Pneumothorax

Pneumothorax is a common respiratory emergency. Understanding its classification is key for management. Primary Spontaneous Pneumothorax (PSP) typically affects young, tall, thin males without underlying lung disease. Secondary Spontaneous Pneumothorax (SSP) occurs in patients with pre-existing lung conditions, most commonly COPD, but also cystic fibrosis, severe asthma, or interstitial lung disease. A Tension Pneumothorax is a critical diagnosis where air enters the pleural space but cannot escape, leading to rapidly increasing intrapleural pressure, mediastinal shift, reduced venous return, and obstructive shock. This is a clinical diagnosis and requires immediate intervention. Diagnosis of a simple pneumothorax is usually confirmed by an erect chest X-ray. Management varies significantly depending on the type, size, and patient's symptoms, guided by BTS guidelines.

The pleural space normally maintains a negative pressure due to the opposing elastic recoil of the lung (inward) and chest wall (outward). A pneumothorax occurs when this seal is breached, allowing air to enter the pleural space. This equalises the pressure, causing the lung to collapse due to its inherent elastic recoil. PSP is often due to rupture of small, apical subpleural blebs or bullae. SSP arises from rupture of diseased lung tissue (e.g., emphysematous bullae in COPD, cysts in CF). In a tension pneumothorax, a 'one-way valve' mechanism allows air into the pleural space during inspiration but traps it during expiration. This rapidly increases intrapleural pressure, compressing the ipsilateral lung, shifting the mediastinum, and kinking the great veins, leading to a critical reduction in cardiac output (obstructive shock).

Patients typically present with **sudden onset pleuritic chest pain** and **dyspnoea**. In tension pneumothorax, these symptoms rapidly worsen, progressing to severe respiratory distress, tachycardia, and hypotension. **Examination findings** include reduced chest expansion on the affected side, hyper-resonant percussion, and diminished or absent breath sounds. In tension, look for tracheal deviation away from the affected side, distended JVP, and displaced apex beat (late signs). **Risk factors** include smoking (increases PSP risk significantly), family history, and underlying lung disease. **Differential diagnoses** are crucial: pulmonary embolism (PE), myocardial infarction (MI), acute asthma exacerbation, pneumonia, or large bullae. **Complications** include re-expansion pulmonary oedema (if a long-standing collapse is drained too rapidly) and persistent air leak requiring surgical intervention.

For a suspected **tension pneumothorax**, **do NOT wait for investigations**; proceed directly to treatment. For stable patients, a **bedside SpO2 and full set of observations** are essential. The **gold standard for diagnosis of simple pneumothorax is an erect expiratory Chest X-ray (CXR)**, which shows a sharp visceral pleural line with absent lung markings peripheral to it. **CT Thorax** is more sensitive and can be used if the diagnosis is unclear (e.g., differentiating from large bullae) or for surgical planning. **Point-of-care ultrasound (POCUS)**, particularly in trauma (FAST scan), can show absence of 'lung sliding' and 'B-lines' (comet tail artefacts) in pneumothorax, though it's less reliable for ruling out small apical pneumothoraces. Remember: **CXR measurement of pneumothorax size is taken at the level of the hilum.**

**Tension Pneumothorax:** Medical emergency. Immediate needle decompression using a large bore cannula (14G or 16G) in the 2nd ICS mid-clavicular line (MCL) or the 5th ICS anterior axillary line (AAL) (preferred in trauma guidelines). Followed by definitive chest drain insertion.

**PSP (Primary Spontaneous Pneumothorax) — BTS 2023 Guidelines:**
The BTS 2023 Pleural Disease Guideline moved to a symptom-led, conservative-first approach for PSP:
- **Minimally symptomatic (regardless of size):** Conservative management — observe, discharge with safety netting and early outpatient review within 2-4 weeks. Patients must be counselled to return if breathlessness worsens.
- **Significantly symptomatic (breathlessness at rest or significant pain):** Active intervention. Ambulatory device (e.g., Rocket pleural vent) or small-bore chest drain as first choice over needle aspiration. Aspiration is no longer routinely recommended as first-line intervention for PSP.

**SSP (Secondary Spontaneous Pneumothorax) — BTS 2023 Guidelines:**
SSP is managed more aggressively due to underlying lung disease:
- **Any SSP with breathlessness or >2cm:** Small-bore chest drain insertion.
- **1-2cm and not breathless:** Aspiration may be attempted; if successful admit for 24h observation.
- **<1cm and not breathless:** Admit for 24 hours observation with supplemental oxygen.

**Chest Drain Insertion:** Safe triangle (5th ICS, mid-axillary line). Always insert above the rib to avoid the neurovascular bundle. Drain clamped once air stops bubbling and CXR confirms re-expansion.

**Surgical Referral (Thoracic Surgery):** Recurrent PSP (second episode), bilateral pneumothorax, persistent air leak >3-5 days, or high-risk occupations. VATS pleurodesis (talc or mechanical) or pleurectomy.