Freediver Mathieu Maraio recounts near-death experience in Chiètres

Freediver Mathieu Maraio survived a near-fatal pulmonary edema incident during a training session in Chiètres, Switzerland, highlighting the severe physiological risks associated with extreme breath-holding. The accident, which involved significant internal bleeding, serves as a reminder of the dangers of "shallow water blackout" and pressure-related lung injuries that can occur even during supervised practice.

The Physiology of Freediving Accidents

When freedivers descend to significant depths, the ambient pressure causes the lungs to compress according to Boyle’s Law. While the human body is adapted to this compression, rapid or repetitive dives can push the pulmonary system beyond its limits. According to the Divers Alert Network (DAN), pulmonary edema in freedivers often results from the blood shifting from the peripheral limbs to the thoracic cavity to compensate for the pressure, which can lead to capillary leakage in the lungs.

In the case of Mathieu Maraio, the incident resulted in hemoptysis—the coughing up of blood—which is a clinical sign of pulmonary barotrauma. This occurs when the delicate alveolar-capillary membrane in the lungs ruptures due to the extreme pressure differential between the gas inside the lungs and the surrounding blood vessels.

Understanding Shallow Water Blackout

While Maraio’s specific incident involved pulmonary trauma, many freediving emergencies are categorized as shallow water blackouts. This phenomenon occurs when the partial pressure of oxygen in the blood drops rapidly during the final stages of an ascent.

• The Mechanism: As a diver ascends, the partial pressure of oxygen in the lungs decreases. If the oxygen level drops below a critical threshold, the brain shuts down to preserve vital functions, resulting in a loss of consciousness.
• The Risk: Because the blackout typically happens in the final 10 meters of a dive, the diver is often near the surface, but unable to initiate the breathing reflex.
• Safety Protocols: Experts emphasize that freediving should never be practiced alone. The presence of a trained safety diver—someone who remains at the surface or monitors the ascent—is the primary defense against drowning during a blackout.

Medical Risks and Recovery

Pulmonary edema requires immediate medical attention. When fluid or blood enters the alveoli, it impairs gas exchange, which can lead to hypoxia. According to clinical guidelines from the Undersea and Hyperbaric Medical Society (UHMS), individuals who experience pulmonary barotrauma must undergo a full medical evaluation before returning to diving. This includes imaging to ensure there is no lingering lung damage or risk of pneumothorax, where air escapes into the space between the lung and the chest wall.

Key Takeaways for Divers

• Never Dive Alone: The "buddy system" is the most effective way to prevent fatal outcomes during a blackout or medical event.
• Listen to Physiological Cues: Divers should monitor for signs of chest pain, shortness of breath, or blood in the sputum, all of which indicate a need to stop training immediately.
• Professional Training: Organizations like AIDA (Association Internationale pour le Développement de l’Apnée) provide standardized safety training that teaches divers how to manage pressure equalization and recognize the signs of lung stress.

The recovery process for incidents involving pulmonary hemorrhage typically requires a period of rest to allow the lung tissue to heal. Returning to the water too quickly can exacerbate inflammation and increase the risk of recurrent injury.