"Professional incompetence" means lack of ability safely and skillfully to practice osteopathic medicine, or to practice one or more of its specified branches, arising from:
1. Lack of knowledge or training;
2. Impaired physical or mental capability of the osteopathic physician;
3. Indulgence in the use of alcohol or any controlled substance; or
4. Any other sole or contributing cause.
(Added to NRS by 1977, 940)