**2. Historic reference**

The WBC method is based on providing the total contact of the patient's skin surface with a cryogenic gas. With a contact duration of up to 3 minutes and a gas temperature of less than 140 K, the WBC procedure provides a number of positive effects that are used in treatment practice [11, 12]. The most demonstrative and controlled sign of the WBC effectiveness is the duration of analgesic action, which can last 6–8 hours [7]. The analgesic effect of WBC was first described and used in treatment practice by a Japanese doctor Yamauchi. For the WBC procedures, a special installation was made, called "Cryotium" by the author of the method [2]. The "Сryotium" design was analogously a refrigeration chamber for long-term storage of perishable products. The chamber was separated from the environment by the lock chamber (**Figure 1**), which was supposed to reduce the loss of cold air from the main chamber.

Given the relatively large size of the chamber, several patients were undergoing the WBC procedures simultaneously (from 5 to 12). To obtain cryogenic temperatures, liquid nitrogen was fed to the "Cryotium" heat exchangers instead of freon. The "Сryotium" design appeared by chance. Yamauchi believed that in order to obtain the maximum treatment outcome, the maximum decrease in temperature should be used. This condition became the basis of the design. To reduce the cost of manufacturing "Сryotium," Japanese engineers used the insulating structure and heat exchangers of the serial refrigeration chamber. The temperature regime in the chamber volume was

*Technique and Technology of Whole-Body Cryotherapy (WBC) DOI: http://dx.doi.org/10.5772/intechopen.83680*

**Figure 1.** *Multi-seat cab for WBC.*

decreased by 30 times. Low prices for equipment provide a high level of sales, so the trend of increasing operating temperature of WBC devices persists. An increase in the temperature level is accompanied by a decrease in the power of systems for cryostatting the WBC zone. The newest installations are equipped with refrigerators with a specific power of the electric driver of not more than 1 kW/m<sup>3</sup>

temperature level of 170 K, a refrigerator with such a power has a heat-removing

Unreasonable changes in WBC technology affect the effectiveness of the procedures. Recently, more and more articles appear, the authors of which express doubt that cryotherapy can provide the healthcare effects described in papers published before 1990 [7, 8]. The reason that many modern WBC systems are not able to provide the conditions for obtaining the healthcare effects described in the last century [1, 2] is the increase in gas temperature in the working zone of new installations. This can be seen even from the titles of the articles [1, 8]. The temperature increase from 170°C (102 K) to 110°C (163 K) changes the absolute value of the temperature by 1.6 times, which cannot but affect the intensity of heat removal, the degree of supercooling of the patient's body surface, etc. From a thermophysical point of view, it is obvious that from 1978 to 2018 the technology, which is commonly referred to as WBC, has qualitatively changed. And, judging by contemporary publications, this qualitative change had a negative impact on the healthcare effectiveness of the procedures, which until recently were successfully used to treat a number of severe diseases: rheumatoid arthritis, bronchial asthma,

In such conditions, the determination of cause–effect relationships between the WBC technological parameters and the magnitude of the healthcare effect acquires high scientific and social significance. Formation of the thermophysical theory of

The WBC method is based on providing the total contact of the patient's skin surface with a cryogenic gas. With a contact duration of up to 3 minutes and a gas temperature of less than 140 K, the WBC procedure provides a number of positive effects that are used in treatment practice [11, 12]. The most demonstrative and controlled sign of the WBC effectiveness is the duration of analgesic action, which can last 6–8 hours [7]. The analgesic effect of WBC was first described and used in treatment practice by a Japanese doctor Yamauchi. For the WBC procedures, a special installation was made, called "Cryotium" by the author of the method [2]. The "Сryotium" design was analogously a refrigeration chamber for long-term storage of perishable products. The chamber was separated from the environment by the lock chamber (**Figure 1**), which was supposed to reduce the loss of cold air

Given the relatively large size of the chamber, several patients were undergoing the WBC procedures simultaneously (from 5 to 12). To obtain cryogenic temperatures, liquid nitrogen was fed to the "Cryotium" heat exchangers instead of freon. The "Сryotium" design appeared by chance. Yamauchi believed that in order to obtain the maximum treatment outcome, the maximum decrease in temperature should be used. This condition became the basis of the design. To reduce the cost of manufacturing "Сryotium," Japanese engineers used the insulating structure and heat exchangers of the serial refrigeration chamber. The temperature regime in the chamber volume was

WBC creates a scientific basis for restoring the production of effective

cryotherapeutic installations at the modern technical level.

heat release of a patient under thermal comfort conditions (150 W) [7].

capacity of not more than 400 W/m<sup>3</sup>

*Low-temperature Technologies*

psoriasis, etc. [9, 10].

**2. Historic reference**

from the main chamber.

**134**

. At a

, which is comparable with the physiological

determined by the requirement of the inadmissibility of air condensation on the surface of a heat exchanger. The temperature of the outer surface of the heat exchanger *THC* must be higher than the condensation temperature T<sup>00</sup> A:

$$T\_{HC} \succ T\_A = \mathbf{81 K} \tag{1}$$

The removal of heat from air to the surface of the heat exchanger was carried out by natural convection.

With natural convection, the calculated temperature gradient between the gas and the heat-removing surface is 20 K:

$$T\_{A-HC} = T\_A - T\_{HC} \approx 20 \text{ K.} \tag{2}$$

Minimum possible air temperature in the cab:

$$T\_A = T\_A^\prime + \Delta T\_{A-HC} \approx 101 \text{ K} (-172^\circ \text{C}). \tag{3}$$

The value of the air temperature during the WBC sessions specified by the method's author [1] is the lowest possible temperature that could be achieved in this cab design. It is important to note that in "Сryotium" the temperature was maintained by choosing the pressure of liquid nitrogen (LN) vapor in the heat exchanger tubes (**Figure 2**). The boiling point of LN depends on pressure; by increasing the vapor pressure to a level of *P* ≥ 0.2 MPa, it is possible to ensure the fulfillment of condition (1) without using the temperature control systems. The lack of a temperature control system has provided "Сryotium" with unique operational advantages over modern WBC devices. Heat exchangers filled with liquid nitrogen successfully dealt with an increase in heat load when patients entered, and the correct choice of operating pressure prevented air condensation.

Thus, the "Сryotium" design determined the WBC technology. Perhaps, that is why the author of the method did not give any reason for the WBC temperature regime in his works. The ratios of the boiling points of nitrogen and air, as well as the design features of the device in which the procedures were performed, have randomly created the conditions for a safe and highly efficient procedure.

temperature. The upper sections of the heat exchanger (HE), through which the nitrogen passes in the vapor state, are heated to a temperature close to the air temperature in the chamber. The temperature of the inner tube surfaces exceeds the

When patients enter the main cab, relatively warm air enters from the lock chamber (*Ts* ¼ 210 K). Because of this, the air temperature in the cab increases by 50 K or more. The temperature controller opens the SV and resumes the supply of LN to the heat exchanger (HE). However, it takes some time to fill the tubes of the heat exchanger; moreover, the temperature of the upper sections of the heat exchanger (HE) exceeds the boiling point of nitrogen by more than 20 K. Because of this, the LN film boiling occurs at which the intensity of heat removal to the liquid is much lower; therefore, the vapor–liquid mixture passes the heat exchanger (HE) and is discharged through valve (V) into the environment. Under such conditions, the heat exchanger does not cope with heat generation from the surface of the patient's bodies and cannot restore the specified temperature mode of the chamber until the patients enter the lock chamber. The WBC procedure takes place at a temperature significantly higher than the nominal �160°C [7]. After the patients leave, the thermal load on the cryostatting system is reduced 10 times, the air temperature drops to the nominal level, and the temperature controller stops the

The increase in the air nominal temperature in the cab for WBC from �170°C to �160°C fundamentally changed the temperature algorithm of the procedure. The transition to the LN film boiling regime caused a significant overrun of the cryoagent. The operational drawbacks of the nitrogen cooling system and the uncertainty of the air temperature requirements in the main procedural cab created conditions for use in the WBC cryostatting system of three-stage chillers and steam cycles on gas mixtures. Refusing LN resulted in an increase in the nominal temper-

Specialists in the field of WBC did not only pay attention to this but also actively promoted the "modernization" of cryotherapy equipment [13–15]. The ability to refuse to use LN and significantly reduce the costs of WBC procedures turned out to be so attractive that the specialists "did not notice" that the efficiency of the procedures in the "nitrogen-free" installations was 10 times lower than in "Сryotium" [7]. At the beginning of the twenty-first century, "Criohome" "cryotherapeutic" devices with a nominal temperature of �85°C was used for WBC procedures, i.e., the tendency to increase the temperature persists. Since 1985, the Russian direction of devices for WBC has been developing independently, based on the use of singleseat installations with a nitrogen cooling system (cryosaunas). The temperature in the cab of a single-seat cryosauna during the whole procedure is no higher than �130°C. The conditional constancy of temperature fundamentally changes the degree of supercooling of the skin surface; therefore, cryosaunas ensure the effectiveness of WBC at the level of the original technology implemented in "Cryotium" but with less energy loss. The current state of WBC in Europe is a consequence of the 40-year use of the method in the absence of a reliable concept of the method for obtaining the cryotherapeutic effect and the uncertainty of the technological requirements to specialized equipment [3–5]. In such conditions, manufacturers of WBC installations have flooded Europe with installations that, by their therapeutic efficacy, do not differ from traditional hypothermia. The popularization of the thermophysical theory of WBC will stop the regression of cryotherapy in Europe

*<sup>A</sup>* þ 20 K*:* (5)

*THC* ! *TA*≈110 K*; THC*>*T*″

LN boiling point by more than 20 K:

*DOI: http://dx.doi.org/10.5772/intechopen.83680*

*Technique and Technology of Whole-Body Cryotherapy (WBC)*

supply of LN to the heat exchanger (HE).

ature in the main cab to �110°C.

and the world.

**137**

**Figure 2.** *The scheme of supplying liquid nitrogen to the heat exchangers of the installations for the WBC: (a) "Cryotium"; (b) "KR-2005."*

Yamauchi used the WBC method for the treatment of rheumatoid arthritis [1]; the technique was so effective that it quickly spread to the countries of Western Europe. In Poland and Germany, devices similar to "Cryotium" were put in production. European manufacturers have tried to reproduce the Japanese installation on the base of available information but, for unknown reasons, have changed the basic operating principle of "Cryotium." This is translated into an increase in the minimum operating temperature from �170 to �160°C [13]. A slight increase in temperature led to a whole chain of changes in cooling technology, which caused a gradual decrease in the efficiency of European (Polish and German) installations for WBC. As already shown above, the temperature level of �170°C was maintained in "Cryotium" without using a temperature control system, only through relief of excess pressure in the LN vapor line (**Figure 2a**).

The liquid level controller (YC) in the heat exchangers of the "Сryotium" installation according to the sensor signals of the Y level controls the operation of the solenoid valve (SV), through which LN enters the system. The cryogenic liquid enters the heat exchanger (HE) tubes, where it partially evaporates due to the supply of heat from the procedural room air. Vaporization reduces the flow density in the tubes; the vapor–liquid mixture is pushed out from the top of the heat exchanger to the liquid separator (LS). In this apparatus, liquid and vapor are separated. The liquid flows into the lower section of the heat exchanger (HE) and again participates in the removal of heat. LN vapors accumulate at the top of the liquid separator (LS). The vapor pressure is controlled by a safety valve (V), which opens at a pressure of 0.22 MPa. The vapor pressure determines the LN boiling point and the temperature of the tubes of the heat exchanger (HE), which must meet condition (1). The air temperature in the main "Cryotium" cab at the presence of patients rises to �170°C. In the pauses between the procedures, when the heat load on the cooling system is reduced by 10 times [7], the air temperature in the main cab approaches the temperature of the heat exchanger tubes:

$$
\Delta T\_{A-HC} \to \text{5 K}; \quad T\_A \to T\_A^{'} + \Delta T\_{A-HC} \approx 86 \text{ K} \left(-187 \text{ }^{\circ}\text{C}\right). \tag{4}
$$

The air temperature in the cab remains at the minimum possible level. In European installations, the air temperature in the cab is controlled by the temperature controller (TC), which, by signals from the temperature sensor (S), opens the liquid nitrogen supply valve (SV). In order to maintain the temperature at �160°C, the TC limits the supply of LN to the heat exchanger (HE) in the period when there are no patients in the cab. The LN level decreases until the sensor (S) registers the set

temperature. The upper sections of the heat exchanger (HE), through which the nitrogen passes in the vapor state, are heated to a temperature close to the air temperature in the chamber. The temperature of the inner tube surfaces exceeds the LN boiling point by more than 20 K:

$$T\_{HC} \longrightarrow T\_A \approx \mathbf{110\ K}; \quad T\_{HC} \gg T\_A^{'} + \mathbf{20\ K}.\tag{5}$$

When patients enter the main cab, relatively warm air enters from the lock chamber (*Ts* ¼ 210 K). Because of this, the air temperature in the cab increases by 50 K or more. The temperature controller opens the SV and resumes the supply of LN to the heat exchanger (HE). However, it takes some time to fill the tubes of the heat exchanger; moreover, the temperature of the upper sections of the heat exchanger (HE) exceeds the boiling point of nitrogen by more than 20 K. Because of this, the LN film boiling occurs at which the intensity of heat removal to the liquid is much lower; therefore, the vapor–liquid mixture passes the heat exchanger (HE) and is discharged through valve (V) into the environment. Under such conditions, the heat exchanger does not cope with heat generation from the surface of the patient's bodies and cannot restore the specified temperature mode of the chamber until the patients enter the lock chamber. The WBC procedure takes place at a temperature significantly higher than the nominal �160°C [7]. After the patients leave, the thermal load on the cryostatting system is reduced 10 times, the air temperature drops to the nominal level, and the temperature controller stops the supply of LN to the heat exchanger (HE).

The increase in the air nominal temperature in the cab for WBC from �170°C to �160°C fundamentally changed the temperature algorithm of the procedure. The transition to the LN film boiling regime caused a significant overrun of the cryoagent. The operational drawbacks of the nitrogen cooling system and the uncertainty of the air temperature requirements in the main procedural cab created conditions for use in the WBC cryostatting system of three-stage chillers and steam cycles on gas mixtures. Refusing LN resulted in an increase in the nominal temperature in the main cab to �110°C.

Specialists in the field of WBC did not only pay attention to this but also actively promoted the "modernization" of cryotherapy equipment [13–15]. The ability to refuse to use LN and significantly reduce the costs of WBC procedures turned out to be so attractive that the specialists "did not notice" that the efficiency of the procedures in the "nitrogen-free" installations was 10 times lower than in "Сryotium" [7]. At the beginning of the twenty-first century, "Criohome" "cryotherapeutic" devices with a nominal temperature of �85°C was used for WBC procedures, i.e., the tendency to increase the temperature persists. Since 1985, the Russian direction of devices for WBC has been developing independently, based on the use of singleseat installations with a nitrogen cooling system (cryosaunas). The temperature in the cab of a single-seat cryosauna during the whole procedure is no higher than �130°C. The conditional constancy of temperature fundamentally changes the degree of supercooling of the skin surface; therefore, cryosaunas ensure the effectiveness of WBC at the level of the original technology implemented in "Cryotium" but with less energy loss. The current state of WBC in Europe is a consequence of the 40-year use of the method in the absence of a reliable concept of the method for obtaining the cryotherapeutic effect and the uncertainty of the technological requirements to specialized equipment [3–5]. In such conditions, manufacturers of WBC installations have flooded Europe with installations that, by their therapeutic efficacy, do not differ from traditional hypothermia. The popularization of the thermophysical theory of WBC will stop the regression of cryotherapy in Europe and the world.

Yamauchi used the WBC method for the treatment of rheumatoid arthritis [1]; the technique was so effective that it quickly spread to the countries of Western Europe. In Poland and Germany, devices similar to "Cryotium" were put in production. European manufacturers have tried to reproduce the Japanese installation on the base of available information but, for unknown reasons, have changed the basic operating principle of "Cryotium." This is translated into an increase in the minimum operating temperature from �170 to �160°C [13]. A slight increase in temperature led to a whole chain of changes in cooling technology, which caused a gradual decrease in the efficiency of European (Polish and German) installations for WBC. As already shown above, the temperature level of �170°C was maintained in "Cryotium" without using a temperature control system, only through relief of

*The scheme of supplying liquid nitrogen to the heat exchangers of the installations for the WBC: (a) "Cryotium";*

The liquid level controller (YC) in the heat exchangers of the "Сryotium" installation according to the sensor signals of the Y level controls the operation of the solenoid valve (SV), through which LN enters the system. The cryogenic liquid enters the heat exchanger (HE) tubes, where it partially evaporates due to the supply of heat from the procedural room air. Vaporization reduces the flow density in the tubes; the vapor–liquid mixture is pushed out from the top of the heat exchanger to the liquid separator (LS). In this apparatus, liquid and vapor are separated. The liquid flows into the lower section of the heat exchanger (HE) and again participates in the removal of heat. LN vapors accumulate at the top of the liquid separator (LS). The vapor pressure is controlled by a safety valve (V), which opens at a pressure of 0.22 MPa. The vapor pressure determines the LN boiling point and the temperature of the tubes of the heat exchanger (HE), which must meet condition (1). The air temperature in the main "Cryotium" cab at the presence of patients rises to �170°C. In the pauses between the procedures, when the heat load on the cooling system is reduced by 10 times [7], the air temperature in the

main cab approaches the temperature of the heat exchanger tubes:

*<sup>A</sup>* <sup>þ</sup> *<sup>Δ</sup>TA*�*HC*≈86 K �187°

The air temperature in the cab remains at the minimum possible level. In European installations, the air temperature in the cab is controlled by the temperature controller (TC), which, by signals from the temperature sensor (S), opens the liquid nitrogen supply valve (SV). In order to maintain the temperature at �160°C, the TC limits the supply of LN to the heat exchanger (HE) in the period when there are no patients in the cab. The LN level decreases until the sensor (S) registers the set

C *:* (4)

*ΔTA*�*HC* ! 5 K*; TA* ! *T*″

excess pressure in the LN vapor line (**Figure 2a**).

**Figure 2.**

**136**

*(b) "KR-2005."*

*Low-temperature Technologies*
