Pneumothorax

Pneumothorax (PTX)

1. Definition

   • air in the pleural space causing partial-to-complete lung collapse

2. Etiology

   • spontaneous PTX: no antecedent trauma or iatrogenic cause

     1. primary spontaneous PTX (SPP): no clinically apparent underlying lung disease

        • definition: PTX in a pt w/o immediately obvious underlying lung disease

        • pathogenesis: rupture of small sub-pleural blebs

          1. blebs are small (< 2 cm) collections of air resulting from ruptured alveoli contained w/in visceral pleura

          2. found near apices of upper lobes or apical segment of lower lobes

          3. thought to result from imbalance in proteases/anti-proteases or oxidants/anti-oxidants

     2. secondary spontaneous PTX (SSP): clinically apparent underlying lung disease

        • COPD & emphysema (50-70%)

          1. PTX is a marker of disease severity and predicts survival

          2. each episode of PTX increases the chance of dying by 4-fold

        • cystic fibrosis (CF)

          1. 3-4% will have SSP during their lifetime

          2. incidence is 16-20% in those who survive > 18-y/o

          3. CF-related SSP usually 2/2 rupture of apical subpleural cysts

        • lung malignancy esp. metastatic sarcoma treated w/pezopanib

        • necrotizing lung infections incl. pneumocystis pneumonitis (PCP), bacterial PNA, tuberculosis, COVID

        • cystic lung disorders incl. lymphangioleiomyomatosis, diffuse Langerhans cell histiocytosis, lymphocytic interstitial pneumonitis (eg, Sjögren syndrome), Birt-Hogg-Dubé syndrome

        • catamenial PTX: occurs in association w/menses due to thoracic endometriosis

   • traumatic PTX: causes incl. blunt chest trauma (sharp stumps of fractured ribs), penetrating chest trauma, blast injury, central line placement, CT-guided lung biopsy, thoracentesis, diving

3. Pathophysiology

   • closed PTX: pleural space does not communicate outside the thorax

     1. amount of air is usually small and reabsorbed over a short period of time

   • open PTX: pleural space communicates outside the thorax → outside air enters pleural space during inspiration → pleural air exits during expiration

     1. requires prompt treatment because repeated shifts in the mediastinum can cause refractory bradycardia or even cardiac arrest

   • tension PTX: air freely enters pleural space but does not exit → increasing pressure → mediastinal shifting → SVC/IVC compression → ↓venous return → ↓CO

4. Epidemiology

   • PSP & SSP is 3-4 times higher in males

     1. 18-28 per 100,000 males vs 1.2-6 per 100,000 females

   • two peaks of incidence

     1. age 20-30: typically PSPs

     2. age 60-70: typically SSPs related to COPD

5. Risk Factors

   • smoking (increases risk by 20 times, dose-dependent)

6. Clinical

   • pleuritic chest pain that becomes steady

   • dry cough

   • dyspnea

   • ↓lung sounds w/tympanic resonance (only notable if lung collapse is significant)

   • tachycardia

   • respiratory distress, anxiety, hypotension (tension)

7. Diagnosis → radiologic confirmation should not delay therapy for unstable patients w/clinical signs & symptoms

   • best initial: upright PA & lateral CXR

     1. radiolucent space between pleura & chest wall

     2. white visceral pleural line separating parietal pleura from pleural space

     3. deep sulcus sign: an abnormally deep costophrenic angle on the affected side, esp. in a non-upright film (air in pleural space collects in anterior  non-dependent lung space)

   • most accurate: CT-chest w/wo contrast

8. Size determination (amount of air contained chest is crucial to determine therapy)

   • most practical ways are those proposed by the

     1. American College of Chest Physicians (ACCP) for spontaneous PTX (CHEST 2001; 119:590-602)

        • determine apex-to-cupola distance on AP CXR

        • small: < 3 cm

        • large: ≥ 3 cm

     2. British Thoracic Society (BTS) for spontaneous PTX (Thorax 2010; 65:ii18-ii31)

        • determine inter-pleural distance at level of the hilum on lateral CXR

        • small: < 2 cm

        • large: ≥ 2 cm

   • others incl. Rhea method, Light index, Collins method

9. Complications

   • tension pneumothorax

   • pneumomediastinum, pneumoperitoneum, subcutaneous emphysema

     1. presence requires ruling out airway injury, esophagus perforation, hollow viscus perforation

   • hemopneumothorax

   • simultaneous bilateral pneumothorax

   • recurrence

10. Therapy

    • small and uncomplicated and asymptomatic

      1. bedrest & observation ≥ 24h

      2. 100% O2 administration (increases gradient for nitrogen absorption from the pleural space)

    • large or complicated or symptomatic

      1. tube thoracostomy w/water seal drainage

         • direct tube towards apex

         • maintain -10 to -20 cmH2O during first 24h

         • remove once air leak has stopped for ≥ 48h

      2. persistent air leak (ie ≥ 48h)

         • allow 4-5 days to resolve