Deep anaesthesia: The Thailand cave rescue and its implications for management of the unconscious diver underwater.

Introduction: In 2018 12 children and one adult were anaesthetised before being extricated through over a kilometre of flooded cave in Thailand. Full face dive masks (FFMs) putatively capable of maintaining constant positive airway pressure (CPAP) were employed. Here we describe the anaesthetic intervention and investigate the CPAP capability of the FFM.

Methods: Pressure was measured inside and outside the Interspiro Divator FFM during 10 tidal and 10 vital capacity breaths in divers at the surface and submerged with the mask deployed on open-circuit scuba (10 divers); and a closed-circuit rebreather (five divers). Relative in-mask pressure was calculated as the difference between inside and outside pressures. We also measured the in-mask pressure generated by activation of the second stage regulator purge valve in open-circuit mode.

Results: When submerged in open-circuit mode the mean relative in-mask pressure remained positive in normal tidal breathing (inhalation 0.6 kPa [95% CI 0.3-0.9]; exhalation 1.1 [0.8-1.4]) and vital capacity breathing (inhalation 0.8 [0.4-1.1]; exhalation 1.2 [0.9-1.4]). As expected, the relative in-mask pressure was predominantly negative when used on closed-circuit with back mounted counter-lungs due to a negative static lung load. Mean in-mask pressure during purge valve operation was 3.99 kPa (approximately equal to 40 cmH2O) (range: 2.56 to 5.3 kPa).

Conclusions: The CPAP function of the Interspiro Divator FFM works well configured with open-circuit scuba. This may have contributed to the success of the Thailand cave rescue. Caution is required in generalising this success to other diving scenarios.