Functional magnetic stimulation for conditioning of expiratory muscles in patients with spinal cord injury

Expiratory abdominal muscle thickness, a new point of care ultrasound measure for respiratory muscle mass in the intensive care unit: a prospective observational cohort study

BACKGROUND

Even if expiratory muscles are key muscles in intensive care unit (ICU) patients, the association between their thickness and mortality has never been assessed. This study aimed to determine whether expiratory abdominal muscle thickness assessed by ultrasonography (US) was associated with 28-day mortality in ICU patients.

BASIC PROCEDURES

US expiratory abdominal muscle thickness was measured within the first 12 h after ICU admission. The primary endpoint was 28-day mortality.

MAIN FINDINGS

In 310 analyzed patients, a thinner total abdominal expiratory muscle thickness at admission was associated with 28-day mortality (median value with interquartile range: 10.8 [10; 14.6] versus 16.5 [13.4; 20.7] mm). Total abdominal expiratory muscle thickness had an area under the curve of 0.78 [0.71;0.86] to discriminate 28-day mortality.

CONCLUSIONS

US expiratory abdominal muscle thickness was associated with 28-day mortality, supporting its use in predicting ICU patient outcome.

Effects of repetitive magnetic stimulation on motor function and GAP43 and 5-HT expression in rats with spinal cord injury

Objectives

Spinal cord injury (SCI) is a disabling central nervous system disorder. This study aimed to explore the effects of repetitive trans-spinal magnetic stimulation (rTSMS) of different spinal cord segments on movement function and growth-associated protein-43 (GAP43) and 5-hydroxytryptamine (5-HT) expression in rats after acute SCI and to preliminarily discuss the optimal rTSMS treatment site to provide a theoretical foundation and experimental evidence for clinical application of rTSMS in SCI.

Methods

A rat T10 laminectomy SCI model produced by transient application of an aneurysm clip was used in the study. The rats were divided into group A (sham surgery), group B (acute SCI without stimulation), group C (T6 segment stimulation), group D (T10 segment stimulation), and group E (L2 segment stimulation).

Results

In vivo magnetic stimulation protected motor function, alleviated myelin sheath damage, decreased NgR and Nogo-A expression levels, increased GAP43 and 5-HT expression levels, and inhibited terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells and apoptosis-related protein expression in rats at 8 weeks after the surgery.

Conclusions

This study suggests that rTSMS can promote GAP43 and 5-HT expression and axonal regeneration in the spinal cord, which is beneficial to motor function recovery after acute SCI.

Changes in Respiratory Muscle Thickness during Mechanical Ventilation: Focus on Expiratory Muscles

BACKGROUND

The lateral abdominal wall muscles are recruited with active expiration, as may occur with high breathing effort, inspiratory muscle weakness, or pulmonary hyperinflation. The effects of critical illness and mechanical ventilation on these muscles are unknown. This study aimed to assess the reproducibility of expiratory muscle (i.e., lateral abdominal wall muscles and rectus abdominis muscle) ultrasound and the impact of tidal volume on expiratory muscle thickness, to evaluate changes in expiratory muscle thickness during mechanical ventilation, and to compare this to changes in diaphragm thickness.

METHODS

Two raters assessed the interrater and intrarater reproducibility of expiratory muscle ultrasound (n = 30) and the effect of delivered tidal volume on expiratory muscle thickness (n = 10). Changes in the thickness of the expiratory muscles and the diaphragm were assessed in 77 patients with at least two serial ultrasound measurements in the first week of mechanical ventilation.

RESULTS

The reproducibility of the measurements was excellent (interrater intraclass correlation coefficient: 0.994 [95% CI, 0.987 to 0.997]; intrarater intraclass correlation coefficient: 0.992 [95% CI, 0.957 to 0.998]). Expiratory muscle thickness decreased by 3.0 ± 1.7% (mean ± SD) with tidal volumes of 481 ± 64 ml (P < 0.001). The thickness of the expiratory muscles remained stable in 51 of 77 (66%), decreased in 17 of 77 (22%), and increased in 9 of 77 (12%) patients. Reduced thickness resulted from loss of muscular tissue, whereas increased thickness mainly resulted from increased interparietal fasciae thickness. Changes in thickness of the expiratory muscles were not associated with changes in the thickness of the diaphragm (R2 = 0.013; P = 0.332).

CONCLUSIONS

Thickness measurement of the expiratory muscles by ultrasound has excellent reproducibility. Changes in the thickness of the expiratory muscles occurred in 34% of patients and were unrelated to changes in diaphragm thickness. Increased expiratory muscle thickness resulted from increased thickness of the fasciae.

EDITOR’S PERSPECTIVE

A Review of Different Stimulation Methods for Functional Reconstruction and Comparison of Respiratory Function after Cervical Spinal Cord Injury

Background

Spinal cord injury (SCI) is a common severe trauma in clinic, hundreds of thousands of people suffer from which every year in the world. In terms of injury location, cervical spinal cord injury (CSCI) has the greatest impact. After cervical spinal cord injury, the lack of innervated muscles is not enough to provide ventilation and other activities to complete the respiratory function. In addition to the decline of respiratory capacity, respiratory complications also have a serious impact on the life of patients. The most commonly used assisted breathing and cough equipment is the ventilator, but in recent years, the functional electrical stimulation method is being used gradually and widely.

Methods

About hundred related academic papers are cited for data analysis. They all have the following characteristics: (1) basic conditions of patients were reported, (2) patients had received nerve or muscle stimulation and the basic parameters, and (3) the results were evaluated based on some indicators.

Results

The papers mentioned above are classified as four kinds of stimulation methods: muscle electric/magnetic stimulation, spinal dural electric stimulation, intraspinal microstimulation, and infrared light stimulation. This paper describes the stimulation principle and application experiment. Finally, this paper will compare the indexes and effects of typical stimulation methods, as well as the two auxiliary methods: training and operation.

Conclusions

Although there is limited evidence for the treatment of respiratory failure by nerve or muscle stimulation after cervical spinal cord injury, the two techniques seem to be safe and effective. At the same time, light stimulation is gradually applied to clinical medicine with its strong advantages and becomes the development trend of nerve stimulation in the future.

Musculoskeletal Ultrasonography Assessment of Functional Magnetic Stimulation on the Effect of Glenohumeral Subluxation in Acute Poststroke Hemiplegic Patients

Background

Glenohumeral subluxation (GHS) is common in patients with acute hemiplegia caused by stroke. GHS and upper limb function are closely related.

Objective

Using musculoskeletal ultrasonography (MSUS) to objectively evaluate the efficacy of functional magnetic stimulation (FMS) in the treatment of GHS in acute hemiplegic patients after stroke.

Methods

The study used prospective case control study. Stroke patients with GHS were recruited and assigned to control group and FMS group. Control group received electrode stimulation at the supraspinatus and deltoid muscles of the hemiplegic side, while FMS group was stimulated at the same locations. Before and after treatment, the distances of the acromion-greater tuberosity (AGT), acromion-lesser tuberosity (ALT), acromiohumeral distance (AHD), supraspinatus thickness (SST), and deltoid muscle thickness (DMT) in patients' bilateral shoulder joint were measured by MSUS, respectively. Meanwhile, Fugl-Meyer Assessment (FMA) was used to evaluate the improvement of upper limb function.

Results

30 patients were recruited. After FMS treatment, there was a significant decrease in the difference value between ipsilateral side and contralateral side of AGT [t = 8.595, P < 0.01], ALT [t = 11.435, P < 0.01], AHD [t = 8.375, P < 0.01], SST [t = 15.394, P < 0.01], and DMT [t = 24.935, P < 0.01], and FMA score increased [t = −13.315, P < 0.01]. Compared with control group, FMS group decreased more significantly in the difference value between ipsilateral side and contralateral side of AGT [t = 2.161, P < 0.05], ALT [t = 3.332, P < 0.01], AHD [t = 8.768, P < 0.01], SST [t = 6.244, P < 0.01], and the DMT [t = 3.238, P < 0.01], and FMA score increased more significantly in FMS group [t = 7.194, P < 0.01].

Conclusion

The study preliminarily shows that the MSUS can objectively and dynamically evaluate the treatment effect of GHS in hemiplegic patients. Meanwhile, compared with control group, the FMS is more effective and has fewer side effects, and the long-term effect of FMS is worth further study. This trial is registered with ChiCTR1800015352.

Modeling Intracochlear Magnetic Stimulation: A Finite-Element Analysis

This study models induced electric fields, and their gradient, produced by pulsatile current stimulation of submillimeter inductors for cochlear implantation. Using finite-element analysis, the lower chamber of the cochlea, scala tympani, is modeled as a cylindrical structure filled with perilymph bounded by tissue, bone, and cochlear neural elements. Single inductors as well as an array of inductors are modeled. The coil strength (~100 nH) and excitation parameters (peak current of 1-5 A, voltages of 16-20 V) are based on a formative feasibility study conducted by our group. In that study, intracochlear micromagnetic stimulation achieved auditory activation as measured through the auditory brainstem response in a feline model. With respect to the finite element simulations, axial symmetry of the inductor geometry is exploited to improve computation time. It is verified that the inductor coil orientation greatly affects the strength of the induced electric field and thereby the ability to affect the transmembrane potential of nearby neural elements. Furthermore, upon comparing an array of micro-inductors with a typical multi-site electrode array, magnetically excited arrays retain greater focus in terms of the gradient of induced electric fields. Once combined with further in vivo analysis, this modeling study may enable further exploration of the mechanism of magnetically induced, and focused neural stimulation.

Functional Magnetic Stimulation of Inspiratory and Expiratory Muscles in Subjects With Tetraplegia

BACKGROUND

Respiratory complications are major causes of morbidity and mortality in persons with a spinal cord injury, partly because of respiratory muscle paralysis. Earlier investigation has demonstrated that functional magnetic stimulation (FMS) can be used as a noninvasive technology for activating expiratory muscles, thus producing useful expiratory functions (simulated cough) in subjects with spinal cord injury.

OBJECTIVE

To evaluate the effectiveness of FMS for conditioning inspiratory and expiratory muscles in persons with tetraplegia.

DESIGN

A prospective before and after trial.

SETTING

FMS Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, OH.

PARTICIPANTS

Six persons with tetraplegia.

METHOD

Each subject participated in a 6-week FMS protocol for conditioning the inspiratory and expiratory muscles. A magnetic stimulator was used with the center of a magnetic coil placed at the C7-T1 and T9-T10 spinous processes, respectively. Pulmonary function tests were performed before, during, and after the protocol.

MAIN OUTCOME MEASUREMENTS

Respiratory variables included maximal inspiratory pressure (MIP), inspiratory reserve volume (IRV), peak inspiratory flow (PIF), maximal expiratory pressure (MEP), expiratory reserve volume (ERV), and peak expiratory flow (PEF).

RESULTS

After 6 weeks of conditioning, the main outcome measurements (mean ± standard error) were as follows: MIP, 89.6 ± 7.3 cm H2O; IRV, 1.90 ± 0.34 L; PIF, 302.4 ± 36.3 L/min; MEP, 67.4 ± 11.1 cm H2O; ERV, 0.40 ± 0.06 L; and PEF, 372.4 ± 31.9 L/min. These values corresponded to 117%, 107%, 136%, 109%, 130%, and 124% of pre-FMS conditioning values, respectively. Significant improvements were observed in MIP (P = .022), PIF (P = .0001), and PEF (P = .0006), respectively. When FMS was discontinued for 4 weeks, these values showed decreases from their values at the end of the conditioning protocol, which suggests that continual FMS may be necessary to maintain improved respiratory functions.

CONCLUSION

FMS conditioning of the inspiratory and expiratory muscles improved voluntary inspiratory and expiratory functions. FMS may be a noninvasive technology for respiratory muscle training in persons with tetraplegia.

Electrical Stimulation of Abdominal Muscles to Produce Cough in Spinal Cord Injury

Background. Surface electrical stimulation of the abdominal muscles, with electrodes placed in the posterolateral position, combined with a voluntary cough can assist clearance of airway secretions in individuals with high-level spinal cord injury (SCI). Objective. To determine whether an increase in stimulus intensity of the trains of electrical stimuli delivered to the expiratory muscles has an increasing effect on a stimulated voluntary cough and to determine at which stimulus intensity a plateau of cough peak expiratory flow occurs. Methods. In 7 healthy individuals with a SCI at and above C7, gastric pressure ( Pga), esophageal pressure ( Pes), peak expiratory cough flow (PEFcough), and expiratory volume were measured as participants coughed voluntarily with simultaneous trains of electrical stimuli delivered over the abdominal muscles (50 Hz, 1-s duration). The intensity of the stimulation was increased incrementally. Results: A plateau in PEFcough occurred in all 7 individuals at a mean of 211 ± 29 mA (range 120-360 mA). Peak values reached for Pga, Pes, and PEFcough were 83.0 ± 8.0 cm H2O, 66.1 ± 5.6 cm H2O, and 4.0 ± 0.4 l/s respectively. Conclusions. The plateau in expiratory cough flow that was associated with increasing expiratory pressures is indicative of dynamic airway compression. This suggests that the evoked cough will be effective in creating more turbulent airflow to further assist in dislodging mucus and secretions.

Respiratory motor control disrupted by spinal cord injury: mechanisms, evaluation, and restoration

Pulmonary complications associated with persistent respiratory muscle weakness, paralysis, and spasticity are among the most important problems faced by patients with spinal cord injury when lack of muscle strength and disorganization of reciprocal respiratory muscle control lead to breathing insufficiency. This review describes the mechanisms of the respiratory motor control and its change in individuals with spinal cord injury, methods by which respiratory function is measured, and rehabilitative treatment used to restore respiratory function in those who have experienced such injury.

Abdominal Muscle Training Can Enhance Cough After Spinal Cord Injury

Background. Respiratory complications in people with high-level spinal cord injury (SCI) are a major cause of morbidity and mortality, particularly because of a reduced ability to cough as a result of abdominal muscle paralysis. Objective. We investigated the effect of cough training combined with functional electrical stimulation (FES) over the abdominal muscles for 6 weeks to observe whether training could improve cough strength. Methods. Fifteen SCI subjects (C4-T5) trained for 6 weeks, 5 days per week (5 sets of 10 coughs per day) in a randomized crossover design study. Subjects coughed voluntarily at the same time as a train of electrical stimulation was delivered over the abdominal muscles via posterolaterally positioned electrodes (50 Hz, 3 seconds). Measurements were made of esophageal (Pes) and gastric (Pga) expiratory pressures and the peak expiratory flow (PEFcough) produced at the 3 time points of before, during, and after the training. Results. During voluntary coughs, FES cough stimulation improved Pga, Pes, and PEFcough acutely, 20-fold, 4-fold, and 50%, respectively. Six weeks of cough training significantly increased Pga (37.1 ± 2.0 to 46.5 ± 2.9 cm H2O), Pes (35.4 ± 2.7 to 48.1 ± 2.9 cm H2O), and PEFcough (3.1 ± 0.1 to 3.6 ± 0.1 L/s). Cough training also improved pressures and flow during voluntary unstimulated coughs. Conclusions. FES of abdominal muscles acutely increases mechanical output in coughing in high-level SCI subjects. Six weeks of cough training further increases gastric and esophageal cough pressures and expiratory cough flow during stimulated cough maneuvers.

Respiratory muscle training for cervical spinal cord injury

BACKGROUND

Cervical spinal cord injury (SCI) severely comprises respiratory function due to paralysis and impairment of the respiratory muscles. Various types of respiratory muscle training (RMT) to improve respiratory function for people with cervical SCI have been described in the literature. A systematic review of this literature is needed to determine the effectiveness of RMT (either inspiratory or expiratory muscle training) on pulmonary function, dyspnoea, respiratory complications, respiratory muscle strength, and quality of life for people with cervical SCI.

OBJECTIVES

To evaluate the efficacy of RMT versus standard care or sham treatments in people with cervical SCI.

SEARCH METHODS

We searched the Cochrane Injuries and Cochrane Neuromuscular Disease Groups' Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 1), MEDLINE, EMBASE, CINAHL, ISI Web of Science, PubMed, and clinical trials registries (Australian New Zealand Clinical Trials Registry, ClinicalTrials, Controlled Trials metaRegister) on 5 to 8 March 2013. We handsearched reference lists of relevant papers and literature reviews. We applied no date, language, or publication restrictions.

SELECTION CRITERIA

All randomised controlled trials that involved an intervention described as RMT versus a control group using an alternative intervention, placebo, usual care, or no intervention for people with cervical SCI were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected articles for inclusion, evaluated the methodological quality of the studies, and extracted data. We sought additional information from the trial authors when necessary. We presented results using mean differences (MD) (using post-test scores) and 95% confidence intervals (CI) for outcomes measured using the same scale or standardised mean differences (SMD) and 95% CI for outcomes measured using different scales.

MAIN RESULTS

We included 11 studies with 212 participants with cervical SCI. The meta-analysis revealed a statistically significant effect of RMT for three outcomes: vital capacity (MD mean end point 0.4 L, 95% CI 0.12 to 0.69), maximal inspiratory pressure (MD mean end point 10.50 cm/H2O, 95% CI 3.42 to 17.57), and maximal expiratory pressure (MD mean end point 10.31 cm/H2O, 95% CI 2.80 to 17.82). There was no effect on forced expiratory volume in one second or dyspnoea. We could not combine the results from quality of life assessment tools from three studies for meta-analysis. Respiratory complication outcomes were infrequently reported and thus we could not include them in the meta-analysis. Instead, we described the results narratively. We identified no adverse effects as a result of RMT in cervical SCI.

AUTHORS' CONCLUSIONS

In spite of the relatively small number of studies included in this review, meta-analysis of the pooled data indicates that RMT is effective for increasing respiratory muscle strength and perhaps also lung volumes for people with cervical SCI. Further research is needed on functional outcomes following RMT, such as dyspnoea, cough efficacy, respiratory complications, hospital admissions, and quality of life. In addition, longer-term studies are needed to ascertain optimal dosage and determine any carryover effects of RMT on respiratory function, quality of life, respiratory morbidity, and mortality.

Repetitive magnetic stimulation of the phrenic nerves for diaphragm conditioning: a normative study of feasibility and optimal settings

Electrical stimulation can enhance muscle function. We applied repetitive cervical magnetic phrenic stimulation (rCMS) to induce diaphragm contractions in 7 healthy subjects (800 ms trains; transdiaphragmatic pressure (Pdi) measurements; tolerance ratings). Each rCMS train produced a sustained diaphragm contraction. Sixty-five percent of the maximal available output at 15 Hz proved the best compromise between Pdi and discomfort with nonfatiguing contractions. rCMS appears feasible and should be investigated for diaphragm conditioning in appropriate clinical populations.

Posterolateral Surface Electrical Stimulation of Abdominal Expiratory Muscles to Enhance Cough in Spinal Cord Injury

Background. Spinal cord injury (SCI) patients have respiratory complications because of abdominal muscle weakness and paralysis, which impair the ability to cough. Objective. This study aims to enhance cough in high-level SCI subjects (n = 11, SCI at or above T6) using surface electrical stimulation of the abdominal muscles via 2 pairs of posterolaterally placed electrodes. Methods. From total lung capacity, subjects performed maximum expiratory pressure (MEP) efforts against a closed airway and voluntary cough efforts. Both efforts were performed with and without superimposed trains of electrical stimulation (50 Hz, 1 second) at a submaximal intensity set to evoke a gastric pressure ( Pga) of 40 cm H2O at functional residual capacity. Results. In the MEP effort, stimulation increased the maximal Pga (from 21.4 ± 7.0 to 59.0 ± 5.7 cm H2O) and esophageal pressure ( Pes; 47.2 ± 11.7 to 65.6 ± 13.6 cm H2O). During the cough efforts, stimulation increased Pga (19.5 ± 6.0 to 57.9 ± 7.0 cm H2O) and Pes (31.2 ± 8.7 to 56.6 ± 10.5 cm H2O). The increased expiratory pressures during cough efforts with stimulation increased peak expiratory flow (PEF, by 36% ± 5%), mean expiratory flow (by 80% ± 8%), and expired lung volume (by 41% ± 16%). In every subject, superimposed electrical stimulation improved peak expiratory flow during cough efforts (by 0.99 ± 0.12 L/s; range, 0.41-1.80 L/s). Wearing an abdominal binder did not improve stimulated cough flows or pressures. Conclusions. The increases in Pga and PEF with electrical stimulation using the novel posterolateral electrode placement are 2 to 3 times greater than improvements reported in other studies. This suggests that posterolateral electrical stimulation of abdominal muscles is a simple noninvasive way to enhance cough in individuals with SCI.

Physiotherapy secretion removal techniques in people with spinal cord injury: a systematic review

OBJECTIVE

To address whether secretion removal techniques increase airway clearance in people with chronic spinal cord injury (SCI).

DATA SOURCES AND STUDY SELECTION

MEDLINE/PubMed, CINAHL, EMBASE, and PsycINFO were searched from inception to May 2009 for population keywords (spinal cord injury, paraplegia, tetraplegia, quadriplegia) paired with secretion removal-related interventions and outcomes. Inclusion criteria for articles were a research study, irrespective of design, that examined secretion removal in people with chronic SCI published in English.

REVIEW METHODS

Two reviewers determined whether articles met the inclusion criteria, abstracted information, and performed a quality assessment using PEDro or Downs and Black criteria. Studies were then given a level of evidence based on a modified Sackett scale.

RESULTS

Of 2416 abstracts and titles retrieved, 24 met the inclusion criteria. Subjects were young (mean, 31 years) and 84% were male. Most evidence was level 4 or 5 and only 2 studies were randomized controlled trials. Three reports described outcomes for secretion removal techniques in addition to cough, whereas most articles examined the immediate effects of various components of cough. Studies examining insufflation combined with manual assisted cough provided the most consistent, high-level evidence. Compelling recent evidence supports the use of respiratory muscle training or electrical stimulation of the expiratory muscles to facilitate airway clearance in people with SCI.

CONCLUSION

Evidence supporting the use of secretion removal techniques in SCI, while positive, is limited and mostly of low level. Treatments that increase respiratory muscle force show promise as effective airway clearance techniques.

Cough following low thoracic hemisection in the cat

A function of the abdominal expiratory muscles is the generation of cough, a critical respiratory defense mechanism that is often disrupted following spinal cord injury. We assessed the effects of a lateral T9/10 hemisection on cough production at 4, 13 and 21 weeks post-injury in cats receiving extensive locomotor training. The magnitudes of esophageal pressure as well as of bilateral rectus abdominis electromyogram activity during cough were not significantly different from pre-injury values at all time points evaluated. The results show that despite considerable interruption of the descending pre-motor drive from the brainstem to the expiratory motoneuron pools, the cough motor system shows a significant function by 4 weeks following incomplete thoracic injury.

Pulmonary function and spinal cord injury

Injury to the cervical and upper thoracic spinal cord disrupts function of inspiratory and expiratory muscles, as reflected by reduction in spirometric and lung volume parameters and static mouth pressures. In association, subjects with tetraplegia have decreased chest wall and lung compliance, increased abdominal wall compliance, and rib cage stiffness with paradoxical chest wall movements, all of which contribute to an increase in the work of breathing. Expiratory muscle function is more compromised than inspiratory muscle function among subjects with tetraplegia and high paraplegia, which can result in ineffective cough and propensity to mucus retention and atelectasis. Subjects with tetraplegia also demonstrate heightened vagal activity with reduction in baseline airway caliber, findings attributed to loss of sympathetic innervation to the lungs. Significant increase in airway caliber following inhalation of ipratropium bromide, an anticholinergic agent, suggests that reduction in airway caliber is not due to acquired airway fibrosis stemming from repeated infections or to abnormal hysteresis secondary to chronic inability of subjects to inhale to predicted total lung capacity. Reduced baseline airway caliber possibly explains why subjects with tetraplegia exhibit airway hyperresponsiveness to methacholine and ultrasonically nebulized distilled water. While it has been well demonstrated that bilateral phrenic nerve pacing or stimulation through intramuscular diaphragmatic electrodes improves inspiratory muscle function, it remains unclear if inspiratory muscle training improves pulmonary function. Recent findings suggest that expiratory muscle training, electrical stimulation of expiratory muscles and administration of a long-acting beta(2)-agonist (salmeterol) improve physiological parameters and cough. It is unknown if baseline bronchoconstriction in tetraplegia contributes to respiratory symptoms, of if the chronic administration of a bronchodilator reduces the work of breathing and/or improves respiratory symptoms. Less is known regarding the benefits of treatment of obstructive sleep apnea, despite evidence indicating that the prevalence of this condition in persons with tetraplegia is far greater than that encountered in able-bodied individuals.

Surface functional electrical stimulation of the abdominal muscles to enhance cough and assist tracheostomy decannulation after high-level spinal cord injury

OBJECTIVE

Evaluation of noninvasive stimulation modalities to augment cough and assist tracheostomy decannulation in high-level tetraplegia.

STUDY DESIGN

Single case study.

METHODS

A 65-year-old man with C4 ASIA C tetraplegia had delayed rehabilitation due to a tracheostomy and recurrent pneumonia primarily resulting from ineffective cough. Anterior surface electrical stimulation (SES) of the abdominal musculature was conducted to train an effective cough and enable decannulation. Training occurred daily for 4 weeks. The patient was tested 1 year later with posterolateral SES to determine the relative clinical effect of this delivery method.

RESULTS

At baseline, the addition of anterior SES increased maximal expiratory pressure (80%), maximal expiratory cough pressure (67%), and peak expiratory flow rate (11%). Three weeks after training began, the patient was decannulated following a program of SES and assisted and voluntary coughing. Upon testing 1 year later, SES with posterolaterally placed electrodes also produced an enhancement of voluntary cough attempts.

CONCLUSIONS

Noninvasive SES can potentially assist decannulation of tracheostomies.

Optimal electrode placement for noninvasive electrical stimulation of human abdominal muscles

Abdominal muscles are the most important expiratory muscles for coughing. Spinal cord-injured patients have respiratory complications because of abdominal muscle weakness and paralysis and impaired ability to cough. We aimed to determine the optimal positioning of stimulating electrodes on the trunk for the noninvasive electrical activation of the abdominal muscles. In six healthy subjects, we compared twitch pressures produced by a single electrical pulse through surface electrodes placed either posterolaterally or anteriorly on the trunk with twitch pressures produced by magnetic stimulation of nerve roots at the T10level. A gastroesophageal catheter measured gastric pressure (Pga) and esophageal pressure (Pes). Twitches were recorded at increasing stimulus intensities at functional residual capacity (FRC) in the seated posture. The maximal intensity used was also delivered at total lung capacity (TLC). At FRC, twitch pressures were greatest with electrical stimulation posterolaterally and magnetic stimulation at T10and smallest at the anterior site (Pga, 30 ± 3 and 33 ± 6 cmH2O vs. 12 ± 3 cmH2O; Pes 8 ± 2 and 11 ± 3 cmH2O vs. 5 ± 1 cmH2O; means ± SE). At TLC, twitch pressures were larger. The values for posterolateral electrical stimulation were comparable to those evoked by thoracic magnetic stimulation. The posterolateral stimulation site is the optimal site for generating gastric and esophageal twitch pressures with electrical stimulation.

Optimal arrangement of magnetic coils for functional magnetic stimulation of the inspiratory muscles in dogs

In an attempt to maximize inspiratory pressure and volume, the optimal position of a single or of dual magnetic coils during functional magnetic stimulation (FMS) of the inspiratory muscles was evaluated in twenty-three dogs. Unilateral phrenic magnetic stimulation (UPMS) or bilateral phrenic magnetic stimulation (BPMS), posterior cervical magnetic stimulation (PCMS), anterior cervical magnetic stimulation (ACMS) as well as a combination of PCMS and ACMS were performed. Trans-diaphragmatic pressure (Pdi), flow, and lung volume changes with an open airway were measured. Transdiaphragmatic pressure was also measured with an occluded airway. Changes in inspiratory parameters during FMS were compared with 1) electrical stimulation of surgically exposed bilateral phrenic nerves (BPES) and 2) ventral root electrical stimulation at C5-C7 (VRES C5-C7). Relative to the Pdi generated by BPES of 36.3 +/- 4.5 cm H2O (Mean +/- SEM), occluded Pdi(s) produced by UPMS, BPMS, PCMS, ACMS, and a combined PCMS + ACMS were 51.7%, 61.5%, 22.4%, 100.3%, and 104.5% of the maximal Pdi, respectively. Pdi(s) produced by UPMS, BPMS, PCMS, ACMS, and combined ACMS + PCMS were 38.0%, 45.2%, 16.5%, 73.8%, and 76.8%, respectively, of the Pdi induced by VRES (C5-C7) (48.0 +/- 3.9 cm H2O). The maximal Pdi(s) generated during ACMS and combined PCMS + ACMS were higher than the maximal Pdi(s) generated during UPMS, BPMS, or PCMS (p < 0.05). ACMS alone induced 129.8% of the inspiratory flow (73.0 +/- 9.4 L/ min) and 77.5% of the volume (626 +/- 556 ml) induced by BPES. ACMS and combined PCMS + ACMS produce a greater inspiratory pressure than UPMS, BPMS or PCMS. ACMS can be used to generate sufficient inspiratory pressure, flow, and volume for activation of the inspiratory muscles.

Relationship between inspiratory muscle strength and cough capacity in cervical spinal cord injured patients

STUDY DESIGN

Prospective single centre study.

OBJECTIVES

Pulmonary rehabilitation focuses on improving the expiratory muscle function in order to increase the reduced cough capacity in patients with cervical spinal cord injuries (SCI). However, an improvement in the inspiratory function is also important for coughing effectively. Therefore, this study was to examine the significance of the inspiratory muscle strength on the cough capacity in the patients with a cervical SCI.

SETTING

SCI unit, Yonsei Rehabilitation Hospital, Seoul, Korea.

METHODS

The vital capacity (VC), maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP) were measured. Moreover, the unassisted peak cough flow (PCF) and assisted PCF under three conditions were evaluated.

RESULTS

All three assisted cough methods showed a significantly higher value than the unassisted method (P < 0.001). The VC correlated with the voluntary cough capacity and the MIP (R = 0.749) correlated more significantly with the VC than the MEP (R = 0.438) (P < 0.01). The MIP showed a higher correlation with both the unassisted PCF and all three assisted PCFs than the MEP (P < 0.001).

CONCLUSIONS

The management of the inspiratory muscle strength should be considered in the pulmonary rehabilitation at cervical SCI patients.

The effect of magnetic stimulation on unloaded soleus muscle of rat: changes in myosin heavy chain mRNA isoforms

This study assessed the potential application and the effectiveness of functional magnetic stimulation (FMS) for preventing skeletal muscle atrophy in adult rats. FMS using magnetic stimulator was performed to rat soleus muscle by placing a round magnetic coil on the back of 3rd-5th lumbar vertebral level at 20 Hz frequency for 60 min/day up to 10 days. A reverse transcriptase-polymerase chain reaction was applied to evaluate relative amounts of mRNAs specific to four myosin heavy chain (MHC) isoforms [MHCIbeta, MHCIIa, MHCIIb, and MHCIId(x)] in rat soleus muscle during contractile activity by magnetic stimulation. Ten-day unloading by hindlimb suspension induced a drastic decrease of MHCIbeta and MHCIIa mRNA expressions, while MHCIIb and MHCIId(x) mRNA was not decreased. The magnetic stimulation resuscitated the down-regulation of the mRNA levels of MHCIbeta and MHCIIa. These results suggest that magnetic stimulation on acute atrophied muscles is useful for preventing the muscle atrophy.

Functional magnetic ventilation in dogs

OBJECTIVE

To investigate the efficacy of the magnetic stimulation of inspiratory muscles as an alternative to mechanical ventilation and functional electric stimulation.

DESIGN

A prospective before-after trial.

SETTING

Functional magnetic stimulation laboratory in a Veterans Administration health care system.

ANIMALS

Six male mongrel dogs, each weighing between 25 and 35 kg.

INTERVENTIONS

Commercially available magnetic stimulators with a round magnetic coil were used. The center of the magnetic coil was placed posteriorly over the C5-7 vertebrae of the spinal cord transected dogs. Magnetic stimulation parameters were set at 80% intensity, 20 Hz, and a 1.2-second on and 3.8-second off pulse train.

MAIN OUTCOME MEASURES

The major outcomes were changes in tidal volume (VT), tracheal pressure (Ptr), and arterial partial pressure of carbon dioxide (PaCO2) and oxygen sustained by magnetic stimulation over time.

RESULTS

The average Vt and Ptr produced during functional magnetic ventilation (FMV) were.47+/-.07 L and -4.7+/-.51 cmH2O, respectively. Blood gas data showed that PaCO2 increased from a baseline of 33 to 75 mmHg, whereas pH decreased from 7.33 to 6.99 at the end of the 1-hour FMV period.

CONCLUSIONS

FMV was achieved for 2 hours in dogs with C2 spinal cord transection. Additional refinements in magnetic stimulation are needed to improve ventilation in animals.

Analysis of efficiency of magnetic stimulation

Magnetic stimulation can activate excitable tissues noninvasively. However, this method requires high energy to operate and can produce equipment heat that leads to inefficient stimulation. In this study, a comprehensive optimization of efficiency for magnetic stimulation has been conducted. A total of 16 781 coil designs were tested in order to determine the optimal coil geometry and inductance for neural excitation. Induced electric fields were calculated to find the optimal stimulation site (OSS) of a given coil. The threshold energy of a magnetic pulse for neural excitation was then calculated based on the transmembrane responses of a nerve model. Simulation results show that there exists an optimal inductance, as a consequence of an optimal pulse duration, corresponding to a minimum threshold energy. A longer pulse width is required to obtain the maximum efficiency for axons with slower membrane dynamics, a longer coil-to-fiber distance, and greater values of resistance (R) and capacitance (C) of the resistance-inductance-capacitance circuit. The optimal geometry features a minimum coil height, suggesting a flat coil design for optimal efficiency. The dimension of the optimal coil design increases with the coil-to-fiber distance. Moreover, the cloverleaf design achieves the highest efficiency for infinitely long fibers whereas the butterfly design is optimal for terminating or bending fibers.

Functional magnetic stimulation facilitates gastric emptying

OBJECTIVE

To evaluate the effect of functional magnetic stimulation (FMS) on gastric emptying in able-bodied and spinal cord injury (SCI) subjects.

DESIGN

A prospective, nonrandomized clinical experiment.

SETTING

SCI and disorder center in a Veterans Affairs medical facility.

PARTICIPANTS

Five healthy, able-bodied subjects and 4 subjects with SCI.

INTERVENTION

A commercially available magnetic stimulator was used; a round magnetic coil was placed along the T9 spinous process. The intensity of the magnetic stimulation was 60%, with a frequency of 20 Hz, and a burst length of 2 seconds for the gastric emptying protocol. Man Outcome Measures: Rate of gastric emptying and time required to reach gastric emptying half-time (GE(t1/2)) with and without FMS. Data fit into linear regression curve.

RESULTS

Accelerated gastric emptying was achieved in both able-bodied and SCI subjects. The mean +/- standard error of mean of the GE(t1/2) at baseline and with FMS was 36+/-2.9 minutes and 33+/-3.1 minutes, respectively, for able-bodied subjects, and 84+/-11.1 minutes and 59+/-12.7 minutes, respectively, for SCI subjects.

CONCLUSION

Gastric emptying was enhanced by FMS in able-bodied subjects and was greatly enhanced in SCI subjects. FMS can be a useful noninvasive therapeutic tool to facilitate gastric emptying in humans.

Spinal cord injury medicine. 3. Rehabilitation outcomes

This self-directed learning module highlights rehabilitation outcomes in spinal cord injury (SCI). It is part of the chapter on SCI medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article focuses on the multiple concerns for functional recovery after SCI, chiefly, the potential for ambulation, upper-extremity recovery, options for functional neuromuscular stimulation (FNS), sexual activity, and optimal outcome after a metastatic lesion. Motor incomplete patients have a better prognosis for ambulation than persons with sensory incomplete injury. Positive predictors for ambulation, including pinprick and lower-extremity motor scores greater than 20, are discussed. Meaningful recovery can occur in the upper extremities for at least 1 year. FNS options have been developed to promote functional control of the upper extremities for persons with tetraplegia, phrenic pacing, and bladder continence. A critical component of an individual's expression of self is his/her sexuality; sexual function after SCI is described in detail, including options for treatment of erectile dysfunction and various birth control methods for women. Expectations for an appropriate rehabilitation stay for a person with metastatic SCI differ for an individual with traumatic SCI. Differences may include changing routine pathways and timelines to focus on patient-centered quality of life for transition to home.

OVERALL ARTICLE OBJECTIVE

To identify potential outcomes in ambulation, upper-extremity function, FNS, and sexual function after SCI and after metastatic cancer.