Many traditional Chinese acupuncturists consider the elicitation of
Interestingly, on one hand, authors strive to differentiate those needle sensations that they regard as aspects of
In an early example, Vincent and colleagues [
A range of psychometric instruments to measure
While many authors have attempted to define the qualities that make up the
This research comprised one component of a comprehensive examination of the effects of different needling parameters on regional pressure pain threshold. All subjects received the same baseline threshold measurements prior to each needling session: this involved them relaxing supine on a treatment table for ten minutes while pressure pain threshold (identified by the subjects as when the pressure sensation first becomes discomforting) was measured with an algometer at sites on the limbs and head. Ethics approval was obtained from the University of Technology, Sydney (UTS) Human Research Ethics Committee prior to commencing the study (UTS HREC 2009-067A). This study closely follows the design and protocols developed in 1999 at UTS and applied to related research into acupuncture and pressure pain threshold in six previous postgraduate research programs [
The aim is to investigate the effect of three needling parameters on the strength and quality of
The study formed one arm of a comprehensive examination of the effects of different acupuncture needling parameters on regional pressure pain threshold in healthy subjects. This needling component of the overall research employed a randomised single blind (subject) within subjects with repeated measures design using a standardised protocol.
The 24 study subjects (12 men and 12 women) were volunteers from the broader university staff and student community, recruited via the UTS Faculty noticeboards and/or word of mouth. Study inclusion criteria were healthy adults with no medical history of chronic musculoskeletal disorder, aged between 18 and 45. Exclusion criteria included regular users of analgesic or other drugs that may dampen pain perception, haemophilia, and use of anticoagulant medication that may interfere with blood clotting. Participants were required to abstain from analgesic medication on experimental intervention days.
For each intervention session, a single 0.22 mm × 30 mm sterile stainless steel disposable needle (Viva USA) was inserted at either the acupoint, LI4 or the nonacupoint, NAP and for either one or 21 minutes. Insertion on all occasions was perpendicular (90°) to the skin and to a depth of 15–20 mm, thereby not only puncturing the skin but also underlying structures such as muscle, fat, and fascia. The intervention was applied unilaterally on the right arm. The needling parameters examined, site of insertion, needle manipulation, and needle retention time, are defined below.
LI4: acupoint, located as the highest point of the
NAP: nonacupoint located within the same dermatome as LI4, on the dorsal aspect of the hand, midway along the medial shaft of the second metacarpal bone (see Figure
Location of LI4 and NAP in relation to the two extra acupoints
Manipulation present—needle manipulation involved rotating the needle for five seconds between the thumb and index finger through a large 540–720° angle in a bidirectional manner. This was applied every three minutes.
Manipulation absent—every three minutes, the acupuncturist rested his hand in the same position as above and lightly moved his fingers on the back of the subject’s hand to mimic movements that would accompany needle manipulation. This is referred to as “simulated manipulation.”
Duration of needle insertion was either one minute or 21 minutes. Note that for the one minute duration needling interventions, the needle was only present during this initial period (
Each intervention involved deep needle insertion and one of the following eight sets of parameters (Table
Intervention | Site | Retention time | Manipulation |
---|---|---|---|
LI4m+1 | LI4 | 1 minute | Present |
LI4m−1 | LI4 | 1 minute | Absent (simulated manipulation) |
LI4m+21 | LI4 | 21 minutes | Present |
LI4m−21 | LI4 | 21 minutes | Absent (simulated manipulation) |
NAPm+1 | NAP | 1 minute | Present |
NAPm−1 | NAP | 1 minute | Absent (simulated manipulation) |
NAPm+21 | NAP | 21 minutes | Present |
NAPm−21 | NAP | 21 minutes | Absent (simulated manipulation) |
Since all subjects received four interventions to each of two needling sites, it was assumed that they would realise that two locations were being used. In previous studies that have used the same protocol and insertion sites, postintervention feedback from subjects (many of whom were final year acupuncture interns at UTS) showed that while most subjects were aware of different locations being needled, both sites were thought to be acupoints and the NAP location was even reported by some subjects to be an extra point [
To control for possible changes in expectations that might gradually develop during the eight experimental sessions, careful stratified randomisation of presentation order of interventions was implemented. This included using an
A random sequencing of the eight interventions for each subject was achieved using an envelope method that was also stratified by gender to match as closely as possible the sequencing by gender. Each sequence was printed on a slip of paper and sealed into an individual envelope marked F or M. At the beginning of their first session, the subjects chose one of the available envelopes and this determined their unique sequence of interventions. Each subject completed eight intervention sessions spaced at least one week apart.
Throughout the 21 minute intervention period, a curtain was positioned to prevent subjects from observing their right arm and the acupuncturist’s activities. This both standardised and restricted interactions with the acupuncturist and facilitated his realistic application of simulated manipulation to an actual or virtual needle. The same acupuncturist applied all interventions; the 21 minute intervention period was standardised; manipulation was applied or simulated every three minutes; all subjects completed all study interventions and data were not analysed until the end of the study to avoid possible biases related to researcher expectations.
Throughout each session, the subject lay supine on the treatment table. Prior to receiving each intervention, as part of the broader research program, a standardised series of baseline pressure pain threshold measurements were recorded from ten regional sites. The study’s acupuncturist (with >35 years of clinical experience) then initiated the 21-minute intervention protocol for this arm of the research, summarised in the following timelines.
Real or simulated needle “manipulation” at VAS pain and needle sensation scores recorded at
Real or simulated needle “manipulation” at Simulated “needle” manipulation at VAS pain and needle sensation scores recorded at
Statistical analyses comprised one way ANOVA for correlated samples with Tukey post hoc testing, Chi square I (goodness of fit), and basic descriptive statistics for each time interval and intervention.
In Figure
The mean pain intensity scores (left hand graph) and the mean sensation intensity scores (right hand graph) for the eight interventions at three-minute intervals during the 21-minute intervention period. The error bars depict ±1 standard error of the mean. The same colour key applies to both graphs.
At time
With respect to both needling pain and needle sensation, the sets of profiles for the remaining six interventions showed similar, rapid decreases in mean scores. In all intervention comparisons, for pain and needle sensation, the values of the ANOVA
These two patterns within the sets of profiles reflected statistically significant differences. With the pain profiles, post hoc analyses (Tukey post hocs, in all cases statistical significance at least
The needle sensation profiles for both LI4m+21 and NAPm+21 showed similar patterns to those for needling pain. However, there were more comparisons where their mean increases did not differ statistically significantly from the means for the remaining six interventions. This was the case for both interventions for four comparisons at
In summary, the continued application of needle manipulation and retention of the needle were important for maintaining elevated needle sensation as well as pain associated with needling. By contrast, both the needle pain and sensation experienced was independent of insertion site.
The following four graphs show for each intervention, the number of subjects at each three-minute recording interval who reported experiencing each of the following: neither pain nor needle sensation; both pain and needle sensation; only pain; or only needle sensation.
From the frequencies of subjects among interventions reporting neither pain nor needle sensation (Figure
Comparison of the eight interventions with respect to the number of subjects at each three-minute recording interval who had: neither pain nor needle sensation (a); both pain and needle sensation (b); only pain (c); or only needle sensation (d). In all cases, total number of subjects = 24.
No pain or needle sensation profile
Pain plus needle sensation profile
Pain without needle sensation profile
Needle sensation without pain profile
By contrast, virtually no subjects reported pain alone (Figure
In summary, the experiences of needle sensation and pain were closely linked with respect to duration and presence of manipulation but not to location of needling.
From the pain and needle sensation profiles for individual interventions shown in Figure
Comparison within each of the eight interventions of the number of subjects at each three-minute recording interval who had neither pain nor needle sensation; both pain and needle sensation; only pain; or only needle sensation. Total number of subjects = 24.
NAPm+21
LI4m+21
NAPm−21
LI4m−21
NAPm+1
LI4m+1
NAPm−1
LI4m−1
The eight profiles clustered into two distinct two response patterns: one shared by the pair with 21-minute needle retention and repeated manipulation, and the other by the remaining six interventions.
Pattern 1: for all measurement intervals including
Pattern 2: for all measurement intervals except
At the end of each session, subjects reported the needling sensations they had experienced during the intervention. Note that subjects were not limited to a single descriptor. Since these unsolicited descriptors reported by subjects were found to be in good agreement with ones from the MMPQ, they have been grouped according to MMPQ categories [
The categories that contain descriptors provided by subjects are shown in Table
Category | Descriptors (in order of intensity rank) |
---|---|
1 | Flickering, pulsing, quivering, throbbing, beating, pounding |
3 | Pricking, boring, drilling, stabbing |
4 | Sharp, cutting, lacerating |
5 | Pinching, pressing, gnawing, cramping, crushing |
6 | Tugging, pulling, wrenching |
7 | Hot, burning, scalding, searing |
8 | Tingling, itchy, smarting, stinging |
9 | Dull, sore, hurting, aching, heavy |
17 | Spreading, radiating, penetrating, piercing |
18 | Tight, numb, squeezing, drawing, tearing |
19 | Cool, cold, freezing |
21 | Electricity |
22 | Warm |
23 | Indescribable |
Study subjects’ results are summarised in Table
Total Number
Intervention | NAPm+ | NAPm− | LI4m+ | LI4m− | ||||
---|---|---|---|---|---|---|---|---|
|
|
|
|
|
|
|
| |
21 min | 81 | 41(2) | 33 | 22(7) | 87 | 43(2) | 53 | 27(6) |
1 min | 43 | 27(3) | 41 | 24(7) | 55 | 29(6) | 41 | 24(7) |
Profiles for each intervention for the frequency
NAPm+21
NAPm−21
LI4m+21
LI4m−21
NAPm+1
NAPm−1
LI4m+1
LI4m−1
The MMPQ based descriptor intensity profiles are shown for the eight interventions in Figures
For all eight interventions, descriptors were reported from the same five descriptor categories that included 8, 9, 18, and the additional 21 (electricity) and 22 (warm). The most frequently reported descriptors were from category 8 and included some form or intensity of tingle, sting or itch. The second most frequently used terms were from category 18 (typically numbness). Less frequent but reported for all interventions were category 9 terms (dull ache). Far less frequent were the ungrouped terms “warm” and “electricity.”
Figure
The findings for both needle sensation and pain among the eight interventions are strikingly consistent in terms of providing both positive and negative instances, all of which support the conclusion that needle manipulation and needle retention are important for maintaining an elevation in needle sensation and pain. By contrast, no additional or differential effect was shown for the site of needling insertion although one was an acupoint (LI4) and the other was not (NAP). These findings related to both quantitative VAS scores as well as to the qualitative descriptors spontaneously reported by subjects and discussed later in this section.
Another clear relationship among the findings was that needling pain and needle sensation overwhelmingly were present or absent together. This may relate to the role of acute pain in helping to protect the body. Its role is one of warning and alerting the conscious organism about the presence of a noxious or potentially harmful sensory stimulus. This is demonstrated by the similar role of pain across such diverse perceptual experiences as, for example, touch, sound, light, or taste. Therefore, piercing the intact skin and underlying tissues with a needle represents an invasive threat and should activate appropriate sensory mechanisms. Deep piercing together with needle manipulation, by involving more stimulation would augment the sensory input and be expected to produce a more intense sensory perception of discomfort and pain. Since “
The qualitative descriptors used by the subjects in this study were the subjects’ own individually and spontaneously provided words. Therefore it is noteworthy first, that the profiles for qualities of needle sensation were similar for NAP and LI4 and second, that the terms fitted almost perfectly into the category groupings developed for the well validated MMPQ [
MacPherson and Asghar [
The study also showed that needle sensation was maintained only when the needle was both retained and received ongoing manipulation (Figure
Subjects spontaneously provided needle sensation descriptors that also describe pain: qualitatively and quantitatively and relevant here is the concept of “pain threshold,” that is, the intensity of a nonpainful sensory stimulus when it begins to take on
The descriptors in the MMPQ are not the sole preserve of pain. They are merely descriptors of sensory experiences, in terms of quality and intensity, and may not necessarily be describing something that is unpleasant or potentially noxious. Even some of the more intense descriptors may, in some sensory experiences and in certain settings, reflect positive and very pleasurable sensations in healthy individuals, as for example with the pressure of deep, strong massage or the spreading and radiating heat from a heat lamp.
Pain may contribute to “
Vincent and colleagues’ early study [
Typically and necessarily, studies of needle sensation have involved healthy study subjects. This is perhaps incongruous, given that the intent of clinical acupuncture interventions is to restore balance or health when there is some imbalance or illness. That is, is it appropriate to assume that needle sensation may be linked in either a causative or a correlative manner with a specific, measurable physiological response; and if so, what clinical response(s) could be regarded as being appropriate to examine in relation to presence or levels of needle sensation in a healthy subject? Pain threshold has been a common choice here. Not only can it be quantified with VAS and MMPQ style instruments, but measurement is neither invasive nor injurious to tissues. However, it may be regarded as counter intuitive that acupuncture, a process hypothesised to restore bodily functional balance, should modify the resting pain threshold in a healthy individual. On the other hand, if needle sensation is regarded as simply part of the sensory system’s alerting of the presence of an invasive, potentially noxious insult to the tissues, then the recruitment of defences would be typical and expected.
It is important to stress that the subjects in this study were selected on the basis of being in good health, since the aim of the study was to obtain baseline information about the influence of the three parameters being researched. Whether the responses to the same set of interventions would be different for patients with specific clinical conditions is unknown. However, the profiles and other data collected in the present research could serve as a baseline for related clinically oriented research.
In the present study, there was little evidence of a significant placebo effect in that in general, subjects did not report further pain or needle sensation after needle removal in the one minute retention interventions. The limited number and range of sensations reported after needling for these interventions typically included numbness and tickling/tingling and Figure
This study examined three needling parameters (site of insertion, manipulation, and retention time) in relation to the outcome measures of intensity of pain or needle sensation and qualitative descriptors of the needle sensation. Results showed that while the levels of needle sensation and pain were similarly intense following needle insertion for all interventions, initial intensity levels faded away rapidly unless the needle was both retained and manipulation repeated. Neither the eliciting nor maintaining of needle sensation or pain was restricted to a designated acupoint, with similar outcomes obtained at both LI4 and NAP. Typically, both pain and needle sensation were present (or absent) together and very few subjects reported pain or needle sensation in isolation.
The needle sensation descriptors spontaneously reported by subjects were in good agreement with the MMPQ pain descriptors. Based on the MMPQ categories, the descriptors reported by subjects did not differentiate between the two needling sites in terms of either quality or the intensity of the terms used. However, they did discriminate between the two 21-minute interventions with manipulation present, compared with the other six interventions. More descriptors and greater intensity scores were reported for the former pair of intervention compared with other interventions, all of which reported very similar lower intensity scores and numbers of descriptors.
All acupuncture sequences were administered by Christopher Zaslawski, School of Medical and Molecular Biosciences, Faculty of Science, University of Technology, Sydney.