Acute Biochemical, Cardiovascular, and Autonomic Response to Hyperbaric (4 atm) Exposure in Healthy Subjects

Abstract

The aim of this study was to explore the effect of a hyperbaric environment alone on the cardiovascular system by ensuring elimination of factors that may mask the effect on hyperbaria. The research was performed in a hyperbaric chamber to eliminate the effect of physical activity and the temperature of the aquatic environment. Biochemical analysis and examination with the Task Force Monitor device were performed before and immediately after exposure. TFM was used for noninvasive examination of the cardiovascular system and the functional evaluation of the autonomic nervous system. Natriuretic peptides were measured as biochemical markers which were involved in the regulation of haemodynamic circulation vasoconstriction (urotensin II). L-arginine acted as a precursor of the level of the nitric oxide whereas angiotensin II and angiotensin (1–7) were involved in cardiac remodeling. The study group is comprised of 18 volunteers who were professional divers of similar age and experience. The results shown in our biochemical studies do not exceed reference ranges but a statistically significant increase indicates the hyperbaric environment is not without impact upon the human body. A decrease in HR, an increase in mBP, dBP, and TPR, and increase in parasympathetic heart nerves activity suggest an increase in heart afterload with a decrease in heart activity within almost one hour after hyperbaric exposure. Results confirm that exposure to a hyperbaric environment has significant impact on the cardiovascular system. This is confirmed both by changes in peptides associated with poorer cardiovascular outcomes, where a significant increase in the studied parameters was observed, and by noninvasive examination.

Exposure to a mild hyperbaric oxygen environment elevates blood pressure

“…HBO at 4 atm for 30 min induced a decreased HR, increased mean BP, DBP, and total peripheral resistance almost 1 h after hyperbaric exposure with 4 ATA. This suggests a rise in heart afterload with decreased heart activity, including HR and contractility 25) . In addition, oxygen exposure at 500 kPa induced increased peripheral vascular resistance in rats 30) .…”

“…In the present study, the increased heart afterload may have been induced by MHO, despite the relatively lower ATA and oxygen than in the HBO condition. Previous studies have investigated the effects of HBO under 2-4 ATA with or without 100% oxygen on BP [25][26][27]30) , although there are no available data on the effects of MHO on BP.…”

“…Additionally, exposure to MHO has recently attracted public attention globally, because it may be an effective method for recovery after training or conditioning for sports 22) , or for anti-aging of skin 23) , however, the detailed changes in the cardiovascular system after exposure to MHO are unclear. Exposure to HBO or MHO induces an increased peripheral oxygen saturation (SpO 2 ) level and a decreased heart rate (HR) 14,24,25) , although a consistent view of the effects of HBO or MHO on BP has not yet been obtained. In a previous study, within almost an hour after hyperbaric exposure at 4 atm for 30 minutes (min), the mean BP and diastolic BP (DBP) increased 25) .…”

“…Exposure to HBO or MHO induces an increased peripheral oxygen saturation (SpO 2 ) level and a decreased heart rate (HR) 14,24,25) , although a consistent view of the effects of HBO or MHO on BP has not yet been obtained. In a previous study, within almost an hour after hyperbaric exposure at 4 atm for 30 minutes (min), the mean BP and diastolic BP (DBP) increased 25) . Conversely, 20 sessions of repeated HBO treatment (HBOT) under 2.5 ATA with 100% oxygen for 90 min decreased systolic BP (SBP) in patients with chronic wounds requiring HBOT 26) .…”

Decrease in Angiotensin-Converting Enzyme activity but not concentration in plasma/lungs in COVID-19 patients offers clues for diagnosis/treatment

“…16,36,40 In addition, Ang (1-7) is not exclusively generated by ACE2 but through other enzymes as well. 41,42 Although Ang (1-7) level in human plasma is diverse, ranging from pg/mL to ng/mL, [43][44][45] significantly reduced Ang (1-7) was observed in COVID-19 patients compared with controls. These findings point toward dysregulated RAS metabolic pathways as the cause for the suppressed enzyme activity.…”