|M.Sc Student||Cohen Katsenelson Ksenya|
|Subject||Prophylactic Hyperoxic Treatment Ameliorates Decompression|
|Department||Department of Medicine||Supervisors||Professor Emeritus Moshe Feinsod|
|Dr. Ran Arieli|
|Dr. Yehuda Arieli|
|Full Thesis text|
During sudden or too rapid decompression, gas is released in the supersaturated tissues in the form of bubbles, which might cause decompression sickness (DCS). It is widely accepted that these bubbles originate in tissue from preexisting gas micronuclei. It was hypothesized that pretreatment with hyperbaric O2 (HBO) would shrink some of the gas micronuclei, thus reducing the number of emerging bubbles.
In the present investigation, the effect of two HBO pretreatment pressures (405 and 709 kPa) was studied in prawns decompressed from a range of pressures between 203-810 kPa. HBO pretreatment at 405 kPa for 5 min significantly reduced the number of bubbles after decompression from 203, 304 and 405 kPa. Pretreatment with HBO at 709 kPa significantly reduced the number of bubbles after decompression from 203, 304, 507 and 608 kPa.
To examine the procedure in mammals, rats were pretreated with HBO at 101, 203, 304, 405 or 507 kPa for 20 min. Shorter pretreatment times, 5 or 10 min, were also tested at 304 kPa. After pretreatment, rats were exposed to air at 1013 kPa for 33 min, followed by fast decompression. Control rats were exposed to the same pressure for 32 min, without HBO pretreatment. On reaching atmospheric pressure, the rat was immediately placed in a rotating cage for 30 min for the diagnosis of DCS according to accepted signs. After 2 h, 65% of the control rats had suffered DCS, whereas 35% had no DCS. HBO pretreatment at 101, 203, 304, 405 and 507 kPa for 20 min significantly reduced the incidence of DCS at the 2-h observation point to 45%, 45%, 40%, 40% and 35%, respectively. HBO pretreatment at 304 kPa for 10 and 20 min reduced the incidence of DCS at the 2-h observation point to 45% and 40%, respectively. After HBO pretreatment at 304 kPa for 5 min, 65% of the rats suffered DCS.
An investigation was then conducted into the effectiveness of HBO pretreatment at 304 kPa for 20 min on neurologic deficit. Rats were decompressed from 1013 kPa with or without HBO pretreatment, and were subsequently monitored by recording somatosensory evoked potentials (SSEPs). In control rats, SSEP recordings were made without prior compression. After decompression without HBO pretreatment, 78% of rats had abnormal SSEP recordings. This was significantly reduced to 44% after HBO pretreatment. DCS assessment by SSEPs seems to be a more sensitive tool than the clinical examination.