Rescue of drowning victims and divers: is mechanical ventilation possible underwater? A pilot study.

Introduction: In-water resuscitation has recently been proposed in the European resuscitation guidelines. Initiation of mechanical ventilation underwater might be considered when an immediate ascent to the surface is impossible or dangerous. The present study evaluated the feasibility of such ventilation underwater.
Methods: A resuscitation manikin was ventilated using an Interspiro® MK II full-face mask or with an Oxylator® ventilator via a facemask or a laryngeal tube, or with mouth-to-tube inflation. Tidal volumes achieved by the individual methods of ventilation were assessed. The ventilation tests were performed during dives in the wet compartment of a recompression chamber and in a lake. Ventilation was tested at 40, 30, 20, 12, 9 and 6 metres' depth.
Results: Ventilation was impossible with the cuffed mask and only sufficient after laryngeal intubation for a small number of breaths. Laryngeal tube ventilation was associated with the aspiration of large amounts of water and the Oxylator failed during the ascent. Efficient ventilation with the MK II full-face mask was also possible only for a short period. An absolutely horizontal position of the manikin was required for successful ventilation, which is likely to be difficult to achieve in open water. Leakage at the sealing lip of the full-face mask and the cuff of the laryngeal tube led to intrusion of water and resulted in subsequent complete failure of ventilation.
Conclusions: The efficacy of underwater ventilation seems to be poor with any of the techniques trialed. Water aspiration frequently makes ventilation impossible and might foster emphysema aquosum-like air trapping and, therefore, increase the risk of pulmonary barotrauma during ascent. Because the limitations of underwater ventilation are substantial even under ideal conditions, it cannot be recommended presently for real diving conditions.