This month’s blog:
30 November 2019 / 0 comments

Safety and effectiveness are significantly related to the WBC technology used.

More and more centers are opening worldwide, providing whole-body cryotherapy services. These centers are using many different technologies. To reach "cryo temperatures” either electricity, nitrogen or a combination is used. This all results in questions from the client: What’s the safest and best technology to reach my goals? 

Which technologies exist? 

Whole-body cryo chambers are chambers (single or multiple patients at once possible) in which the client is entirely exposed to the cold treatment. Partial-body cryotherapy units (head out) has reported lower operating temperatures compared to whole-body cryo chambers by evaporating liquid nitrogen being sprayed onto the body (“direct” contact). Information on the exact temperatures during exposure is often lacking, which has an impact on controlling safety and physiological responses.  

Table 1: an overview of the different cryotherapy technologies, temperature ranges and safety values 

 Cryochamber (Electrical) Cryochamber (Nitrogen Indirect) Cryo Unit (Nitrogen Indirect) Cryo sauna   (Nitrogen Direct) 
Technique of cooling  Electricity is used to extract heat A heat exchanger cools regular air with nitrogen A heat exchanger cools regular air with nitrogen Evaporating liquid nitrogen sprayed on the body 
Temperature range (°C/ °F)  Fixed at -110°C  (-166°F) [-90°C to -140°C]/ ([-130°F to -220°F]) [-90°C to -140°C]/ ([-130°F to -220°F]) [-110°C to -195°C]/ ([-166°F to -319°F]) 
Number of persons 2-8 2-8 

(* A new technology published by Bouzigon and colleagues based on forced convection (wind chill) is not considered yet as hardly any data on this technology is published). 

Safety and technology 

Different factors should be considered regarding safety: contraindications, precautions, used protocol, individual characteristics, body composition and the used technology. The technology is responsible for the actual exposure temperature and the temperature distribution. First, there appears to be a large difference between the set temperature and actual temperature. And second, often the actual temperature is much colder at the lower legs compared to for example the temperature at the chest and shoulders. The actual temperature and temperature distribution are responsible for the resulting physiological effects, like its effect on skin temperature.  

Various studies have shown that skin and core temperatures remain within a safe range [1-2], even after the most intensive treatment protocols. However, the skin temperatures reported in studies are most often general skin temperatures, a product of different local skin temperatures. If we look at local skin temperature at a specific location on the body, the skin temperature, especially on the lower legs and triceps, occasionally shows a temperature that is lower than the accepted barrier of 8°C/46.4°F, these are dangerous local skin temperatures, see figure 1. These can lead to unwanted events such as local skin damage or cold burns. However, they are rare but reported [3-5]. This is, of course, a reaction that varies from individual to individual, but it is necessary to be aware of this safety-related problem which is highly related to the technology used. 

(Figure 1: local shin skin temperature of 10 participants following a 3-minutes treatment at –110°C/202°F) 

Effectiveness and technology 

What can we say about effectiveness comparing the different technologies? Do technologies provide different effects? And is a session of 3 minutes at -90°C/-130°F providing different effects compared to a session at -130°C/-202°F?  

First, let us define the thermal state. The thermal state is described as the total of the thermophysiological responses in the body implying, skin-, core and muscle temperature changes together with subjective measures as thermal comfort and sensation. The variation in the thermal state is traditionally assessed to measure the efficacy. Following a session the thermal state is altered; skin-, core- and muscle temperature, thermal comfort and sensation decrease.  

A study from Hausswirth and colleagues [6] was the first comparing an electrically cooled chamber (3 minutes at -110°C/- 166°F) to a “direct," nitrogen cooled sauna (3 minutes at -160°C/-256°F). Skin temperature (see figure 2), directly after, differed a lot. Conclusions of the study were that whole-body cooling was more significant than partial-body cooling in the activation of the autonomic nervous system (the system responsible for nerve function and cellular activation). Outcomes prove that the treatment effect is a direct result of the change in thermal state, in this example, a uniform skin temperature reduction. 

(Figure 2: thermal image directly after exposure to partial body cooling (A) and whole-body cooling (B), blue being colder than green, green being colder than red, a figure from Hausswirth et al.2013). 

A limitation of the electronic chamber is that one cannot change temperature settings, and it appears that for the “direct” nitrogen sauna’s the temperature distribution is less homogeneous 

Is a session of 3 minutes at -90°C/-166°F providing different effects compared to a session at -130°C/ -202°F? 

Data comparing different treatment temperatures is scarce and more data is warranted. However, own data, showed a difference in the thermal state following protocol A (3 minutes at -90°C/-166°F) and B (3 minutes at -130°C/-202°F). No differences are found in core temperature, but a significant difference is found for the drop in skin temperature directly after the session until 40 minutes into recovery, see figure 3. 

Figure 3: Average core- and skin temperature (N=10) following two different whole-body cryotherapy protocols (A &B). 

Regarding safety and effectiveness, the main conclusions are: 

  • "Direct" systems have a higher risk of asphyxia. Skin damage and cold burns can occur in all technologies and are depending on the actual exposure temperature and temperature distribution. 
  • An equal distribution of the cold over the full-body results in a more optimal change in thermal state. With this thermal state regarded as the proxy for the wanted effects for the client.  
  • More intense treatment protocols (i.e., lower temperatures) trigger more significant skin temperature drops directly after exposure and for over 40 minutes into recovery. 
  • Besides taking individual characteristics into account [7], the treatment duration in line with treatment temperature should be considered. 

References 

  1. Bleakley, C. M., Bieuzen, F., Davison, G. W. & Costello, J. T. Whole-body cryotherapy: empirical evidence and theoretical perspectives. Open Access J Sports Med 5, 25–36 (2014). 
  2. Bouzigon, R., Grappe, F., Ravier, G. & Dugue, B. Whole- and partial-body cryostimulation/cryotherapy: Current technologies and practical applications. J. Therm. Biol. 61, 67–81 (2016). 
  3. Whole-Body Cyrotherapy Caused Cold Burn Injury. (2018). Available at: https://www.medpagetoday.com/dermatology/generaldermatology/76932. (Accessed: 19th December 2018) 
  4. Casady, M. Cryotherapy Co. Sued Over Texas Woman’s 2nd-Degree Burns - Law360. Available at: https://www.law360.com/articles/1116908/cryotherapy-co-sued-over-texas-woman-s-2nd-degree-burns. (Accessed: 17th January 2019) 
  5. 2 Missouri State players injured after cryotherapy treatment. usatoday Available at: https://www.usatoday.com/story/sports/ncaab/2018/01/29/2-missouri-state-players-injured-after-cryotherapy-treatment/109903402/. (Accessed: 28th January 2019) 
  6. Hausswirth, C. et al. Parasympathetic activity and blood catecholamine responses following a single partial-body cryostimulation and a whole-body cryostimulation. PLoS ONE 8, e72658 (2013). 
  7. Cuttell, S., Hammond, L. E., Langdon, D. & Costello, J. T. Individualising the exposure of -110C whole body cryotherapy: The effects of sex and body composition. Journal of Thermal Biology 1879, (2017). 
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