Advantages in comparison with other phrenic nerve stimulators
Several advantages results:
Since stimulation occurs at “quadrant” frequency (4.5 to 5.5 Hz) to reach fusion contraction at normal frequency (18 to 22 Hz) only a portion of available muscle capacity is needed for sufficient breathing. Breathing volume can be readily adjusted to meet the metabolic need of a patient.
Only a portion of motor units in the diaphragm muscle is working by activation of a single stimulus pulse in the nerve. Most of the motor units are at rest during successive stimulus pulses, thus allowing them an extended recovery time after the contractile phase.
Partial contraction of the muscle and changing composition of activated muscle fibers after each stimulus pulse makes the perfusion (blood supply) of the muscle more effective compared to tetanus like contraction in unipolar stimulation.
The diaphragm muscle will not fatigue even by continuous sequential multipole stimulation of the phrenic nerves.
Conditioning time (time to wean a patient from mechanical ventilator) is shorter compared to unipolar stimulation since no adaptation to low-frequency stimulation is needed.
- unipolar/multipolar sequential animation.
- Atrostim PNS can be used in parallel with cardiac pacemakers or other implanted medical devices.
Possible loss of the only active contact will mean a re-operation for the device user.
Animation of One Active Nerve Contact versus Four Active Nerve Contacts (Atrostim PNS)
Comparison to Unipolar Stimulation – One Active Nerve Contact
Same motor units in the diaphragm are working without a rest. At normal stimulation frequency the muscle contraction is unphysiologic and the diaphragm fatigue is unavoidable.
Diaphragm muscle needs to be trained at low-frequency stimulation in order to prevent fatigue.
As a consequence part of the muscle strength, i.e. breathing or tidal volume is lost. Less trained muscle capacity is available for a temporarily increased need (sitting, coughing, sigh). Weaning from the ventilator will take longer.
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