Autonomic and Cognitive Function Response to Normobaric Hyperoxia Exposure in Healthy Subjects. Preliminary Study

Abstract

Background and objective: This is the first study to investigate the effect of high-flow oxygen therapy, using a normobaric chamber on cognitive, biochemical (oxidative stress parameters and the level of neurotrophins), cardiovascular and autonomic functioning. Materials and methods: 17 healthy volunteers, eight males and nine females, with a mean age of 37.5 years, were examined. The experimental study involved ten two-hour exposures in a normobaric chamber with a total pressure of 1500 hPa, in air adjusted to 37% oxygen, 1.079% carbon dioxide and 0.44% hydrogen. Cognitive function was assessed by using Trail Making Test parts A, B and difference in results of these tests (TMT A, TMT B and TMT B-A); California Verbal Learning Test (CVLT); Digit symbol substitution test (DSST); and Digit Span (DS). Fatigue (Fatigue Severity Scale (FSS)), cardiovascular, autonomic and baroreceptor functioning (Task Force Monitor) and biochemical parameters were measured before and after intervention. Results: After 10 sessions in the normobaric chamber, significant decreases in weight, caused mainly by body fat % decrease (24.86 vs. 23.93%, p = 0.04 were observed. TMT part A and B results improved (p = 0.0007 and p = 0.001, respectively). In contrast, there was no statistically significant influence on TMT B-A. Moreover, decrease in the number of symbols left after a one-minute test in DSST was noted (p = 0.0001). The mean number of words correctly recalled in the CVLT Long Delay Free Recall test improved (p = 0.002), and a reduction in fatigue was observed (p = 0.001). Biochemical tests showed a reduction in levels of malondialdehyde (p < 0.001), with increased levels of Cu Zn superoxide dismutase (p < 0.001), Neurotrophin 4 (p = 0.0001) and brain-derived neurotrophic factor (p = 0.001). A significant increase in nitric oxide synthase 2 (Z = 2.29, p = 0.02) and Club cell secretory protein (p = 0.015) was also noted. Baroreceptor function was significantly improved after normobaric exposures (p = 0.003). Significant effect of normobaric exposures and BDNF in CVLT Long Delay Free Recall was noted. Conclusions: This study demonstrates that 10 exposures in a normobaric chamber have a positive impact on visual information and set-shifting processing speed and increase auditory-verbal short-term memory, neurotrophic levels and baroreceptor function. A response of the respiratory tract to oxidative stress was also noted. There is a need to rigorously examine the safety of normobaric therapy. Further studies should be carried out with physician examination, both pre and post treatment.

Prolonged oxygen exposure causes the mobilization and functional damage of stem or progenitor cells and exacerbates cardiac ischemia or reperfusion injury in healthy mice

“…Unexpectedly, the intracellular ROS level in PBMNCs remained unchanged after oxygen exposure for either 20 or 60 min. The minor changes in arterial blood oxygen concentration in healthy subjects receiving hyperbaric oxygen therapy have been reported in earlier studies (Kujawski et al, 2020; Siński et al, 2016). Although we did not measure the oxygen saturation in mice in this study, we speculated that the harmful effects of prolonged oxygen exposure may not be primarily associated with enhanced oxidative stress to stem/progenitor cells.…”

“…Several past studies have shown the beneficial effects of oxygen administration to patients with critical disorders (Bourke et al, 2018; Golledge & Singh, 2019; Jaber et al, 2016; Levy et al, 2016; Martin & Grocott, 2013; Moradkhan & Sinoway, 2010; Renda et al, 2018; Rockswold et al, 2013; Weaver et al, 2002) as well as to healthy individuals, such as athletes (Ishii et al, 2005; Kujawski et al, 2020). Conversely, the issue of oxygen toxicity is also well known, as molecular oxygen induces cell damage directly or indirectly by interacting with other free radicals (Ciarlone et al, 2019; Frank et al, 1978; Kuksal et al, 2017; Matute‐Bello et al, 2008; Ramani et al, 2019).…”

“…Several past studies have shown the beneficial effects of oxygen administration to patients with critical disorders (Bourke et al, 2018;Golledge & Singh, 2019;Jaber et al, 2016;Levy et al, 2016;Martin & Grocott, 2013;Moradkhan & Sinoway, 2010;Renda et al, 2018;Rockswold et al, 2013;Weaver et al, 2002) as well as to healthy individuals, such as athletes (Ishii et al, 2005;Kujawski et al, 2020).…”

Exploring Hyperoxia Effects in Cancer—From Perioperative Clinical Data to Potential Molecular Mechanisms

“…Hyperoxia increases ROS and activates cell defence systems in order to keep ROS within physiological range, as previously discussed. BDNF is one of the molecules that are upregulated in response to hyperoxia exposure, as shown in various experimental settings, including the peribronchial smooth muscle of neonatal rats [ 95 ], the Alzheimer mouse model [ 96 ], the breast cancer mouse model [ 93 ] and healthy volunteers [ 97 ]. Interestingly, some healthy volunteers enrolled in the study [ 97 ] resigned due to the side effects, although the tested oxygen concentration was only 37% O 2 .…”

“…BDNF is one of the molecules that are upregulated in response to hyperoxia exposure, as shown in various experimental settings, including the peribronchial smooth muscle of neonatal rats [ 95 ], the Alzheimer mouse model [ 96 ], the breast cancer mouse model [ 93 ] and healthy volunteers [ 97 ]. Interestingly, some healthy volunteers enrolled in the study [ 97 ] resigned due to the side effects, although the tested oxygen concentration was only 37% O 2 . BDNF and its main receptor, tropomyosin receptor kinase B (TrkB) have been reported to promote alveolar epithelial regeneration after lung injury [ 98 ] or to exert neuroprotective effects [ 99 , 100 , 101 , 102 , 103 , 104 ].…”