How to Survive 33 min after the Umbilical of a Saturation Diver Severed at a Depth of 90 msw?

Abstract

In 2012, a severe accident happened during the mission of a professional saturation diver working at a depth of 90 m in the North Sea. The dynamic positioning system of the diver support vessel crashed, and the ship drifted away from the working place, while one diver's umbilical became snagged on a steel platform and was severed. After 33 min, he was rescued into the diving bell, without exhibiting any obvious neurological injury. In 2019, the media and a later 'documentary' film suggested that a miracle had happened to permit survival of the diver once his breathing gas supply was limited to only 5 min. Based on the existing data and phone calls with the diver concerned (Dc), the present case report tries to reconstruct, on rational grounds, how Dc could have survived after he was cut off from breathing gas, hot water, light and communication while 90 m deep at the bottom of the sea. Dc carried bail-out heliox (86/14) within two bottles (2 × 12 L × 300 bar: 7200 L). Calculating Dc's varying per-minute breathing gas consumption over time, both the decreased viscosity of the helium mix and the pressure-related increase in viscosity did not exhibit a breathing gas gap. Based on the considerable respiratory heat loss, the core temperature was calculated to be as low as 28.8 °C to 27.2 °C after recovery in the diving bell. In accordance with the literature, such values would be associated with impaired or lost consciousness, respectively. Relocating Dc on the drilling template by using a remotely operated vehicle (ROV), the transport of the victim to the bell and subsequent care in the hyperbaric chamber must be regarded as exemplary. We conclude that, based on rational arguments and available literature data, Dc's healthy survival is not a miracle, as it can be convincingly explained by means of reliable data. Remaining with a breathing gas supply sufficient for five minutes only would not have ended in a miracle but would have ended in death by suffocation. Nevertheless, survival of such an accident may appear surprising, and probably the limit for a healthy outcome was very close. We conclude, in addition, that highly effective occupational safety measures, in particular the considerable bail-out heliox reserve, secured the healthy survival. Nevertheless, the victim's survival is likely to be due to his excellent diving training, together with many years of diving routine. The rescue action of the second diver and Dc's retrieval by the ROV operator are also suggestive of the behavior of carefully selected crew members with the high degree of professional qualification needed to correctly function in a hostile environment.

Keywords: accident; heliox; respiratory heat loss; saturation diving; umbilical.

Figure 1

The divers’ support vessel ‘Bibby Topaz’ accommodates in its hull four hyperbaric chambers which are connected to each other. A diving bell can be connected to two of these chambers. Divers can be transported within these bells in the vicinity of the workplace. Reprinted with permission from [1]. Copyright 2006 Dräger Safety AG & Co. KgaA.

Figure 2

Examples of umbilical cross sections. Different supply lines exist for different purposes. (A): Umbilical from diving bell to diver (Ø: ~4.5 cm). (B): Umbilical from diver’s support vessel to diving bell (Ø: ~6 cm). Reprinted with permission from Miller [4]. Copyright 2021 Bay-Tech Industries.

Figure 3

Works on an oil rig. The divers are supplied from a diving bell that in turn is supplied by a diver support vessel (see Figure 2). The divers are surveyed by a remotely-operated vehicle (ROV). Reprinted with permission from [5]. Copyright 2012 slideshare.net.

Figure 4

The remotely operating vehicle (ROV) finds Dc on top of the steel construction. Reprinted with permission from [6]. Copyright 2014 Floating Harbour.

Figure 5

Oxygen hemoglobin dissociation curve for high O₂ partial pressures. The pO₂ in the present case was about 1050 mmHg, thus 3 mL O₂/100 mL blood could physically be dissolved.

Figure 6

Dc’s maximum ventilation volume (MVV) with air as a function of depth (red). Similar curves are presented for untrained (dotted) and trained (dashed) divers [16], and for divers down to 60 m [17] (blue). The black line is extrapolated from a 50-m value contained in the ISO standards (EN 250) [18].

Figure 7

Depth-dependent maximum ventilation values (MVV) for heliox 79/21 (red). This curve was extrapolated from one single value (MVV: 130 L/min; depth: 20 m) [19] using Equation (2). The MVV for heliox 86/14 (blue) is shifted upwards somewhat, because that mix is less dense and viscous. The green curve represents respiration values during very severe work.

Figure 8

Linear extrapolation of the maximum ventilation volume (MVV) for heliox 86/14 from air and heliox 79/21 values. A surface value of 221 L/min resulted for heliox 86/14.

Figure 9

Real time gas consumption during 33 min, i.e., from the umbilical severing to the rescue in the diving bell. See also Table S1 at the end of this case report.

Figure 10

Dry suit with hot water supply. Reprinted with permission form Ref. [29]. Copyright 2004 Prof. Hans Örnhagen, SE.

Figure 11

Core temperature. During 33 min after the umbilical had severed, the temperature decreased to 28.8 °C (black: hypothesis 1) and to about 27.2 °C (red: hypothesis 2).