[abstract] CHANGES IN CARDIAC AUTONOMIC NERVOUS FUNCTION AND STRESS HORMONES DURING HELIOX SATURATION DIVES TO 4.5Mpa.

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[abstract] CHANGES IN CARDIAC AUTONOMIC NERVOUS FUNCTION AND STRESS HORMONES DURING HELIOX SATURATION DIVES TO 4.5Mpa.

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Title: [abstract] CHANGES IN CARDIAC AUTONOMIC NERVOUS FUNCTION AND STRESS HORMONES DURING HELIOX SATURATION DIVES TO 4.5Mpa.
Author: Nakabayashi, K; Hirayanagi, K; Ohiwa, H; Ohtsuka, H
Abstract: BACKGROUND: It is well known that hyperbaric bradycardia is an obvious concern regarding autonomic cardiovascular function due to hyperoxia associated with saturation diving. Saturation diving places mental stress on divers, therefore, a sympathetic nervous function is activated. Thus, we studied the functional changes of autonomic nerve and stress hormones during saturation diving. MATERIALS AND METHODS: Heliox dry saturation dives to 4.5 MPa (440 msw) were conducted three times using six healthy divers each in 2004, 2005, and 2006. Heart rate (HR), systolic and diastolic arterial pressure (SAP, DAP), and salivary cortisol and cromogranin A (CgA) of 18 divers were measured in a horizontal supine position at 14 junctures of time during five different dive periods: pre-dive (control), compression, saturation (bottom), decompression, and post-dive. High- and low-frequency power spectra (HF, LF) and the ratio of LF/HF were calculated from 5 min R-R intervals of ECG under a respiration rate controlled at 15 breaths/min. RESULTS: Although HF, an index of cardiac parasympathetic activity, showed a significant increase during the compression period, HR, LF/HF, SBP, and DBP did not show significant changes compared with the pre-dive control values. While HF decreased, HR and LF/HF increased during the decompression and post-dive periods. While salivary cortisol showed a significant decrease during the post-dive period, salivary CgA showed a significant increase after one week from the start of the post-dive period. CONCLUSIONS: The present study, with a comparatively large sample size, indicates that the cardiac parasympathetic nervous system is the primary modulator of hyperbaric bradycardia and is clearly manifested in the compression period. Tachycardia was observed during the decompression and post-dive periods probably due to the dominant cardiac sympathetic nervous system. Most of these post-dive phenomena continued for at least two weeks after the return to normobaric daily living. Responses in salivary cortisol and CgA do not quite collaborate each other during the post-dive period.
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 14-16, 2007. Ritz-Carlton Kapalua Maui, Hawaii (http:www.uhms.org)
URI: http://archive.rubicon-foundation.org/5200
Date: 2007

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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