Scubadoc’s Ten Foot Stop

May 3, 2009

Nitroglycerine Reduces Bubble Formation In Wet and Dry Dives

Filed under: Article, Publication — admin @ 8:15 pm
1: Med Sci Sports Exerc. 2006 Aug;38(8):1432-5.

Exogenous nitric oxide and bubble formation in divers.

Departments of Physiology, University of Split School of Medicine, Split, Croatia. zdujic@bsb.mefst.hr

PURPOSE: Prevention of bubble formation is a central goal in standard decompression procedures. Previously we have shown that exercise 20-24 h prior to a dive reduces bubble formation and increases survival in rats exposed to a simulated dive. Furthermore, we have demonstrated that nitric oxide (NO) may be involved in this protection; blocking the production of NO increases bubble formation while giving rats a long-lasting NO donor 20 h and immediately prior to a dive reduces bubble formation. This study determined whether a short-lasting NO donor, nitroglycerine, reduced bubble formation after standard dives and decompression in man. METHODS: A total of 16 experienced divers were randomly assigned into two groups. One group performed two dives to 30 m of seawater (msw) for 30 min breathing air, and performed exercise at an intensity corresponding to 30% of maximal oxygen uptake during the bottom time. The second group performed two simulated dives to 18 msw for 80 min breathing air in a hyperbaric chamber, and remained sedentary during the bottom period. The first dive for each diver served as the control dive, whereas the divers received 0.4 mg of nitroglycerine by oral spray 30 min before the second dive. Following the dive, gas bubbles in the pulmonary artery were recorded using ultrasound. RESULTS: The open-water dive resulted in significantly more gas bubbles than the dry dive (0.87 +/- 1.3 vs 0.12 +/- 0.23 bubbles per square centimeter). Nitroglycerine reduced bubble formation significantly in both dives from 0.87 +/- 1.3 to 0.32 +/- 0.7 in the in-water dive and from 0.12 +/- 0.23 to 0.03 +/- 0.03 bubbles per square centimeter in the chamber dive. CONCLUSION: The present study demonstrates that intake of a short-lasting NO donor reduces bubble formation following decompression after different dives.

PMID: 16888456 [PubMed - indexed for MEDLINE]

Benefit from surfactant on eustachian tube function in divers?

Filed under: Article, Publication — admin @ 8:06 pm
1: Mil Med. 2008 Dec;173(12):1225-32.Links

A pilot study evaluating surfactant on eustachian tube function in divers.

Naval Submarine Medical Research Laboratory, Naval Submarine Base New London, Box 900, Groton, CT 06349-5900, USA.

BACKGROUND: Middle ear barotrauma (MEBT) is the most common medical complication in diving, aviation, and hyperbaric medicine. Eustachian tube dysfunction (ETD) quantifies the inability to open the eustachian tube (ET), risking MEBT. Surfactant administration improved ET function and efficaciously treated otitis media in a host of animal models. We performed a pilot study evaluating the efficacy of intranasal surfactant administration in reducing MEBT in repetitive diving. METHODS: Eight divers participated in a subject-blinded, placebo-controlled, random order, multiarm (air and O2)-repeated measures trial investigating the relative efficacy of intranasally administered surfactant, acetylcysteine and oxymetazoline, and orally administered pseudoephedrine versus saline-placebo in middle ear equilibration during repetitive, multiday diving. Subjects were tested with the Nine-Step Inflation/Deflation Tympanometry Test (NSI/DT) and sonotubometry (testing eustachian tube opening pressure [ETOP]) before and immediately after each dive. RESULTS: Significant interaction effects were found for drug-by-test (F8,668 = 4.05; p < 0.001) and the three-way interaction of drug-by-dive-by-test (F16,668 = 2.47; p = 0.001) in sonotubometry testing. The ETOP revealed trends toward lowered (improved) values post-versus predive in all treatment arms, which was significant for oxymetazoline (p = 0.04). Only four of the eight subjects experienced any holds during diving. Statistical analysis of the NSI/DT data showed that none of the drug interventions resulted in improvements in ET function over that expected by chance. CONCLUSIONS: There is large intra- and intersubject variability in daily functioning of the ET as measured using the NSI/DT and sonotubomtery (ETOP). Sonotubometry engendered trends toward lowered (improved) values post-versus predive in all treatment arms. The repetitive dives did not result in a significant decrease in ET function as evidenced in the saline-placebo trials, circumventing an ability to detect superiority among the various treatment arms in our subject population. Additionally, since our study was underpowered to detect significant effects, we can only assert that various inhalational agents may improve middle ear ventilation in repetitive diving warranting further study. A larger subject population including subjects diagnosed with ET dysfunction may provide more statistical power to discern the benefit of inhaled agents as a useful prophylactic for preventing or reducing ET dysfunction during diving and/or hyperbaric/hypobaric pressure changes.

PMID: 19149344 [PubMed - indexed for MEDLINE]

Polish Article on Treatment of Decompression Illness

Filed under: Article, Publication — admin @ 8:02 pm
1: Int Marit Health. 2008;59(1-4):69-80

Recompression treatment for decompression illness: 5-year report (2003-2007) from National Centre for Hyperbaric Medicine in Poland.

National Centre for Hyperbaric Medicine, Institute of Maritime and Tropical Medicine in Gdynia, Medical University of Gdańsk, Poland. jkot@amg.gda.pl

A serious diving accident can occur in recreational diving even in countries where diving is not very popular due to the fact that diving conditions there are not as great as in some tropical diving locations. The estimated number of injured divers who need recompression treatment in European hyperbaric facilities varies between 10 and 100 per year depending on the number of divers in the population, number of dives performed annually, and number of hyperbaric centres in the country. In 5 years of retrospective observation in Poland (2003-2007) there were 51 cases of injured recreational divers recorded. They either dived locally or after returning home by air from a tropical diving resort. All of them were treated with recompression treatment in the National Centre for Hyperbaric Medicine in Gdynia which has capability to treat any patient with decompression illness using all currently available recompression schedules with any breathing mixtures including oxygen, nitrox, heliox or trimix. The time interval between surfacing and first occurrence of symptoms was significantly lower in the group of patients with neurological decompression sickness or arterial gas embolism (median 0.2 hours) than in the group of patients with other types of decompression sickness (median 2.0 hours). In both groups, there were different types of recompression tables used for initial treatment and different number of additional sessions of hyperbaric oxygenation (HBO) prescribed, but the final outcome was similar. Complete resolution of symptoms after initial recompression treatment was observed in 24 cases, and this number was increased to 37 cases after additional HBO sessions (from 1 to 20). In the final outcome, some residual symptoms were observed in 12 cases. In 2 cases initial diagnosis of decompression sickness type I was rejected after initial recompression treatment and careful re-evaluation of diving profiles, risk factors and reported symptoms.

Scuba Diving and The Older Diver

Filed under: Article, Publication — admin @ 12:18 pm

The Older Diver

Problem — The Older Diver
To my knowledge there is no specified age limit to sport diving.

Diving Concerns

* Condition Related

Most elderly divers are not capable of sustaining the work load required by all but the least physically demanding dives. The majority of elderly divers do not exercise regularly or adequately.

* Treatment Related

Physical training can definitely minimize the decline in physical capacity in older divers.

* Diver Related

Chronological age and physiological age can differ markedly; and each individual ticks to his own genetic clock.

Risk Assessment

* Risk from the Condition

General health, agility and stregth decrease with age. Maximum heart rate, oxygen uptake and lung compliance decrease with age. [Parker, 'The Sport Diving Medical']
Good screening is necessary. Older divers have a higher incidence of chronic diseases; i.e., cardiovascular disease and chronic lung disease. Appropriate screening evaluations of the heart and coronary arteries with exercise testing is useful in older divers before instituting a diving program.
Osteoporosis (men and women) increases with age and increased incidence of fractures becomes a factor.

* Risks from treatment

The older diver is more prone to be taking multiple drugs and medicines, some of which have effects that are adverse to diving. These should be listed and evaluated prior to allowing diving. See web page at http://scuba-doc.com/drugsdiv.htm .

* Risks to the Diver

–Atherosclerosis affects the blood flow to the brain, heart, kidneys and limb muscles and therefore the function of these organs.
–Inability to self rescue due to decreased strength from muscle atrophy would be an important consideration.
–The older diver is more prone to hypothermia due to decreased tissue perfusion, decreased fat stores and decreased metabolism.
–Decompression sickness increases with age. [Edmonds] This may be due to decreased tissue perfusion and arthritic changes in the joints.

Advising the Diver

Most very old divers arrange for a personal dive guide to assist them in suiting up, donning gear, managing their entrances and exits from the water and accompanying them during the dive. The problem comes in getting the elderly to recognize when the time comes to ask for help! It’s hard to get an old diver out of the water!

* Potential for injury from future diving

Myocardial infarction, heart failure account for a high percentage of deaths while diving. [Caruso]
Increased risk of pulmonary edema [additive effects of pulmonary edema of diving with borderline heart failure from intrinsic heart disease.
Increased risk of fractures [hip]
Increased risk of decompression sickness
Inability to self rescue or manage unexpected water movements [current, surges, wave action].

* Modifiers

Regular Checkups.
Good physical conditioning
Absence of cardiovascular-pulmonary disease
Mentally alert
Diving Experience
Alteration of diving profiles with shallower, shorter diving, longer and deeper safety stops and longer surface intervals

* Dive or not dive

If an older diver is in good physical condition and is mentally alert enough to do adequate problem solving at depth, then I would personally have no qualms in certifying him to dive. The older diver is more likely to take fewer chances and to obey the rules. There are few 70 year-old ‘Buccaneers’!
Genetic clocks

To my knowledge there is no specified age limit to sport diving. Chronological age and physiological age can differ markedly; and each individual ticks to his own genetic clock. This having been said, most elderly divers are not capable of sustaining the work load required by all but the least physically demanding dives. The majority of elderly divers do not exercise regularly or adequately. Physical training can definitely minimize the decline in physical capacity in older divers.
Good screening necessary

Older divers have a higher incidence of chronic diseases; i.e., cardiovascular disease and chronic lung disease. Atherosclerosis affects the blood flow to the brain, heart, kidneys and limb muscles and therefore the function of these organs. Appropriate screening evaluations of the heart and coronary arteries with exercise testing is useful in older divers before instituting a diving program.

“I’m gonna live (dive) forever!”

If a 90 year old is in good physical condition, able to perform self and buddy rescue and is mentally alert enough to do adequate problem solving at depth, then I would personally have no qualms in certifying him to dive.

Ask for Help

Most very old divers arrange for a personal dive guide to assist them in suiting up, donning gear, managing their entrances and exits from the water and accompanying them during the dive. The problem comes in getting us old GCFD’s (“geezer-codger-fogy- duffers”) to recognize when the time comes to ask for help! It’s darned hard to get an old surgeon out of the O.R. – but doubly hard to get an old diver out of the water!

Older-Safer!

The obverse may also be operative; the older diver is more likely to take fewer chances and to obey the rules. There are few 70 year-old ‘Buccaneers’!

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