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. 2022 Jan 30;5:79–82. doi: 10.1016/j.crphys.2022.01.007

Oxygen-enriched air reduces breathing gas consumption over air

JD Schipke a,∗, A Deussen b, F Moeller c, U Hoffmann c, T Muth d, A Zenske e, A Koch f
PMCID: PMC9743045  PMID: 36518885

Abstract

Owing to the unfamiliar environment, recreational and professional diving is confronted with several challenges. Usage of self-contained under-water breathing apparatuses during the dive provides the indispensable breathing gas supply for the diver. Instead of air, oxygen-enriched breathing gases (EANx or nitrox) are used with increasing frequency. Unfortunately, their usage implies negative effects because the elevated oxygen partial pressure (pO2) increases oxidative stress. As a result, the increased formation of reactive oxygen species exerts negative effects on the central nervous system, lungs, vasculature and eyes. However, these disadvantages can be avoided if appropriate rules are followed, e.g. a pO2<1.4 bar. EANx breathing gases have, on the other hand, major advantages as they help reducing narcotic nitrogen effects and bubble formation.

Several land-based studies had proven a reduced ventilation of exercising subjects if EANx was used instead of air. As breathing gas is the most valuable under-water good, we wanted to translate the on-land results into under-water results. Appropriate studies now demonstrate a novel EANx property as under-water ventilation is also reduced with EANx. In this short communication, we present this additional advantage of EANx-breathing. This benefit seems to be of particular importance as it delays unforeseen running-out-of-gas and thus, contributes to further improving diving safety.

Keywords: Exercise, Ventilation, Diving, Hyperoxia

Highlights

  • •

    Several ‘on-land’ studies had proven a reduced ventilation of exercising subjects in hyperoxia.

  • •

    As O2-enriched breathing gas (ANx) is increasingly used published on-land results were translated into under-water results.

  • •

    We demonstrate a novel EANx characteristic as under-water ventilation is also reduced with EANx compared with using air.

  • •

    This benefit is seemingly of importance as it delays unforeseen running-out-air. It thus contributes to diving safety.

1. Oxygen-enriched air

Possibly, Henry Fleuss made in 1874 what was the first oxygen-enriched air (=EANx or nitrox) dive using a rebreather (Lang, 2006). More than 100 years later, teaching nitrox use for recreational diving was begun in spite of heavy scepticism by the diving community. Still, the British Sub-Aqua Club started in 1995 nitrox training (Allen, 1996). More than 25 years later, nitrox has become the second most-used breathing gas besides air in recreational diving (Möller et al., 2021). Hence, quite a few effects of EANx on professional and recreational divers are well described.

In consequence to the increased oxygen partial pressure (pO2), oxidative stress exerts acute negative effects on the lungs (Doering et al., 2018) (Zenske et al., 2019) that are reversible (Tetzlaff and Thomas, 2017) (Castagna et al., 2019). In line, regular diving with nitrox at shallow depths over a 3-yr period did not impair pulmonary function (Fitzpatrick and Conkin, 2003). Conversely, oxidative stress could ultimately lead to non-reversible pulmonary pathological changes (van Ooij et al., 2013).

Oxidative stress has also been postulated to importantly contribute to central nervous system (CNS) oxygen toxicity (Kot et al., 2003). During dives a pO2 > 1.4 bar can ultimately lead to unconsciousness and convulsions (Harabin et al., 1995), while convulsions at a pO2 < 1.3 bar have not been reported (Arieli et al., 2002). Yet, factors like physical activity might modify the susceptibility towards CNS oxygen toxicity (Koch et al., 2013).

One other target constitutes the vascular system. Already a single air dive causes transient endothelial dysfunction (Culic et al., 2014). Expectedly, the flow mediated dilatation was significantly reduced after nitrox diving and after HBO-therapy, thus, arterial stiffness was increased (Marinovic et al., 2012) (Zenske et al., 2019) (Wunderlich et al., 2017).

Among other organs, the eyes can also be affected, and divers should be aware of the risk of lenticular oxygen toxicity when conducting intensive diving with a PO2 between 1.3 and 1.6 ATM. (Butler et al., 1999) (Brügger et al., 2020).

In contrast, the decreased partial nitrogen pressure (pN2) of nitrox exerts beneficial effects, particularly with respect to reducing N2 bubble formation after simulated (Souday et al., 2016) and real dives (Marinovic et al., 2012) (Brebeck et al., 2018), thereby reducing the risk of decompression sickness. In addition, nitrox could protect against decreased neuro-cognitive performance induced by inert gas narcosis (Germonpre et al., 2017) (Lafere et al., 2019) (Rocco et al., 2019), and so help to maintain alertness and memory (Brebeck et al., 2017). Thus, nitrox could be the breathing gas of choice in situations with the need for precise decisions or accurate assessments and actions.

In the following, one novel beneficial effect of nitrox breathing will be presented.

2. Breathing gas consumption

Minute ventilation (V̇E) is a crucial factor for both the duration and safety of a dive, and sudden running-out-of-gas is one among other factors associated with diving fatalities (Vann and Lang, 2011). Such a dangerous situation might develop due to an unexpectedly high ventilation during fin-swimming at depth and might result in an emergency ascent and severe diving accident. One other factor is mentioned that exposes the diver to a risk and is related to ventilation, as well. Some of the divers perform skip breathing to conserve their breathing gas and try to dive as long as possible with their limited gas supply. However, due to prolonged dive times, the risk of decompression increases. In addition, CO2 is retained, and the increased CO2 levels might lead to CNS oxygen toxicity (Arieli et al., 2014).

To answer the question, whether hyperoxia has any effect on V̇E, results from land-based studies are presented, first.

In an older, extremely worth reading review article on V̇E, the author concludes:

‘… the data appear to indicate that in animal experiments respiratory minute volume is diminished by breathing O2; the same may be expected to be true for man but the data … are not unequivocal and for this one may perhaps question to what extent, if any, psychological factors may be responsible’ (Bean, 1945).

In a more recent meta-analysis on the same topic, 40 manuscripts on the effects of acute hyperoxia on healthy subjects exercising on land on bicycle or treadmill ergometers were analysed. If oxygen in the breathing gas was enriched by 30% or more exercise performance was increased (Mallette et al., 2018). However, in these studies the breathing gas supply was not in the focus. Because of this, any effects of hyperoxia on V̇E remained unreported.

Thus, some single studies are presented to underline the ergogenic effects of hyperoxia by providing different parameters of performance and V̇E in particular. One such parameter is time to exhaustion that is prolonged by hyperoxia (Adams and Welch, 1980) (Plet et al., 1992) (Ohya et al., 2016) (Mallette et al., 2018), Likewise, endurance was increased (Amann et al., 2008) together with the maximal power output (Ulrich et al., 2017) (Manselin et al., 2017). Other results would suggest an increased maximal aerobic power (Manselin et al., 2017), and a delayed onset of anaerobic metabolism, respectively (Miyamoto and Niizeki, 1995). Finally, while exercising and breathing EANx, V̇E was decreased compared with matched loads and breathing air (Miyamoto and Niizeki, 1995) (Ulrich et al., 2017). Similar reductions in V̇E were also reported from handgrip exercise during hyperoxia (Pokorsko et al., 1990). As a consequence of a reduced V̇E at comparable work loads in hyperoxia and normoxia, dyspnoea perception was less during hyperoxia (Chronos et al., 1988) (Ulrich et al., 2017).

A quite different study from the professional world is added. Firefighters performed submaximal work employing self-contained breathing apparatuses. Breathing EAN40 compared with air, reduced V̇E by 10% together with a reduced perceived breathing distress (Eves et al., 2002).

The beneficial hyperoxic effects on V̇E and power output in healthy subjects might also apply to patients with pulmonary diseases. During exhausting leg work, asthmatics inhaled either air or 100% oxygen, the latter producing significantly less obstruction and a lower V̇E (Resnick et al., 1979). Similarly, V̇E in COPD patients was significantly less when breathing 100% oxygen than when breathing air during exercising on the same work load (Scano et al., 1982). In another group of COPD patients, hyperoxia clearly improved exercise endurance (O'Donell et al., 2001). In patients with interstitial lung disease (ILD), exercise-induced increases in V̇E were attenuated by breathing 100% oxygen during exercise testing, demonstrating both a decreased ventilatory drive and an increased efficiency at achieved work loads (Cournoyer et al., 2020). These results suggest that hyperoxia could enhance the ability of patients with pulmonary diseases to train at higher work loads, resulting in more effective rehabilitation.

3. Increased pO2 and V̇E

Studies on the effects of increased pO2 values on V̇E in the context with diving are scarce. In one own study, volunteers performed exercise during dry dives in a hyperbaric chamber. At comparable workloads, V̇E at an ambient pressure of 3 bar (pO2 = 0.63 bar) was about 20% lower than at 1 bar (Kramkowski et al., 2021). In another study, divers performed exercise in the wet part of a hyperbaric chamber at 1 bar and 4.7 bar (pO2 = 1.0 bar). Hyperoxia under these circumstances reduced V̇E by roughly 15% compared with normoxia (Peacher et al., 2010). It is mentioned that in contrast with these two studies, pO2 in EANx gases is not elevated due to the increased ambient pressure but due to the O2 enrichment.

Inspired by the latter two studies, two own studies were performed. (1) Recreational divers performed 40-min open-water dives to 25 m depth using air or EAN40. Apart from better preserved cognitive properties, V̇E was significantly reduced by 12% with the hyperoxic breathing gas (Zenske et al., 2019). (2) To underscore the latter results, an earlier study with recreational divers under on-land conditions is cited. In an underwater ergometry system, scuba divers needed to fin-swim within a hexagonal parcours at a depth of 4 m with incrementally increased velocities until exhaustion (Steinberg et al., 2011). In concert with our previous study, V̇E with EAN40 on the higher velocities was significantly reduced by 20% compared with air (Möller et al., 2021).

4. Mechanisms

Hyperoxic gas mixtures improve exercise tolerance in humans. In addition, V̇E of these gases is reduced compared with normoxic gases. However, the underlying mechanisms remain unclear: thus, different hypotheses exist that, at least in part, are not convincing.

The O2 consumption during hyperoxic exercise (EAN30) was increased over that during normoxic exercise suggesting changes in skeletal muscle fibre type recruitment or in metabolic response (Prieur F. et al., 2002). This, however, would rather shorten the duration of oxygen availability. Based on similar results but employing EAN60, a shift toward increased fatty acid metabolism in the hyperbaric test was suggested (B. A. Wilson et al., 1975). However, a shift from glucose to fatty acid metabolism reduces the amount of energy produced per mole of oxygen consumed. Another hypothesis suggests that with a decreased V̇E the cost of breathing is decreased resulting from the relative hypoventilation in hyperoxia (G. D. Wilson and Welch, 1980). Breathing work contributes approximately 2% to whole body oxygen consumption under resting conditions and may increase to 20% during very heavy workload (Thews, 1995). Data from our own studies nicely fit into this range: 12% reduction during dives on 25 m (Zenske et al., 2019), 20% reduction during heavy work at hyperbaric conditions (Kramkowski et al., 2021), and 20% during dives at high velocities (Möller et al., 2021). It is therefore not entirely clear, whether this effect can fully account for the observed extension of diving duration. According to a fourth hypothesis, hyperoxia enhances performance through a more efficient pulmonary gas exchange and a greater availability of oxygen to muscles and the brain (cerebral motor and sensory neurons) (Ulrich et al., 2017). Obviously, an improved O2 diffusion to the muscle will delay the metabolic acidosis from lactate accumulation (Miyamoto and Niizeki, 1995). However, enhanced steady state lactate concentrations are expected only at severe workload and therefore would not apply for calm recreational diving. Nevertheless, other studies have reported on decreased lactate accumulation during hyperoxic exercise (B. A. Wilson et al., 1975) (Stellingwerff et al., 2006). In turn, muscle efficiency appears to be already optimized in normoxia and is unlikely to contribute to the well-established improvement in exercise capacity induced by hyperoxia (Layec et al., 2015). Finally, it was described that cerebral oxygenation is limiting the exercise performance. Thus, a better cerebral oxygenation is suggested to be responsible for the improved performance with hyperoxia (Oussaidene et al., 2013). In addition, heart rate is decreased with hyperoxia thereby decreasing myocardial load (Wunderlich et al., 2017). After all, not only one single mechanism might be involved.

5. Conclusion

The roughly 75-year old contention must be rejected that hyperoxia reduces V̇E could be explained by psychological factors (Bean, 1945). Numerous human studies with different degrees of hyperoxia, employing both cycle and treadmill ergometry, have shown reduced V̇E during hyperoxic settings together with beneficial effects on power output, time to exhaustion and dyspnoea perception. Different hypotheses are provided that try to explain the underlying mechanism that might well be not a single one.

Acceptedly, hyperoxia is associated with an increased oxidative stress that might impair the CNS, the lungs and blood vessels of a diver. In case, instructions are followed, e.g. maximum pO2 ≤ 1.4 bar is followed, CNS oxygen toxicity will not become a major challenge. Then, advantages of EANx over air prevail like less narcotic effects, i.e. maintained cognitive performance, less bubble formation, and a better preserved sympathovagal balance.

Although several studies show that diving with EANx supply reduces minute ventilation, the mechanism(s) which may cause this effect are less clear. A potential mechanism may be a reduction of breathing work when supplying a gas with enhanced oxygen fraction. Although our data point in this direction, it is still unclear, whether this reduced breathing work may fully explain the reduction in minute volume. Such a reduction with O2-enriched gases has significant practical implications contributing to increase the safety of SCUBA diving, in particular in delaying unexpected running out-of-gas.

Author contribution

We submit a short communication, where articles are included that were already published earlier. Therefore, we understand that the otherwise useful CRediT author statements do not apply here.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Contributor Information

J.D. Schipke, Email: j.schipke@gmx.org.

A. Deussen, Email: andreas.deussen@tu-dresden.de.

F. Moeller, Email: f.moeller@dshs-koeln.de.

U. Hoffmann, Email: u.hoffmann@dshs-koeln.de.

T. Muth, Email: Thomas.Muth@uni-duesseldorf.de.

A. Zenske, Email: andre.zenske@hotmail.de.

A. Koch, Email: koch@email.uni-kiel.de.

References

  1. Adams R.P., Welch H.G. Oxygen uptake, acid-base status, and performance with varied inspired oxygen fractions. J. Appl. Physiol. 1980;49(5):863–868. doi: 10.1152/jappl.1980.49.5.863. [DOI] [PubMed] [Google Scholar]
  2. Allen C. BSAC gives the OK to nitrox. SPUMS J. (South Pacific Underw. Med. Soc.) 1996;26(3) [Google Scholar]
  3. Amann M., Hopkins W.G., Marcora S.M. Similar sensitivity of time to exhaustion and time-trial time to changes in Endurance. Med. Sci. Sports Exerc. 2008;40(3):574–578. doi: 10.1249/MSS.0b013e31815e728f. [DOI] [PubMed] [Google Scholar]
  4. Arieli R., Eynan M., Ofir D., Arieli Y. Brief screening test of ventilatory sensitivity to CO(2) cannot replace the mandatory test for susceptibility to CNS oxygen toxicity. Mil. Med. 2014;179(8):926–932. doi: 10.7205/MILMED-D-14-00026. [DOI] [PubMed] [Google Scholar]
  5. Arieli R., Yalov A., Goldenshluger A. Modeling pulmonary and CNS O(2) toxicity and estimation of parameters for humans. J. Appl. Physiol.(Bethesda, Md) 2002;92(1):248–256. doi: 10.1152/japplphysiol.00434.2001. 1985. [DOI] [PubMed] [Google Scholar]
  6. Bean J.W. Effects of oxygen at increased pressure. Physiol. Rev. 1945;25(1):1–147. doi: 10.1152/physrev.1945.25.1.1. [DOI] [Google Scholar]
  7. Brebeck A.-K., Deussen A., Range U., Balestra C., Cleveland S., Schipke J.D. Beneficial effect of enriched air nitrox on bubble formation during scuba diving. An open-water study. J. Sports Sci. 2018;36(6):605–612. doi: 10.1080/02640414.2017.1326617. [DOI] [PubMed] [Google Scholar]
  8. Brebeck A.-K., Deussen A., Schmitz-Peiffer H., Range U., Balestra C., Cleveland S., Schipke J.D. Effects of oxygen-enriched air on cognitive performance during SCUBA-diving—an open-water study. Res. Sports Med. 2017;25(3):345–356. doi: 10.1080/15438627.2017.1314289. [DOI] [PubMed] [Google Scholar]
  9. Brügger J.W., Rauscher G.A., Florian J.P. Hyperoxic myopia: a case series of four divers. Undersea Hyper. Med.: J.Undersea.Hyper.Med. Soc.Inc. 2020;47(2):261–265. [PubMed] [Google Scholar]
  10. Butler F.K., White E., Twa M. Hyperoxic myopia in a closed-circuit mixed-gas scuba diver. Undersea Hyper. Med.: J.Undersea.Hyper.Med. Soc.Inc. 1999;26(1):41–45. [PubMed] [Google Scholar]
  11. Castagna O., Bergmann C., Blatteau J.E. Is a 12-h Nitrox dive hazardous for pulmonary function? Eur. J. Appl. Physiol. 2019 doi: 10.1007/s00421-019-04248-w. [DOI] [PubMed] [Google Scholar]
  12. Chronos N., Adams L., Guz A. Effect of hyperoxia and hypoxia on exercise-induced breathlessness in normal subjects. Clinical Science. 1988;74(5):531–537. doi: 10.1042/cs0740531. [DOI] [PubMed] [Google Scholar]
  13. Cournoyer J., Ramos C.F., Sturgill B., Tang F., DeLuca N., Mirsaeidi M., Jackson R.M. Effects of 100 % oxygen during exercise in patients with interstitial lung disease. Respir. Physiol. Neurobiol. 2020;274:103367. doi: 10.1016/j.resp.2019.103367. [DOI] [PubMed] [Google Scholar]
  14. Culic V.C., Van Craenenbroeck E., Muzinic N.R., Ljubkovic M., Marinovic J., Conraads V., Dujic Z. Effects of scuba diving on vascular repair mechanisms. Undersea Hyper. Med. : J.Undersea.Hyper.Med. Soc.Inc. 2014;41(2):97–104. [PubMed] [Google Scholar]
  15. Doering K., Muth T., Cleveland S., Schipke J.D. Effects of recreational tech diving on measures of respiration. N. Z. J. Sports Med. 2018;44:70–76. [Google Scholar]
  16. Eves N.D., Petersen S.R., Jones R.L. The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus. Ergonomics. 2002;45(12):840–849. doi: 10.1080/00140130210159995. [DOI] [PubMed] [Google Scholar]
  17. Fitzpatrick D.T., Conkin J. Improved pulmonary function in working divers breathing nitrox at shallow depths. Aviat Space Environ. Med. 2003;74(7):763–767. [PubMed] [Google Scholar]
  18. Germonpre P., Balestra C., Hemelryck W., Buzzacott P., Lafere P. Objective vs. Subjective Evaluation of cognitive performance during 0.4-MPa dives breathing air or nitrox. Aero. Med. Hum. Perform. 2017;88(5):469–475. doi: 10.3357/AMHP.4608.2017. [DOI] [PubMed] [Google Scholar]
  19. Harabin A.L., Survanshi S.S., Homer L.D. A model for predicting central nervous system oxygen toxicity from hyperbaric oxygen Exposures in humans. Toxicol. Appl. Pharmacol. 1995;132(1):19–26. doi: 10.1006/taap.1995.1082. [DOI] [PubMed] [Google Scholar]
  20. Koch A.E., Koch I., Kowalski J., Schipke J.D., Winkler B.E., Deuschl G., Meyne J., Kahler W. Physical exercise might influence the risk of oxygen-induced acute neurotoxicity. Undersea Hyper. Med. : J.Undersea.Hyper.Med. Soc.Inc. 2013;40(2):155–163. [PubMed] [Google Scholar]
  21. Kot J., Sicko Z., Wozniak M. Oxidative stress during oxygen tolerance test. Int. Marit. Health. 2003;54(1–4):117–126. [PubMed] [Google Scholar]
  22. Kramkowski D., Koch A., Holzum M., Kähler W., Klapa S., Rieger B., Weisser B., Schipke J.D. CAISSON. 15. Wissenschaftliche Tagung der GTÜM; Wiesbaden: 2021. UW-Spiroergometrie-System: messung tauchspezifischer variablen. [Google Scholar]
  23. Lafere P., Hemelryck W., Germonpre P., Matity L., Guerrero F., Balestra C. Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency. Diving.Hyper. Med. 2019;49(2):119–126. doi: 10.28920/dhm49.2.119-126. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Lang M. The state of oxygen-enriched air (nitrox) Diving Hyperb Medicine. 2006;36(2):87–93. https://www.oceanfdn.org/sites/default/files/Lang2006DHMNitrox.pdf [Google Scholar]
  25. Layec G., Bringard A., Le Fur Y., Micallef J.-P., Vilmen C., Perrey S., Cozzone P.J., Bendahan D. Opposite effects of hyperoxia on mitochondrial and contractile efficiency in human quadriceps muscles. Am. J. Physiol. Regul. Integr. Comp. Physiol. 2015;308(8):R724–R733. doi: 10.1152/ajpregu.00461.2014. [DOI] [PubMed] [Google Scholar]
  26. Mallette M.M., Stewart D.G., Cheung S.S. The Effects of hyperoxia on sea-level Exercise performance, training, and recovery: a meta-analysis. Sports Med. 2018;48(1):153–175. doi: 10.1007/s40279-017-0791-2. [DOI] [PubMed] [Google Scholar]
  27. Manselin T.A., Södergård O., Larsen F.J., Lindholm P. Aerobic efficiency is associated with the improvement in maximal power output during acute hyperoxia. Physiological Reports. 2017;5(2):e13119. doi: 10.14814/phy2.13119. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Marinovic J., Ljubkovic M., Breskovic T., Gunjaca G., Obad A., Modun D., Bilopavlovic N., Tsikas D., Dujic Z. Effects of successive air and nitrox dives on human vascular function. Eur. J. Appl. Physiol. 2012;112(6):2131–2137. doi: 10.1007/s00421-011-2187-6. [DOI] [PubMed] [Google Scholar]
  29. Miyamoto Y., Niizeki K. Ventilatory responses during incremental Exercise in men under hyperoxic conditions. Jpn. J. Physiol. 1995;45(1):59–68. doi: 10.2170/jjphysiol.45.59. [DOI] [PubMed] [Google Scholar]
  30. Möller F., Jacobi E., Hoffmann U., Muth T., Schipke J.D. Oxygen-enriched air decreases ventilation during high-intensity fin-swimming underwater. Int. J. Sports Med. 2021 doi: 10.1055/a-1554-5093. a-1554-5093. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. O’Donell D.E., D’Arsigny C., Webb K.A. Effects of hyperoxia on ventilatory LimitationDuring Exercise in advanced chronic obstructive pulmonary disease. Am. J. Respir. Crit. Care Med. 2001;163:892–898. doi: 10.1164/ajrccm.163.4.2007026. [DOI] [PubMed] [Google Scholar]
  32. Ohya T., Yamanaka R., Ohnuma H., Hagiwara M., Suzuki Y. Hyperoxia Extends time to Exhaustion during high-intensity intermittent Exercise: a randomized, crossover study in male cyclists. Sports Medicine - Open. 2016;2(1):34. doi: 10.1186/s40798-016-0059-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Oussaidene K., Prieur F., Bougault V., Borel B., Matran R., Mucci P. Cerebral oxygenation during hyperoxia-induced increase in exercise tolerance for untrained men. Eur. J. Appl. Physiol. 2013;113(8):2047–2056. doi: 10.1007/s00421-013-2637-4. [DOI] [PubMed] [Google Scholar]
  34. Peacher D.F., Pecorella S.R.H., Freiberger J.J., Natoli M.J., Schinazi E.A., Doar P.O., Boso A.E., Walker A.J., Gill M., Kernagis D., Uguccioni D., Moon R.E. Effects of hyperoxia on ventilation and pulmonary hemodynamics during immersed prone exercise at 4.7 ATA: possible implications for immersion pulmonary edema. J. Appl. Physiol.(Bethesda, Md) 2010;109(1):68–78. doi: 10.1152/japplphysiol.01431.2009. 1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Plet J., Pedersen P.K., Jensen F.B., Hansen J.K. Increased working capacity with hyperoxia in humans. Eur. J. Appl. Physiol. Occup. Physiol. 1992;65(2):171–177. doi: 10.1007/BF00705076. [DOI] [PubMed] [Google Scholar]
  36. Pokorsko M., Masuda A., Pauley P.-E., Sakakibara Y., Ahn B., Takaishi S., Nishibayashi Y., Honda Y. Ventilatory and cardiovascular responses to hypoxic and hyperoxic statis handgrip exercise in man. Respir. Physiol. 1990;81(2):189–201. doi: 10.1016/0034-5687(90)90045-Z. [DOI] [PubMed] [Google Scholar]
  37. Prieur F., Benoit H., Busso T., Castells J., Geyssant A., Denis C. Effects of moderate hyperoxia on oxygen consumption during submaximal and maximal exercise. Eur. J. Appl. Physiol. 2002;88(3):235–242. doi: 10.1007/s00421-002-0707-0. [DOI] [PubMed] [Google Scholar]
  38. Resnick A.D., Deal E.C., Ingram R.H., McFadden E.R. A critical assessment of the mechanism by which hyperoxia attenuates exercise-induced asthma. J. Clin. Invest. 1979;64(2):541–549. doi: 10.1172/JCI109492. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Rocco M., Pelaia P., Di Benedetto P., Conte G., Maggi L., Fiorelli S., Mercieri M., Balestra C., De Blasi R.A. Inert gas narcosis in scuba diving, different gases different reactions. Eur. J. Appl. Physiol. 2019;119(1):247–255. doi: 10.1007/s00421-018-4020-y. [DOI] [PubMed] [Google Scholar]
  40. Scano G., van Meerhaeghe A., Willeput R., Vachaudez J.P., Sergysels R. Effect of oxygen on breathing during exercise in patients with chronic obstructive lung disease. Eur. J. Respir. Dis. 1982;63(1):23–30. [PubMed] [Google Scholar]
  41. Souday V., Koning N.J., Perez B., Grelon F., Mercat A., Boer C., Seegers V., Radermacher P., Asfar P. Enriched air nitrox breathing reduces venous gas bubbles after simulated scuba diving: a double-blind cross-over randomized trial. PLoS One. 2016;11(5) doi: 10.1371/journal.pone.0154761. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Steinberg F., T T., Steegmanns A., Dalecki M., Röschmann M., Hoffmann U. Fit2dive -A field test for assessing the specific capability of underwater fin swimming with SCUBA. Int. J. Perform. Anal. Sport. 2011;11:197–208. [Google Scholar]
  43. Stellingwerff T., LeBlanc P.J., Hollidge M.G., Heigenhauser G.J.F., Spriet L.L. Hyperoxia decreases muscle glycogenolysis, lactate production, and lactate efflux during steady-state exercise. Am. J. Physiol. Endocrinol. Metabol. 2006;290(6):E1180–E1190. doi: 10.1152/ajpendo.00499.2005. [DOI] [PubMed] [Google Scholar]
  44. Tetzlaff K., Thomas P.S. Short- and long-term effects of diving on pulmonary function. Eur. Respir. Rev. : Off. J. Eur. Respir.Soc. 2017;26(143) doi: 10.1183/16000617.0097-2016. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Thews G. Physiologie des Menschen. 24th ed. Springer; 1995. Lungenatmung; pp. 565–591. [DOI] [Google Scholar]
  46. Ulrich S., Hasler E.D., Müller-Mottet S., Keusch S., Furian M., Latshang T.D., Schneider S., Saxer S., Bloch K.E. Mechanisms of improved Exercise performance under hyperoxia. Respiration. 2017;93(2):90–98. doi: 10.1159/000453620. [DOI] [PubMed] [Google Scholar]
  47. van Ooij P.J.A.M., Hollmann M.W., van Hulst R.A., Sterk P.J. Assessment of pulmonary oxygen toxicity: relevance to professional diving; a review. Respir. Physiol. Neurobiol. 2013;189(1):117–128. doi: 10.1016/j.resp.2013.07.014. [DOI] [PubMed] [Google Scholar]
  48. Vann R., Lang M. Recreational diving fatalities. Undersea Hyper. Med.: J.Undersea.Hyper.Med. Soc.Inc. 2011;38(4):257–260. [PubMed] [Google Scholar]
  49. Wilson B.A., Welch H.G., Liles J.N. Effects of hyperoxic gas mixtures on energy metabolism during prolonged work. J. Appl. Physiol. 1975;39(2):267–271. doi: 10.1152/jappl.1975.39.2.267. [DOI] [PubMed] [Google Scholar]
  50. Wilson G.D., Welch H.G. Effects of varying concentrations of N2/O2 and He/O2 on exercise tolerance in man. Med. Sci. Sports Exerc. 1980;12(5):380–384. [PubMed] [Google Scholar]
  51. Wunderlich T., Frey N., Kahler W., Lutz M., Radermacher P., Klapa S., Koch I., Tillmans F., Witte J., Koch A. Influence of hyperoxia on diastolic myocardial and arterial endothelial function. Undersea Hyper. Med. : J.Undersea.Hyper.Med. Soc.Inc. 2017;44(6):521–533. doi: 10.22462/11.12.2017.3. [DOI] [PubMed] [Google Scholar]
  52. Zenske A., Kähler W., Koch A., Oellrich K., Pepper C., Muth T., Schipke J.D. Does oxygen-enriched air better than normal air improve sympathovagal balance in recreational divers? An open-water study. Res. Sports Med. 2019:1–16. doi: 10.1080/15438627.2019.1694930. [DOI] [PubMed] [Google Scholar]

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