Figures
Acute reversal of abdominal inspiratory paradox with pacing. A sample recording from patient 1 captures gastric pressure (Pga), raw and integrated electromyographic (EMG) signals, and flow waveforms during resting mechanical ventilation (MV) settings, lowest tolerated MV support, and lowest MV support plus pacing. Reduced MV settings resulted in slower peak flow, and a rapid, shallow breathing pattern was accompanied by negative inflections of the gastric pressure waveform (gray arrows), reflecting an abdominal paradox. At the same reduced MV settings, the addition of diaphragm pacing improved flow and restored positive inspiratory gastric pressures (black arrows).
Right and left hemidiaphragm asynchrony in patient 3. Evidence of asynchrony and loss of phasic inspiratory activity of the left hemidiaphragm reflects denervation of phrenic motor units and altered control of breathing, which may have influenced the lower functional recovery of breathing in patient 3. (A) Respiratory plethysmography and diaphragm electromyographic (EMG) tracings, recorded spontaneous diaphragm activity during full mechanical ventilation, 1 month after implantation of the diaphragm pacemaker. Shaded areas show inspiration. (B) Gray cutout box from graph A illustrates expiratory phase activity (circles), which could be co-contraction to generate positive end-expiratory pressure and offset malacia. In addition, intermittent periods of inspiratory quiescence and large amplitude inspiratory bursts are apparent on the left hemidiaphragm (top) EMG tracing. (C) Black cutout box from graph B shows bursting pattern from a single motor unit. The large-amplitude complex bursts and repetitive discharges suggest partial denervation of this motor unit.
Tidal volume and ventilator-free time increased after diaphragm conditioning with pacing. After 1 month of conditioning, modest gains in tidal volume (A) were detected, but the effect was variable among patients. Ventilator-free time (B) progressively increased in the first 3 months of diaphragm conditioning, which is consistent with published reports of pacing in spinal cord injury. Graphs depict median and range.
Improved diaphragm activation after conditioning. Representative right hemidiaphragm electromyographic (EMG) activity from patient 1 captured during resting mechanical ventilation (MV) settings, unassisted breathing (no assistance by MV or diaphragm pacing), and maximal inspiratory pressure maneuvers. Electromyographic activity from POD5 (left) to POD80 (right) reveals that adjacent diaphragm motor units became progressively more active under all conditions. In conjunction, the patient tolerated both a progressively longer time without MV support and greater minute ventilation with pacing. Similar increases in diaphragm EMG activity were observed in the other patients. POD=postoperative day.
Normalized activity of the diaphragm increased after 1 month of pacing. Spontaneous electromyographic activity of the diaphragm was recorded during full mechanical ventilation (MV) support (A) and unsupported spontaneous breathing (B) and normalized to the within-session maximal voluntary effort. Within 1 month, the averaged normalized root mean square (RMS) of the diaphragm was higher, suggesting the muscle was more active during these behaviors. Graphs depict median and range.
Supplementary Data
eAppendix
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This PDF contains the following supplements:
- eAppendix. Neuromuscular Rehabilitation by Diaphragm Pacemakers in Pompe Disease
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