Calculation of Decompression Schedules for Nitrogen-Oxygen and Helium- Oxygen Dives

Workman, R. D.

doi:10.21236/ad0620879

Cited by 48 publications

(16 citation statements)

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“…Based on human models, long half-time tissues (e.g. fat, bone marrow) may have time constants from tens of minutes to in excess of 400min (Lundin, 1960;Schreimer, 1967;Sicko et al, 2003;Workman, 1965;Wienke, 2003). Significant supersaturation of these tissues would take considerably longer dive bouts and/or longer individual dives than performed in this study.…”

Section: Relevance Of Findings To the Vascular Bubble Hypothesismentioning

confidence: 99%

Investigation of the potential for vascular bubble formation in a repetitively diving dolphin

Houser

Dankiewicz-Talmadge

Stockard

et al. 2010

Journal of Experimental Biology

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SUMMARYThe production of venous gas emboli (VGE) resulting from altered dive behavior is postulated as contributing to the stranding of beaked whales exposed to mid-frequency active sonar. To test whether nitrogen gas uptake during repetitive breath-hold diving is sufficient for asymptomatic VGE formation in odontocetes, a bottlenose dolphin (Tursiops truncatus Montagu) was trained to perform 10-12 serial dives with 60s surface intervals to depths of 30, 50, 70 or 100m. The dolphin remained at the bottom depth for 90s on each dive. Doppler and/or two-dimensional imaging ultrasound did not detect VGE in the portal and brachiocephalic veins following a dive series. Van Slyke analyses of serial, post-dive blood samples drawn from the fluke yielded blood nitrogen partial pressure (P N2 ) values that were negligibly different from control samples. Mean heart rate (HR; ±1s.d.) recorded during diving was 50±3beatsmin -1 and was not significantly different between the 50, 70 and 100m dive sessions. The absence of VGE and elevated blood P N2 during post-dive periods do not support the hypothesis that N 2 supersaturation during repetitive dives contributes to VGE formation in the dolphin. The diving HR pattern and the presumed rapid N 2 washout during the surface-interval tachycardia probably minimized N 2 accumulation in the blood during dive sessions.

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Section: Relevance Of Findings To the Vascular Bubble Hypothesismentioning

confidence: 99%

Investigation of the potential for vascular bubble formation in a repetitively diving dolphin

Houser

Dankiewicz-Talmadge

Stockard

et al. 2010

Journal of Experimental Biology

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“…For recreational exposures, the RGBM collapses to a dissolved gas algorithm. This is reflected in the risk estimates above, where estimates for both models differ little [9,20,23,36,86].…”

Section: Nonstop and Repetitive Air Divingmentioning

confidence: 93%

“…The excitation radius, , depends on material properties [4,28,[86][87][88], and is taken for nitrogen (μm), [14,47]. Both expression above represent fits to RGBM mixed gas data across lipid and aqueous bubble films [4,60], and are different from other phase models [32,92].…”

Section: G = Pmentioning

confidence: 99%

“…Tables were published by US Navy investigators [5,73], and Table 4 tabulates the corresponding nonstop time limits (p =0.05, 0.01), and also includes the standard US Navy (Workman) limits [21,23,86] for comparison. Later re-evaluations of the standard set of nonstop time limits estimate a probability rate of 1.25% for the limits.…”

Section: Probabilisticsmentioning

confidence: 99%

“…Outside of World Navies, few diving sectors today even contemplate air decompression diving to 200 fsw. Risks in air dives beyond 150 fsw are known to increase by factors of 10 over similar dives at shallower depth [65,86]. This is, of course, one major reason why trimix and heliox become mixtures of choice for deep and decompression diving worldwide, across commercial, scientific, exploration, and research sectors.…”

Section: French Navy Deep Stop Schedulesmentioning

confidence: 99%

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On Validation of a Popular Sport Diving Decompression Model

Wienke¹

2009

TOSSJ

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Linking deep stop model and data, we detail the LANL reduced gradient bubble model (RGBM), dynamical principles, and correlation with the LANL Data Bank. Table, profile, and meter risks are obtained from likelihood analysis, and pertinent applications include nonstop air diving, the Bennett and Maronni 2.5 minute recreational deep stop, C & C Team 450/20 multiple RB dive sequence at 1.4 atm, NEDU deep stop tests, and French Navy deep stop profiles. The algorithm enjoys extensive and utilitarian application in mixed gas diving, both in recreational and technical sectors, and forms the bases for released tables, software, and decompression meters used by scientific, commercial, and research divers. The LANL Data Bank is described, and the methods used to deduce risk are detailed. Risk functions for dissolved gas and bubbles are summarized. Parameters that can be used to estimate profile risk are tallied. To fit data, a modified Levenberg-Marquardt routine is employed. The LANL Data Bank presently contains 2879 profiles with 20 cases of DCS across nitrox, trimix, and heliox deep and decompression diving. This work establishes needed correlation between global mixed gas diving, specific bubble model, and deep stop data. The objective is operational diving, not clinical science. The fit of bubble model to deep stop data is chi squared significant to 93%, using the logarithmic likelihood ratio of null set (actual set) to fit set. The RGBM model is thus validated within the LANL Data Bank. Extensive and safe utilization of the model as reflected in user statistics for tables, meters, and software also points to real world validation, that is, one without noted nor reported DCS spikes among RGBM divers. Collecting real world diving data is a global alternative to differential wet and dry testing, a very precise but limited statistical procedure. The approach here for technical, mixed gas, and serious decompression diving parallels the Project Dive Exploration (PDE) effort at DAN for recreational air and nitrox diving, but does not overlap quite obviously. The issue of deep stops versus shallow stops in diving is a hotly debated topic today, and this study reaffirms the efficacy of deep stops, especially as they link naturally to the LANL dual phase bubble model and data. The operational issue of deep stops and staging is one of timing, with questions of time and depth at all stops only addressed within consistent model and ranging data frameworks.

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Hyperbaric Conditions

Doolette

Mitchell

2010

Comprehensive Physiology

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Exposure to elevated ambient pressure (hyperbaric conditions) occurs most commonly in underwater diving, during which respired gas density and partial pressures, work of breathing, and physiological dead space are all increased. There is a tendency toward hypercapnia during diving, with several potential causes. Most importantly, there may be reduced responsiveness of the respiratory controller to rising arterial CO₂, leading to hypoventilation and CO₂ retention. Contributory factors may include elevated arterial PO₂, inert gas narcosis and an innate (but variable) tendency of the respiratory controller to sacrifice tight control of arterial CO₂ when work of breathing increases. Oxygen is usually breathed at elevated partial pressure under hyperbaric conditions. Oxygen breathing at modest hyperbaric pressure is used therapeutically in hyperbaric chambers to increase arterial carriage of oxygen and diffusion into tissues. However, to avoid cerebral and pulmonary oxygen toxicity during underwater diving, both the magnitude and duration of oxygen exposure must be managed. Therefore, most underwater diving is conducted breathing mixtures of oxygen and inert gases such as nitrogen or helium, often simply air. At hyperbaric pressure, tissues equilibrate over time with high inspired inert gas partial pressure. Subsequent decompression may reduce ambient pressure below the sum of tissue gas partial pressures (supersaturation) which can result in tissue gas bubble formation and potential injury (decompression sickness). Risk of decompression sickness is minimized by scheduling time at depth and decompression rate to limit tissue supersaturation or size and profusion of bubbles in accord with models of tissue gas kinetics and bubble formation and growth.

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Calculation of Decompression Schedules for Nitrogen-Oxygen and Helium- Oxygen Dives

Cited by 48 publications

References 0 publications

Investigation of the potential for vascular bubble formation in a repetitively diving dolphin

Investigation of the potential for vascular bubble formation in a repetitively diving dolphin

On Validation of a Popular Sport Diving Decompression Model

Hyperbaric Conditions

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