Introduction
Cupping therapy is a treatment to release toxins from the body by using special cups to generate suction and adsorption at the surface of the skin. Both Eastern and Western countries have used cupping therapy since ancient times, and in Korea, the practice of cupping is included in Donguibogam [1].
Cupping therapy is simple, safe, and very effective. Given the simplicity of cupping treatment it can be used in clinical practice and its wider clinical applications, and it is now used regularly in modern medicine [2].
Cupping therapy has been covered as a medical procedure by the National Health Insurance in Korea since 1987. It is used as a treatment for various diseases, and many studies have been conducted on the efficacy of cupping therapy [3]. However, research on the effectiveness of treatment according to cupping pressure is insufficient, so cupping therapy remains nonstandardised. As there are no clear criteria for pressure settings during cupping therapy, scientists are conducting research in a random manner and clinicians are using cupping in various ways in clinical practice. In this study, we aimed to review the body of evidence detailing the cupping pressure used, with a view to standardising the practice of cupping therapy.
Materials and Methods
Research method
Database search
The following domestic (Korean) academic databases were searched: Korean Information Service System (KISS), National Securities Depository Ltd. (NDSL), Regional Information Sharing Systems (RISS), and DBpia. The following foreign databases were also searched: National Center for Biotechnology Information (NCBI) PubMed, Excerpta Medica database (EMBASE).
Search period and method
The search period for domestic studies was inclusive until June 30, 2019 and included both dissertations, and studies published in academic journals. The search period for foreign studies was inclusive until June 30, 2019 using the search criteria “humans, English”.
Fig. 2 shows the flow chart of study selection. One researcher conducted the search and produced the results, and another researcher reviewed them and agreed on the final studies for inclusion in this review. These studies were checked to ensure that they conformed to the study topic, and duplicate studies were excluded.
Results
Characteristics of research studies
The characteristics of the included studies are summarized in Table 1 (domestic) and Table 2 (foreign).
In the domestic research studies, manual and plastic cupping devices were the most common types. The most common cupping site was the back. The number of studies that used silicon rubber plates increased after 2008. The thickness of silicon rubber sheets varied between 3 mm and 10 mm. Cupping pressure varied between 60 mmHg and 600 mmHg. The duration of cupping was between 1 minute and 20 minutes (Table 1).
In the foreign research studies, the most common types of cupping devices were motor-operated cups and glass cups. The most common cupping site was the lower back. The cupping pressure ranged from 60 mmHg to 750 mmHg (100 kPa). The cupping duration ranged between 6 minutes and 20 minutes (Table 2).
The biggest difference between the domestic and foreign studies was regarding the type of cupping device used.
The criteria to classify constant pressure or maximum pressure in the research articles included in this review, was according to the content of the article. If recorded measurements were up to the maximum pressure, it was classified as maximum pressure. Without any records of maximum pressure, if there were measurements taken at a specific pressure for specific time, it is classified as constant pressure (Tables 3-6).
Classification by year
Of the 27 total studies, 19 (70.4%) were domestic and 8 (29.6%) were foreign. Domestic studies that contained details of cupping pressure showed a frequency of 3 in 2008, 1 in 2009, 3 in 2010 and 2 in 2011 and the numbers of studies declined after 2013. Foreign studies showed an increase from 1 study before 2010, to 7 studies after 2010 (Fig. 3).
Categorisation by pressure
Domestic research - constant negative pressure
The constant negative pressure in the studies by Im and Moon [5], Park and Lee [7], Kweon et al [9], and Lee et al [10] was 60 mmHg. The constant negative pressure was 225 mmHg in the study by Kim et al [15], 240 mmHg in the study by Shin et al [6], and 400 mmHg in the study by Oh and Kim [8]. In comparison, the constant negative pressure in the studies by Shin [4], Ryu et al [11], Kim et al [16], Kim et al [18], and Kim et al [20] was 600 mmHg (Table 3).
In the 12 domestic studies, there were 5 studies that used 600 mmHg, 4 that used 60 mmHg, 1 that used 225 mmHg, 1 that used 240 mmHg, and 1 that used 400 mmHg. Reports that included the diameter and volume of the cups were insufficient.
Domestic research - maximum negative pressure
The maximum negative pressure in the studies by So et al [12] and Kim et al [20] was 300-400 mmHg for cup size 1. Size 1, 2, 3, 4 and 5 cups have the same diameter. The maximum negative pressure in the studies by Kim et al [13], Yi et al [14] and Yi et al [17] was 550-650 mmHg (Table 4).
In the 5 domestic studies, the maximum negative pressure was 550-650 mmHg in 3 studies, and 300-400 mmHg in 2 studies. Very few studies reported on the volume of the cups.
Foreign research - constant negative pressure
The constant negative pressure in the study by Blunt and Lee [22] was 75-150 mmHg, and 75 mmHg, 225 mmHg, and 375 mmHg in the study by Tham et al [21]. The constant negative pressure in the study by Teut et al [27] was 112.5-262.5 mmHg, and 750 mmHg in the study by Blunt and Lee [22] (Table 5).
There were 4 foreign studies using constant negative pressure. There were insufficient reports on the diameter and volume of cups in the foreign studies.
Foreign research - maximum negative pressure
The maximum negative pressure in the study by Huber et al [23] was 420 mmHg using the Alcohol Flame (AF) method. It was 236.3 mmHg in the study by Emerich et al [25] using the Healthy Volunteers (HV) method, and it was 60 mmHg in the study by Duh and Chiu [26] (Table 6).
Electronic cupping devices were used in 3 foreign studies. There were insufficient reports on the diameter of the cups in the literature.
Discussion
Cupping therapy was introduced to Korea, Japan and Southeast Asia a long time ago and it is still used today. Specially made glass cups, ceramic cups or bamboo cups are placed on the part of the human body being treated for disease [28]. Over time, various technologies to assist cupping have been developed. Recently, interest in cupping methods has resurfaced and a number of studies on cupping therapy have been undertaken [29,30]. Currently, the majority of Korean medicine doctors perform cupping for musculoskeletal problems and internal diseases. Despite this, there are no studies on post-treatment side effects such as blisters, with the exception of 1 study by Yun et al [31], and no standardised treatment procedure. In this study, a total of 27 studies related to cupping therapy were reviewed to establish the correlation between cupping pressure and treatment effects so that cupping therapy can be standardised.
It was observed that constant negative pressure used in domestic research varied widely, ranging from 60 mmHg to 600 mmHg. The diameter of the cups also varied widely, ranging between 25 mm and 50 mm, and the volume of cups was largely unreported. Therefore, further experimental studies are needed on the relative results using different diameters and volumes of cups with the same constant negative pressure.
In addition, the maximum negative pressure used in domestic research varied widely, ranging from 300–400 mmHg to 540–660 mmHg (using an electronic cupping device). Only 5 studies actually reported maximum negative pressure settings. Therefore, due to insufficient reporting, a conclusion could not be proposed.
Moreover, the reported constant negative pressure in 4 foreign studies also varied widely, ranging from 75 mmHg to 375 mmHg depending on the method of cupping used. The reported maximum constant negative pressure in the 4 foreign studies also ranged widely. Only 2 studies reported on the diameter of the cups, and this range was 40 mm to 50 mm. The number of studies was quite small and there was limited information about the volume of the cups, so conclusions could not be drawn.
Furthermore, the reported maximum negative pressure in the foreign studies varied widely (between 60 mmHg and 420 mmHg) although electronic cupping was used for all studies. Two studies reported the volume of the cup which was 168 cc. Unfortunately, the information provided on maximum negative pressure in the foreign studies was not sufficient to generalise the results.
Conclusion
In conclusion, although we investigated 27 studies, including domestic and foreign studies, there were large differences in the cupping devices used, the constant negative pressure, the maximum negative pressure, the cup size, and the cup volume. It was evident that there are no specific criteria for standardised cupping treatment, and we could not directly compare the results of these studies. Furthermore, many studies lacked detail on the methods used for cupping. Therefore, we could not make any conclusive recommendations about cupping therapy. In this context, further experimental studies are needed to establish standardised cupping therapy procedures.
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