What is Barotrauma
Barotrauma is physical injury to body tissues caused by pressure differences between gas-filled spaces within or adjacent to the body and the surrounding environment, occurring when ambient pressure changes during activities like diving, flying, or mechanical ventilation. 1, 2
Core Mechanism
The fundamental physics underlying barotrauma follows Boyle's law: as pressure increases, gas volume decreases proportionally, and vice versa 3. This pressure differential affects any gas-containing body cavity that cannot equilibrate with environmental pressure changes 4.
Affected Organ Systems
The organs at highest risk include:
- Lungs (most serious and potentially fatal)
- Middle and inner ear (most common)
- Paranasal sinuses
- Gastrointestinal tract
- Teeth (particularly with recent dental work or abscesses)
- Eyes
- Skin (in diving, related to suit compression) 1, 4, 3
Types of Barotrauma
Pulmonary Barotrauma
During descent (compression): "Lung squeeze" from breath-hold diving or equipment failure causes alveolar exudation, hemorrhage, and wall rupture, presenting with cough, hemoptysis, and dyspnea. This is rare 1.
During ascent (expansion) - "Burst Lung": This is more frequent and far more dangerous 1. When a diver breathes compressed gas at depth and ascends, lung gas expands. If exhalation is impeded at whole lung or segmental level, rupture occurs. This happens when:
- Compressed gas supply runs out at depth
- Loss of buoyancy control causes rapid uncontrolled ascent
- "Skip breathing" (intermittent breathing pattern) is used
- Very large breaths are taken 1
Critical complications include:
- Pneumomediastinum - gas tracks to the hilum and mediastinum, presenting with central chest discomfort, hoarseness, and dyspnea
- Pneumothorax - gas enters pleural space (tension pneumothorax risk increases if it occurs at depth with continued ascent)
- Arterial gas embolism - gas enters pulmonary venous system and systemic circulation, presenting with major neurological symptoms, impaired consciousness, convulsions, or sudden death from coronary embolism 1
Otic Barotrauma
Middle ear barotrauma is the most common form overall, occurring during pressure changes in aviation or diving 5, 6. It presents with acute otalgia, hearing loss, and sometimes hemotympanum with or without tympanic membrane perforation. Rarely, facial nerve paralysis can occur if the tympanic segment is dehiscent within the middle ear 6.
Risk Factors for Pulmonary Barotrauma
Increased risk occurs with:
- Localized or generalized airway narrowing
- Asthma (major risk factor in documented cases) 1
- Bullae formation
- Any localized lung parenchymal weakness
- Lower forced vital capacity (FVC) - inversely related to risk during submarine escape training 1
- Less distensible lungs and airways 1
Clinical Context Beyond Diving
Barotrauma also occurs from:
- Mechanical ventilation - positive pressure can cause lung injury 7, 4
- Apnea testing - particularly with higher-than-recommended oxygen flow rates 8
- Commercial air travel - especially after recent dental procedures or with sinus/ear pathology 9, 5
- Pressure vessel decompression 2
Severity and Mortality
Over a 20-year period at the Institute of Naval Medicine, 140 cases of pulmonary barotrauma were recorded, including one death. Of these, 58 had arterial gas embolism signs 1. Serious barotrauma can occur even after shallow dives - one case involved pneumomediastinum, bilateral pneumothorax, and air embolism with subsequent paraparesis after diving to only 5 meters 1, highlighting that the greatest volume changes per pressure change occur near the surface.
Key Clinical Pitfall
Do not assume depth correlates with severity. The pressure-volume relationship means the most dramatic gas expansion occurs in the final meters before surfacing, making shallow water ascents potentially as dangerous as deep water ascents 1.