Hyperbaric Medicine

Development and preliminary test of a new plateau hyperbaric chamber

a b s t r a c t

Objective: The objective of this study is to validate the performance, define its limits, and provide details on a new plateau Hyperbaric chamber at 355-, 2880-, and 4532-m high altitude.

Methods: A new multiplace plateau hyperbaric chamber was designed to satisfy the needed of patients who have acute mountain sickness. Tests were conducted inside the chamber at 355-, 2880-, and 4532-m high altitude. The safely and conveniences of the new plateau hyperbaric chamber were estimated.

Results: Minimum pressures of the main compartment can reach up to 0.029, 0.022, and 0.02 MPa at 355-, 2880-, and 4532-m high altitude. During pressurization, there was no leak of air around the chamber. The time lag of pressure equilibration between main and buffer compartment varies from 30.3 +- 2.01 to 200.5 +- 5.44 seconds and between buffer compartment and ambient pressure varies from 60.2 +- 4.13 to 215.9 +- 6.76 seconds.

Conclusions: The chamber can be applicated for acute mountain sickness treatment safety and convenience. However, further experience about animals and human within the chamber is needed to improve the hardware and establish conditions of effective utilization of this equipment in the high altitude.

Introduction

Acute mountain sickness is a common clinical problem affecting otherwise fit individuals who ascend to high altitude. The se- verity of AMS depends upon a number of factors, including rate of ascent, altitude achieved, recent previous acclimatization, and the susceptibility of the individual to the syndrome. Overall, in laborers [1] and soldiers [2], the incidence of AMS was much higher due to the requirements for laboring or completion of missions under hypobaric hypoxia.

As a common pathogenesis of high-altitude illnesses has been sug- gested, early successful treatment of AMS may prevent the develop- ment of high-altitude cerebral edema or pulmonary edema [3,4]. Studies had been shown that the severity of AMS correlates inversely with Arterial oxygen saturation [5,6]. Therefore, the most important treatment for AMS is rapidly improving arterial oxygen saturation of the patients. Supply of additional oxygen is effective [7]; but cylinders are heavy, expensive, and only a limited supply can be carried.

Rapid descent is another important treatment; however, the treatment of choice is often not possible while trekking for topographical reasons or while mountaineering because of adverse Weather conditions

* Corresponding author. Tel.: +86 22 60578941; fax: +86 22 60578671.

E-mail address: [email protected] (J. Zhang).

or difficult terrain. If immediate descent is not possible, using a portable hyperbaric chamber to simulate descent is recommended [8].A portable hyperbaric chamber is an inflatable cylindrical tube made of heavy rub- ber or durable fabric that increases the atmosphere sealed within it to that of a much lower altitude. However, treatment of sick subjects within the very confined space of the chamber can be difficult, and prolonged treatment makes considerable demands on the individuals required to maintain pressure with the foot pump [9]. And this is not always an acceptable therapy alternative in a predominantly elderly population. Moreover, most type of portable hyperbaric chambers are monoplace chambers. If many persons have AMS, such as laborers and soldiers, the portable hyperbaric chamber may be ineffective.

Hyperbaric oxygen therapy has been recommended and used in a wide variety of medical conditions, and its efficacy has been validated by extensive clinical experience and scientific studies for decompres- sion sickness and high-altitude illnesses [10,11]. And most types of hyperbaric oxygen chambers are multiplace chambers. However, the potential risks, shortage of oxygen supply, and complexity of the operation of hyperbaric oxygen have often been limited its application in the treatment of AMS.

Based on the principles of increasing pressure in the chamber, a new multiplace plateau hyperbaric chamber was designed to satisfy the pa- tients who have AMS. The specific merits of the plateau hyperbaric chamber are big volume, removable, and ease of operation. Different from other portable hyperbaric chamber, atmospheric pressure is

1498 L. Sun et al. / American Journal of Emergency Medicine 33 (2015) 1497–1500

Fig. 1. The new multiplace plateau hyperbaric chamber (1, compressor; 2, doors; 3, control device; 4, desk; 5, beds; 6, gas vent; 7, air evacuation valve; 8, windows; 9, main compartment; 10, buffer compartment; 11, intake tube; and 12, silencer).

increased inside the chamber by adjusting the opening of the expiration valve in proportion to the ambient pressure. Hence, carbon dioxide inside the chamber will not be accumulated during pressurization. This study was carried out to assess the feasibility of the new plateau hyperbaric chamber for the treatment of AMS.

Subjects and methods
1. Location and subjects

The tests were carried out at 3 different high altitude in Xian City and Kunlun Mountains. The new plateau hyperbaric chamber was stored in a truck and transported to different high altitude by the truck when it was tested.

The chamber is a windowed cylindrical hyperbaric chamber con- structed of 3-layer material (anticorrosion steel plate inner, inorganic foaming material thermal insulation in middle layer, and glass steel in outer layer). The complete device is 800-cm long, has a diameter of 340 cm, and a volume of 72.63 m³ (Fig. 1). The chamber was divided into main and buffer compartment, which connected with a door. Pressure was supplied by a electrically driven centrifugal compressor, which power is 3.5 kW, and the high air flow was 200 m³/h. The electri- cally driven centrifugal compressor continuously flushes ambient air into the chamber through the chamber environment resulting in a no- risk environment to the occupant. The plateau hyperbaric chamber compensates for hyperbaric pressure by adjusting the opening of the expiration valve in proportion to the ambient pressure.

Living facilities (stool, bed, and the bureau) are installed in the chamber, ensuring a more comfortable chamber environment (Fig. 2).

Fig. 2. The new multiplace plateau hyperbaric chamber.

The custom sound baffle system decreases the sound signature of the compressor, making it quiet enough to use in a medical office or small apartment. The patient in the chamber can be observed through the window.

1. Study design

Because this plateau hyperbaric chamber is said to provide a useful tool for the treatment of AMS, this needed us to estimate the following:

(1) minimum pressure can be achieved in main compartment at differ- ent high altitude, (2) time lag of pressure equilibration between main and buffer compartment, (3) time lag of pressure equilibration between buffer compartment and outside, (4) noise in the main compartment at working, and (5) temperature changes before and after pressurization. Pressures of the main and buffer compartment were measured by an M307086 barometer (Western Instrument Technology Co, Ltd, WuHan Hu Bei of China). Noise in the main compartment at working was measured by a CEL-231 digital sound level meter (Casella CEL, London of England). The temperature was measured by a CENTER 313 digital temperature and humidity meter (Taiwan Qunte Company, New Taipei City of China). Time was measured by a Casio stopwatch (Iraq Business Electronic Technology Co Ltd, Shen Zhen of China).

The procedure is as follows:(1) place the chamber on a surface as smooth as possible; (2) check that the equipments are in proper loca- tion; (3) tester enter into the main compartment; (4) close all the doors and ensure valve stem in a closed position; (5) adjust pressure value of barometer to zero and record the temperature, noise in the main compartment as basic data; (6) begin pressurization; (7) record time required and temperature, noise changed when pressure rise every 0.01 MPa until minimum pressure in main compartment acquired; (8) open valve stem of the door between main and buffer compartment; (9) record time when pressure equilibration between main and buffer compartment; (10) open valve stem of the door between buffer compartment and outside; (11) record time when pressure equilibration between buffer compartment and outside;

(12) return valve stem to closed position; (13) check whether leak of air around the chamber; (14) stop pressurization; and (15) document procedure.

Table 1

The results obtained at 355 m are displayed

Pressure	Time (s)	Noise	Temperature
0.00	0	48.3 +- 3.25	0
0.01	90.3 +- 3.63	67.4 +- 2.92	1.1 +- 0.32
0.02	210.1 +- 4.12	68.5 +- 3.34	1.2 +- 0.53
0.029	510.4 +- 4.78	69.0 +- 2.45	1.5 +- 0.21

Table 2

The results obtained at 2880 m are displayed

L. Sun et al. / American Journal of Emergency Medicine 33 (2015) 1497–1500

1499

Pressure	Time (s)	Noise	Temperature
0.00	0	47.6 +- 2.28	0
0.01	110.3 +- 3.84	64.5 +- 3.14	1.3 +- 0.34
0.02	370.6 +- 5.42	74.8 +- 2.83	1.6 +- 0.57
0.022	750.2 +- 4.32	67.0 +- 1.83	2.0 +- 0.43

The plateau hyperbaric chamber was tested 6 times at each altitude. The SPSS statistical software package 20.0 (Chicago, IL) and GraphPad prism V4.0 were used to perform the statistical analysis. Data are presented are in a descriptive fashion (mean +- SD).

Results

Tables 1 to 3 show the results obtained at 355-, 2880-, and 4532-m high altitude. Fig. 3 shows the minimum pressure of the main compart- ment at different high altitude in different time. Regarding altitude, minimum pressures of the main compartment and the time of mini- mum pressure rise were progressively affected with higher ambient pressures. Minimum pressure of the main compartment can reach up to 0.029 MPa within 510.4 +- 4.78 seconds at 355-m high altitude. However, minimum pressures of the main compartment just reached up to 0.022 MPa within 750.2 +- 4.32 seconds at 2880 m and 0.02 MPa within 785.7 +- 3.74 seconds at 4532 m.

Table 4 shows the time lag of pressure equilibration between main and buffer compartment and between buffer compartment and ambi- ent pressure at different high altitude. The time lag of pressure equili- bration between main and buffer compartment is 30.3 +- 2.01 seconds and between buffer compartment and ambient pressure is 60.2 +-

4.13 seconds at 355 m. However, the time is extending to 190.7 +-

6.89 seconds, 200.4 +- 5.54 seconds at 2880 m, 200.5 +- 5.44 seconds,

and 215.9 +- 6.76 seconds at 4532 m.

During pressurization, there was no leak of air around the chamber and noise and temperature were little changed.

Discussion
1. The possible applications of the chamber for AMS treatment

The chamber was originally designed for treatment of high-altitude disorders. Our results confirmed that the plateau hyperbaric chamber could compensate for hyperbaric pressure by adjusting the inlet and outlet air flow. Minimum pressure of the main compartment can reach up to 0.022 and 0.02 MPa at 2880- and 4532-m high altitude, equivalent to descending more than 2000 m (Table 5). Theoretical predictions say it may lead to greater relief of symptoms of AMS imme- diately for patients after treatment.

1. Use of the chamber safely

The pressure threshold of the chamber was originally set at 0.2 MPa (atmospheric pressure) over ambient pressure, which is relatively high for hyperbaric therapy and sufficiently effective for the treatment of high-altitude disorders. However, pressures applied while in the cham- ber are usually 0.02 to 0.029 MPa. Therefore, the chamber is enough

Table 3

Fig. 3. Minimum pressure of the main compartment at different high altitude in different time.

solid to withstand the higher pressures used in standard hyperbaric ther- apy at 355-, 2880-, and 4550-m high altitude.

The duration of treatment for patients may last for a long time [12]. Therefore, appropriate monitoring is essential during treatment, and fa- cilities for resuscitation and immediate mechanical ventilation should be available. Obviously, the volume of the chamber is big enough to place these medical facilities. And, after the stable hyperbaric phase, pressure in the chamber decompressed linearly at different high altitude to allow the subject escaping once life-threatening injuries occurred. Furthermore, pressure inside the chamber was supplied by a electrically driven centrifugal compressor and will not extend to the compressor delivery pressure. And when the compressor stops work- ing, pressure inside the chamber will drop faster.

1. Use of the chamber convenience

Frostbite and hypothermia also represent 2 severe diseases that frequently occur at high altitude. If the patient is conscious and has frostbite, he should be rehydrated and kept warm with a hot beverage in the hyperbaric chamber [13]. Living facilities (desk, bed, and electric radiator) are installed in the chamber, ensuring a more comfortable chamber environment. And temperature inside the chamber could be adjusted if necessary.

The chamber was divided into main and buffer compartment. Our results indicate that the time lag of pressure could redress balance between main and buffer compartment varies from 30.3 +- 2.01 to

200.5 +- 5.42 seconds. Therefore, it is convenient to stop treatment for a patient through buffer compartment without affecting other patients. And the buffer compartment can provide a space to let patients adapting to the change of pressure, avoiding the discomfort caused by sudden decompression. Furthermore, the chamber can be transported to the exact location of an accident by a truck, and hyper- baric therapy can be started immediately, thus maximizing the efficacy of hyperbaric therapy.

Table 4

The time lag of pressure equilibration between main and buffer compartment and be- tween buffer compartment and ambient pressure at different high altitude

The results obtai	ned at 4532 m are displayed			Altitude (m)	Between main and	Between buffer compartment
Pressure	Time (s)	Noise	Temperature		buffer compartment (s)	and ambient pressure (s)
0.00	0	43.4 +- 4.12	0	355	30.3 +- 2.01	60.2 +- 4.13
0.01	380.5 +- 4.02	64.5 +- 5.37	1.7 +- 0.33	2880	190.7 +- 6.89	200.4 +- 5.54
0.02	785.7 +- 3.74	56.3 +- 2.31	1.8 +- 0.29	4532	200.5 +- 5.42	215.9 +- 6.76

1500 L. Sun et al. / American Journal of Emergency Medicine 33 (2015) 1497–1500

Table 5

barometric pressure-altitude relationships

Altitude (m)	Standard atmosphere	Standard atmosphere
	(mm Hg)	(MPa)
0	760	0.101
1000	674	0.091
2000	596	0.080
3000	526	0.071
4000	462	0.061
5000	405	0.054
6000	354	0.047
7000	308	0.041
8000	267	0.036
9000	231	0.031
10000	199	0.027

Limitations

This test has emphasized the positive aspects of the chamber, but there is clearly a potential for negative effects. Although the chamber represents a option for AMS treatment, its correct handling at high alti- tude under difficult weather conditions is strenuous. And, as with the rigid chamber used in clinical practice, it must be ensured that staff should be trained in the use of the transportable chamber. Moreover, the effectiveness of the chamber on high-altitude disorders has not been well established. And whether some complications such as cough and reversible falls in pulmonary function will occur with repeated treatment is unknown. Furthermore, hypobaric environment may pose a challenge for compressor; the alternatives to the compressor also have limitations.

Conclusions

In conclusion, we have demonstrated the safety and convenience of the chamber and have suggested possible applications for the chamber in AMS treatment. However, further experience about animals and human within the chamber will be needed to improve the hardware

and establish conditions of effective utilization of this equipment in the high altitude.

Acknowledgments

The authors thank the research doctors, nursing, and other medical staff for their assistance during the study.

References

319:841-5 [PMID:3045554].

AJEM

Development and preliminary test of a new plateau hyperbaric chamber

a b s t r a c t

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