Functional Magnetic Stimulation of Inspiratory and Expiratory Muscles in Patients with Tetraplegia Xiaoming Zhang 1,2, Honglian Huang 1,2, Vinoth Ranganathan 1,2, Vernon Lin 1,2 1. Physical Medicine and Rehabilitation, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio 2. Department of Physical Medicine and Rehabilitation, Cleveland Clinic, Cleveland, OH RESULTS Respiratory dysfunctions are major areas of concern in patients with spinal cord injury/disorders (SCI/D). Injury to the cervical spinal cord disrupts function of inspiratory and expiratory muscles, as reflected by reduction in spirometric and lung volume parameters. Traditional therapy is composed of postural drainage, airway suctioning, percussion, vibration, breathing exercises, cough stimulation techniques including assisted cough, and functional electrical stimulation (FES). Functional magnetic stimulation (FMS) is a non-invasive method that promotes the contraction of muscles through nerve activation. Previously, our group has demonstrated efficacy of using FMS technology for stimulating expiratory muscles in animals, normal subjects, and patients with SCI/D (1-3). The main purpose of this investigation is to evaluate the effectiveness of functional magnetic stimulation (FMS) for conditioning inspiratory and expiratory muscles in patients with spinal cord injury (SCI). INTRODUCTION METHODS Subjects: Six patients with tetraplegia (C4-C7) were enrolled in a 6-week FMS protocol for conditioning the inspiratory and expiratory muscles through the Louis Stokes Cleveland VA Medical Center (LSCVAMC). The mean age, time since injury, height, and weight of our study population were 48 ± 7.1 years, 16 ± 8.5 years, ± 4.6 cm, and 91 ± 21.3 Kg, respectively. Patients with cardiac pacemakers, other metallic devices, high blood pressure, or with active pulmonary conditions were excluded. Pulmonary Function Tests Evaluation: Before the protocol, subject underwent screening histories and physical examinations. A baseline pulmonary function tests (PFTs) were then evaluated and recorded with subjects in a sitting position. Subject was instructed to maintain regular diets and their routine activities of daily living. We used a respiratory pressure meter (MicroRPM, Micro Direct Inc., Lewiston ME) to determine pressure and an EasyOne spirometer system (ndd Medizintechnik, Zurich, Switzerland) to measure flow and volume. Maximum inspiratory pressure (MIP), inspiratory reserve volume (IRV), peak inspiratory flow (PIF), maximum expiratory pressure (MEP), expiratory reserve volume (ERV), and peak expiratory flow (PEF) were measured. FMS conditioning protocol: A commercially available MagPro R30 magnetic stimulator (Medtronic, Skovlunde, Denmark) with a race-track magnetic coil designed by our lab was used. The experimental protocol continued for 6 weeks (20 min twice a day, 5 days/week) in the patients’ room. During this conditioning program, a PFT was repeated at 2- week intervals, ending with a 4-week post-conditioning PFT. FMS parameters were initially set at 40% intensity, 20Hz frequency, and 2-second burst length. Intensity was gradually increased from 40% to 70%. The centers of the magnetic coil were placed at C7 spinous process for inspiratory muscle conditioning and T9 spinous process for expiratory muscle conditioning, respectively.  In this study, we applied FMS to restore respiratory functions in six SCI patients by using a 6-week FMS respiratory muscle- training program. There was no adverse effects observed.  After 6 weeks of conditioning, the values for main outcome measures (mean ± standard error) were: MIP, 78.3 ± 8.0 cmH 2 O; MEP 61.6 ± 10.7 cmH 2 O; IRV, 1.77 ± 0.35 liter; ERV, 0.30 ± 0.05 liter; PIF, 223 ± 31 L/min; and PEF, 301 ± 26 L/min. These values corresponded to 117%, 109%, 107%, 130%, 135%, and 123% of pre-FMS conditioning values respectively.  When FMS was discontinued for 4 weeks, these values had the following decrements (MIP, 4.3%; IRV, 6.0%; PIF, 5.5%; MEP, 0.9%; ERV, 4.9%; PEF, 8.1%), when compared with FMS data. This suggests that continual FMS may be necessary to maintain improved respiratory functions.  This study demonstrated that FMS of cervical and lower thoracic regions resulted in substantial improvements in both inspiratory and expiratory functions. FMS may be considered as a useful and noninvasive respiratory muscle conditioning tool for patients with SCI/D. Acknowledgment: This project was supported by grant from VA Rehabilitation Research and Development Service. The authors also thank Janice Leinter for PFT training. CONCLUSION Figure 4: Changes of maximal expiratory pressure (MEP) throughout the conditioning protocol. Figure 2: Changes of inspiratory reserve volume (IRV) throughout the conditioning protocol. Figure 5: Changes of expiratory reserve volume (ERV) throughout the conditioning protocol. Figure 6: Changes of peak expiratory flow (PEF) throughout the conditioning protocol. Figure 3: Changes of peak inspiratory flow (PIF) throughout the conditioning protocol. 1. Lin VW, Hsiao I, Deng X, Lee YS, and Sasse S, Functional magnetic ventilation in dogs. Arch Phys Med Rehabil. 2004, 85: Lin VW, Hsiao IN, Zhu E, and Perkash I, Functional magnetic stimulation for conditioning of expiratory muscles in patients with spinal cord injury. Arch Phys Med Rehabil. 2001, 82: Lin VW, Hsieh C, Hsiao IN, and Canfield J, Functional magnetic stimulation of expiratory muscles: a noninvasive and new method for restoring cough. J Appl Physiol. 1998, 84: REFERENCES Figure 1: Changes of maximal inspiratory pressure (MIP) throughout the conditioning protocol. An example of magnetic stimulator and magnetic coil. The size of the stimulator is 210 x 530 x 400 mm (H x W x D).