PURPOSE: Diaphragm contraction is necessary for ventilation although the driving mechanism for 24 hour control is incompletely understood and includes the special somatic respiratory nuclei of the brainstem, the cerebral cortex and the carotid body among others. EMG assessment of the diaphragm is difficult due to its location. This report analyzes initial feasibility of continuous EMG assessment of the diaphragm in patients implanted with the diaphragm pacing stimulation (DPS) system(Synapse Biomedical, Ohio).
METHODS: Amyotrophic lateral sclerosis(ALS) and spinal cord injured (SCI) patients who were implanted with electrodes at the motor point with DPS system were analyzed utilizing a home polysomnography system(CleveMed, Ohio). Continuous EMG was recorded from the implanted diaphragm electrodes.
RESULTS: Four implanted patients were studied. Two SCI patients had intact phrenic nerves but no diaphragm movement without the DPS system. The first SCI patient studied showed no spontaneous diaphragm EMG activity. Consistent EMG activity was observed on the contralateral diaphragam when the other was stimulated with DPS. The second SCI patient showed right diaphragm EMG activity when either utilizing accessory muscles to breath or when the contralateral diaphragm was stimulated with the DPS. The two ALS patients studied showed that diaphragms with less volitional or stimulated movement under fluoroscopy also had a reduction in the generated motor response demonstrated by the EMG tracings. During a sleep diaphragm EMG in an ALS patient receiving non-invasive positive pressure ventilation, there was significant periods of absent diaphragm EMG activity and apparent increasing EMG activity during decreased O2 saturation.
CONCLUSION: The SCI results show that some of the respiratory reflux activity is below the injury of C3 and is separate from the Hering-Breuer reflex. For ALS patients with the DPS system, continuous EMG recordings of the diaphragm may allow more rapid analyses of dysfunction and subsequent corrective therapy.
CLINICAL IMPLICATIONS: Utilizing these techniques in further trials may help assess the critical function of the diaphragm during sleep. Early implantation of the DPS system in SCI may help recruit dormant but natural activity.
DISCLOSURE: Raymond Onders, No Product/Research Disclosure Information; Shareholder Myself, my university and my hospital have intellectual property rights and founded a company that manufactures some technology used in this study