BCN cheat sheet

Biofeedback is the operant conditioning of a physiologic response using amplified real-time signals; the signal must be perceivable, the response must be controllable, and feedback must be contingent on the response.

Biofeedback modalities and typical units: surface EMG (microvolts), thermal (degrees Fahrenheit/Celsius at fingertip), electrodermal (microsiemens), respiratory (breaths per minute), HRV (milliseconds or bpm), EEG (microvolts by band power).

Skin temperature feedback exploits vasoconstriction from sympathetic arousal; training aims at warmth (typically 95-97 F at the fingertip), a sign of peripheral vasodilation.

Electrodermal activity reflects eccrine sweat gland activity driven by sympathetic cholinergic fibers; skin conductance level rises with arousal and is measured in microsiemens.

Surface EMG electrode placement over the muscle belly with interelectrode distance of a few centimeters; 50/60 Hz notch filtering and proper skin prep reduce artifact; raw signal is rectified and averaged (RMS or moving average).

Respiratory training targets slow paced breathing near 6 breaths per minute (about 0.1 Hz), which increases respiratory sinus arrhythmia and baroreflex gain.

Therapist scope of practice: biofeedback certification requires knowledge of instrumentation, but clinical interpretation and treatment planning remain within the clinician's licensed scope; never diagnose outside licensure.

Artifact sources to rule out before interpreting a signal: 60 Hz electrical interference, movement, poor electrode contact, cardiac artifact in EMG, and respiration artifact in HRV or EEG.

Standard EEG bands: delta <4 Hz, theta 4-8 Hz, alpha 8-13 Hz, beta 13-30 Hz, and high beta/gamma above 30 Hz; band power is quantified by FFT or by digital filtering.

Arousal model: theta and alpha generally index underarousal or relaxed states, beta indexes alert focus, and excess high beta or EMG artifact can mimic tension; sensorimotor rhythm (SMR) is 12-15 Hz over sensorimotor cortex.

Common protocols: alpha/theta training (eyes closed, posterior sites) for relaxation; SMR uptraining with theta/beta downtraining for attention and hyperactivity; beta uptraining for alertness.

Theta/beta ratio (TBR) is computed as theta power divided by beta power at a specified site; higher TBR is associated with inattention in some populations but is not diagnostic.

Reward/inhibit thresholds are set so the client succeeds roughly 70-80% of epochs; thresholds are adjusted adaptively as performance changes.

Electrode sites follow the 10-20 system (Fz, Cz, Pz, C3, C4, T3/T4, O1/O2); referential, sequential, and Laplacian montages differ in spatial specificity and artifact sensitivity.

Neurofeedback requires artifact control: eye blinks raise frontal delta/theta, jaw clenching raises temporal EMG, and drowsiness shifts spectra toward theta and alpha.

QEEG is a statistical comparison of a client's EEG to a normative database; it informs protocol selection but is not a stand-alone diagnosis, and clinician scope of practice governs its use.

Heart rate variability (HRV) is the beat-to-beat variation in R-R intervals; higher vagally mediated HRV generally indicates greater parasympathetic (vagal) tone.

Time-domain metrics: SDNN reflects overall variability; RMSSD and pNN50 reflect short-term vagal activity; these are computed from R-R (N-N) interval series.

Frequency-domain bands: VLF <0.04 Hz, LF 0.04-0.15 Hz, HF 0.15-0.40 Hz; HF power reflects respiratory sinus arrhythmia and vagal tone; LF/HF is a contested index of autonomic balance.

Resonance frequency is the breathing rate (typically 4.5-6.5 breaths/min, near 0.1 Hz) that maximizes HRV amplitude for an individual; it is found by paced-breathing sweeps and then used for training.

During resonance breathing, HR and respiration become phase-synchronized; the goal is a smooth, high-amplitude sinusoidal HR pattern, not merely a slow rate.

Breathing at resonance increases baroreflex gain and RSA amplitude; typical training sessions use 10-20 minutes of paced breathing with real-time HRV display.

HRV is confounded by age, posture, medications (beta-blockers), caffeine, hydration, and time of day; interpret trends within-person rather than against a single cutoff.

The LF band overlaps with baroreflex activity (~0.1 Hz), so peak LF power near 0.1 Hz during slow breathing is expected and is not evidence of sympathetic dominance.

Pelvic floor muscle (PFM) biofeedback uses surface EMG (vaginal or anal sensor, or surface electrodes) to teach contraction and relaxation; typical units are microvolts.

A correct PFM contraction shows increased EMG amplitude with an abdominal and gluteal muscle quieting; accessory muscle recruitment (abdominal, gluteal, hip adductor) indicates substitution.

Baseline resting tone is recorded before contraction; elevated resting EMG suggests hypertonicity or guarding, and training then emphasizes downtraining and relaxation rather than strengthening.

Typical contraction parameters: hold 5-10 seconds, rest 10 seconds or more between contractions, with a work-to-rest ratio that avoids fatigue; the exact prescription is individualized.

Incontinence (stress and urge) and pelvic pain are the common indications; pelvic pain and hypertonic dysfunction call for relaxation/downtraining, while stress incontinence often calls for strength and endurance training.

Patient education includes correct identification of the PFM (the 'stop the flow of urine' cue is for identification only, not for regular exercise), relaxed breathing, and avoiding breath-holding or Valsalva.

Outcome is tracked with EMG amplitude, endurance (hold time), coordination, and validated symptom questionnaires; progress is judged against the patient's own baseline.

Contraindications and cautions to screen before internal sensors: active vaginal or urinary infection, recent surgery, pregnancy-related precautions, and patient discomfort; obtain informed consent and follow infection-control procedures.