Biomedical subjects

Bernard Gardette

Publications and source records attributed to Bernard Gardette.

2 recordsLinked to original sources

PubMed2006

Activity-based rate-adaptive pacemakers under hyperbaric conditions.

OBJECTIVES: The aim of this study was to test a variety of currently available activity-based rate-adaptive pacemakers under hyperbaric conditions. BACKGROUND: Sports divers with pacemakers can dive under certain circumstances. The rate response of activity-sensing pacing under hyperbaric conditions has rarely been evaluated. MATERIALS AND METHODS: We manufactured a miniaturized hyperbaric chamber. A pacemaker inside was kept close to the corresponding telemetry wand placed on top of the chamber. An inflation device for coronary balloon angioplasty was used to create hydraulic pressure. Group I pacemakers were exposed to a 30 msw/98 fsw/4 ATA and after a 1-month waiting period to 60 msw/197 fsw-depth/7 ATA. Group II was exposed to only one dive to 60 msw. The electrogram and event marker telemetry were used to monitor the pacing stimuli and measurements were made for case distortion. RESULTS: The baseline pacing rate did not change in 27 tests. Return to baseline was shown during 18 tests after transient sensor-driven rate. There was a sensor rate response to manual brief shaking during and following testing. A case distortion was shown in 15 of 29 tests at 60 m. CONCLUSIONS: Modern accelerometers showed no sensitivity to pressure on the pacemaker can at 30 msw/98 fsw and 60 msw/197 fsw but in some devices responded to pressure changes. There was no pacing dysfunction or suppression of the sensor response despite the high incidence of case distortion at 60 msw/197 fsw. As a general rule, diving should not be allowed at depths greater than 20 msw/65 fsw.

Diving↗

PubMed2005

Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops.

OBJECTIVES: The French Navy uses the Marine Nationale 90 (MN90) decompression tables for air dives as deep as 60 msw. The resulting incidence of decompression sickness (DCS) for deep dives (45-60 msw) is one case per 3000 dives. METHODS: Three protocols with experimental ascent profiles (EAPs) were tested in the wet compartment of a hyperbaric chamber. For each protocol, eight subjects dove to 50 or 60 msw and ascended according to the standard MN90 table or an EAP. Precordial bubbles were monitored with Doppler sensors at 30-min intervals after surfacing. Protocol I went to 60 msw and used deep stops beginning at 27 msw. Protocol II was a repetitive dive to 50 msw with a 3-h surface interval; the EAP made the first deep stop at 18 msw. Protocol III again went to 60 msw, but the EAP used a single, shorter deep stop at 25 msw. RESULTS: For Protocol I, all divers developed bubbles at Spencer grade 2-3 and still had bubbles 120 min after surfacing; there was no statistical difference between bubbling for the MN90 and EAP, but one diver presented a case of DCS after the EAP. For Protocol II, the EAP produced severe bubbling for the eight divers. Those findings led to stopping the EAPs with the longer deep stops used in Protocols I and II. Protocol III again showed no difference between the standard and modified profiles. DISCUSSION: The addition of deep stops requires careful consideration. Two of our EAPs made no difference and one produced increased bubbling.

Adult↗