Effect of varying deep stop times and shallow stop times on precordial bubbles after dives to 25 msw (82 fsw).

In our previous research, a deep 5-min stop at 15 msw (50 fsw), in addition to the typical 3-5 min shallow stop, significantly reduced precordial Doppler detectable bubbles (PDDB) and "fast" tissue compartment gas tensions during decompression from a 25 msw (82 fsw) dive; the optimal ascent rate was 10 msw (30 fsw/min). Since publication of these results, several recreational diving agencies have recommended empirical stop times shorter than the 5 min stops that we used, stops of as little as 1 min (deep) and 2 min (shallow). In our present study, we clarified the optimal time for stops by measuring PDDB with several combinations of deep and shallow stop times following single and repetitive open-water dives to 25 msw (82 fsw) for 25 mins and 20 minutes respectively; ascent rate was 10 msw/min (33 fsw). Among 15 profiles, stop time ranged from 1 to 10 min for both the deep stops (15 msw/50 fsw) and the shallow stops (6 msw/20 fsw). Dives with 2 1/2 min deep stops yielded the lowest PDDB scores--shorter or longer deep stops were less effective in reducing PDDB. The results confirm that a deep stop of 1 min is too short--it produced the highest PDDB scores of all the dives. We also evaluated shallow stop times of 5, 4, 3, 2 and 1 min while keeping a fixed time of 2.5 min for the deep stop; increased times up to 10 min at the shallow stop did not further reduce PDDB. While our findings cannot be extrapolated beyond these dive profiles without further study, we recommend a deep stop of at least 2 1/2 mins at 15 msw (50 fsw) in addition to the customary 6 msw (20 fsw) for 3-5 mins for 25 meter dives of 20 to 25 minutes to reduce PDDB.

A deep stop during decompression from 82 fsw (25 m) significantly reduces bubbles and fast tissue gas tensions.

In spite of many modifications to decompression algorithms, the incidence of decompression sickness (DCS) in scuba divers has changed very little. The success of stage, compared to linear ascents, is well described yet theoretical changes in decompression ratios have diminished the importance of fast tissue gas tensions as critical for bubble generation. The most serious signs and symptoms of DCS involve the spinal cord, with a tissue half time of only 12.5 minutes. It is proposed that present decompression schedules do not permit sufficient gas elimination from such fast tissues, resulting in bubble formation. Further, it is hypothesized that introduction of a deep stop will significantly reduce fast tissue bubble formation and neurological DCS risk. A total of 181 dives were made to 82 fsw (25 m) by 22 volunteers. Two dives of 25 min and 20 min were made, with a 3 hr 30 min surface interval and according to 8 different ascent protocols. Ascent rates of 10, 33 or 60 fsw/min (3, 10, 18 m/min) were combined with no stops or a shallow stop at 20 fsw (6 m) or a deep stop at 50 fsw (15 m) and a shallow at 20 fsw (6 m). The highest bubbles scores (8.78/9.97), using the Spencer Scale (SS) and Extended Spencer Scale (ESS) respectively, were with the slowest ascent rate. This also showed the highest 5 min and 10 min tissue loads of 48% and 75%. The lowest bubble scores (1.79/2.50) were with an ascent rate of 33 fsw (10 m/min) and stops for 5 min at 50 fsw (15 m) and 20 fsw (6 m). This also showed the lowest 5 and 10 min tissue loads at 25% and 52% respectively. Thus, introduction of a deep stop significantly reduced Doppler detected bubbles together with tissue gas tensions in the 5 and 10 min tissues, which has implications for reducing the incidence of neurological DCS in divers.

Hyperbaric oxygen and surgery.

Hyperbaric oxygen (HBO) therapy, that is the administration of 100% oxygen delivered under pressure, has a beneficial effect in several surgical conditions. Its use has been assessed and audited and its pharmacological effects demonstrated. It is appropriate for use in several surgical conditions as evidence-based therapy. These are: (i) gas gangrene; (ii) crush injuries, compartment syndromes and acute traumatic ischemias; (iii) enhancement of healing in selected problem wounds; (iv) exceptional blood loss anaemia; (v) necrotising soft-tissue infections; (vi) refractory osteomyelitis; (vii) radionecrosis; (viii) compromised skin grafts and flaps; (ix) thermal burns; (x) intracranial abscess. HBO therapy has been used inappropriately in the past; there is also lack of knowledge regarding its application, and scarce hyperbaric facilities. Hyperbaric therapy, when properly supervised by a physician trained in its use, working closely with a surgeon, and ethically used for appropriate indications, can be a useful adjunct to surgical practice.

Hyperbaric oxygen in trauma and surgical emergencies.

Hyperbaric oxygen therapy (HBO), that is the administration of 100% oxygen delivered under pressure, has a beneficial effect in several surgical conditions. Its use has been assessed and audited and its pharmacological effects demonstrated. It is appropriate for use in several acute surgical conditions as evidence-based therapy. These are: Gas Gangrene Crush Injuries, Compartment Syndromes & Acute Traumatic Ischaemias Enhancement of Healing in Selected Problem Wounds Exceptional Blood loss Anaemia Necrotising Soft Tissue Infections Compromised Skin Grafts & Flaps Thermal Burns HBO therapy suffers from previous inappropriate use, lack of knowledge, and scarce hyperbaric facilities. Hyperbaric therapy, when properly supervised by a physician trained in its use, working closely with a surgeon, and ethically used for appropriate indications, can be a useful adjunct to surgical practice. Military surgeons may be in a situation in which they can utilize HBO in acute surgical conditions and trauma. They are urged to identify HBO facilities, both fixed and portable, and to establish communication with hyperbaric therapy colleagues.

A review of the Marx protocols: prevention and management of osteoradionecrosis by combining surgery and hyperbaric oxygen therapy.

The 30/10 protocol is employed in the treatment of established osteoradionecrosis. No surgery should be attempted before the first 30 HBO treatments have provided sufficient angiogenesis to support surgical wounding. After 30 treatments surgical management can be staged according to the extent of improvement achieved after HBO and the size of sequestrum or area of osteolysis. If the ORN extends to the inferior border of the mandible or if it manifests as an orocutaneous fistula or pathological fracture, discontinuity resection of the necrotic bone and soft tissue will be required to resolve the disease. Unless HBO and surgery are combined in the management of ORN, the results are not long lasting or satisfactory. Even though resection of stage three ORN seems unduly aggressive, it has stood the test of time. By using the Marx protocols in the treatment of ORN, more than 95 per cent of patients can be successfully cured of their disease with predictable, functional and aesthetically acceptable outcomes.