Hyperbaric oxygen increases parasympathetic activity in professional divers.
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), O(2) 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.
Lund
V
V
Department of Anaesthesiology, Turku University Hospital, Turku, Finland.
Kentala
E
E
Scheinin
H
H
Klossner
J
J
Sariola-Heinonen
K
K
Jalonen
J
J
D000704:Analysis of Variance; D001146:Arrhythmia, Sinus / Q000503:physiopathology*; D001274:Atmospheric Pressure; D004242:Diving / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006931:Hyperbaric Oxygenation; D008297:Male; D010275:Parasympathetic Nervous System / Q000502:physiology