Biomedical subjects

V W Lin

Publications and source records attributed to V W Lin.

17 recordsLinked to original sources

PubMed2001

Functional magnetic stimulation of the colon in persons with spinal cord injury.

OBJECTIVE: To evaluate the usefulness of functional magnetic stimulation (FMS) as a noninvasive method to stimulate the colon in individuals with spinal cord injury (SCI). DESIGN: A prospective before-after trial consisting of 2 protocols. SETTING: FMS laboratories of 2 SCI centers. PARTICIPANTS: Two able-bodied men and 13 men with SCI levels ranging from C3 to L1. Protocol 1 consisted of 9 subjects, 2 of whom were excluded from the analysis. Protocol 2 consisted of 4 subjects. INTERVENTION: Commercially available magnetic stimulators with round magnetic coils (MCs) were used. Protocol 1 measured the effects of FMS on rectal pressure by placing the MC on the transabdominal and lumbosacral regions. Protocol 2 consisted of a 5-week stimulation period to investigate the effects of FMS on total and segmental colonic transit times (CTTs). MAIN OUTCOME MEASURE: An increase in rectal pressure and a decrease in CTT by magnetic stimulation. RESULTS: Data were averaged and the standard error of the mean was calculated. Statistically significant changes in rectal pressure and CTT were also measured. Rectal pressures increased from 26.7 +/- 7.44cmH(2)O to 48.0 +/- 9.91cmH(2)O, p =.0037, with lumbosacral stimulation, and from 30.0 +/- 6.35cmH(2)O to 42.7 +/- 7.95cmH(2)O, p =.0015, with transabdominal stimulation. With FMS, the mean CTT decreased from 105.2 to 89.4 hours, p =.02. CONCLUSION: FMS is able to stimulate the colon and reduce CTT. FMS is a noninvasive, technological advancement for managing neurogenic bowel in patients with SCI.

Adult↗

PubMed2001

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

OBJECTIVE: To evaluate the effectiveness of functional magnetic stimulation (FMS) in conditioning expiratory muscles patients with spinal cord injury (SCI). DESIGN: A prospective before-after trial. SETTING: The Functional Magnetic Stimulation Laboratory of the SCI Health Care Group, VA Long Beach Health Care System, and the Spinal Cord Injury Services, Department of Veterans Affairs, Palo Alto Health Care System. PARTICIPANTS: Eight men with tetraplegia. INTERVENTION: Expiratory muscle training was achieved by placing a magnetic stimulator with a round magnetic coil along subjects' lower thoracic spine. MAIN OUTCOME MEASURES: Measures taken were the maximal expired pressure at total lung capacity (MEP-TLC) and at functional residual capacity (MEP-FRC), expiratory reserve volume (ERV), and the forced expiratory flow rate at TLC (FEF-TLC) and at FRC (FEF-FRC) by subjects' voluntary maximal efforts. RESULTS: After 4 weeks of conditioning, the mean +/- standard error of the mean values were: MEP-TLC, 55.3 +/- 8.6cmH(2)O; MEP-FRC, 29.6 +/- 5.6cmH(2)O; ERV,.57 +/-.08L; FEF-TLC, 4.3 +/- 0.5L/s; and FEF-FRC, 1.9 +/- 0.2L/s. These values correspond to, respectively, 129%, 137%, 162%, 109%, and 127% of pre-FMS conditioning values. When FMS was discontinued for 2 weeks, the MEP-TLC returned to its pre-FMS training value. CONCLUSION: A 4-week protocol of FMS of the expiratory muscles improves voluntary expiratory muscle strength significantly, indicating that FMS can be a noninvasive therapeutic technology in respiratory muscle training for persons with tetraplegia.

Analysis of Variance↗

PubMed2001

Functional magnetic stimulation facilitates colonic transit in rats.

OBJECTIVE: To investigate the effect of functional magnetic stimulation (FMS) on colonic transit in rats. DESIGN: Experimental. SETTING: Functional magnetic stimulation laboratory in a Veterans Administration health care system. ANIMALS: Twenty-four female Wistar rats, divided into an experimental group and a control group. INTERVENTIONS: All rats had technetium 99m (Tc 99m) infused through a cecal catheter to assess colonic transit times. FMS was performed over the cervical region; a figure of 8 magnetic coil was used in the experimental group. The colon was removed and sectioned into 10 segments, and a stool sample was taken in both groups. MAIN OUTCOME MEASURES: Distribution of radioactivity within the large intestine and stool were measured. RESULTS: Geometric center calculations showed significant differences (p <.001) between the control group and the experimental group when the distribution of radioactivity along the colon was measured. The percentage of Tc 99m recovered from the stool in the experimental group was significantly higher than the percentage recovered from the control group. CONCLUSION: FMS facilitates colonic transit in a rat model.

Animals↗

PubMed2001

Improved coil design for functional magnetic stimulation of expiratory muscles.

Our studies have demonstrated effective stimulation of the expiratory muscles in patients with spinal cord injury (SCI) using functional magnetic stimulation (FMS). The observed contraction of the expiratory muscles and functional improvement of the pulmonary functions make functional magnetic stimulation an appropriate tool for expiratory muscle training. To fully capitalize on the benefits of FMS for expiratory muscle training, this study aimed to optimize the magnetic coils (MCs). The primary goal of this study was to investigate how two parameters of the MC size and winding structure, would affect expiratory muscle training. By varying these parameters, our approach was to conceptualize and evaluate the induced electric field and nerve activation function distributions of six coils, round 9.2, 13.7, and 20 cm, and spiral 9.2-, 13.7-, and 20-cm coils in the computer modeling phase. Round 9.2 cm, spiral 13.7 cm, and spiral 20-cm coils were also evaluated in experimental studies for induced electrical field and in clinical studies of expiratory muscles. Both the computer models and experimental measurements indicated that the spiral 20-cm coil can not only stimulate more expiratory spinal nerves but can also stimulate them more evenly. In addition, coils with larger diameters had better penetration than those with smaller diameters. The clinical results showed that the spiral 20-cm coil produced higher expiratory pressure, flow, and volume in five able-bodied subjects, and it was the coil of choice among the subjects when asked their preferences. In our attempt to optimize MC design for FMS of expiratory muscle training, we followed the designing guidelines set out in our previous study and arrived at a more effective tool.

Breathing Exercises↗

PubMed2000

Functional magnetic stimulation facilitates gastrointestinal transit of liquids in rats.

The purpose of this study was to investigate the effect of a relatively novel technology, functional magnetic stimulation (FMS), on gastrointestinal transit of liquids in rats. Orogastric gavage with technetium-99 solution was used to assess gastric emptying and gastrointestinal transit time in 92 rats. FMS was performed over the anterior cervical and/or dorsal thoracolumbar regions using a figure-8 coil. Stimulation protocols were 1, 2, or 4 h in length. FMS accelerated gastric emptying and decreased gastrointestinal transit time. The acceleration was dependent on the stimulation parameters used as well as on the duration of the protocol; high levels of FMS produced a quicker effect, whereas lower levels were effective at later times. This study provides evidence that FMS could be an alternative or adjunct therapy to treat disorders in gastrointestinal motility.

Analysis of Variance↗

PubMed2000

Magnetic coil design considerations for functional magnetic stimulation.

Our studies have demonstrated effective stimulation of the bladder, bowel, and expiratory muscles in patients with spinal cord injury using functional magnetic stimulation. However, one limitation of the magnetic coils (MC) is related to their inability to specifically stimulate the target tissue without activation of surrounding tissue. The primary goal of this study was to determine the governing parameters in the MC design, such as coil configuration, diameter, and number of turns in one loop of the coil. By varying these parameters, our approach was to design, construct, and evaluate the induced electric field distributions of two sets of novel MC's. Based on the slinky coil design, the first set of coils was constructed to compare their abilities in generating induced electric fields for focal nerve excitation. The second set of coils was built to determine the effect that changes in two parameters, coil diameter and number of turns in one loop, had on field penetration. The results showed that the slinky coil design produced more focalized stimulation when compared to the planar round coils. The primary-to-secondary peak ratios of the induced electric field from slinky 1 to 5 were 1.00, 2.20, 2.85, 2.62, and 3.54. We also determined that coils with larger diameters had better penetration than those with smaller diameters. Coils with less number of turns in one loop had higher initial field strengths; when compared to coils that had more turns per loop, initial field strengths remained higher as distance from the coil increased. In our attempt to customize MC design according to each functional magnetic stimulation application and patients of different sizes, the parameters of MC explored in this study may facilitate designing an optimal MC for a certain clinical application.

Computer Simulation↗

PubMed1999

Effects of pulsed magnetic stimulation of GFAP levels in cultured astrocytes.

The present study evaluates the physiological effects of magnetic stimulation on astrocyte cultures. Cell cultures were exposed to pulsed magnetic stimulation (10 Hz, 10 sec) at the following levels: 0.10 tesla (T; Group A); 0.21 T (Group B); 0.42 T (Group C); and 0.63 T (Group D). Glial fibrillary acidic protein (GFAP) levels from immunoblots, total protein concentrations, and cellular morphology were analyzed at 0, 1, 3, 5, 7, 13, and 20 days poststimulation. Significantly higher GFAP levels were observed in Group D at day 3 (P = 0.0114). The change was transient as the GFAP levels quickly returned to control levels by day 5. No other significant changes in GFAP levels were observed. In comparison to control protein levels at day 0, concentrations from Groups B, C, and D were significantly lower (P < 0.006), whereas at day 3, Groups C and D were significantly higher (P < 0.02). Differences in astrocyte morphology due to magnetic stimulation were not observed. This study demonstrated that high intensity magnetic stimulation for only 10 sec induced a transient biological response.

Animals↗

PubMed1999

Methicillin-resistant Staphylococcus aureus in patients with spinal cord injury.

During the past decade, methicillin-resistant Staphylococcus aureus (MRSA) has become a major cause of nosocomial and community-acquired infections in the United States. A retrospective chart review of MRSA-positive cases from January 1990 to December 1994 was done to assess the extent of the problem, the factors associated with MRSA acquisition, and the effectiveness of a Center for Disease Control (CDC) protocol to treat MRSA infection in a population with spinal cord injury (SCI). Seventy-four percent of the patients acquired MRSA during their hospitalization. Urine was the most common site of colonization, and 73 percent of the patients with positive urine cultures managed their bladders with indwelling catheters. Implementation of the CDC protocol in 1991 was associated with a decrease in the MRSA incidence rate in subsequent years. Other simple methods of treatment, such as bladder irrigation, were also effective. To control the spread of MRSA, a continual concerted effort by hospital staff through education and implementation of the MRSA protocol is necessary.

Adult↗

PubMed1999

Expiratory muscle activation by functional magnetic stimulation of thoracic and lumbar spinal nerves.

OBJECTIVE: This study was conducted to stimulate respiratory muscles by functional magnetic stimulation (FMS) of the spinal nerves (T1-L5) to obtain maximum expiratory function. DESIGN: A prospective before and after trial. SETTING: Functional Magnetic Stimulation Laboratory, Spinal Cord Injury Service, VA Palo Alto Health Care System, Palo Alto, CA. PARTICIPANTS: Twelve normal able-bodied subjects. INTERVENTION: A commercially available magnetic stimulator with a round magnetic coil (MC) was used. Respiratory muscle activation was achieved by placing the MC at each spinous process ranging from T1 to L5 vertebral levels. MAIN OUTCOME MEASURE: The planned major outcome was to determine the optimal MC placement for producing maximal expiratory pressure (MEP) and expiratory reserve volume (ERV) by FMS. These measurements were compared with the subjects' voluntary maximal efforts. A profile with varying stimulation intensities was also obtained in select individuals for determining the highest expiratory pressure. RESULTS: Stimulation at the T9 spinal level resulted in the highest mean MEP and ERV. Stimulation between T8 and L5 produced similar MEP and ERV as obtained from the T9 MC placement. The mean maximum MEP and ERV produced by FMS were 76.8 +/- 6.4 cm H2O (7.52 +/- 0.62 kPa) and 1.28 +/- 0.15 L, which were 67% and 79% of the subjects' voluntary maximal efforts, respectively. A stimulation intensity of 80% resulted in the highest expiratory pressure. CONCLUSION: FMS of lower thoracic and lumbar regions produced significant expiratory pressures and volumes. FMS of the expiratory muscles may prove to be a valuable technique for restoring cough in patients with spinal cord injury or other neurologic diseases, and in critical care or perioperative settings.

Adult↗

PubMed1999

Functional magnetic stimulation: a new modality for enhancing systemic fibrinolysis.

OBJECTIVE: To investigate whether functional magnetic stimulation (FMS) of the leg muscles could enhance systemic fibrinolysis. DESIGN: A within-subject analysis of systemic fibrinolysis before and after 60 minutes of FMS. SETTING: The Functional Magnetic Stimulation and Special Coagulation Laboratories in the Spinal Cord Injury Service at a Veterans Administration health care facility. PARTICIPANTS: Twenty healthy volunteers were recruited. The exclusion criteria were: (1) personal or family history of venous or arterial thrombosis, (2) personal or family history of cardiac arrythmias, (3) current use of medication, and (4) the presence of a cardiac pacemaker or other metallic implants. MAIN OUTCOME MEASURES: Whole blood clot lysis time (WBCLT) and tissue plasminogen activator (t-PA) antigen determined at baseline and 10 and 60 minutes after FMS. RESULTS: A significant decrease was observed in the mean WBCLT after FMS. The WBCLT decreased from 17+/-1.3 h before FMS to 12+/-1.0 h and 11+/-0.8 h at 10 and 60 minutes post-FMS, respectively. The mean t-PA antigen levels did not show a significant change (p = .6701) from pre-FMS (6.7+/-0.91 ng/mL) to 10 min post-FMS (6.8+/-0.91 ng/mL) and 60 min post-FMS (7.0+/-1.02 ng/mL). Several patterns of fibrinolytic response to FMS were observed. They differed in relation to the degree of enhancement, the period at which maximum enhancement occurred, and the corresponding t-PA antigen levels observed. CONCLUSIONS: The FMS-induced contractions of the leg muscles enhanced systemic fibrinolysis ex vivo. The improvement in fibrinolysis occurred immediately after FMS and was also observed at 60 minutes post-FMS. FMS appears to produce a sustained enhancement of systemic fibrinolysis that may prove useful in deep-vein thrombosis prophylaxis.

Adult↗

PubMed1998

Functional magnetic stimulation of the respiratory muscles in dogs.

This study assessed the ability of functional magnetic stimulation (FMS) to activate the respiratory muscles in dogs. With the animal supine, FMS of the phrenic nerves using a high-speed magnetic stimulator was performed by placing a round magnetic coil (MC) at the carotid triangle. Following hyperventilation-induced apnea, changes in volume (deltaV) and airway pressure (deltaP) against an occluded airway were determined. FMS of the phrenic nerves produced substantial inspired function (deltaV = 373 +/- 20.5 mL and deltaP = -20 +/- 2.0 cm H2O). After bilateral phrenectomies, maximal inspired deltaV (219 +/- 12.2 mL) and deltaP (-10 +/- 1.0 cm H2O) were produced when the MC was placed near the C6-C7 spinous processes, while maximal expired deltaV (-199 +/- 22.5 mL) and deltaP (11 +/- 2.3 cm H2O) were produced following stimulation near the T9-T10 spinous processes. We conclude: (1) FMS of either the phrenic or upper intercostal nerves results in inspired volume production; (2) FMS of the lower intercostal nerves generates expired volume production; and (3) FMS of the respiratory muscles may be a useful noninvasive tool for artificial ventilation and assisted cough in patients with spinal cord injuries or other neurological disorders.

Animals↗

PubMed1998

Functional magnetic stimulation for restoring cough in patients with tetraplegia.

OBJECTIVE: To evaluate the usefulness of functional magnetic stimulation (FMS) as a noninvasive method for assisting cough in patients with tetraplegia. DESIGN: A prospective before-after trial. SETTING: The functional magnetic stimulation laboratory of a spinal cord injury (SCI) service. PARTICIPANTS: Thirteen male SCI patients, with injury levels between C4 and C7. INTERVENTION: A commercially available magnetic stimulator with a round magnetic coil (MC) was used. Expiratory muscle activation was achieved by placing the MC along the lower thoracic spine. MAIN OUTCOME MEASURE: The planned major outcome measures were the maximal expired pressure (MEP), expiratory reserve volume (ERV), and forced expiratory flow rate (FEF) by FMS compared with voluntary maximal efforts. Another outcome was the optimal MC placement and stimulation intensity that would result in highest expired pressure. RESULTS: The mean (+/-SEM) MEP, ERV, and FEF generated by FMS were 66.40 +/- 6.69 cmH2O, .77 +/- .14 L, and 5.28 +/- .42 L/sec, respectively. They were 118%, 169%, and 110% of voluntary maximum efforts. MC placement at the T10 to T11 spinous process and stimulation intensity at 80% produced the highest MEP and FEF. CONCLUSION: FMS of the expiratory muscles produced significant expired pressures, volumes, and flow rates when compared with voluntary maximum efforts; therefore, FMS can be used as an effective method to restore cough in tetraplegic patients.

Abdominal Muscles↗

PubMed1998

Functional magnetic stimulation of expiratory muscles: a noninvasive and new method for restoring cough.

The purpose of this study was to assess the effectiveness of functional magnetic stimulation (FMS) for producing expiratory function in normal human subjects. Twelve able-bodied normal subjects were recruited for this study. FMS of the expiratory muscles was performed by using a magnetic stimulator and placing the magnetic coil along the lower thoracic spine. Results showed that peak expired pressure, volume, and flow rate generated by FMS at the end of normal inspiration (102.5 +/- 13.62 cmH2O, 1.6 +/- 0.16 liters, and 4.8 +/- 0.35 l/s, respectively) were comparable to their voluntary maximal levels (P > 0.1). The optimal coil placement was between T7 and T11, and the optimal stimulation parameters were a frequency of 25 Hz and 70-80% of maximal intensity. We conclude that 1) FMS of the lower thoracic nerves in normal subjects resulted in a significant expiratory function comparable to their voluntary maximum; 2) FMS was noninvasive and was well tolerated by all subjects; and 3) FMS may be useful to produce cough in patients in critical care or perioperative settings, or in patients with neurological disorders.

Action Potentials↗

PubMed1997

Micturition by functional magnetic stimulation in dogs: a preliminary report.

The effectiveness of functional magnetic stimulation (FMS) technology on bladder contraction and bladder emptying was evaluated in ten normal neurologically intact male dogs. In seven animals, FMS of the bladder was performed by using a commercially available magnetic coil (non-water-cooled) for stimulating the sacral nerves or over the suprapubic region. With sacral stimulation, the mean change in bladder pressure (Pves) was 68.0 +/- 12.96 cm H2O; with suprapubic stimulation, the mean change in Pves was 40.7 +/- 8.08 cm H2O. This change in Pves by sacral stimulation was higher than suprapubic stimulation (P < 0.01). In three additional animals, voiding was demonstrated by using a specialized water-cooled magnetic coil and by stimulating the sacral nerves with an intermittent stimulation sequence. Voiding occurred in all three animals and was reproducible. In summary, FMS of the bladder has the potential to be a useful non-invasive technology for bladder emptying and bladder training in patients with neurogenic bladder.

Animals↗

PubMed1997

Micturition by functional magnetic stimulation.

Effectiveness of functional magnetic stimulation (FMS) technology on bladder contraction and bladder emptying was evaluated in twenty-two spinal cord injured subjects. FMS of the bladder was performed by stimulating the sacral nerves or the suprapubic region using a commercially available magnetic stimulator with a round coli. With sacral stimulation, the mean change in bladder pressure (Pves) was 24.4 +/- 4.88 cm H2O; with suprapubic stimulation, the mean change in Pves was 16.5 +/- 4.44 cm H2O. The change in Pves with sacral stimulation was higher than with suprapubic stimulation (p < .01). Seventeen subjects demonstrated voiding, either with sacral or suprapubic stimulation. Using a water-cooled coli, one subject demonstrated complete bladder emptying. FMS of the bladder has the potential to be a useful non-invasive technology for bladder emptying and bladder training in patients with neurogenic bladders.

Adult↗

PubMed1997

Effect of radionuclide renograms on treatment of patients with spinal cord injuries.

OBJECTIVE: Urinary tract problems stemming from neurologic dysfunction are a major cause of morbidity in patients with spinal cord injury. Radionuclide renograms have been used to monitor renal function in these patients. However, the effect of renographic results on the treatment of patients has not been studied. A retrospective study was done to determine the effect of radionuclide renography on the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury. MATERIALS AND METHODS: The records of 199 patients with spinal cord injuries were reviewed. A decline in effective renal plasma flow of 20% or more, a low effective renal plasma flow for age, and abnormal tracer time-activity curves were correlated with diagnostic procedures and therapeutic interventions. Diagnostic procedures included renal sonography, CT, excretory urography, and urodynamics. Therapeutic interventions included changes in medication, changes in bladder management, and surgery. RESULTS: Patients with abnormal findings on renograms underwent more diagnostic procedures and therapeutic interventions. A significant correlation was found between abnormal tracer time-activity curves and use of excretory urography. A decline in effective renal plasma flow was the best predictor of therapeutic intervention. CONCLUSION: Radionuclide renograms influence the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury.

Female↗

PubMed1991

Laser Doppler velocimetry of tracheal blood flow in sheep.

A laser-Doppler velocimetry (LDV) apparatus was adapted to assess sheep airway blood flow. The LDV signal obtained was compared to microsphere determinations of blood flow to tracheal tissues utilizing 15 microns radioactive microspheres injected before and after intubation and anesthesia, during hemorrhagic hypotension, and after reinfusion-resuscitation. During hemorrhagic hypotension, airway wall blood flow decreased to 16% of control by the microsphere method and to 30% by LDV. After reinfusion-resuscitation, airway wall blood flow increased over control values 40% and 33% by the two methods, respectively. Although at low flows LDV values were greater than microsphere determinations, the overall LDV recordings correlated with airway microsphere flow determinations of tracheal wall blood flow (R = 0.85) and tracheal mucosa flow (R = 0.81), but not with tracheal muscularis flow (R = 0.32). With certain but significant limitations, such as calibration in absolute units, stability of position placement, motion artifacts, and the effects of mechanical irritation-induced hyperemia, LDV represents a relatively noninvasive means for qualitatively evaluating changes in the microcirculatory blood flow of airway mucosa.

Animals↗