Objective: To compare the differences in the needling sensation with acupuncture needles surface treated with nitrogen applied supercritical fluid (SCF-N) and stainless steel needles.

Materials and Methods: This was a double-blind prospective cohort study. The acupuncture needles were randomly used in this experiment, including the SCF-N-treated needles and the control stainless steel needles. LI 4 (Hegu) and LI 11 (Quchi) acupuncture points in the Yangming Large Intestine Meridian of Hand were treated. Physical electrical resistance , scanning electron microscopy, energy dispersive spectrometry, and visual analog scale score including the sensations of soreness, numbness, distention, and heaviness were assessed.

This was a double-blinded prospective cohort study. The acupuncture needles were first separated into two groups. One group of needles was subjected to SCF-N treatment while the other was not. The needles were then randomly analyzed with scanning electron microscope and energy dispersive X-ray spectroscopy to ensure quality and minimize experimental error. For each participant, one hand was randomly assigned to the treatment group with SCF-N-treated acupuncture needles and the other hand was assigned to the control group with the stainless steel needles. The time interval between the acupuncture treatment of the two groups was about two hours. In order to examine and distinguish the difference between the two groups, de-qi VAS score was recorded by the volunteers during needle insertion and the electrical resistance by electrical measurement.

The acupuncture needles used in this experiment, including the SCF-N-treated needles and the control stainless steel needles, were produced under the same conditions, in the same factory (Dong Bang acupuncture Inc.), and on the same day, to minimize experimental error.

The process of SCF treatment:. First, the stainless steel chamber and quartz carrier were sterilized using alcohol and autoclaving. Next, the needles were placed on the quartz carrier with the tip pointing upwards and then placed in the chamber and covered. Carbon dioxide was used to remove atmospheric components from the chamber and required volume of ammonia gas was passed. The pressure was increased up to 3000 pound per square inch(psi) and temperature up to 120℃. An hour later, the pressure was relieved and the process of SCF treatment completed. After completion of the treatment, the needles were then randomly selected for material analysis and electrical measurement. Following this, the needles were stored in a vacuum bag. This was done to reduce the influence of atmospheric contaminants on the needles after treatment, resulting in oxidation and rusting. Finally, there would be heterogeneous contact between the inorganic metal and the acupuncture needle. Hence, nitrogen was selected as the main agent for SCF treatment.

Inclusion Criteria:

• Healthy volunteer aged 20 to 40 years
• Provided informed consent

Exclusion Criteria:

• Women with pregnancy or breast feeding
• Bleeding tendencies (platelet counts less than 20000 and/or thrombocytopenic purpura)
• Volunteers with chronic medical conditions and anti-coagulants use
• Volunteers with pacemakers
• Fasting
• Unwilling to provide informed consent

The gross appearance of the two groups of needles were the same. They could be identified under microscope only.