Aesthetic-Therapeutic Applications and Physiological Effects of Cryofrequency

Author(s): Valton da Silva Costa* and Tatiana Catarina Alburquerque Clementino dos Santos Introduction: Cryofrequency is a non-abrasive and non-invasive aesthetic treatment method aimed at complaints related to localized adiposity and cutaneous flaccidity. The method consists of the generation of radiofrequency waves that in contact with the subcutaneous tissues produce heat. The differential of the cryofrequency is that this method uses a system of superf ... Abstract View Full Article View DOI: 10.17352/2455-5487.000072


Introduction
Cryofrequency is a non-abrasive and non-invasive facial and body aesthetic treatment method that has been used relatively recently. The method enjoys wide dissemination in the various media, increasing acceptance by professionals in the fi elds of aesthetics and health, and so it has become a new alternative of treatment for people with complaints related mainly to localized adiposity and skin and muscle fl accidity [1,2]. The national companies and manufacturers responsible for the sale and dissemination of cryofrequency technology, as well as the products and devices that enable its application, defend the use of the technique, which according to them, allows the gain of immediate results, detectable since the fi rst day of application [2,3].
The method consists in the generation of radiation called radiofrequency, a range of the electromagnetic spectrum that goes from 3 Hz to 300 GHz, and the consequent deposition of thermoelectric energy on a given treatment area [4]. This radiation is said to be non-ionizing due to the low levels of energy produced from the generation of electric current so that its effect on the organism is purely thermal. The difference between cryofrequency and classic radiofrequency revolves around the existence of a cooling system in the cryofrequency apparatus. The term "cryofrequency" is mainly used in Brazil, whereas on a worldwide scale the most used term is radiofrequency, in this case, associated with a cooling system [4].
Radiofrequency has been used in medical treatments for almost a century, especially for surgery and ablative procedures.
However, as a non-ablative aesthetic treatment, that is, performed without the need of destroying the epidermis, its use dates back to more recent decades [5]. Most treatments utilize frequencies of up to 10 MHz, being this parameter the most important once it relates to the depth at which the energy reaches the tissue [5]. Cryfrequency is applied in at least two distinct but complementary manners. The fi rst manner is the application of monopolar, bipolar, and/or multipolar electromagnetic waves in an isolated or combined manner with intensity enough to generate heating around 60°C deeply in the dermis and hypodermis through a mechanism of energy conversion that occurs from the inside out of the tissues. And, the second manner is the simultaneous cooling (around -10°C) on the surface of the skin that is produced by the cryofrequency apparatus [2,6]. It is argued that this combination of high and low temperatures causes a sort of thermal shock, which would be one of the main mechanisms behind the therapeutic effects of the method.
According to cryofrequency supporters, that thermal shock leads to the destabilization of local metabolism, causing physiological changes that ultimately result in aesthetic benefi ts. The main aesthetic-therapeutic benefi ts of its application would be the immediate "lifting" of the skin and the breakdown and absorption of adipose tissue, in this manner combating tissue fl accidity and localized adiposity simultaneously, as well as related aesthetic complaints with similar pathophysiological mechanisms. The physiological effects evoked by the application of cryofrequency are related to changes in local metabolism such as vasodilation and increased oxygenation, contraction of collagen fi bers, renewal of collagen, and apoptosis of adipose cells [2,3].
The method is applied over any region of the face and the body, in areas such as the glutes, arms, back, legs, fl anks, abdomen, face, and neck. It is referred that cooling the epidermis causes a comfortable sensation, minimizing any discomfort caused by the deep heating of the tissues. Thus, in the most current radiofrequency devices, the coupling of an infrared thermometer allows the monitoring of the tissue temperature, which leads to a safer application of the radiofrequency waves during treatments. These treatments are usually carried out in sessions that last around 30 minutes and are done weekly or with a specifi c periodization according to the body region and the treatment objectives [2,3].
As general prerogatives, the patient needs to be in good eating and hydration habits so that the results of the treatment become evident. Furthermore, it is recommended that cryofrequency is used in conjunction with other aesthetic treatments, maximizing the effects, and improving the general aspect of the treating area [7]. Since it is an electrotherapeutic treatment, cryofrequency has the classic contraindications cited in the specialized literature and also emphasized by the manufacturers of the thermoelectrotherapy devices, to name some: use of pacemakers, metal and silicone implants in the area to be treated, neoplasia, dermatitis, epilepsy, pregnancy, etc [8].
Considering the widespread use of cryofrequency by professionals in the fi elds of aesthetics and health, as well as the wide dissemination in media and market on its shortonset and long-duration benefi ts, a critical exposure about this method must be made with an adequate description of its effects, both observed in clinical practice and experimentally proven by scientifi c studies. As a result, the use of the cryofrequency method may be used wisely, rationally, and safely, based on evidence.
To this end, we present here a review of the literature, with an emphasis on scientifi c sources that deal with the cryofrequency method (including radiofrequency with cooling systems). This article is divided into three parts. The fi rst part will deal with the aesthetic-therapeutic applications of cryofrequency. The second part will address the physiological effects underlying these applications. Finally, the third part will take a look at the scientifi c evidence available around the use of cryofrequency.

Method
A bibliographic review was carried out with a search for articles, book chapters, and other specialized sources related to the topic under study. It was considered sources from the last two decades, and older if regarded important to clarify the topic.
Most of these were from English-language sources. However, as cryofrequency seems to be a market brand in Brazil, we have also considered articles written in Portuguese, which were very few. The search for sources of scientifi c information took place manually and electronically, and all articles, books, and other electronic or printed sources considered relevant for this research were included in the review. From the entire bibliography found, 23 sources among articles and book chapters were subjected to screening by relevance and then included for reading. The results are presented in a descriptive and summarized way under the subtopics presented in the next sessions and discussed simultaneously.

Results and discussion
Bibliographic collection of the aesthetic and therapeutic applications of cryofrequency. From the collected and analyzed data, it is possible to identify two main therapeutic applications of cryofrequency. They are the use of the method to reduce tissue fl accidity for both the face and the body and other complaints related to aging, especially wrinkles, and the application of cryofrequency to reduce body measures, that is, to reduce localized adiposity. Besides these two main applications, cryofrequency has also been used for a wide range of other aesthetic and functional complaints, such as in the treatment of cellulitis and non-aesthetic dysfunctions [9].
A study that received much attention for having provided the basis for the approval of the use of radiofrequency as a face treatment by the Food and Drug Administration of the United States of America in 2004 was the study carried out by Fitzpatrick and collaborators [10]. This study with 86 participants showed that monopolar radiofrequency (with superfi cial cooling) applied only once led to a reduction in periorbital wrinkles and skin fl accidity in the supraorbital region, in addition to a high level of satisfaction by the participants (assessed using objective and subjective measures). It is interesting to note that that multicenter study indicated that the results persisted 6 months after the end of treatment. That study is aligned in its quantitative results with the controlled clinical study carried out by Bassichis, Dayan, and Thomas [11], which showed that cryofrequency was able to decrease the fl accidity of the upper third of the face, which, on the other hand, was not correlated with the participants' perception of improvement, unlike the aforementioned study.
A more recent pilot study, although not controlled and with a reduced sample (20 subjects), showed high to moderate results in the reduction of the periorbital region, even six months after the end of the study [12]. Similar results have also been reproduced in other studies with greater methodological limitations [13][14][15]. Previous searches of the literature on the use of radiofrequency with a cooling system pointed out that the method was effective in the treatment of localized adiposity and body remodeling [5].
In one of these studies, eight treatment sessions with a oneweek interval were carried out. It was applied to the regions of the abdomen, thighs, and buttocks for sessions of 20 minutes  [18], conducted a study with eleven women complaining of second-and third-degree cellulite in the gluteus region. Ten sessions were applied with a minimum interval of 24 hours, with the evaluation of objective measures through cirtometry of the region of the fl anks, hips, and breeches, as well as graduation tests for cellulitis and photographs. The results, in general, point out improvements in the aspects of cellulitis. However, the small sample size of the study, the use of some non-objective measures, and the absence of a control group limit the generalization of the results.

Bibliographic collection of the physiological effects of cryofrequency
Overall, the physiological effects of the method consist of the classic thermal effects of electrothermotherapy: vasodilation, increased oxygenation, and removal of debris in the tissues [8]. However, in the case of cryofrequency given the concomitant cooling of the epidermis, many have attributed some physiological effects to the so-called thermal shock caused by the "encounter" between the two stimulated temperatures: cold on the skin surface and more intense heat in the dermis. This is because radiofrequency generates heat when it encounters tissues. Thus, the greater the resistance of these tissues to electrical current, the greater the intensity of heat generated. Besides, heat spreads more deeply into the skin from the water present in these tissues. The heat then diffuses through the tissues in a three-dimensional manner with depth controlled according to the parameters of the energy source and the cooling system [6].
The ability of heat to cause collagen denaturation and the consequent neocollagenesis is widely accepted and proven, thus representing one of the main physiological effects of cryofrequency. This effect is of high clinical and aesthetic value since during the aging process there is a important loss of collagen content and an increase in elastin, leading to the condition of fl accidity both at the cutaneous and at the muscular levels [6,19]. Hsu and Kaminer [13], based on animal models, observed that the heating of the skin layers leads to the denaturation of collagen and the consequent stiffening and shortening of collagen fi brils, in addition to the increase in fi broblastic activity and neocollagenesis during many months after initial applications. This is because when properly heated the collagen fi bers change their conformation, contracting due to the breakdown of hydrogen bonds, assuming a more stable structure and shortening the collagen fi bers. These molecular processes are responsible for the "lifting" or skin tightening effect. The fi nal effect of that is a more robust and youthful appearance of the skin [9,19]. and clinical effect [6,19]. It has also been observed that heat stimulates fi broblasts to produce collagen, which makes the deposition of type 1 collagen and its reorganization the main mechanism behind that remodeling.
It is indicated that the collagen shrinkage temperature is between 57 and 61°C. In millisecond exposures this optimum temperature rises to 85°C, and for longer exposure times (of many seconds) this temperature may be between 60 and 65°C [6]. So, it can be assumed that there is an optimal combination of exposure time and temperature for an effective and safe result, associated with appropriate protection of the epidermis, which occurs due to the cooling caused by the cryofrequency device before, during and after the generation of heat. The physiological mechanism of cryofrequency is, therefore, of two natures: the immediate contraction of collagen (which is immediate to its denaturation) and the natural curative response of the organism that involves remodeling by collagen deposition and the subsequent increase in its density [20].
The reduction in localized adiposity is mainly attributed to the breakdown of fat caused by the deposition of heat. The underlying cellular process would be the apoptosis of fat cells, that is, there would be a programmed cell death process in the tissues treated with cryofrequency. Thus, there would be a reduction of reserve fat in tissues due to the high internal temperature, so that triglycerides would be broken down into fatty acids and glycerols, a process called lipolysis [8].
A clinical study by Franco and colleagues [21], was able to show that the availability of fat cells decreased markedly after the application of radiofrequency during 1 to 3 minutes of treatment (from 89% to 20%) and that this result was related to the temperature intensity reached in the hypodermis.
Despite not using a superfi cial cooling system, no harmful effects were observed in the most superfi cial layers because the radiofrequency produced a heat gradient, with an ever lower intensity until reaching the epidermis. The study also attested to the occurrence of vascular changes (vasodilation, congestion) after the fourth day of treatment and adipocyte necrosis on the ninth day of treatment within 4.5-19 mm of skin depth.
The study by McDaniel and collaborators [22], used a pig animal model to study the effects of monopolar radiofrequency on reducing abdominal fat. This study demonstrated the method's ability to generate deep heat and complete preservation of the epidermis simultaneously. Using histological analysis, they proved that the process of apoptosis of adipocytes does occur in the tissues under treatment, with mild signs of infl ammation in the treated area. They concluded that an 11-minute treatment was suffi cient to cause adipose tissue breakdown in a 20cm x 10cm treatment area, which occurred at increasing rates in subsequent treatment sessions with a peak of up to 53% in the apoptotic index. Thus, both the process of necrosis due to adipose tissue injury and the process of apoptosis is behind the physiological effects of applying cryofrequency to reduce localized adiposity.
Although the effect of the thermal shock generated by cryofrequency devices may affect the outcomes of the treatment, the aforementioned study [22], did not attribute the observed effects to the temperature shock, but the high temperatures reached in the subcutaneous tissues. The cooling of the epidermis was used to protect the layer from the harmful action of these high temperatures. The main effects produced by cryofrequency, namely, shortening of collagen fi bers, neocollagenesis, and the death of fat cells seem to be responsible for the range of benefi ts observed in the treatments [23].

Analysis of available scientifi c evidence
Many devices aimed at aesthetic treatments are built and perfected very quickly, in many cases much faster than the ability of scientifi c studies to be carried out and have the prerogatives of a treatment's clinical effects analyzed.
Therefore, when research data fi nally becomes available, these devices are already outdated or have already been widely used by consumers [6]. Older studies report the occurrence of some side effects related to the use of the devices and the application of radiofrequency, such as burns, erythema, mild edema, infl ammatory process and pain [10,13,14]. However, with the improvement of that technology, many of these events have been minimized. With the advancement of refrigeration systems attached to the device and monitoring through the coupling of infrared thermometers, burns and pain are no longer common events, making the application of the method easier to be applied by the practitioners and safer for the users [9].
Considering all the evidence discussed here, we can see that there is a solid basis for confi rming the aesthetic and physiological effects usually attributed to cryofrequency treatment. In any case, many studies still need to improve their methodological quality. One previous literature review [6] showed that the level of evidence from the studies carried out so far was still low (considering 12 studies). Even studies with good quality still do not often meet sample randomization methods and/or do not use control groups. Another observation that can be made is that many of those studies usually use subjective measures, such as before-and-after approaches, photograph visual analyses, and self-perception questionnaires as the lead method of evaluating the treatment effects. However, in recent years an increasing number of studies with better experimental designs have been carried out. Some of these studies, as mentioned in the present review, made good use of more objective outcomes associated with subjective measures (individual satisfaction, self-perception of improvement, etc).

Conclusions
The purpose of this review was to search the specialized bibliography for both the aesthetic-therapeutic and the physiological effects of the cryofrequency method, and fi nally to analyze the evidence surrounding it. It was found that cryofrequency or the application of radiofrequency with concomitant cooling of the epidermis has at least two main applications: reduction of skin fl accidity and localized adiposity. The evidence that cryofrequency is effective in reducing these aesthetic complaints comes from both animal and clinical studies, although many of the clinical studies still have limitations regarding the experimental design and the evaluation method. Higher methodological quality studies are therefore necessary to reduce the biases arising from the different types of cryo/radiofrequency devices and consequently support its use.