The Effect of Mild-Pressure Hyperbaric Therapy (Oasis O<sub>2</sub>) on Fatigue and Oxidative Stress

doi:10.4236/health.2011.37071

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Vol.3, No.7, 432-436 (2

doi:10.4236/health.2011.37071

011) Health

The effect of mild -pressure hyperb aric therapy (Oas is O2)

on fatigue and oxidative stress

Sungdo Kim1,2 ,Takehiko Yukishita1, Keiko Lee1, Shinichi Yokota1, Ken Nakata1, Daichi Suzuki3,

Hiroyuki Kobay ashi1*

1Department of Hospital Administration, Graduate School of Medicine, Juntendo University School of Medicine, Tokyo, Japan;

Corresponding Author: koba@juntendo.ac.jp

2Mizue Orthopedic Clinic, Tokyo, Japan;

3Department of Sports Science, Graduate School of Health and Sports Science, Juntendo University, Tokyo, Japan.

Received 15 April 2011; revised 20 May 2011; accepted 2 June 2011.

ABSTRACT

Mild-pressure hyperbaric therapy (mHBT) has

become increasingly popular among elite ath-

letes and most recently among the general pub-

lic yet there is very little scientific underpin-

nings on its therapeutic use. In this study, fif-

teen healthy volunteers (8 men, 7 w omen, mean

age 29.7 ± 8.1 years) were exposed to 1.3 at-

mospheres absolute (ATA) for 40 minutes in a

mild hyperbaric chamber called “Oasis O2” to

determine th e effe ct of am bient air at 1.3 A TA o n

oxidative stress, antioxidant potential, fatigue,

and blood chemistry. Reactive oxygen metabo-

lites (ROMs), an index of oxidative stress, sig-

nificantly reduced by 11% (p = 0.006), while bi-

ological antioxidant potential (BAP), an index of

antioxidant capacity, did not show a significant

change (p = 0.749). WBC count significantly

reduced by 10.4% (p = 0.005) whereas WBC dif-

ferential did not show a marked change. The

mean visual analog scale (VAS) score for fa-

tigue significa ntly decreased fro m 5.0 to 2.1 (p <

0.001). Our findings suggest that mild-pressure

hyperbaric therapy reduces oxidative stress as

indicated by a significant decrease in serum

ROM, and also helps improv e fa tigu e as se en by

a significant decrease in VAS fatigue scores.

Keywords: Mild-Pressure Hyperbaric Chambe;

Oxidative Stress; Free Radicals; Reacti ve Oxygen

Species (RO S)

1. INTRODUCTION

Mild-pressure hyperbaric therapy (mHBT) has be-

come increasingly popular among elite athletes and most

recently among the general public as a modality to im-

prove fatigue, enhance overall health and well-being,

heal sports-related injuries, and promote anti-aging. The

hyperbaric chambers used for these purposes are soft-

sided chambers made of elastic fiber such as the “Oasis

O2” used in this study. Many manufacturers distribute

similar chambers for widespread use and they are collec-

tively referred to as “mild-pressure hyperbaric cham-

bers”. These are frequently mistaken for hospital grade

hyperbaric oxygen therapy (HBO) chambers despite the

vastly different specifications between HBO and mHBT.

The “Oasis O2” uses 1.3 atmospheres absolute (ATA)

ambient air whereas HBO is the intermittent administra-

tion of 100% oxygen at therapeutic pressures of 2-3 ATA

with more than 60 minutes of depressurization time.

HBO is claimed to “revitalize” hypoxic tissues, sup-

plement oxygen to under-oxygenated tissues, reduce

edema, promote fibroblast proliferation for tissue regen-

eration, mobilize white blood cells (WBCs), and im-

prove resistance and immunity against infection and

inflammation [1]. HBO has been traditionally indicated

for decompression sickness and acute carbon monoxide

poisoning; its clinical applications have since expanded

to include the treatment of other conditions such as ex-

ternal injuries and central nervous system disorders be-

cause of its tissue regenerative capacity [2]. The value of

oxygen therapy has long been known and HBO is a

modern form of this treatment that provides enriched

oxygen under high pressure to promote tissue regenera-

tion. However, the delivery of high-density, pressurized

oxygen has also been found to create problems by gen-

erating free radicals. Oxygen toxicity is a side effect of

HBO that results from breathing high partial pressures of

oxygen accompanied by an uncontrolled increase in re-

active oxygen species (ROS) [3]. Normally the living

organism has an “antioxidant system” that controls the

development of ROS, but when this system’s scavenging

capacity is overcome by the enhanced formation of ROS,

S. Kim et al. / Health 3 (2011) 432-436

433

the resulting state is called “oxidative stress”. Excessive

free radicals can damage lipids, proteins, and DNA

which main structural and functional integrity of the

organism, as well as accelerate aging and cause a variety

of diseases [4]. For these reasons, mHBT uses lower

concentration and pressure than HBO to deliver oxygen

to the tissues while checking the development of free

radicals.

Although mild-pressure hyperbaric chambers have

become widely prevalent, few researches about mHBT

have been made so far. Saito reports mHBT has no sig-

nificant effect for oxidative stress [5]. On the other hand,

mHBT shortens a treatment period of acute lower leg

muscle strain in professional soccer players [6] and de-

creases blood levels of lactate acid and physical fatigue

[7]. Scientific validation of their efficacy and mecha-

nisms of action are still necessary to be explored. There-

fore, our reason for this study was to determine the ef-

fects of mild hyperbaria on oxidative stress, antioxidant

potential, and fatigue.

2. MATERIALS AND METHODS

2.1. Stud y Design and Subjects

Fifteen healthy volunteers (8 men, 7 women, mean

age 29.7 ± 8.1 years) provided oral consent and were

instructed to refrain from intense physical exercise be-

fore participating in the study. All participants were ex-

posed to 1.3 ATA for 40 minutes in “Oasis O2”, a

mild-pressure hyperbaric chamber. Changes in subjec-

tive sensation of fatigue and blood chemistry were eva-

luated before and after hyperbaric exposure to determine

the effects of mHBT on those parameters.

Blood chemistry analysis included assessing the de-

rivatives of reactive oxygen metabolites (d-ROMs) as a

convenient test to measure the level of oxidative stress in

clinical practice, biological antioxidant potential (BAP)

as an index of antioxidant capacity, and differential leu-

kocyte count. Blood samples were obtained from par-

ticipants immediately before and after hyperbaric cham-

ber exposure.

For the d-ROM and BAP tests, the free radical analy-

sis system (FRAS4) (Diacron International, Italy) con-

sisting of a dedicated photometer with an incorporated

centrifuge was used. ROM values were reported in

Carratelli Unit (CARR.U.) with one CARR.U. equaling

0.08 mg/100 mL of hydrogen peroxide. BAP was ex-

pressed as μmol/L.

To evaluate the participants’ subjective sensation of

physical fatigue, a visual analog scale (VAS) for fatigue

(Japanese Society of Fatigue Science) [8] was adminis-

tered immediately before and after the exposure. The

fatigue VAS consisted of a 100 mm horizontal line and

participants were asked to mark the point on the line

with an “x” that represented the perception of their fa-

tigue level. The possible score ranged from 0 to 100,

with “0” on the far left indicating “no fatigue/full of en-

ergy” to “100” on the far right indicating “worst possible

fatigue/listlessness”. The score was obtained by measur-

ing the length of line from “0” to the point indicated by

the participant that represented their current state. This

was divided by 10 to yield a fatigue rating on a 0 to 10

scale.

2.2. Statistical Anlysis

Student’s t-test was used to compare the means of se-

rum ROM, serum BAP and differential leukocyte count

obtained from participants immediately before and after

mHBT. The significance level for all cases was set at 5%.

The SPSS Ver.11.5 software was used for analysis.

3. RESULTS

The mean serum ROM before exposure to mild hy-

perbaria was 269.4 ± 49.7 CARR.U., which significantly

reduced by 11% to 239.7 ± 30.4 CARR.U. after the ex-

posure (p = 0.006) (Figure 1). In contrast, mean serum

BAP values before and after hyperbaric exposure were

2288.3 ± 350.4 μmol/L and 2265.4 ± 284.7 μmol/L, re-

spectively. There was no significance between the two

BAP values (p = 0.749) (Figure 2).

The mean WBC count before hyperbaric exposure

was 6233.3 ± 1173.3/uL, which significantly decreased

by 10% to 5580.0 ± 984.3/uL after the exposure (p =

0.005) (Figure 3). There was no significant difference in

WBC differential before and after the exposure (Figure

4).

The mean VAS fatigue score was 5.0 ± 1.8 before ex-

posure to hyperbaric chambers, which significantly re-

duced to 2.1 ± 1.6 after the exposure (p < 0.001) (Figure

5).

Figure 1. Change in serum ROM after mild HBT. A sig-

nificant decrease of 11% in mean serum ROM was ob-

served before (Pre) and after (Post) hyperbaric exposure

(Pre: 269.4 ± 48.7 CARR.U.; Post: 239.7 ± 30.4 CARR.U; p

= 0.006).

S. Kim et al. / Health 3 (2011) 432-436

434

Figure 2. Change in serum BAP after mild HBT. Mean

serum BAP decreased from 2288.3 ± 350.4 μmol/L before

hyperbaric exposure to 2265.4 ± 284.7 μ after exposure, but

the difference was not significant (p = 0.749).

Figure 3. Change in WBC after mild HBT. A significant

decrease of 10.4% in mean WBC count was observed be-

fore (Pre) and after (Post) hyperbaric exposure (Pre: 6233.3

± 1173.3/uL; Post: 5580.0 ± 984.3/uL; p = 0.005).

Figure 4. Change in WBC Differentiation after mild HBT.

No significant changes were observed in the differential

WBC count before and after hyperbaric exposure.

4. DISCUSSION

Our findings revealed that mHBT was effective in lo-

wering oxidative stress. A significant reduction in serum

ROM was noted after the therapy whereas there was no

change in BAP or antioxidative capacity.

These findings contrast with those obtained by Kon-

goji et al. and Yamami et al. which showed elevated

ROM and BAP values immediately after exposure to HBO

Figure 5. Change in VAS after mild HBT. Mean VAS fa-

tigue scores dropped significantly before (Pre) and after

(Post) hyperbaric exposure (Pre: 5.0 ± 1.8; Post: 2.1 ± 1.6; p

< 0.001).

[9,10]. Despite conflicting results, our data are highly

meaningful because of the paucity of reports on mHBT.

The differences in the results may be attributed to the

relatively faster exhaustion of antioxidant enzymes and

substances due to their increased activity after HBO to

counteract oxidative damage. In general, as the level of

oxidative stress rises, antioxidative enzymes and sub-

stances are mobilized by the body as a defense mecha-

nism to clear ROS and to restore the balance between

oxidative stress and antioxidant activity [4]. We sur-

mised that in our study mHBT-induced ROS were effec-

tively eliminated in a relatively short period because our

participants were young, were free from underlying dis-

eases, and had strong antioxidative capacity.

In addition, it is empirically known that 100% oxygen

administered at pressures greater than 3 ATA induces

oxygen toxicity, while pure oxygen at pressures greater

than 1.75 ATA demonstrably causes a higher incidence

of oxygen toxicity than 1.5 ATA [11]. Accordingly, we

used compressed air at a very low pressure of 1.3 ATA in

this study to eliminate the need for providing additional

oxygen and minimize oxygen poisoning - a worrisome

side effect of HBO.

Moreover, we found that mHBT had a beneficial ef-

fect on fatigue. VAS fatigue scores significantly im-

proved after the therapy in nearly all the participants

who felt the physical improvement. These findings are in

line with Ishihara’s data that showed reduced blood lac-

tate level and improved muscle stiffness and fatigue in

college volleyball players after exposure to 35% oxygen

at 1.25 ATA [12]. It is possible that a placebo effect from

mHBT may have influenced a subjective symptom like

fatigue; however, the effect of mild hyperbaria in allevi-

ating fatigue was confirmed by all the participants who

reported feeling “refreshed”, “warmer”, or “lighter” af-

terwards. For this study, data were obtained from par-

ticipants who abstained from intense physical activity

before undergoing mHBT. To further probe the efficacy

S. Kim et al. / Health 3 (2011) 432-436

435

of mHBT on fatigue, future studies would benefit from

manipulating fatigue induction and evaluating the effects

in participants undergoing similar physical load.

Although WBC count significantly decreased after

mHBT, WBC differential did not show a remarkable

change. These findings are congruent with Osbourne et

al.’s data which showed a decrease in WBC count by

32% and 13% in rats exposed to hyperbaric pressures at

4 ATA with 100% oxygen for 90 minutes and at 4 ATA

with 21% oxygen for 90 minutes, respectively. Addi-

tionally, the investigators hypothesized that stress from

HBO induced greater adrenal cortisol secretion, which in

turn caused a decrease in WBCs [13]. In this study

WBCs decreased in almost all the participants after

mHBT; however, WBC differential did not change in

response to the therapy. A re-evaluation of the latter 4-6

hours after the exposure is warranted as differential leu-

kocyte activity is known to change over time.

Much controversy currently exists over the efficacy of

mHBT. In May 2006, a panel entitled “Round table dis-

cussion on mild HBT” was held at the Third Annual

Meeting of Japanese Association for Clinical Hyperbaric

Oxygen and Diving (JACHOD). At this meeting, a vig-

orous debate over the efficacy of mHBT ensued between

JACHOD, an opponent of mHBT, and Japan Interna-

tional Hyperbaric Association Inc. (JIHA), a proponent

of mHBT. Although the main purpose of HBO is to raise

the levels of oxygen in body fluids, most oxygen carried

in the blood is bound to hemoglobin, rendering absolute

hemoglobin concentration as the limiting factor for oxy-

gen uptake. However, the mechanism of HBO rests on

Henry's Law that states a gas is dissolved by a liquid in

direct proportion to its partial pressure, i.e., HBO utilizes

increased atmospheric pressure to enhance oxygen dis-

solution in the plasma and resultant higher concentration

of liquefied oxygen to reverse hypoxia. Further, mHBT

was developed and based on the theory that liquefied

oxygen is more refined than conjugated oxygen and

therefore has a greater capacity to transport oxygen to

peripheral tissues. However, several studies have found

that mild hyperbaria at 1.3 ATA yields 0.57 mL/dL of

liquefied oxygen, which is significantly less than 2.0

mL/dL of liquefied oxygen from compressed air at 1.0

ATA, leading to some investigators to refute the ability

of mHBT (pressurized ambient air at 1.3 ATA) to deliver

the benefits of oxygen therapy [14-16].

Meanwhile, Ishii et al. studied the effects of various

hyperbaric pressures and discovered that lactate clear-

ance rate after maximal exercise at 1.3 ATA and 100%

oxygen was significantly greater than the rate at normal

atmosphere and room air; hence, the authors reported

that atmospheric pressure need not be raised to 2.0 ATA

because 1.3 ATA, which imposes comparatively less stress

than 2.0 ATA on the biological system, was sufficiently

effective [7]. Moreover, Ikeda et al. found that com-

pressed air at 1.3 ATA using Oasis O2 for the treatment

of acute lower leg muscle strain in professional soccer

players significantly reduced the time to return to sport

after injury, as observed from the difference in recovery

time between the non-treatment group versus the treat-

ment group (2.9 ± 1.4 weeks vs. 1.9 ± 0.5 weeks) [6]. It

appears that further research is necessary to clarify the

dearth of studies on the controversial effects of 1.3 ATA

5. CONCLUSIONS

Our findings suggest that mHBT is helpful in reducing

oxidative stress and improving fatigue while posing mi-

nimal risks, yet its effect on antioxidant capacity is less

clear. Research will be needed to examine the therapeu-

tic significance of 1.3 ATA in health promotion and dis-

ease prevention.

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