Impact Of Repeated, Hyperoxic Exercise Dives On Pulmonary Force Production Before And After Endurance Runs

Abstract

Few studies have described maximal inspiratory/expiratory pressures (MIP/MEP) following hyperoxic dives. PURPOSE: Quantify changes in pulmonary force production pre- and post- run-to-fatigue before, after, and 72 hr post single and consecutive 6-hr hyperoxic exercise dives. METHODS: 14 military trained divers (age 30.6 ± 2.2 yrs) performed a single 6-hr dive (SD) and five consecutive 6-hr dives with 18-hr surface intervals (DW) breathing 100% oxygen at 1.35 ATA while alternating between 30-minute rest and exercise periods. An 85% V̇O2max endurance run was performed three days before SD and DW (PRE), within 2 hrs (2-POST) and 72 hrs (72-POST) after SD or dive 5 of DW. Three trials of MIP/MEP were recorded before and after each run. Data were analyzed using a 2 (Run: pre/post run) x 3 (Diving: PRE, 2-POST, 72-POST) repeated measures analysis of variance (ANOVA) with significance set at p < 0.05. Data presented as mean ± SEM. RESULTS: There was a significant main effect of the run on MIP for both SD (pre-run: -116.5 ± 0.8 cm H2O vs. post-run: -111.5 ± 0.5 cm H2O, p = 0.016) and DW (pre-run: -118.2 ± 1.3 cm H2O vs. post-run: -111.1 ± 0.5 cm H2O, p = 0.034). There was no main effect of diving or run x diving interaction on MIP for SD or DW. There was a significant main effect of the run on MEP (pre-run: 150.2 ± 4.4 cm H2O vs post-run: 144.6 ± 3.9 cm H2O, p = 0.032), and a significant main effect of diving (Pre-dive: 154.7 ± 5.8 cm H2O vs 2-POST: 140.4 ± 6.4 cm H2O vs 72-POST 147.1 ± 5.8 cm H2O p = 0.002). DW post-test analysis showed that 2-POST pre-run (143.2 ± 9.4 cm H2O, p < 0.001), 2-POST post-run (137.6 ± 9.1 cm H2O, p < 0.001), 72-POST pre-run (149.0 ± 8.4 cm H2O, p = 0.015), and 72-POST post-run (145.2 ± 8.3 cm H2O, p < 0.001) were significantly lower than PRE pre-run MEP (158.4 ± 8.4 cm H2O). There was no significant difference compared to PRE post-run (151.1 ± 8.3 cm H2O). There were no significant main effects or interactions for MEP during SD. There were no significant correlations between percent change in run time and percent change in MIP or MEP. CONCLUSION: Reductions in expiratory, but not inspiratory, force following repeated, long-duration hyperoxic immersions suggests repetitive 100% O2 exposure differentially affects expiratory force production, potentially due to hyperoxia-induced impairment of expiratory muscle contraction. Funded by ONR and NAVSEA DSBD