~0 | ~10% |
| Air leak resolution | Fast | Slow - prolonged air leak common |
| Recurrence | ~30% | ~40-50% |
| Management | Conservative/ambulatory often appropriate | Almost always admit |
- >50 years with significant smoking history is treated as secondary even if no lung disease is known
Epidemiology
- SSP incidence ~6/100,000/yr men, ~2/100,000/yr women
- COPD is the commonest cause - accounts for the majority
- Peak age 60-65; M>F
- Mortality ~10% (vs essentially zero in PSP) - driven by the underlying lung disease
- Recurrence ~40-50% without definitive treatment
Aetiopathogenesis
Underlying diseases
- Airways - *COPD/emphysema (commonest), severe asthma, cystic fibrosis (~3-4% lifetime; marker of advanced disease*), bronchiectasis
- Infection - **Pneumocystis jirovecii (HIV - classically with cystic upper lobe change), TB**, necrotising bacterial pneumonia, lung abscess, septic emboli
- ILD - IPF and other fibrotic ILD (poor prognostic sign; poor healing, high mortality), sarcoidosis (stage IV), pneumoconiosis
- Cystic lung disease - lymphangioleiomyomatosis (LAM) (young women, recurrent bilateral pneumothoraces, chylothorax, renal angiomyolipoma), Birt-Hogg-Dube (FLCN; skin fibrofolliculomas, renal tumours, basal cysts), Langerhans cell histiocytosis (smokers, upper zone cysts and nodules)
- Malignancy - primary or metastatic (sarcoma metastases classically cavitate and rupture)
- Connective tissue - Marfan, vascular Ehlers-Danlos, rheumatoid nodules
- Catamenial pneumothorax - thoracic endometriosis; right-sided, within 72 h of menstruation, recurrent
- Drugs - bleomycin, sirolimus; crack cocaine and cannabis (Valsalva against a closed glottis)
Mechanism
- Rupture of a subpleural bleb, bulla, cyst or necrotic focus -> air into the pleural space
- -> loss of negative intrapleural pressure -> lung collapses along its elastic recoil
- -> inc shunt and V/Q mismatch -> hypoxaemia (more severe than in PSP because the remaining lung is also diseased)
- Tension pneumothorax: a one-way valve -> progressive accumulation -> mediastinal shift, dec venous return, obstructive shock
- A clinical diagnosis - do not wait for imaging
Diagnosis
Clinical
- Sudden dyspnoea (dominant symptom in SSP), pleuritic chest pain
- Symptoms grossly out of proportion to the radiographic size - the defining feature
- Reduced expansion, hyper-resonance, reduced breath sounds and vocal resonance on the affected side
- In emphysema these signs are already present bilaterally - the diagnosis is easy to miss clinically
Tension pneumothorax - treat before imaging
- Severe distress, hypotension, tachycardia, raised JVP, tracheal deviation away, silent hemithorax, hypoxia
- -> immediate needle decompression (large-bore cannula, 4th-5th intercostal space anterior/mid-axillary line, in preference to the older 2nd space mid-clavicular route in adults), then a chest drain
Imaging
- Erect PA CXR - visible visceral pleural line with no lung markings beyond it
- Expiratory films add nothing; supine films miss pneumothoraces (look for deep sulcus sign)
- Size (BTS): measured at the level of the hilum - >=2 cm = "large" (roughly 50% of hemithorax volume)
- Size now informs, rather than dictates, management
- Thoracic ultrasound - absent lung sliding, absent comet-tail artefact, "barcode/stratosphere sign" on M-mode, lung point (pathognomonic); more sensitive than supine CXR
- CT chest - essential when distinguishing a large bulla from a pneumothorax (a catastrophic error to drain a bulla), for complex/loculated collections, and to characterise the underlying disease
Management
The 2023 BTS paradigm shift
*Management is now driven by symptoms and clinical stability, not by the size of the pneumothorax alone.*
- Assess: breathlessness, haemodynamic stability, hypoxaemia, underlying disease severity, patient priorities
- Size still matters in SSP because there is no reserve - but it is one input, not the algorithm
A. Secondary spontaneous pneumothorax - admit almost everyone
1. High-flow oxygen (unless CO2 retention risk - then controlled oxygen)
- Accelerates pleural air resorption ~4-fold by washing out nitrogen and increasing the pleural-to-capillary nitrogen gradient
2. Small (<1 cm) and minimally symptomatic -> observe with oxygen, admit, repeat CXR
3. Symptomatic or >=2 cm -> intercostal chest drain (small-bore 8-14F is adequate and better tolerated)
- Needle aspiration is much less likely to succeed in SSP than in PSP - go to a drain in symptomatic patients
4. Never clamp a bubbling drain
5. Suction (-10 to -20 cmH2O, high-volume low-pressure) if the lung fails to re-expand after 48 h - not routinely from the outset (risk of re-expansion pulmonary oedema)
6. Persistent air leak >3-5 days -> thoracic surgical referral
7. Treat the underlying disease - bronchodilators, antibiotics, steroid
B. Definitive management to prevent recurrence
- Indications (lower threshold than in PSP)
- First episode of SSP in severe COPD or other significant lung disease - chemical pleurodesis can be considered even at the first episode where the patient decompensated
- Second ipsilateral, first contralateral, bilateral, persistent air leak, tension
- High-risk occupation: pilots, divers (diving is permanently contraindicated unless definitive bilateral surgical pleurectomy has been performed)
- VATS with bullectomy + pleurectomy or pleural abrasion - recurrence <5%; the preferred option if fit
- Chemical pleurodesis (talc or doxycycline) via the drain - for those unfit for surgery; painful - give adequate analgesia
- Autologous blood patch for persistent air leak in the unfit
- Endobronchial valves for persistent air leak where surgery is not possible
C. Discharge and advice
- Repeat CXR before discharge and at follow-up
- Smoking cessation - reduces recurrence substantially; the single most important advice
- No air travel until radiographic resolution - typically at least 1-2 weeks after full resolution (airlines commonly require 2 weeks); confirm with a CXR
- *Diving is contraindicated for life* unless definitive bilateral surgery
- Warn about recurrence and to present immediately with recurrent symptoms
- Outpatient respiratory follow-up and treatment of the underlying disease
Associations
- COPD and emphysema - the dominant association
- Cystic fibrosis - pneumothorax marks advanced disease; pleurodesis was historically avoided because of transplant implications, but is no longer an absolute contraindication
- HIV with PJP - cystic upper lobe change, often bilateral and refractory
- LAM and Birt-Hogg-Dube - recurrent bilateral pneumothoraces in a young patient should prompt CT and consideration of genetic testing
- IPF and fibrotic ILD - poor healing, high mortality
- Marfan and vascular EDS, homocystinuria
- Catamenial pneumothorax - thoracic endometriosis
- Cannabis and crack cocaine use
- Mechanical ventilation and positive pressure - barotrauma (consider in any ventilated patient who deteriorates suddenly)
Natural history & complications
- Air reabsorbs at only ~1.25-2.2% of hemithorax volume per day on room air -> a large pneumothorax would take weeks to resolve spontaneously; high-flow oxygen accelerates this fourfold
- Recurrence 40-50% without definitive intervention; most within the first year
- Mortality ~10%, largely determined by the underlying lung disease
Complications
- Tension pneumothorax - obstructive shock, cardiac arrest
- Persistent air leak (>3-5 days) - the commonest reason for prolonged stay and surgical referral
- Re-expansion pulmonary oedema - after rapid re-expansion of a large, long-standing pneumothorax; drain slowly, avoid immediate high-pressure suction, limit initial drainage
- Drain-related: malposition, intercostal vessel or organ injury (liver, spleen, heart), surgical emphysema, empyema, pain, blocked/dislodged drain
- Bronchopleural fistula, empyema
- Respiratory failure requiring ventilation (positive pressure worsens the leak)
- Chronic pain after pleurodesis or surgery
Follow-up
- CXR at 2-4 weeks
- Investigate for underlying disease if not already characterised - CT chest, and consider LAM/BHD, alpha-1 antitrypsin deficiency, HIV, connective tissue disease in the young or atypical
- Document the lifetime diving prohibition and air travel advice in the discharge summary
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