DEPTH Blog

The most useful snippets from our authors, all in one place. DEPTH discusses topics of diving, equipment and environment, physics and physiology, technique and technology, and hyperbarics.

Nitrox Breathing Mixtures

Divers have used air as a breathing gas since the beginning of diving. Its principal advantages are that it is readily available and inexpensive to compress into cylinders or use directly from compressors with surface-supplied diving equipment. Air is not the “ideal” breathing mixture for diving because of the decompression liability it imposes. Since decompression obligation is dependent on exposure to inspired PN2 (nitrogen partial pressure), this obligation can be reduced by replacing a portion of the nitrogen content of the diver’s breathing gas with oxygen, which is metabolized by the body. This is the fundamental benefit of enriched air nitrox (Nx) diving (Wells 1989). Historically, the two most commonly used nitrox mixtures in NOAA have been 32% and 36% oxygen. Once called NOAA Nitrox 32 (NN32) and NOAA Nitrox 36 (NN36), such mixtures are now identified using a more general nomenclature as Nx32 and Nx36. The remaining gas in nitrox mixes is considered to be nitrogen, even though it may contain other inert gases like argon. “Nitrox” is a generic term that can be used for any gaseous mixture of nitrogen and oxygen, but in the context of this chapter, the implication is that nitrox is a mixture with a higher concentration of oxygen than that of air. Using such oxygen enhanced mixtures can significantly increase the amount of time a diver can spend at depth without incurring additional decompression when compared to air diving.

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Contingency Planning

Performing repetitive dives requires a the use of a dive plan. The diver must know what the no-stop dive time limits will be for the dives prior to descending so as not to incur additional decompression obligations. A planned dive schedule will work assuming the diver adheres to the maximum depth and time parameters defined before descending; however, this does not always occur. There are many reasons why divers may find themselves deeper than planned. Some of these might include: higher than normal tides while working on a specific site, down-welling currents, the need to descend deeper to pick up tools or experimental apparatus that may have been dropped, the unexpected need to provide assistance to divers who are working at deeper depths (either on a routine or emergency basis), or perhaps just plain inattention of the divers.

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Thermal Stress Irrespective of Ambient Temperature

Thermal Stress Irrespective of Ambient Temperature
Hypothermia is not a problem exclusive to frigid environments—it can occur irrespective of ambient temperature. Similarly, divers may also suffer extremes of hot and cold thermal stress simultaneously during the same dive. There have been documented cases of severe heat exhaustion in arctic waters by commercial divers as a result of wearing thick, occlusive drysuits, aggravated by dehydration from breathing dry compressed gas and perspiring from prolonged underwater swimming or heavy underwater work. Perspiration from excessive or from pre-dive overheating can also cause the diver’s drysuit underwear to lose insulation, thus predisposing him to hypothermia.

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Why Do Patients Quit Hyperbaric Therapy?

In this podcast and article by Roque Wicker, MBA, author of HBOTechBlog.com, and creator of the Hyperbaric Oxygen Therapy Patient Safety Instructions we explore the relationship between effective patient education on hyperbaric compliance, patient satisfaction, and reimbursement. 

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Divers Should Never Leave Home Without It...

When you prepare for a dive trip, there are things you pack that are on the "must have" list, such as mask, fins, BCD, and regulator. Then there are the things that you "should have" such as wetsuit, defog, and sunscreen. All of the other items typically fall onto the "it would be nice to have" list, such as snacks, sunglasses, and a camera. The question we have for you today is, onto which list do your dive rescue and dive accident management skills fall?

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Oxygen and the Brain: The Journey of Our Lifetime by Dr. Philip James

Oxygen and the Brain: The Journey of Our Lifetime by Dr. Philip James

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New Diver Recruitment Strategy and Resources

New Diver Recruitment Strategy and Resources

Attention Dive Shop Owners and Operators: are you looking to recruit new divers? Check out the great article that ran on DiveNewsWire about a new diver recruitment opportunity using BPC's book, The Simple Guide to Snorkeling Fun, 2nd Edition. Find the DNW article here http://www.divenewswire.com/NewsITems.aspx?newsID=13173. DNW referenced BPC's book "The Simple Guide to Snorkeling Fun" as a great resource for training snorkelers and soon to be divers.

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Rebreathers and the Recreational Diver by Jeffrey Bozanic, Ph.D.

Rebreathers and the Recreational Diver by Jeffrey Bozanic, Ph.D.

When rebreather use started becoming common at the beginning of the twenty-first century, it was the deep, cave, and wreck divers who adopted the new technology. This equipment allowed them to go deeper, penetrate farther, and conserve expensive helium breathing gas. Because they could push the envelope of diving beyond where they could with traditional OC (open circuit) scuba, they were willing to tolerate the numerous increased maintenance responsibilities (as well as pay the hefty price tag associated with rebreathers, often $10,000 to $15,000 or more). But times have changed.

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