Teresa Biber, M.S., CCC-SLP
Eating and drinking are uniquely tied to socialization with others and often combined with a deep cultural and symbolic association. Yet, the ability to eat and drink food and liquid safely and efficiently is a very complex process including both volitional and reflexive activities involving more than 36 muscles and 6 cranial nerves. The term used to describe difficulty swallowing is Dysphagia. A recent population-based study by the dysphagia committee of the International Association of Logopedics and Phoniatrics found the overall worldwide prevalence of dysphagia to be 13.5%. Dysphagia is not a disease but a disorder and often a manifestation of other conditions including but not limited to stroke, head and neck cancer, neurodegenerative diseases (Parkinson’s, MS, ALS etc), dementia, and acid reflux. Any surgery of the brain, head, neck, lung and heart can also result in dysphagia. Dysphagia is often the cause of death for many of these conditions as it can lead to aspiration (food or liquid entering the lungs), choking, malnutrition and dehydration. Aspiration pneumonia is the most common cause of death in patients with dysphagia due to neurologic disorders. Aspiration pneumonia, is the 5th leading cause of death in the US and the 4th leading cause of death in the elderly. (Itasca, Marik) It is now the 3rd leading cause of death in Japan outweighing stroke. (Ebihara et al) The healthcare costs associated with dysphagia are massive. In the US the treatment of aspiration pneumonia alone is over $3 billion dollars annually and the cost associated with feeding tubes (often placed when someone is unable to eat or drink) is $370 million.
Altman, Yu, and Schaefer examined 77 million hospital records and analyzed the impact of dysphagia on length of stay and discovered that “The median number of hospitalization days for all patients with dysphagia was 4.04 compared with 2.40 days for those patients without dysphagia. Mortality increased substantially in patients with dysphagia” they concluded with “Dysphagia has a significant impact on hospital length of stay and is a bad prognostic indicator. Early recognition of dysphagia and intervention in the hospitalized patient is advised to reduce morbidity and length of hospital stay.”
The consequences of dysphagia can be severe and have a far reaching impact on nutrition, hydration, quality of life and social isolation. However, it is aspiration (especially if not immediately recognized and properly treated) that will often be the deciding factor that precipitates a significant decline in a patient's outcome including increased risk of mortality.
The repercussions of dysphagia on patients with stroke, heart disease, pneumonia and laryngopharyngeal abnormalities are well known. Early identification of dysphagia is critical to prevent the deleterious effects often associated with the disorder but treatment is often relegated to management only and not rehabilitation. Placement of feeding tubes and keeping patient nil by mouth (NPO) does nothing to restore the ability of the patient to rejoin the community in eating and drinking again. Dr. Marik reports in the New England Journal of Medicine “Feeding tubes offer no protection from colonized oral secretions, which are a serious threat to patients with dysphagia. Furthermore, scintigraphic studies have revealed evidence of aspiration of gastric contents in patients fed by gastrostomy tube. Over the long term, aspiration pneumonia is the most common cause of death in patients fed by gastrostomy tube.” Indeed presence of a feeding tube does not necessarily prevent aspiration pneumonia and may in some instances actually contribute to it. Balen et al and Cole et al reported the same. Finucane et al found no evidence to suggest that feeding tubes in patients with advanced dementia prevented aspiration pneumonia, prolonged survival, reduced the risk of pressure sores or infections, improved function, or provided palliation. Thus identified yet unresolved dysphagia can still result in death and also cause depression, infections, social isolation and increased suicide risk.
The Biber Protocol® has been designed as a rehabilitation method utilizing NMES to restore swallow function in patients suffering from dysphagia. The proper use of this protocol can be instrumental in not only saving millions of lives but also millions of dollars to the health care system of any nation.
The use of NMES to restore swallow function is exceptionally well documented in the literature with well over over 130 published articles for NMES. The first peer reviewed journal article on electrical stimulation for the treatment of dysphagia was published in 1973 by George Larsen. In this study the stimulation applied above the thyroid notch (the submental region) to 5 patients with 4/5 demonstrating carryover and improved swallow function. Several more studies were then published in the 80’s by Bauer and Boswell on post radiation patients with dysphagia with positive outcomes. Talal, Quinn and Daniels conducted a multi-center randomized double blind placebo controlled study in 1992 on 77 patients with Sjogren’s Syndrome with a statistically significant improvement in the production of saliva, swallowing and burning tongue. An article published in 2014 by Miller et al identified 180 studies for effects of NMES on facial and laryngeal paresis, dysphonia and dysphagia and stated “Evidence collected to date is encouraging; particularly for the treatment of certain forms of dysphagia and laryngeal paresis”.
In 1999, Teresa Biber was working as an independent contractor for the renowned Cleveland Clinic in Florida and developed an electrical stimulation protocol for treating dysphagia and tested it on 50 patients while participating in the initial NOMS data project. The result was a 2.5 point gain on the ASHA NOMS compared to the entire US dysphagia outcomes. (Biber) The first advertised ASHA CEU course for using this modality in the US was taught by Teresa Biber in 2001 as part of the Arizona Speech and Hearing Association conference. Since 2001 the use of the Biber Protocol® has been adopted by hundreds if not thousands of clinicians worldwide without any reported adverse events and overwhelmingly positive outcomes.
The standards for using electrical stimulation for neuromuscular re- education have been long established in the physical therapy literature. The Biber Protocol® is based on those standards with clear, objective, supporting data from a variety of outside sources. An optimal NMES system for muscle re-education utilizes the minimal stimulus frequency that produces a fused response. Sheffler & Chae also suggest a shorter phase duration than the 300 μsec as used in the described publications above to ensure an optimal outcome of NMES. In 1956 Doty & Bosma published a study in which they found that the fire frequency of the laryngeal nerves is around 30 Hz. This publication supports the use of a low-frequent stimulation when applying NMES in dysphagia treatment. These parameters were also used in the Burnett- study, in which a “clear motor response was found at this frequency in combination with a 200μs phase duration.”
The information provided in Table 1 is based on work by the Los Amigos Research Center and copied directly from the text, NeuroMuscular Electrical Stimulation, A Practical Guide. Los Amigos Research and Engineering Institute, Third Edition. 1993.
The following parameter options should be considered to ensure the successful use of NMES.
Wave form selection:
Symmetrical - large muscles
Asymmetrical - small muscles
Use the largest electrode providing the desired response, without causing overflow to the other muscles.
NOTE: Distance between electrodes will determine depth of current: greater distance = deeper current flow.
Affects the quality of a muscle contraction and fatigue.
Rates in range of tetany: 25 - 50pps
Higher rates to illicit muscle fatigue (80pps)
Using the minimum rate that produces a good, tetanized contraction will help to control onset of fatigue.
Ramp up/down time
Aids comfort of treatment and can be used to mimic normal recruitment.
0-3 seconds is typical; longer ramp time may be beneficial in minimizing stretch reflex when spasticity is a factor.
Pulse durations between 200-400 microseconds are typically used.
Affects the magnitude of muscular response.
Higher amplitudes will generate an increase in the number of motor units activated.
On/Off times (Duty Cycle):
Affects the fatigue rate.
Initial treatments with NMES may require longer off times to delay onset of fatigue.
Typical On:Off ratios:
Muscle re-education: minimum 1:3
Muscle spasm: 1:1
Further support of these parameters for NMES are found in an exert from the section on muscle reeducation in the book entitled; Therapeutic Modalities in Sports Medicine by W. Prentice, 1986:
"Muscular inhibition after surgery or injury is the primary indication for muscle reeducation. If the neuromuscular mechanisms as a muscle have not been damaged, then the central nervous system inhibition of this muscle is usually a factor in loss of control. A muscle contraction can usually be caused by electrically stimulating the muscle. Forcing the muscle to contract causes an increase in the sensory input from that muscle. The patient feels the muscle contract, sees the muscle contract, and can attempt to duplicate this muscular response."
1) Intensity- High enough for contraction and low enough to be comfortable.
2) Pulses per second- 35-50 pps.
3) Interrupted or surge mode.
4) On time- 1 to 2 sec.
5) Off time- 2 to 4 sec.
6) Patient should help the contraction occur.
7) Treatment time- 15 to twenty minutes.
Every textbook ever written on the subject of electrotherapy consistently provides the same range of parameters which are necessary for muscle contraction and subsequent reeducation. The use of these specific parameters is considered neuromuscular electrical stimulation or NMES. Gad Alon, noted expert in electrotherapy defines NMES as; “ The use of electrical pulses that are modified and manipulated to excite peripheral nerves and evoke an action potential through a transcutaneous medium i.e. surface electrodes”. The key words here are modified and manipulated. A true NMES protocol must allow the clinician to modify and manipulate the parameters in order to achieve maximum physiological response i.e muscle contraction. “Proper use of NMES dictates that you stimulate the right muscle, at the right time with the right parameters, to achieve the desired outcome” (Alon)
Doucet, Lam and Griffin stated in the Yale Journal of Biology and Medicine; “The delivery of electrical stimulation can be customized to reduce fatigue and optimize force output by adjusting the associated stimulation parameters. A full understanding of the settings that govern the stimulation is vital for the safety of the patient and the success of the intervention. Consideration should be given to the frequency, pulse width/duration, duty cycle, intensity/amplitude, ramp time, pulse pattern, program duration, program frequency, and muscle group activated.”
Amedysis, the largest home health care company in America with over 400,000 speech therapy visits per year converted from VitalStim to the Biber Protocol® and saved $1,000,000 in the first year. After the conversion to the Biber Protocol® Amedysis Dysphagia NOMS outcomes were 19% higher than any other company in the nation. Additionally there have been no adverse effects ever reported in spite of the hundreds of thousands of treatments administered.
This demonstrates that when an electrical stimulation protocol is applied properly as well as comfortably and without undue financial risk, patients are likely to improve. Each one of the parameters of electrical stimulation provides a unique contribution to the overall outcome or physiological response. The Biber Protocol® is based on an intimate understanding of those principles.
Tim Watson; Editor of Electrotherapy: Evidence Based Practice states:
“Dose selection is critical. The effects of the treatment are modality dependent but dose dependent as well. It is important to select the most appropriate modality but also deliver it at the optimal dose. Many research publications have identified a lack of effect of intervention X yet other researchers have shown it to work at a different dose. Dose and treatment parameters must be taken into consideration."
Table 2 provides the adjustable parameter settings for the NMES component of the FDA cleared Aspire2 device which is based on the Biber Protocol®
Aspire2 Device Biber Protocol® (NMES)
Interrupted pulses A1, A2, A3, A4
50 pps A1, A2, A3, A4
175 uSec A1, 450uSec A2, 135 uSec A3, 200 uSec A4
4 seconds A1, A2, A3 10 seconds A4
12 seconds A1, A2, A3 10 seconds A4
2 seconds A1, A2, A3, A4
0.3 seconds A1, A2, A3, A4
Submental A1, A2, A3 Facial A4
Total Treatment Time
Strong but comfortable contraction
The above table provides the settings for each of the 4 pre-set programs in the Aspire2 with allowance to freely customize any settings using the App via an I-Pad. The following section will provide scientific rationale for each of the parameters chosen.
However The Biber Protocol® can be used in any standard NMES device as long as there are adjustable parameters and the clinician has been properly educated via the Biber method.
The duty cycle for all NMES protocols requires an interrupted pulses mode. This allows for the contracting muscle to contract, relax, and recover before the next cycle of stimulation occurs. (Alon) This is normal muscle reeducation. A continuous cycle is never used in muscle reeducation and there is no supporting evidence or physiological rationale for using such.
Boom et al reports “continuous stimulation (duty cycle 100%) resulted in a faster decay of the muscle output than intermittent stimulation (duty cycle 32%)
Frequency refers to the number of pulses (not phases) that occur in one second of time. Modulation of frequency is essential to determine the type of contraction elicited. A low frequency will elicit a twitch contraction and a high frequency will elicit a fatiguing contraction. Standard frequencies in NMES are between 30-50 hz. Gorge and Dudley reported “Increasing the frequency results in a sigmoidal increase in torque production but concurrently accelerates muscle fatigue” Several clinical trials have shown that increasing the frequency and the amplitude directly impact the outcomes due to limitations by the rapid onset of muscle fatigue and the subject's tolerance to the delivered current. (Chou & Binder-Macleod, Binder-Macleod et al)
Phase duration is defined as the elapsed time from the initiation of each phase until its end within a waveform. Phase duration begins when the electrical current departs from 0 and ends when it returns back to 0.
There is a common misconception that the term phase duration is synonymous with pulse duration. This is only true when referring to a monophasic wave form. All NMES devices utilize a biphasic waveform which means that there are 2 phases in each waveform so the pulse duration is at least double that of the phase duration or possibly higher if there is an interphase interval.
Geddes et al reports “The strength-duration curve is a plot of the lowest (threshold) current required for stimulation versus pulse duration; it forms the basis for describing the excitability of a given tissue. It is extremely useful in all manner of studies in which excitable tissues are stimulated because it describes the manner in which the current required is changed when the pulse duration is changed.” There is a direct inverse relationship between pulse duration and amplitude and it is imperative that the clinician be able to manipulate that parameter in order to maximize patient comfort. This is the rationale behind the A3 setting which is designed for the more sensitive patient. As shown in the strength duration curve illustrated on the last page, the higher the pulse duration the closer the proximity to pain fibers. Liebano et.al reported “We found that discomfort, subjectively assessed and reported using a VAS, increases significantly with phase duration over the range examined (p=.008). Strength-duration curves for sensory, motor, and pain tolerance thresholds converge at longer phase durations, i.e. there is less separation between pain and motor thresholds, so the increase in discomfort with phase duration is perhaps not unexpected.” High pulse duration is indicated in very large muscle groups or in to penetrate very dense, fibrotic or adipose tissue such as indicated in the A2 setting designed for the head and neck cancer patient with post radiation fibrosis. Recommended pulse duration for small muscle groups with normal tissue is within the 175usec of the A1 protocol. (Alon, Gorgey & Dudley, Sheffler & Chae)
The duty cycle of an interrupted pulses mode requires a specific on and off time to allow for proper activation of the muscle fibers and much needed rest and recovery. The 4 second on and 12 second off in the A1, A2 and A3 protocols are consistent with the 1:3 work rest ratio recommended in the literature. (Doucet, Robinson, Baker, Alon) “Early work in persons with SCI demonstrated that when periods of force development were interrupted with silent periods, muscle tissue was able to recover more quickly and produced greater torque as compared to when constant stimulation patterns were used. Cycling pulses on and off (intermittent stimulation) is a common practice to preserve force development and simultaneously increase comfort for the patient. Duty cycle describes the actual on and off time of an NMES program and is usually stated in ratio form, such as 1:2 (10 seconds on, 20 seconds off) or percentages such as 70 percent, indicating time on percentage when compared to total on and off time combined. Common clinical applications use a 1:3 duty cycle as standard, but this ratio can be modified to accommodate the needs of the patient as well as the goals of the treatment.” (Doucet et al). The A4 setting is designed with a longer contraction times and a 1/1 work to rest ratio for facial stimulation to correspond with the demands of facial expression.
The principles of NMES dictate that the muscles stimulated must represent a normal movement patterns and the movement must be paired with an actual task. The timing of the stimulation should match that of an actual swallow factoring in any delay and allowing for a sufficient ramp up. The ramp up allows for the gradual introduction of each cycle of stimulation when it occurs. “Frequently, a gradation of stimulation up to the desired frequency and intensity is used for patient comfort.” “Ramp times of 1 to 3 seconds are common in rehabilitation regimens with longer ramp times sometimes used for hypertonic or spastic musculature or for the patient with an increased sensitivity to stimulation.” (Doucet, et al).
In addition to the substantive evidence supporting the parameters of the Biber Protocol® there is also considerable evidence supporting a single bipolar placement of electrodes in the submental region for dysphagia.(Bogaardt, Palmer et al, Kim and Han, Park et al) Electrode placement is never on the anterior neck as there is no evidence or biologically plausible rationale to support any other configurations in this anatomical region. The only accessible swallowing muscles for external electrode placement are the suprahyoids and infrahyoids. Stimulation of the suprahyoids using an NMES protocol with 2 electrodes in the submental region facilitates an observable and palpable hyolaryngeal excursion. The combination of purposeful skilled electrical stimulation combined with the active task of real swallowing results in true neuromuscular reeducation. The goal is to promote motor recovery by facilitating and improving the movement pattern not inhibiting it. The A1, A2 and A3 programs utilize the submental placement. The A4 program is designed for facial stimulation with recommend placement of a single base electrode at the trunk of the facial nerve and another electrode along any of the 5 branches of the facial nerve. This is the only biologically plausible placement.
The standard treatment time for any NMES protocol is between 15-30 minutes. There is no supporting evidence for any longer treatment time. (Alon, Baker et al, Doucet et al, Robinson)
The final parameter is amplitude which in a proper NMES protocol is dictated by the patient not the clinician. The standard instructions are for the patient to alert the clinician when the stimulus is “strong but not uncomfortable”. Amplitude is defined as the total area contained in the wave form magnitude/height/maximum value. The value corresponds with equivalent amount of current in terms of heating power. It is also referred to as output, Rms value to intensity. Amplitude is directly associated with the number of motor units recruited, insufficient level will not achieve a contraction. (Adams et al) However simply increasing the amplitude at the expense of patient comfort is not only unnecessary but also constitutes unreasonable potential for harm. (Binder-Macleod) A pulse duration set too high will cause pain and not allow for the amplitude sufficient to recruit enough motor units which is why manipulation of pulse duration is essential and directly tied to amplitude. (Gorgey and Dudly) If a patient is unable to tolerate enough amplitude to elicit a contraction the pulse duration can be lowered to allow for a comfortable increase in amplitude. The goal is to achieve a contraction of either the suprahyoid muscles in the submental region or a contraction of the various facial muscles. The primary means by which NMES has a positive effect and functional outcome is through the cortical reorganization that occurs. This cannot be achieved with passive stimulation alone. The principles of NMES dictate that the stimulation MUST be combined with task specific activity. (Alon, Baker, Robinson) The task that must be performed is an actual swallow timed simultaneously with the stimulation. This swallow can be volitional i.e ask the patient to swallow each time they feel the stimulation or facilitated i.e present a single bolus or ice chip or other means of eliciting a swallow such as with a cold, sour swab. In the cases of facial stimulation the same principles apply. The patent performs the facial movement while the impaired region is stimulated.
There have been no reported actual adverse events associated with the Biber Protocol® and it has been successfully used on both pediatric and adult patients for approximately one million treatments worldwide.
The Biber Protocol® was developed in 1999 and has been taught to other therapists all over the world by Teresa Biber, M.S.CCC-SLP since that time. To date thousands of patients have received this therapy without any adverse events and with continued significant documented success. Patients receiving therapy for dysphagia via The Biber Protocol® appear to benefit not only in the improvement of swallow function but also in the prevention of and/or reduction of risk for aspiration pneumonia. The Biber Protocol® is a safe and efficacious treatment option for both adults and children suffering from dysphagia.
1. Adams GR, Harris RT, Woodard D, Dudley GA. Mapping of electrical muscle stimulation using MRI. J Appl Physiol 1993; 74:532–537.
2. Alon, G. Principles of Electrical Stimulation In Clinical Electrotherapy, 3rd ed.: Nelson, KM, Hayes, KW and Currier, DP (eds): Connecticut: Appleton and Large, 1997 pp 55-139.
3. Amedisys Announces Clinical Excellence in Speech Language Pathology. Baton Rouge, La., Feb. 25, 2015 (GLOBE NEWSWIRE)
4. Baker, L., Parker, K., and Sanderson, D. (1983) Neuromuscular Electrical Stimulation for the Head-Injured Patient. Physical Therapy, 63, (12), 1967-1974.
5. Baker C, Wederich D, McNeal C, Newsam R, Waters R. Neuromuscular Electrical Stimulation: A Practical Guide. 4th edition. Downey, CA: Los Amigos Research & Education Institute; 2000.
6. Balan KK, Vinjamuri S, Maltby P, et al. Guidelines for adjustment of stimulation parameters.
7. Bauer W. Electrical treatment of severe head and neck cancer pain. Arch Otolaryngol. Jun 1983;109(6):382-383.
8. Biber T, Mollo P, Albertini E. Neuromuscular Electrical Stimulation for the Treatment of Dysphagia. Dysphagia. 2005, March, 20, (1), 85.
9. Biber T, Barrera M. Guardian Therapy NMES Manual, Spectramed, 2012
10. Binder-Macleod SA, McDermond LR. Changes in the force-frequency relationship of the human quadriceps femoris muscle following electrically and voluntarily induced fatigue. Phys Ther. 1992;72:95–104.
11. Binder-Macleod SA, Snyder-Mackler L. Muscle fatigue: clinical implications for fatigue assessment and neuromuscular electrical stimulation. Phys Ther. 1993;73:902–910.
12. Binder-Macleod SA, Halden EE, Jungles KA. Effects of stimulation intensity on the physiological responses of human motor units. Med Sci Sports Exerc. 1995;27:556–565.
13. Bogaardt H, van Dam D, Wever NM, Bruggeman CE, Koops J, Fokkens WJ. Use of neuromuscular electrostimulation in the treatment of dysphagia in patients with multiple sclerosis. Annals of Otology, Rhinology and Laryngology. 2009;118(4):241–246
14. Boom HBK, Mulder AJ, Veltink PH: Fatigue during functional neuromuscular stimulation. Progr Brain Res 97:409-418, 1993.
15. Boswell N. Neuroelectric therapy eliminates xerostomia during radiotherapy-a case history. Med Electron. 1989 (115):105-107.
16. Boswell N, Bauer W. Noninvasive electrical stimulation for the treatment of radiotherapy side effects. American Journal of Electromedicine. 1985;2(3).
17. Bracciano AG. Physical Agent Modalities. Bethesda, MD: AOTA Press; 2008.38.
18. Burnett, T.A., Mann, E.A., Cornell, S.A., Ludlow, C.L. Laryngeal elevation achieved by neuromuscular stimulation at rest. Journal of Applied Physiology. 2003. 94, 128-134.
19. Chou LW, Binder-Macleod SA. The effects of stimulation frequency and fatigue on the force-intensity relationship for human skeletal muscle. Clin Neurophysiol. 2007. pp. 1387–1396.
20. Cole MJ, Smith JT, Molnar C, Shaffer EA. Aspiration after percutaneous gastrostomy: assessment by Tc-99m labeling of the enteral feed. J Clin Gastroenterol 1987;9:90-5.
21. Deley G, Kervio G, Verges B, et al. Comparison of low-frequency electrical myostimulation and conventional aerobic exercise training in patients with chronic heart failure. Eur J Cardiovasc Prev Rehabil. 2005;12:226–233.
22. Dellito, A and Synder-Mackler, L. (1990) Two Theories of Muscle Strength Augmentation Using Percutaneous Electrical Stimulation. Physical Therapy, 70, (3), 158-164.
23. Doty, R.W., Bosma, J.F. An electromyographic analysis of reflex deglutition. Journal of Neurophysiology. 1956. 19, 44-60.
24. Doucet, B. M., Lam, A., & Griffin, L. (2012). Neuromuscular Electrical Stimulation for Skeletal Muscle Function. The Yale Journal of Biology and Medicine, 85(2), 201–215.
25. Electrical Stimulation: Enhancement of Muscle Function, An American Physical Therapy Association Anthology 1993. (Available through APTA website)
26. Ebihara, S., Sekiya, H., Miyagi, M., Ebihara, T., & Okazaki, T. (2016). Dysphagia, dystussia, and aspiration pneumonia in elderly people. Journal of Thoracic Disease, 8(3), 632–639.
27. Finucane, T.E., & Bynum, J.P. (1996). Use of tube feeding to prevent aspiration pneumonia. Lancet, 248, 1421-1424.
28. Galnz, M., Klawansky, S, Stason, W, Berkley, C, and Chambers, TC. (1996) Functional Electrostimulation in Post Stroke Rehabilitation: A Meta-Analysis of the Randomized Controlled Trials. Physical Medicine and Rehabilitation, 77, 549-553.
29. Geddes, L.A.; Bourland, J.D., The Strength-Duration Curve. Biomedical Engineering, June 1985. no.6, pp.458,459
30. Gorgey AS, Dudley GA. The Role of Pulse Duration and Stimulation Duration in Maximizing the Normalized Torque During Neuromuscular Electrical Stimulation. The Journal of orthopaedic and sports physical therapy. 2008;38(8):508-516
31. International Association of Logopedics and Phoniatrics FAQ’s from the Dysphagia Committee www.IALP.info 2014
32. Itasca, IL. National Safety Council: Injury Facts, 2001 Edition. pp. 8-11, 16-18, 30, 152.
33. Kesar T, Chou LW, Binder-Macleod SA. Effects of stimulation frequency versus pulse duration modulation on muscle fatigue. J Electromyogr Kinesiol. 2007.
34. Kim SJ, Han TR. Effect of surface electrical stimulation of suprahyoid muscles on hyolaryngeal movement. Neuromodulation. 2009 Apr;12(2):134-40.
35. Larsen GL. Conservative management for incomplete dysphagia paralytica. Arch Phys Med Rehabil. 1973 Apr;54(4):180-5
36. Liebano, Richard E. et al . The influence of stimulus phase duration on discomfort and electrically induced torque of quadriceps femoris. Oct. 2013 Braz. J. Phys. Ther., São Carlos, v. 17, n. 5, .
37. Marik P. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. 2001;344:665-671.
38. McLoda TA, Carmack JA. Optimal burst duration during a facilitated quadriceps femoris contraction. J Athl Train. 2000;35:145–150.
39. Miller S, Kühn D, Jungheim M, Schwemmle C, Ptok M. Neuromuscular electric stimulation therapy in otorhinolaryngology. HNO. 2014 Feb;62(2):131-8
40. NeuroMuscular Electrical Stimulation, A Practical Guide. Los Amigos Research and Engineering Institute, Third Edition. 1993.
41. Palmer PM, Luschei ES, Jaffe D, McCulloch TM. Contributions of individual muscles to the submental surface electromyogram during swallowing. J Speech Lang Hear Res. 1999;42(6):1378-91.
42. Prentice, WE. Therapeutic Modalities in Sports Medicine. Oxford Blackwell Scientific, 1986
43. Robinson, Andrew J; Lynn Snyder-Mackler (2007-09-01). Clinical Electrophysiology: Electrotherapy and Electrophysiologic Testing (Third ed.). Lippincott Williams & Wilkins.
44. Sheffler, L.R. & Chae J.. Neuromuscular electrical stimulation neurorehabilitation. Muscle Nerve . 2007. 35, 562-590.
45. Talal N, Quinn JH, Daniels TE. The clinical effects of electrostimulation on salivary function of Sjogren's syndrome patients. Rheumatology Int. 1992;12:43–5.
46. Toyama K, Matsumoto S, Kurasawa M, Setoguchi H, Noma T, Takenaka K, Soeda A, Shimodozono M, Kawahira K. Novel neuromuscular electrical stimulation system for treatment of dysphagia after brain injury. Neurol Med Chir (Tokyo). 2014;54(7):521-8. Epub 2014 Mar 27. PubMed PMID: 24670314.
47. Vanderthommen, M. & Crielaard, J.M. (2001). Muscle electric stimulation in sports medicine [in French]. Revue Medicale de Liege 56, 391-395.
48. Wakamatsu, Hideyuki & Nagamachi, Shigeki & Nishii, Ryuichi & Higaki, Kazutaka & Kawai, Keiichi & Kamimura, Kiyohisa & Fujita, Seigo & Futami, Shigemi & Tamura, Shozo. (2008). Effect of percutaneous endoscopic gastrostomy on gastrointestinal motility: Evaluation by gastric-emptying scintigraphy. Nuclear medicine communications. 29. 562-7.
49. Umarova, R.M., Chernikova, L.A., Tanashian, M.M., Krotenkova. M.V. (2005). Neuromuscular electrostimulation in acute ischemic stroke [in Russian]. Vopr Kurortol Fizioter Lech Fiz Kult 4, 6-8.