Editing Biofeedback (section)

==Sensor modalities==

===Electromyograph===
[[File:Muscle Whistler with EMG surface electrodes (1971).jpg|thumb|The "Muscle Whistler", shown here with surface EMG electrodes, was an early biofeedback device developed by [[Harry Garland]] and [[Roger Melen]] in 1971.<ref>{{Cite journal | journal = Popular Electronics | title = Build the Muscle Whistler | last1 = Garland | first1 = Harry | last2 = Melen | first2 = Roger | name-list-style = vanc | volume = 35 | issue = 5 | pages = 60–62 | year = 1971 }}</ref><ref name="Whistler"/>]]
An [[electromyograph]] ([[Electromyography|EMG]]) uses surface electrodes to detect muscle action potentials from underlying skeletal muscles that initiate muscle contraction. Clinicians record the surface electromyogram (SEMG) using one or more active electrodes that are placed over a target muscle and a reference electrode that is placed within six inches of either active. The SEMG is measured in [[microvolt]]s (millionths of a volt).<ref>{{cite book | vauthors = Tassinary LG, Cacioppo JT, Vanman EJ | date = 2007 | chapter = The skeletomotor system: Surface electromyography. | veditors = Cacioppo JT, Tassinary LG, Berntson GG | title = Handbook of psychophysiology | edition = 3rd | location = New York | publisher = Cambridge University Press }}</ref><ref>{{cite book | vauthors = Florimond V | date = 2009 | title = Basics of surface electromyography applied to physical rehabilitation and biomechanics | location = Montreal | publisher = Thought Technology Ltd. }}</ref>

In addition to surface electrodes, clinicians may also insert wires or needles intramuscularly to record an EMG signal. While this is more painful and often costly, the signal is more reliable since surface electrodes pick up cross talk from nearby muscles.  The use of surface electrodes is also limited to superficial muscles, making the intramuscular approach beneficial to access signals from deeper muscles. The electrical activity picked up by the electrodes is recorded and displayed in the same fashion as the surface electrodes.<ref>{{cite web|title=Electromyography (EMG)|url=http://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/electromyography_emg_92,P07656/|work=Johns Hopkins Medicine|access-date=2014-03-18}}</ref> Prior to placing surface electrodes, the skin is normally shaved, cleaned and exfoliated to get the best signal. Raw EMG signals resemble noise (electrical signal not coming from the muscle of interest) and the voltage fluctuates; therefore, they are processed normally in three ways: rectification, filtering, and integration. This processing allows for a unified signal that is then able to be compared to other signals using the same processing techniques.

Biofeedback therapists use EMG biofeedback when treating [[anxiety]] and [[worry]], [[chronic pain]], computer-related disorder, [[essential hypertension]], headache (migraine, mixed headache, and [[tension-type headache]]), [[low back pain]], [[physical rehabilitation]] ([[cerebral palsy]], incomplete spinal cord lesions, and [[stroke]]), [[temporomandibular joint dysfunction]] (TMD), [[torticollis]], and [[fecal incontinence]], [[urinary incontinence]], and [[pelvic pain]].<ref>{{cite book | vauthors = Peper E, Gibney KH | year = 2006 | title = Muscle biofeedback at the computer: A manual to prevent repetitive strain injury (RSI) by taking the guesswork out of assessment, monitoring, and training | location = Amersfoort, The Netherlands | publisher = BFE | url = http://www.aapb.org/tl_files/AAPB/files/biof_35_2_biofeedback.pdf | archive-url = https://web.archive.org/web/20101019023511/http://aapb.org/tl_files/AAPB/files/biof_35_2_biofeedback.pdf | archive-date = 2010-10-19 }}</ref><ref name = Yucha2008>{{cite book | vauthors = Yucha C, Montgomery D | year = 2008 | title = Evidence-based practice in biofeedback and neurofeedback | location =Wheat Ridge, CO | publisher = AAPB | url = http://www.isnr.org/uploads/EvidenceBasedYuchaMontgomeryW.pdf | archive-url = https://web.archive.org/web/20101009135554/http://isnr.org/uploads/EvidenceBasedYuchaMontgomeryW.pdf | archive-date = 2010-10-09 }}</ref> Physical therapists have also used EMG biofeedback for evaluating muscle activation and providing feedback for their patients.<ref name="Whistler">{{cite journal | vauthors = Forward E | title = Patient evaluation with an audio electromyogram monitor: "The Muscle Whistler" | journal = Physical Therapy | volume = 52 | issue = 4 | pages = 402–3 | date = April 1972 | pmid = 5012359 | doi = 10.1093/ptj/52.4.402 }}</ref>

===Feedback thermometer===
A feedback thermometer detects skin temperature with a [[thermistor]] (a temperature-sensitive resistor) that is usually attached to a finger or toe and measured in degrees Celsius or Fahrenheit. Skin temperature mainly reflects [[arteriole]] diameter. Hand-warming and hand-cooling are produced by separate mechanisms, and their regulation involves different skills.<ref name="Andreassi, J. L. 2007">{{cite book | vauthors = Andreassi JL | date = 2007 | title = Psychophysiology: Human behavior and physiological response | edition = 5th | location = Hillsdale, NJ | publisher = Lawrence Erlbaum and Associates, Inc }}</ref> Hand-warming involves arteriole [[vasodilation]] produced by a beta-2 adrenergic hormonal mechanism.<ref>{{cite journal | vauthors = Cohen RA, Coffman JD | title = Beta-adrenergic vasodilator mechanism in the finger | journal = Circulation Research | volume = 49 | issue = 5 | pages = 1196–201 | date = November 1981 | pmid = 6117377 | doi = 10.1161/01.res.49.5.1196 | doi-access = free }}</ref> Hand-cooling involves arteriole [[vasoconstriction]] produced by the increased firing of [[Sympathetic nervous system|sympathetic]] [[C-fiber]]s.<ref>{{cite journal | vauthors = Freedman RR, Sabharwal SC, Ianni P, Desai N, Wenig P, Mayes M | title = Nonneural beta-adrenergic vasodilating mechanism in temperature biofeedback | journal = Psychosomatic Medicine | volume = 50 | issue = 4 | pages = 394–401 | year = 1988 | pmid = 2842815 | doi = 10.1097/00006842-198807000-00007 | s2cid = 24316214 }}</ref>

Biofeedback therapists use temperature biofeedback when treating chronic pain, [[edema]], headache (migraine and tension-type headache), essential hypertension, [[Raynaud's phenomenon|Raynaud's disease]], anxiety, and [[Stress (biology)|stress]].<ref name = Yucha2008/>

===Electrodermograph===
An electrodermograph (EDG) measures skin electrical activity directly (skin conductance and skin potential) and indirectly (skin resistance) using electrodes placed over the digits or hand and wrist. Orienting responses to unexpected stimuli, arousal and worry, and cognitive activity can increase [[eccrine]] sweat gland activity, increasing the conductivity of the skin for electric current.<ref name="Andreassi, J. L. 2007"/>
 
In ''skin conductance'', an electrodermograph imposes an imperceptible current across the skin and measures how easily it travels through the skin. When anxiety raises the level of sweat in a sweat duct, conductance increases. Skin conductance is measured in microsiemens (millionths of a [[siemens (unit)|siemens]]). In ''skin potential'', a therapist places an active electrode over an active site (e.g., the palmar surface of the hand) and a reference electrode over a relatively inactive site (e.g., forearm). Skin potential is the voltage that develops between eccrine sweat glands and internal tissues and is measured in millivolts (thousandths of a volt). In ''skin resistance'', also called [[galvanic skin response]] (GSR), an electrodermograph imposes a current across the skin and measures the amount of opposition it encounters. Skin resistance is measured in kΩ (thousands of ohms).<ref>{{cite book | vauthors = Dawson ME, Schell AM, Filion DL | date = 2007 | chapter = The electrodermal system. | veditors = Cacioppo JT, Tassinary LG, Berntson GG | title = Handbook of psychophysiology | edition = 3rd | location = New York | publisher = Cambridge University Press }}</ref>

Biofeedback therapists use electrodermal biofeedback when treating [[anxiety disorders]], [[hyperhidrosis]] (excessive sweating), and stress.<ref name = Yucha2008/><ref>{{cite book | vauthors = Moss D | date = 2003 | chapter = The anxiety disorders. | veditors = Moss D, McGrady A, Davies T, Wickramasekera I | title = Handbook of mind-body medicine in primary care | pages = 359–375 | location = Thousand Oaks, CA | publisher = Sage }}</ref> Electrodermal biofeedback is used as an adjunct to psychotherapy to increase client awareness of their emotions.<ref name="Toomim, M. 1975">{{cite journal | vauthors = Toomim MK, Toomim H | year = 1975 | title = GSR biofeedback in psychotherapy: Some clinical observations | journal = Psychotherapy: Theory, Research & Practice | volume = 12 | issue = 1| pages = 33–8 | doi = 10.1037/h0086402 }}</ref><ref>{{cite journal | vauthors = Moss D | year = 2005 | title = Psychophysiological psychotherapy: The use of biofeedback, biological monitoring, and stress management principles in psychotherapy | journal = Psychophysiology Today  | volume = 2 | issue = 1| pages = 14–18 }}</ref> In addition, electrodermal measures have long served as one of the central tools in [[polygraphy]] ([[lie detection]]) because they reflect changes in anxiety or emotional activation.<ref>{{cite journal | vauthors = Pennebaker JW, Chew CH | title = Behavioral inhibition and electrodermal activity during deception | journal = Journal of Personality and Social Psychology | volume = 49 | issue = 5 | pages = 1427–33 | date = November 1985 | pmid = 4078683 | doi = 10.1037/0022-3514.49.5.1427 }}</ref>

===Electroencephalograph===
An [[electroencephalograph]] (EEG) measures the electrical activation of the brain from scalp sites located over the human cortex.  The EEG shows the amplitude of electrical activity at each cortical site, the amplitude and relative power of various wave forms at each site, and the degree to which each cortical site fires in conjunction with other cortical sites (coherence and symmetry).<ref>{{cite book | vauthors = Kropotov JD | date = 2009 | title = Quantitative EEG, event-related potentials and neurotherapy. | location = San Diego, CA | publisher = Academic Press }}</ref>

The EEG uses precious metal electrodes to detect a voltage between at least two electrodes located on the scalp. The EEG records both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) that largely occur in dendrites in pyramidal cells located in macrocolumns, several millimeters in diameter, in the upper cortical layers. [[Neurofeedback]] monitors both slow and fast cortical potentials.<ref name="Thompson, M. 2003">{{cite book | vauthors = Thompson M, Thompson L | date = 2003 | title = The biofeedback book: An introduction to basic concepts in applied psychophysiology. | location = Wheat Ridge, CO | publisher = Association for Applied Psychophysiology and Biofeedback }}</ref>

Slow cortical potentials are gradual changes in the membrane potentials of cortical dendrites that last from 300 ms to several seconds. These potentials include the [[contingent negative variation]] (CNV), [[readiness potential]], [[movement-related potentials]] (MRPs), and [[P300 (neuroscience)|P300]] and [[N400 (neuroscience)|N400]] potentials.<ref name="Stern, R. M. 2001">{{cite book | vauthors = Stern RM, Ray WJ, Quigley KS | date = 2001 | title = Psychophysiological recording | url = https://archive.org/details/psychophysiologi00robe | url-access = registration | edition = 2nd | location = New York | publisher = Oxford University Press }}</ref>

Fast cortical potentials range from 0.5&nbsp;Hz to 100&nbsp;Hz.<ref>{{cite book | vauthors = LaVaque TJ | date = 2003 | chapter = Neurofeedback, Neurotherapy, and quantitative EEG | veditors = Moss D, McGrady A, Davies T, Wickramasekera I | title = Handbook of mind-body medicine for primary care | pages = 123–136 | location = Thousand Oaks, CA | publisher = Sage }}</ref> The main frequency ranges include delta, theta, alpha, the sensorimotor rhythm, low beta, high beta, and gamma. The thresholds or boundaries defining the frequency ranges vary considerably among professionals. Fast cortical potentials can be described by their predominant frequencies, but also by whether they are synchronous or asynchronous wave forms. Synchronous wave forms occur at regular periodic intervals, whereas asynchronous wave forms are irregular.<ref name="Thompson, M. 2003"/>

The synchronous [[delta rhythm]] ranges from 0.5 to 3.5&nbsp;Hz. Delta is the dominant frequency from ages 1 to 2, and is associated in adults with deep sleep, critical for memory, cognition, sleep maintenance, and mental health. Disorders that disrupt sleep such as insomnia, traumatic brain injury, obstructive sleep apnea, and other neuropsychiatric conditions are also associated with the delta rhythm.<ref>{{Cite journal |last1=Uygun |first1=David S. |last2=Basheer |first2=Radhika |date=2022-10-01 |title=Circuits and components of delta wave regulation |journal=Brain Research Bulletin |volume=188 |pages=223–232 |doi=10.1016/j.brainresbull.2022.06.006 |issn=1873-2747 |pmc=9680038 |pmid=35738502}}</ref>

The synchronous [[theta rhythm]] ranges from 4 to 7&nbsp;Hz. Theta is the dominant frequency in healthy young children and is associated with drowsiness or starting to sleep, REM sleep, hypnagogic imagery (intense imagery experienced before the onset of sleep), hypnosis, attention, and processing of cognitive and perceptual information.

The synchronous [[alpha rhythm]] ranges from 8 to 13&nbsp;Hz and is defined by its waveform and not by its frequency. Alpha activity can be observed in about 75% of awake, relaxed individuals and is replaced by low-amplitude desynchronized beta activity during movement, complex problem-solving, and visual focusing. This phenomenon is called alpha blocking.

The synchronous [[sensorimotor rhythm]] (SMR) ranges from 12 to 15&nbsp;Hz and is located over the sensorimotor cortex (central sulcus). The sensorimotor rhythm is associated with the inhibition of movement and reduced muscle tone.

The [[beta rhythm]] consists of asynchronous waves and can be divided into low beta and high beta ranges (13–21&nbsp;Hz and 20–32&nbsp;Hz). Low beta is associated with activation and focused thinking. High beta is associated with anxiety, [[hypervigilance]], [[panic]], peak performance, and [[worry]].

EEG activity from 36 to 44&nbsp;Hz is also referred to as gamma. Gamma activity is associated with perception of meaning and meditative awareness.<ref name="Thompson, M. 2003"/><ref>{{cite book | vauthors = Steriade M | date =  2005 | chapter = Cellular substrates of brain rhythms. | veditors = Niedermeyer E, Lopes da Silva F | title = Electroencephalography: Basic principles, clinical applications, and related fields | edition = 5th | location = Philadelphia | publisher = Lippincott Williams & Wilkins }}</ref><ref name="Shaffer">{{cite book | vauthors = Shaffer F, Moss D | date = 2006 | chapter = Biofeedback | veditors = Yuan CS, Bieber EJ, Bauer BA | title = Textbook of complementary and alternative medicine | edition = 2nd | pages = 291–312 | location = Abingdon, Oxfordshire, UK | publisher = Informa Healthcare }}</ref>

Neurotherapists use EEG biofeedback when treating [[Substance use disorder|addiction]], [[attention deficit hyperactivity disorder]] (ADHD), [[learning disability]], anxiety disorders (including [[worry]], [[obsessive-compulsive disorder]] and posttraumatic stress disorder), [[Major depressive disorder|depression]], migraine, and [[generalized seizures]].<ref name = Yucha2008/><ref>{{cite book | vauthors = Budzynski TH, Budzynski HK, Evans JR, Abarbanel A | date = 2009 | title = Introduction to quantitative EEG and neurofeedback | edition = 2nd | location = Burlington, MA | publisher = Academic Press }}</ref>

===Photoplethysmograph===
[[File:EmWave2, powering up.jpg|thumb|180px|upright|An ''emWave2'' photoplethysmograph for monitoring heart rate variability]]

[[File:Photoplethysmograph - Biofeedback HRV with ear sensor.jpg|thumb|180px|upright| ''Stone'' computer-based photoplethysmograph with ear sensor]]

A [[photoplethysmograph]] (PPG) measures the relative blood flow through a digit using a photoplethysmographic (PPG) sensor attached by a Velcro band to the fingers or to the temple to monitor the [[Superficial temporal artery|temporal artery]]. An infrared light source is transmitted through or reflected off the tissue, detected by a [[phototransistor]], and quantified in arbitrary units. Less light is absorbed when blood flow is greater, increasing the intensity of light reaching the sensor.<ref name="Combatalade, D. 2009">Combatalade, D. (2009). ''Basics of heart rate variability applied to psychophysiology''. Montreal, Canada: Thought Technology Ltd.</ref>

A photoplethysmograph can measure blood volume pulse (BVP), which is the phasic change in blood volume with each heartbeat, heart rate, and [[heart rate variability]] (HRV), which consists of beat-to-beat differences in intervals between successive heartbeats.<ref name="Lehrer, P. M. 2007 P. M">{{cite book | vauthors = Lehrer PM | date = 2007 | chapter = Biofeedback training to increase heart rate variability. | veditors = Lehrer PM, Woolfolk RM, Sime WE | title = Principles and practice of stress management | edition = 3rd | location = New York | publisher = The Guilford Press }}</ref><ref>{{cite journal | vauthors = Peper E, Harvey R, Lin IM, Tylova H, Moss D | year = 2007 | title = Is there more to blood volume pulse than heart rate variability, respiratory sinus arrhythmia, and cardio-respiratory synchrony? | journal = Biofeedback | volume = 35 | issue = 2| pages = 54–61 }}</ref>

A photoplethysmograph can provide useful feedback when temperature feedback shows minimal change. This is because the PPG sensor is more sensitive than a thermistor to minute blood flow changes.<ref name="Shaffer" />  Biofeedback therapists can use a photoplethysmograph to supplement temperature biofeedback when treating chronic pain, edema, headache (migraine and tension-type headache), essential hypertension, Raynaud's disease, anxiety, and stress.<ref name = Yucha2008/>

===Electrocardiogram===
The [[electrocardiogram]] (ECG) uses electrodes placed on the torso, wrists, or legs, to measure the electrical activity of the heart and measures the [[interbeat interval]] (distances between successive [[R-wave]] peaks in the [[QRS complex]]). The interbeat interval, divided into 60 seconds, determines the heart rate at that moment. The statistical variability of that interbeat interval is what we call heart rate variability.<ref>{{cite book | vauthors = Berntson GG, Quigley KS, Lozano D | date = 2007 | chapter = Cardiovascular psychophysiology. | veditors = Cacioppo JT, Tassinary LG, Berntson GG | title = Handbook of psychophysiology | edition = 3rd | location = New York | publisher = Cambridge University Press }}</ref> The ECG method is more accurate than the PPG method in measuring heart rate variability.<ref name="Combatalade, D. 2009"/><ref name=":0">{{cite journal | author = Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology | title = Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology | journal = Circulation | volume = 93 | issue = 5 | pages = 1043–65 | date = March 1996 | pmid = 8598068 | doi = 10.1161/01.cir.93.5.1043 }}</ref>

Biofeedback therapists use [[heart rate variability]] (HRV) biofeedback when treating [[asthma]],<ref>{{cite journal | vauthors = Lehrer PM, Vaschillo E, Vaschillo B, Lu SE, Scardella A, Siddique M, Habib RH | title = Biofeedback treatment for asthma | journal = Chest | volume = 126 | issue = 2 | pages = 352–61 | date = August 2004 | pmid = 15302717 | doi = 10.1378/chest.126.2.352 }}</ref> [[COPD]],<ref>{{cite journal | vauthors = Giardino ND, Chan L, Borson S | title = Combined heart rate variability and pulse oximetry biofeedback for chronic obstructive pulmonary disease: preliminary findings | journal = Applied Psychophysiology and Biofeedback | volume = 29 | issue = 2 | pages = 121–33 | date = June 2004 | pmid = 15208975 | doi = 10.1023/B:APBI.0000026638.64386.89 | s2cid = 21774729 }}</ref> depression,<ref name="Preliminary results of an open labe">{{cite journal | vauthors = Karavidas MK, Lehrer PM, Vaschillo E, Vaschillo B, Marin H, Buyske S, Malinovsky I, Radvanski D, Hassett A | display-authors = 6 | title = Preliminary results of an open label study of heart rate variability biofeedback for the treatment of major depression | journal = Applied Psychophysiology and Biofeedback | volume = 32 | issue = 1 | pages = 19–30 | date = March 2007 | pmid = 17333315 | doi = 10.1007/s10484-006-9029-z | s2cid = 31614375 }}</ref> anxiety,<ref>{{cite journal | vauthors = Trousselard M, Canini F, Claverie D, Cungi C, Putois B, Franck N | title = Cardiac Coherence Training to Reduce Anxiety in Remitted Schizophrenia, a Pilot Study | journal = Applied Psychophysiology and Biofeedback | volume = 41 | issue = 1 | pages = 61–9 | date = March 2016 | pmid = 26346569 | pmc = 4749648 | doi = 10.1007/s10484-015-9312-y }}</ref> [[fibromyalgia]],<ref>{{cite journal | vauthors = Hassett AL, Radvanski DC, Vaschillo EG, Vaschillo B, Sigal LH, Karavidas MK, Buyske S, Lehrer PM | display-authors = 6 | title = A pilot study of the efficacy of heart rate variability (HRV) biofeedback in patients with fibromyalgia | journal = Applied Psychophysiology and Biofeedback | volume = 32 | issue = 1 | pages = 1–10 | date = March 2007 | pmid = 17219062 | doi = 10.1007/s10484-006-9028-0 | s2cid = 17033799 }}</ref> [[heart disease]],<ref>{{cite journal | vauthors = Cowan MJ, Pike KC, Budzynski HK | title = Psychosocial nursing therapy following sudden cardiac arrest: impact on two-year survival | journal = Nursing Research | volume = 50 | issue = 2 | pages = 68–76 | year = 2001 | pmid = 11302295 | doi = 10.1097/00006199-200103000-00002 }}</ref> and unexplained [[abdominal pain]].<ref>{{cite journal | vauthors = Humphreys PA, Gevirtz RN | title = Treatment of recurrent abdominal pain: components analysis of four treatment protocols | journal = Journal of Pediatric Gastroenterology and Nutrition | volume = 31 | issue = 1 | pages = 47–51 | date = July 2000 | pmid = 10896070 | doi = 10.1097/00005176-200007000-00011 | doi-access = free }}</ref> Research shows that HRV biofeedback can also be used to improve physiological and psychological wellbeing in healthy individuals.<ref name = "Barrios-Choplin_1997">{{cite journal | vauthors = Barrios-Choplin BO, McCraty RO, Cryer B |date=July 1997 |title=An inner quality approach to reducing stress and improving physical and emotional wellbeing at work|journal=Stress Medicine |volume=13 |issue=3 |pages=193–201 |doi=10.1002/(sici)1099-1700(199707)13:3<193::aid-smi744>3.0.co;2-i }}</ref>

HRV data from both polyplethysmographs and electrocardiograms are analyzed via mathematical transformations such as the commonly-used [[fast Fourier transform]] (FFT).<ref name=":0" /> The FFT splits the HRV data into a [[Spectral density|power spectrum]], revealing the waveform's constituent frequencies.<ref name="Combatalade, D. 2009" /> Among those constituent frequencies, high-frequency (HF) and low-frequency (LF) components are defined as above and below .15&nbsp;Hz, respectively. As a rule of thumb, the LF component of HRV represents sympathetic activity, and the HF component represents parasympathetic activity. The two main components are often represented as a LF/HF ratio and used to express sympathovagal balance.<ref name="Combatalade, D. 2009" /> Some researchers consider a third, medium-frequency (MF) component from .08&nbsp;Hz to .15&nbsp;Hz, which has been shown to increase in power during times of appreciation.<ref>{{cite journal | vauthors = McCraty R, Atkinson M, Tiller WA, Rein G, Watkins AD | title = The effects of emotions on short-term power spectrum analysis of heart rate variability | journal = The American Journal of Cardiology | volume = 76 | issue = 14 | pages = 1089–93 | date = November 1995 | pmid = 7484873 | doi = 10.1016/s0002-9149(99)80309-9 }}</ref>

===Pneumograph===
A [[pneumograph]] or respiratory strain gauge uses a flexible sensor band that is placed around the chest, abdomen, or both. The strain gauge method can provide feedback about the relative expansion/contraction of the chest and abdomen, and can measure [[respiratory rate]] (the number of breaths per minute).<ref name="Stern, R. M. 2001"/> Clinicians can use a pneumograph to detect and correct dysfunctional breathing patterns and behaviors. Dysfunctional breathing patterns include [[clavicular breathing]] (breathing that primarily relies on the [[external intercostals]] and the [[accessory muscles of respiration]] to inflate the lungs), reverse breathing (breathing where the abdomen expands during exhalation and contracts during inhalation), and [[thoracic breathing]] (shallow breathing that primarily relies on the external intercostals to inflate the lungs). Dysfunctional breathing behaviors include [[apnea]] (suspension of breathing), gasping, sighing, and wheezing.<ref name="Peper, E. 2008">{{cite book | vauthors = Peper E, Tylova H, Gibney KH, Harvey R, Combatalade D | date = 2008 | title = Biofeedback mastery: An experiential teaching and self-training manual | location = Wheat Ridge, CO | publisher = Association for Applied Psychophysiology and Biofeedback }}</ref>

A pneumograph is often used in conjunction with an [[electrocardiograph]] (ECG) or photoplethysmograph (PPG) in heart rate variability (HRV) training.<ref name="Lehrer, P. M. 2007 P. M"/><ref>{{cite journal | vauthors = Lehrer PM, Vaschillo E, Vaschillo B | title = Resonant frequency biofeedback training to increase cardiac variability: rationale and manual for training | journal = Applied Psychophysiology and Biofeedback | volume = 25 | issue = 3 | pages = 177–91 | date = September 2000 | pmid = 10999236 | doi = 10.1023/A:1009554825745 | s2cid = 163754 }}</ref>

Biofeedback therapists use pneumograph biofeedback with patients diagnosed with anxiety disorders, asthma, chronic pulmonary obstructive disorder (COPD), essential hypertension, [[panic attacks]], and stress.<ref name = Yucha2008/><ref name="Fried, R. 1987">{{cite journal | vauthors = Fried R | date = 1987 | title = The hyperventilation syndrome: Research and clinical treatment | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 51 | issue = 12 | pages = 1600–1 | location = Baltimore | publisher = Johns Hopkins University Press | doi = 10.1136/jnnp.51.12.1600-b | pmid = 3146617 | pmc = 1032792 }}</ref>

===Capnometer===
A [[capnometer]] or [[capnograph]] uses an infrared detector to measure end-tidal {{chem|CO|2}} (the partial pressure of carbon dioxide in expired air at the end of expiration) exhaled through the nostril into a latex tube. The average value of end-tidal {{chem|CO|2}} for a resting adult is 5% ({{convert|36|torr|kPa|abbr=on|disp=or}}). A capnometer is a sensitive index of the quality of patient breathing. Shallow, rapid, and effortful breathing lowers {{chem|CO|2}}, while deep, slow, effortless breathing increases it.<ref name="Peper, E. 2008"/>

Biofeedback therapists use capnometric biofeedback to supplement respiratory strain gauge biofeedback with patients diagnosed with anxiety disorders, asthma, chronic pulmonary obstructive disorder (COPD), essential hypertension, panic attacks, and stress.<ref name = Yucha2008/><ref name="Fried, R. 1987"/><ref>{{cite book | vauthors = Fried R | date = 1993 | title = The psychology and physiology of breathing | location = New York | publisher = Plenum Press }}</ref>

===Rheoencephalograph===

[[Rheoencephalography]] (REG), or brain blood flow biofeedback, is a biofeedback technique of a conscious control of blood flow. An electronic device called a [[rheoencephalograph]] [from Greek {{lang|grc-Latn|rheos}} 'stream, anything flowing', from {{lang|grc-Latn|rhein}} 'to flow'] is utilized in brain blood flow biofeedback. Electrodes are attached to the skin at certain points on the head and permit the device to measure continuously the electrical conductivity of the tissues of structures located between the electrodes. The brain blood flow technique is based on non-invasive method of measuring bio-impedance. Changes in bio-impedance are generated by blood volume and blood flow and registered by a rheographic device.<ref>{{cite conference | vauthors = Tokarev VE | title = A Rheoencephalogram (REG) Variability System Based on ISKRA-226 Personal Computer | conference = Institute for Complex Problem of Hygiene Healthcare Conference | location = Novokuznetsk, Russia | date = 1989 | pages = 115–116 }}</ref> The pulsative bio-impedance changes directly reflect the total blood flow of the deep structures of brain due to high frequency impedance measurements.<ref>{{cite conference | vauthors = Tokarev VE | title = Regulatory Mechanisms of Physiological Systems During REG Biofeedback | conference = 25th Annual Meeting of Association of Applied Psychophysiology and Biofeedback | location = Atlanta, USA | date =  1994 }}</ref>

===Hemoencephalography===
[[Hemoencephalography]] or HEG biofeedback is a functional [[infrared]] imaging technique. As its name describes, it measures the differences in the color of light reflected back through the scalp based on the relative amount of oxygenated and unoxygenated blood in the brain. Research continues to determine its reliability, validity, and clinical applicability. HEG is used to treat [[ADHD]] and migraine, and for research.<ref>{{cite book | vauthors = Toomim H, Carmen J | chapter = Homoencephalography: Photon-based blood flow neurofeedback. | veditors = Budzynski TH, Budzynski HK, Evans JR, Abarbanel A | date = 2009 | title = Introduction to quantitative EEG and neurofeedback | edition = 2nd | location = Burlington, MA | publisher = Academic Press }}</ref>

=== Pressure ===
Pressure can be monitored as a patient performs exercises while resting against an air-filled cushion.<ref>{{Cite web|url=http://www.sportstek.net/pressure_biofeedback.htm|title=Chattanooga Stabilizer Pressure Biofeeedback}}</ref>  This is pertinent to [[physiotherapy]]. Alternatively, the patient may actively grip or press against an air-filled cushion of custom shape.<ref>[http://pressureairbiofeedback.com/index.html pab®, Pressure Air Biofeedback]</ref>