stress da fuga e mdd

J Appl Physiol 104: 50-56, 2008. First published November 1, 2007;
doi:10.1152/japplphysiol.00465.2007
8750-7587

Oxygen or carbogen breathing before simulated submarine escape
M. Gennser and S. L. Blogg
Swedish Defence Research Agency (FOI), Centre for Environmental
Physiology, Karolinska Institute, Stockholm, Sweden

Submitted 30 April 2007 ; accepted in final form 25 October 2007


Raised internal pressure in a distressed submarine increases the risk of
bubble formation and decompression illness after submarine escape. The
hypothesis that short periods of oxygen breathing before submarine
escape would reduce decompression stress was tested, using
Doppler-detectable venous gas emboli as a measure. Twelve goats breathed
oxygen for 15 min at 0.1 MPa before exposure to a simulated submarine
escape profile to and from 2.5 MPa (240 m/seawater), whereas 28 control
animals underwent the same dive without oxygen prebreathe. No
decompression sickness (DCS) occurred in either of these two groups.
Time with high bubble scores (Kisman-Masurel 3) was significantly (P <
0.001) shorter in the prebreathe group. In a second series, 30 goats
breathed air at 0.2 MPa for 6 h. Fifteen minutes before escape from 2.5
MPa, animals were provided with either air (n = 10), oxygen (n = 12), or
carbogen (97.5% O2 and 2.5% CO2) gas (n = 8) as breathing gas. Animals
breathed a hyperoxic gas (60% O2-40% N2) during the escape. Two animals
(carbogen group) suffered oxygen convulsions during the escape but
recovered on surfacing. Only one case of DCS occurred (carbogen group).
The initial bubble score was reduced in the oxygen group (P < 0.001).
The period with bubble score of Kisman-Masurel 3 was also significantly
reduced in the oxygen group (P < 0.001). Oxygen breathing before
submarine escape reduces initial bubble scores, although its
significance in reducing central nervous system DCS needs to be
investigated further.

submarine escape; decompression sickness; venous gas emboli