Hyperbaric oxygen increases parasympathetic activity in professional divers

Authors:
  • EKE Kentala
    E Kentala
  • JKJ Klossner
    J Klossner
  • SHSariola‐ Heinonen
    Sariola‐ Heinonen
  • JJJ Jalonen
    J Jalonen
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Abstract
The role of autonomic nervous system in hyperoxic bradycardia was evaluated by using the power‐spectral analysis of heart‐rate variability (HRV). Ten professional divers went through two hyperbaric hyperoxic experiments: (1) hyperbaric oxygen (HBO), 100% oxygen at 2.5 ATA, (2) hyperbaric air (HBAIR), O2 21% at 2.5 ATA. Four‐minute traces of ECG were registered and subjected to power‐spectral analysis. Cardiac conduction parameters were evaluated by a diagnostic 12‐lead ECG and arrhythmias by a continuous 3‐lead ECG. Statistical analysis was made using analysis of variance for repeated measurements. Heart rate decreased (P < 0.001), but the response was similar during both treatments (P=0.14). Total power increased significantly more during HBO than HBAIR (P=0.003). High‐frequency (HF) power (P < 0.001), Hayano’s index (P=0.001) and normalized units of HF power (P=0.002) increased and LF/HF index (P < 0.001) decreased more during HBO than HBAIR. There were no changes in cardiac conduction or incidence of arrhythmias. In conclusion, 100% oxygen at 2.5 ATA caused marked increase in parasympathetic tone compared with 21% oxygen at 2.5 ATA.

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