PURPOSE: Diaphragm Pacing Stimulation (DPS), using intramuscular electrodes implanted at the diaphragm motor points, is effective in replacing mechanical ventilation (MV) for tetraplegics. DPS has also demonstrated safety and preliminary efficacy in a pilot study to maintain diaphragm strength in patients with ALS.
METHODS: The effect of DPS on respiratory system compliance (CRS), peak airway pressure (PAW), and ability to trigger positive pressure MV in pressure support mode was conducted during intra-operative testing in SCI and ALS patients. DPS was synchronized with MV and the change in CRS was viewed qualitatively on the volume-pressure tracing and recorded numerically. PAW was recorded with and without DPS to determine the ability of DPS to reduce pressures while maintaining or increasing tidal volumes.
RESULTS: Ten patients (six SCI and four ALS) were studied. Without stimulation CRS = 58 ± 5.7 ml/cm H2O and increased with stimulation to CRS = 69 ± 5.7 ml/cm H2O, a 19% increase. Depending on the timing of synchronization between the DPS and mechanical ventilation the resulting volume-pressure tracing was viewed as progressing to negative pressure ventilation initially or reducing the pressure when the DPS commenced. Peak pressures were substantially decreased with the addition of DPS. Without DPS PAW = 20 ± 4.2 cm H2O and VT = 747 ± 125 ml. With DPS PAW = 15 ± 4.3 cm H2O and VT = 916 ± 194 ml, a 21% decrease in PAW with a 24% increase in VT. DPS was able to trigger the ventilator in all 10 patients. No adverse hemodynamic effects were observed.
CONCLUSION: The addition of negative pressure ventilation with DPS increases the respiratory system compliance, decreases peak airway pressures and increases tidal volumes in SCI and ALS patients. Further studies to examine these potential benefits are planned.
CLINICAL IMPLICATIONS: These findings suggest a potential role for DPS in critically ill ventilator dependent ICU patients with atelectasis, pneumonia, barotrauma or diaphragm dysfunction.
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