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Transiently augmented endothelium dependent vasodilatory capacity following repeated 6‐hour air dives
Author(s) -
Morgan Richard Garrett,
Bergeron Elizabeth,
Shykoff Barbara E,
Florian John P.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.763.15
Subject(s) - medicine , vasodilation , repeated measures design , reactive hyperemia , anesthesia , heart rate , blood pressure , cardiology , statistics , mathematics
Background Military divers routinely participate in operations that involve long duration (≥ 6hr) air dives at shallow (≤ 60 FSW) depths that are repeated daily until mission completion. These dive operations have been linked to impairments in aerobic exercise performance and orthostatic tolerance after egress from the water. Alterations in endothelium‐dependent vasodilation and blood flow may play a role in cardiovascular dysfunction associated with long duration repeated air dives. Methods To test this unexplored hypothesis, we measured reactive hyperemia index (RHI), mean arterial pressure (MAP) and resting heart rate (RHR) using the Endo‐PAT2000 plethysmographic peripheral arterial tone (PAT) device in 11 military divers (21–40y) before and after single 6hr air dives at 15 FSW and 6hr air dives at 15 FSW repeated daily for four days. We compared pre and post RHI, MAP and RHR from a single dive and between repeated dives. Results We found no differences in RHI, MAP or RHR following completion of a single 6hr air dive at 15 FSW (all P ≥ 0.39). Over the course of four dives repeated daily, we found a main effect of dive day for RHI ( P = 0.03), such that pre‐ and post‐dive RHI increased by at least 30% between dives one and three, but returned to baseline by dive four. There was no effect of dive on RHI, determined by pre‐ and post‐dive testing, during each dive day ( P = 0.26). We found no effect of dive or dive day on MAP (all P ≥ 0.15); however, pre‐dive RHR was 4–6 bpm higher on the fourth dive day than the second and first day (all P < 0.01), and post‐dive RHR was ~4 bpm lower than pre‐dive RHR across all dive days ( P < 0.02). Conclusions These findings demonstrate that repeated shallow air dives lead to transiently augmented vasodilatory capacity with a parallel increase in RHR. Increased RHI may help maintain perfusion to the periphery following immersion‐induced diuresis and subsequent reductions in blood volume, while a compensatory increase in RHR occurs to maintain mean arterial pressure. Support or Funding Information NAVSEA DSBDP and ONR