Inclusion Criteria:

   1. Age 21 or older.

   2. Participants with familial or sporadic ALS diagnosed as laboratory-supported probable,
   probable, or definite according to the World Federation of Neurology El Escorial
   criteria.

   3. Bilateral phrenic nerve function clinically acceptable as demonstrated by bilateral
   diaphragm movement with fluoroscopic sniff test or with EMG recordings and nerve
   conduction times.

   4. Chronic hypoventilation was documented by at least one of the following:

      - FVC less than 50% predicted, or

      - |MIP| less than 60 cmH2O, or

      - PaCO2 greater than or equal to 45 mmHg, or

      - Nocturnal SaO2 less than or equal to 88% for at least five continuous minutes

   5. Suitable surgical candidate.

   6. Negative pregnancy test in female participants of childbearing potential.

   7. Informed consent from patient or designated representative.

Exclusion Criteria:

   1. Underlying cardiac or pulmonary disease that would increase the risk of general
   anesthesia.

   2. Underlying pulmonary diseases that were present prior to ALS that would affect
   pulmonary tests independent of ALS.

   3. Uncontrolled excessive secretions.

   4. FVC less than 45% predicted at time of surgery.

   5. Preexisting implanted electrical device such as pacemaker or cardiac defibrillator.

   6. Pre-existing diaphragm abnormality such as a hiatal hernia or paraesophageal hernia of
   abdominal contents going into the thoracic cavity.