Signal Detection

Surface electrodes summate the electrical action potentials from the contracting muscle and establish electrical pathways from skin contact of the monitored muscle site (Fig. 13.2).9 The sEMG instrument receives and processes this electrical correlate of a muscle activity measured in microvolts (||V) (Fig. 13.3). Muscle contraction involves the pulling together of the two anchor points; therefore, active electrodes should be placed between anchor points along the long axis of the muscle.9 The interelectrode distance determines the volume of muscle monitored. Various types of electrodes are used with sEMG devices for pelvic muscle rehabilitation. The most direct measure of the sEMG activity from the pelvic musculature occurs when using internal sensors. Binnie et al14 compared fine-wire electrodes to sensors with longitudinal electrodes and circumferential electrodes during rest, squeeze and push. Internal sensors with longitudinal electrodes correlated better with fine-wire electrodes in all three categories (Fig. 13.4). Current internal sensors may detect one or two channels of sEMG activity. The two-channel multiple electrode probe (MEP) anal EMG sensor (Fig. 13.5) allows discrimination between proximal and distal external anal sphincter (EAS) activity, thereby allowing the clinician to target specific areas of EAS inactivity in the rehabilitation process.

Table 13.3. Exercise program suitable for each patient to achieve the ultimate goal of efficient pelvic floor muscle function: components of pelvic muscle rehabilitation (PMR) utilizing surface electromyography (sEMG) instrumentation sEMG instrumentation Signal detection Signal processing Data acquisition and display sEMG evaluation Abdominal muscles Pelvic floor muscles Pelvic muscle exercise principles Overload Specificity Maintenance Reversibility Biofeedback treatment goals Short-term Long-term Behavioral strategies Patient education Dietary modification

Habit training for difficult, infrequent, or incomplete evacuation Urge suppression for urinary and fecal incontinence Biofeedback-assisted pelvic muscle exercises

Kegel exercises: isolated pelvic muscle contractions Beyond Kegel exercises: obturator and adductor assist Quick contractions Valsalva or push maneuver Physiologic quieting techniques Diaphragmatic breathing Progressive relaxation techniques: hand warming

Figure 13.4. The SenseRx internal vaginal and anal sensors with longitudinal electrodes that maintain proper orientation to muscle fiber for accurate EMG monitoring. (Courtesy of SRS Medical, Redmond,WA.)

Figure 13.2. Disposable surface electromyograph (EMG) electrodes. (From Vickers D, Davila GW. Kegels and biofeedback. In: Davila GW, Ghoniem GM, Wexner SD, eds. Pelvic Floor Dysfunction: A Multidisciplinary Approach. London: Springer-Verlag, 2006:303-310.)

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