Sobering reading.........
An extract from
..Undersea and Hyperbaric Medicine, Vol 20, No2, 1993
Air Embolism With Bilateral Pneumothorax After A 5m Dive
I. Friehs, G.m. Friehs and G.B. Friehs
University Clinic of Surgery, Department of Thoracic and Hyperbaric Surgery, and University Clinic of Neurosurgery, University of Graz, Medicical School Graz, Austria.
Air embolism with bilateral pneumothorax after a five meter dive. Undersea and Hyperbaric Med 1993: 20(2):155-157.- After an emergency ascent from very shallow depth, a diver suffered a triad of symptoms after bilateral barotrauma of the lungs: air embolism with subsequent paraparesis, pneumomediastinum, and bilateral pneumothorax.
The two main causes for diving accidents while using scuba devices are DCS (caisson disease) and barotraumas of the lung with consequent air embolism. Inexperienced divers sometimes fail to comply with recommended ascent rates, especially in emergency situations. With breath holding or air trapping, the volume of air in the lungs inhaled at depth expands on ascent in direct relation to the decrease in surrounding pressure (Boyle-Marriottes Law). When the lungs elasticity of approximately 100mbar is exceeded, the pulmonary parenchyma is damaged, sometimes resulting in pneumomediastinum and pneumothorax. Air bubbles entering the pulmonary circulation are transported into the arterial blood stream and cause neurologic deficits of differing degrees. Symptoms may occur as soon as the victim reaches the surface.
CASE REPORT
A 24 year old male, admitted to our hospital after a diving accident, reported that at a depth of only 5m he had planned and undertaken an emergency ascent. At a depth of 1m he held his breath rather than exhale. On reaching the water surface the patient complained of sudden onset of dizziness, paraparesis of the lower extremeties, and shortness of breath. On auscultation, a left side pneumothorax was noted. An x-ray taken in the local hospital confirmed the suspected diagnosis and revealed an extensive mediastinal emphysema. Chest drainage was instituted immediately, and the patient transported to our hospital by helicopter, flying no higher than 850m above sea level while breathing 100% oxygen. A subsequent x-ray in the emergency room showed the left lung was fully expanded, but an incomplete pneumothorax was diagnosed on the right
DISCUSSION
As opposed to bends (caisson disease), lung barotraumas associated with diving is not dependant on time or depth. Barotrauma can occur even at a depth of 1 2 m. The main reason for this type of accident is panic emergency ascent by young, inexperienced divers. Divers should ascend to the water surface by continuously exhaling to compensate for gas expansion in the lungs. An intrapulmonary airway pressure that exceeds the pressure produced by the lungs elasticity results in extraalvolar air leakage. The perivascular sheaths then mediate the air to the mediastinum, to the subcutaneous tissues, and to the intrapleural space. This explains the occurrence of mediastinal and subcutaneous emphysema. The rupture of lung parenchyma may also allow gas to enter small blood vessels, and anterograde migration of bubbles in pulmonary venules may then lead to arterial emboli formation. Possible platelet aggregation and other coagulation disorders induced by bubble surface and plasma interaction, followed by vessel occlusion and reduction of perfusion, lead to hypoxic damage of the organs supplied by these vessels. Resulting neurologic deficits range from bypesthia to decerebrate symptoms, to death in worst cases