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Biomedical subjects

B Gardette

Publications and source records attributed to B Gardette.

28 records · Page 2Linked to original sources
PubMed1997

Circulating bubbles and breath-hold underwater fishing divers: a two-dimensional echocardiography and continuous wave Doppler study.

Since the 1960s, decompression illness after breath-hold diving has been widely debated. The aim of this study was to detect circulating bubbles after breath-hold diving in underwater fishing divers. We used continuous Doppler (DUG, COMEX Pro) and transthoracic two-dimensional (2D) echocardiography (Kontron Sigma 1). This study was conducted during a training course organized by the French Federation of Subaquatic Sports at Minorca (Balearic Islands). Ten breath-hold divers performed repeated breath-hold dives for periods ranging from 2 to 6 h [mean maximum depth 35 meters of seawater (msw)]. A dive computer (Maestro Pro Beuchat, analyst PC interface) was used to record diving patterns. No circulating bubbles were detected in the right heart cavities (2D echocardiography) or in the pulmonary artery (continuous Doppler). However, this study had some limits: only 10 subjects were studied and the earliest detection was 3 min after immersion, further studies will thus be required.

Adult↗
PubMed1996

[Techniques of underwater intervention: means, methods, research and outlook].

In France, diving activities are practised by a large number of people, included recreational or sport divers, commercial and military divers. Different diving technics are used, depending on depth and duration of underwater interventions: human intervention under pressure (diving), one atmosphere submarine, remotely operated vehicle (ROV). The diver used specific equipment and procedures with air, heliox (oxygen -helium), hydrox (oxygen-hydrogen) or hydreliox (oxygen-hydrogen-helium) breathing gas mixtures; and for decompression, specific tables adapted to gas mixtures and underwater time exposures. In 1988, six Comex and French Navy divers worked at a record depth of 534 msw with hydreliox and in 1992 a world record onshore dive at 701 msw was performed by Comex in Marseille. These dives showed the efficiency of hydrogen diving at very deep depth. Among a lot of submarines built for undersea works, the latest in the range of Comex's innovative submarines, the "Remora 2000" combines the functions and instrumentation of an oceanographic subsea vessel with eye catching design of a recreational submarine. Now, ROV's replace more and more the diver on oil subsea offshore fields.

Decompression↗
PubMed1989

[Decompression of deep divers].

For industrial saturation dives over 50 m, Heliox (He-O2) is now used routinely as respiratory gas mix. The decompression after such dives has been investigated thoroughly as well on the animal (minipig, monkeys) as on humans. Results show that for a given ascending speed, the number of bubbles detectable by the Doppler method in the bloodstream rises according to the maximal depth. The incidence of decompression accidents follows the same trend. This finding prompted us to adopt since 1979 slower decompression speeds. Moreover we modified the ascension profile, using henceforth a linear decompression in maintaining a constant speed for a given partial oxygen pressure. For our research program Hydra, we replaced in part Helium by Hydrogen in the respiratory gas mix. We were thus able to do the first hydrogen saturation decompression between 450 and 200 meters, during our Hydra V (1985) experiment. During our following diving research program Hydra VI (1986), 8 divers were decompressed under Hydreliox (H2-He-O2) mix from 500 to 300 m by eliminating hydrogen by chemical means. We used for this purpose a dehydrogenation apparatus developed by our engineering team. These decompressions took place without any difficulty and only a low number of bubbles detected. It is therefore possible to use decompression speeds for hydrogen and helium which are very similar. A confirmatory experiment on mice, where we exposed them to a 2000 m depth dive under Hydreliox (H2-He-O2), gave good results. This gives us the possibility, to perform gas exchange studies on small animals and to extrapolate the results to humans.

Animals↗
PubMed1987

Effects of exponential compression curves with nitrogen injection in humans.

Two series of experiments were carried out on humans to study the effects of fast and slow exponential compression curves with N2 additions. Eight subjects in the first series and 13 subjects in the second series were analyzed up to the depths of 400-450 m of seawater (msw). The data indicated that injections of N2 in He-O2 mixture reduced or suppressed the hyperbaric tremor in the two series. Electroencephalographic (EEG) changes were recorded with the two types of compression, but these changes (increase in slow waves, decrease in alpha-activity, appearance of microsleep EEG traces) were more important with the fast exponential compression curves between 200 and 300 msw than with the slow exponential curves. The effects of the fast rates of compression on EEG activities were not compensated by addition of 4-5% N2. Consequently, the fast exponential compression curves, even with N2 injections, cannot be used without risk and must be avoided; the slow exponential compression curve with N2 injection allowed a human subject to reach 450 msw in satisfactory condition, i.e., without tremor and with light EEG changes.

Brain↗
PubMed1984

Effects of addition of nitrogen during rapid compression of baboons.

A series of dives was carried out to depths of 600 and 800 m seawater (msw) using baboons (Papio papio). Experiments were designed to study the effects of compression and the use of a He-N2-O2 gas mixture on high-pressure nervous syndrome (HPNS). When N2 was added to the He-O2 mixture at the beginning of a linear compression (200 msw/h), the symptoms associated with HPNS were still seen; in addition, the electroencephalogram (EEG) changes were more severe than those seen without N2. By use of an identical mixture, a 2-h exponential compression to 600 msw produced less severe signs of HPNS than the nonexponential profile. By use of a 2-h exponential compression to 600 msw and with addition of N2 at the end of compression, the HPNS that had been started under the He-O2 mixture decreased. Progressive addition of N2 during compression reduced the behavioral signs of HPNS without further EEG changes. These results show that the action of N2 is more complex than can be explained by a simple narcotic pressure antagonism and that the HPNS differed according to the gas mixture used.

Animals↗
PubMed1984

HPNS of baboons during helium-nitrogen-oxygen slow exponential compressions.

From the results obtained with the experimental series CORASIN (fast compression with He-N2-O2), a method of compression has been developed for the baboon (Papio papio) to dive deeper than 600 m. This method utilizes an exponential compression profile with stages of 40 min every 100 m and with the introduction of N2 before each stage from 200 m onward to maintain a concentration of 5.5%. Between 0 and 800 m, this procedure did not produce myoclonus or epileptic seizures; tremor appeared beyond 400 m (578 +/- 109 m) but remained slight. If N2 was not introduced, the tremor appeared earlier (266 +/- 52 m) and became severe; between 600 and 800 m, muscular hypertonus, myoclonus, and muscular cramps occurred. The modifications of the electroencephalogram were slight; the increase in slow activity did not exceed 300% with or without N2. Beyond 800 m, the compression procedure with N2 injections revealed new phenomena. There was a general depression of EEG activity starting at 800 m; from 1,000 m and deeper, there were periods of motor disturbances (hypertonus, spasms, and shaking), palpebral clonus, and eye movements associated with peak EEG activities localized in the posterior region of the skull that sometimes evolved toward an epileptic seizure localized in this region. These symptoms differed from the classical description of high-pressure nervous syndrome, which comprises an increase in tremor followed by convulsions. These differences may perhaps be linked to our compression procedure using N2 injection, to the effect of the pressure itself, or to a combination of the two.

Animals↗
PubMed1979

Correlation between decompression sickness and circulating bubbles in 232 divers.

Doppler monitoring examinations were carried out during 67 simulated helium-oxygen dives in the pressure chambers of the Centre d'Etudes Hyperbares (CEH) COMEX Marseille, and involved a total of 232 COMEX professional divers. Three to five detections were done in each 24-h period, each consisting of an observation at rest and an observation after deep knee bends. Recordings of the Doppler signals were subsequently analyzed by experienced listeners and graded according to the system described by Spencer and Johanson (1974). The two vestibular decompression accidents in this series were associated with bubble scores of grade 3 at rest; one occurred during the rapid initial phase of a bounce dive decompression and the other after return to the storage depth after an excursion dive. Twenty-five cases of muscular or joint pains were observed. A higher incidence of this type of problem was found with higher bubble grades in general, although it was not possible to predict pain.

Adult↗
PubMedDate not supplied

Heart rate responses during a breath-holding competition in well-trained divers.

The diving response elicited by breath-holding (BH) and immersion mainly consists of bradycardia, decreased cardiac output, and peripheral vasoconstriction. These responses reduce oxygen consumption and thereby prolong the duration of the dive. They may also lead to cardiac arrhythmias or hypoxia, however, which in turn may play a role in the occurrence of syncope during BH. The aim of the present study was to analyze the cardiac responses to prolonged breath-holding in elite divers during a competition. Heart rate behaviour and the incidence of arrhythmia were recorded in 16 well-trained breath-hold divers (BHD) using a cardio-frequency meter (for 15 divers) and a Holter (for one diver) during maximal static breath-holding. Anthropometric, spirometric, and training characteristics such as percentage of body fat, pulmonary volumes and years of BH training were also determined. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV (1)) were higher than the predicted values (+7.7%, p<0.05 and+6.6%, p<0.05, respectively). During the static BH, divers presented apneic bradycardia (-44%) correlated with static BH times (p<0.05); this was associated with cardiac arrhythmias (supraventricular extrasystoles and ventricular extrasystoles) in the Holter-equipped subject. These results are in agreement with those obtained in laboratory conditions and confirm the existence of cardiac arrhythmias in well-trained BHD.

Adaptation, Physiological↗