Pneumothorax
Air in pleural space between visceral and parietal pleura.
Sub atmospheric intrapleural pressure -5 cmH2O keeps lungs expanded.
When lost due to air in space lung collapses.
Air gains access via parietal or visceral pleura.
Causes
Trauma
Spontaneous
Underlying chest disease
Iatrogenic
Parietal (outer)
Trauma
Penetrating chest trauma.
Oesophageal, tracheal or mediastinal perforation.
Surgery - Laparoscopy, tracheostomy, nephrectomy, thoracic spine.
Visceral (inner)
Iatrogenic - needle puncture - IJ, SVC, brachial plexus, paravertebral, intercostal
Alveolar rupture – gas escapes, dissects towards the hilum and ruptures the mediastinal pleura (pleura covering mediastinal structures between the lungs)
COPD (bullae)
Barotrauma
Blast injury
Asthmatics
Alveolar weakening – infection, connective tissue disease
Diagnosis
Respiratory distress - ↑RR, SOB, hypoxia, pleuritic chest pain
CVS compromise - ↑HR, ↓BP
Tracheal deviation away
↓ breath sounds
Hyperresonance
CXR
↑ airway pressures / ↓ TV
Management
Stop N2O
100% O2
Needle decompression
Chest drain
- Underwater seal – 3cm depth – too shallow → air entrainment; too deep → pressure too great to drain air.
- 100cm below chest as max insp effort can generate -80cmH2O.
- Drainage can be by gravity or low pressure high volume suction.
- Absence of oscillations may indicate obstruction of the drainage system by clots or kinks, loss of sub-atmospheric pleural pressure (spont) or positive pressure (IPPV) (?why) or complete re-expansion of the lung.