Pain threshold
In acoustics and medicine, the pain threshold , also known as pain threshold or pain threshold , denotes the lowest strength of a stimulus that is perceived as painful by the test person . The term "sensing threshold" is also used. It can be determined with quantitative sensory testing .
Acoustic pain threshold
The acoustic pain threshold of humans cannot be clearly defined in a generally valid way, because on the one hand exposure of test persons up to the pain threshold is very unpleasant and can cause irreparable hearing damage and on the other hand the pain perception is individually different. In the literature, sound pressure levels between 120 dB and 140 dB and sound pressures between 20 Pa and 200 Pa are given as pain thresholds .
| Pain threshold | ||
|---|---|---|
| Sound pressure level | Sound pressure | |
| 140 dBSPL | 200 Pa | |
| 137.5 dBSPL | 150 Pa | |
| 134 dBSPL | 100 Pa | |
| 130 dBSPL | 63 Pa | |
| 120 dBSPL | 20 Pa | |
The pain threshold is less dependent on the frequency than the hearing threshold and limits the listening area upwards. Below the pain threshold there is the discomfort threshold .
Thermal pain thresholds
The pain thresholds for nociceptors of the skin are - depending on the examination technique - around + 44 ° C in the warm range and + 17 ° C in the cold range. The threshold values for the excitation of isolated pain nerve fibers of type Aδ ( Aδ fibers ) are +42 ° C ( heat pain ) and +7.6 ° C ( cold pain ), those isolated C fibers are +40.3 ° C (heat pain) or +10.1 ° C (cold pain). If thermal effects exceed the threshold values for a certain duration, tissue damage occurs ( burns , scalds , frostbite ). The thermal pain thresholds are increased when the number of Aδ and C fiber nociceptors is reduced in certain nerve diseases (e.g. polyneuropathy of the feet with atrophy of the nerve endings due to diabetes mellitus ). As a result of pathologically increased pain thresholds for heat / cold stimuli, burns / frostbite are not perceived in time.
Mechanical pain threshold (pressure pain)
Isolated mechanical nociceptors at the endings of Aδ nerve fibers (the same ones that are also activated by thermal pain stimuli) are excited by the application of force of at least 10 mN (threshold value). For the excitation of mechanical nociceptors at the endings of isolated C nerve fibers (the same, which are also activated by thermal pain stimuli), a stimulus strength of at least 24 mN is required. The pressure pain threshold is increased in certain nerve diseases (e.g. polyneuropathy of the feet ) because the nerve endings of the Aδ and C fibers in the feet atrophy. The consequence of a pathologically increased pressure pain threshold is that pressure-related skin damage and wounds are not noticed in time.
Decreased pain thresholds
Nociceptors are only activated by tissue irritation, during which the body's own substances are released (including cytokines, serotonin, histamine). Local inflammations in turn release additional cell substances that increase the sensitivity of the nociceptors, with the result that the pain threshold is reduced in the case of inflammation (inflamed tissue is over-sensitive, even to slight, otherwise painless irritations such as touch; hyperalgesia ). After the inflammation subsides, the pain threshold returns to normal. The same goes for wound pain .
Increased pain thresholds
An increase in the pain threshold is usually due to a disease, due to a reduction in the number of Aδ and C fiber nociceptors or a disruption of their function. In rare, genetic diseases, there is lifelong insensitivity to pain stimuli, i. H. the pain thresholds are immeasurably increased (innate insensitivity to pain, " congenital insenitivity to pain "). With certain nerve diseases (e.g. diabetic polyneuropathy of the feet ), the nerve endings of the Aδ and C fibers (i.e. the nociceptors) gradually wither, with the result that temperature-related and mechanical skin damage can ultimately no longer be perceived in time (diabetic polyneuropathy is incurable). In diabetic foot syndrome, the mechanical pain threshold (pinprick) is higher than 512 mN. The pain threshold increases temporarily and a. When the corresponding nerve fibers are cooled: the operating temperature of the fibers falls below the required temperature, the electrical impulses sent by the nociceptors come to a halt within the nerve fibers. Chilled tissue is less sensitive to pain, even to strong pain stimuli. Certain drugs, so-called local anesthetics , are used to artificially increase the pain threshold temporarily.
Others
In the BDSM area, the phenomenon of algolagnia is known, in which a tactile stimulus is no longer perceived as painful, but as pleasurable in certain situations. This is also referred to as a “pain threshold”.
literature
- Martin S. Angst, Nicholas G. Phillips u. a .: Pain sensitivity and opioid analgesia. A pharmacogenomic twin study . In: Pain , Vol. 153 (2012), Issue 7, pp. 1397-1409, ISSN 0304-3959 doi : 10.1016 / j.pain.2012.02.022
Web links
- Threshold determination - absolute threshold and pain threshold
- Table of sound pressure levels with pain threshold
- Pain threshold - sound pressure and sound level
Individual evidence
- ↑ Ruth Defrin, Avi Ohry, Nava Blumen, Gideon Urca: Sensory determinants of thermal pain . In: Brain . tape 125 , 2002, pp. 501-510 ( oxfordjournals.org [PDF]).
- ^ Eva-Maj Malmström, Johanna Stjerna, Edward D. Högestätt, Hans Westergren: Quantitative sensory testing of temperature thresholds: possible biomarkers for persistent pain? In: Journal of Rehabilitation Medicine . tape 48 , 2016, p. 43-47 ( medicaljournals.se ).
- ↑ a b David M. Cain, Sergey G. Khasabov, Donald A. Simone: Response properties of mechanoreceptors and nociceptors in mouse glabrous skin: an in vivo study. In: Journal of Neurophysiology . tape 85 , 2001, p. 1561-1574 .
- ↑ T. Wienemann, EA Chantelau: The diagnostic value of measuring pressure pain perception in patients with diabetes mellitus. In: Swiss Medical Weekly. October 4, 2012, pp. 1–6 , accessed on May 18, 2020 .