Doctors Bios

Stanley Gunstream, MD, FCCP

Stanley Gunstream, MD, FCCP is a Board-Certified Physician of Internal Medicine, Pulmonary Medicine, and Critical Care Medicine.

Dr. Gunstream earned his Doctor of Medicine at the University of California in Los Angeles, CA.  He completed an Internal Medicine Internship and Internal Medicine Residency, serving as Chief Resident at St. Joseph Hospital in Denver, CO.  Dr. Gunstream performed a Pulmonary Fellowship at the University of Arizona in Tuscon, AZ.

Dr. Gunstream is a member of the American Thoracic Society, National Association of Medical Directors of Respiratory Care, Colorado Medical Society, Larimer County Medical Society, American Medical Association, American College of Chest Physicians, Northern Colorado IPA, and Society of Critical Care Physicians. 

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Mark Petrun, MD, FCCP, FAASM

Mark Petrun, MD, FCCP, FAASM is a Physician of Internal Medicine, Pulmonary Disease, Critical Care Medicine, and Sleep Medicine.  Dr. Petrun is Board-Certified in Internal Medicine and Sleep Medicine.  He is Board-Certified and ReCertified in Pulmonary Disease and Sleep Medicine.

Dr. Petrun earned his Doctor of Medicine at the University of Colorado School of Medicine in Denver, CO.  He completed an Internship in Internal Medicine at St. Luke's Hospital in Denver, CO.  Dr. Petrun performed a Residency in Internal Medicine, serving as Chief Resident at Presbyterian/St. Luke's Medical Center in Denver, CO.  He completed a Fellowship in Pulmonary Research and Instructor of Medicine at Pennsylvania State University, Milton S. Hershey Medical Center, in Hershey, PA.

Dr. Petrun is distinguished as a Fellow of the American College of Chest Physicians.  He is a member of the Colorado Medical Society, Larimer County Medical Society, American Sleep Disorders Association, Colorado Trudeau Society, American Thoracic Society, Northern Colorado IPA, Society of Critical Care Medicine, and American Academy of Sleep Medicine.

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James Hoyt, MD, FCCP

James Hoyt, MD is Board-Certified and ReCertified in Internal Medicine, Pulmonary Disease, and Critical Care Medicine. 

Dr. Hoyt earned his Doctor of Medicine at the University of South Dakota, School of Medicine.  He completed an Internship and Residency in Internal Medicine, as well as Fellowship-Training in Critical Care Medicine at Hennepin County Medical Center in Minneapolis, MN.  Dr. Hoyt performed a Pulmonary Medicine Fellowship at the University of Minnesota in Minneapolis, MN. 

Dr. Hoyt is a member of the American Medical Association, Colorado Medical Society, Larimer County Medical Society, Northern Colorado IPA, American Thoracic Society, American College of Chest Physicians, and Society of Critical Care Medicine.

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Diana Breyer, MD

Diana Breyer, MD is a Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.  Dr. Breyer is Board-Certified and ReCertified in Internal Medicine and Pulmonary Disease.  She is Board-Certified in Critical Care Medicine.

Dr. Breyer earned her Doctor of Medicine at St. Louis University Medical School in St. Louis, MO.  She completed a Residency in Internal Medicine at the University of Iowa Hospitals and Clinics in Iowa City, Iowa.  Dr. Breyer performed Fellowship-Training in Pulmonary Disease and Critical Care Medicine at the University of Iowa Hospitals and Clinics in Iowa City, Iowa.

Dr. Breyer is a member of the American Thoracic Society, Colorado Medical Society, Larimer County Medical Society, Northern Colorado IPA, American College of Chest Physicians, and Society of Critical Care Medicine. 

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Kristin Wallick, MD, FCCP

Kristin Wallick, MD, FCCP is a Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.  Dr. Wallick is Board-Certified in Pulmonary Disease and Critical Care Medicine.  She is Board-Certified and ReCertified in Internal Medicine.

Dr. Wallick earned her Doctor of Medicine at the University of Colorado Health Sciences Center in Denver, CO.  She completed her Residency in Internal Medicine and Fellowship-Training in Pulmonary and Critical Care at the University of Colorado Health Sciences Center in Denver, CO.  Prior to earning her Medical Degree, Dr. Wallick earned a Bachelor of Science, Cum Laude, from the University of Northern Colorado at Greeley, CO.

Dr. Wallick is a member of the American Thoracic Society, American College of Chest Physicians, Society of Critical Care Medicine, Colorado Medical Society, Larimer County Medical Society, American Medical Association, and Northern Colorado IPA.

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Eric Stevens, MD, FCCP

Eric Stevens, MD, FCCP is a Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.  Dr. Stevens is Board-Certified in Internal Medicine.  He is Board-Certified and ReCertified in Pulmonary Disease and Critical Care Medicine.

Dr. Stevens earned his Doctor of Medicine at the Washington School of Medicine in St. Louis, MO.  He completed an Internship and Residency in Internal Medicine at Columbia-Presbyterian Medical Center in New York, NY, where Dr. Stevens served as Chief Resident.  He performed Fellowhip-Training in Pulmonary and Critical Care at the University of Colorado Health Science Center in Denver, CO. 

Dr. Stevens is a member of the Northern Colorado IPA, Colorado Medical Society, Larimer County Medical Society, American Medical Association, Society of Critical Care Medicine, American College of Chest Physicians, and American Thoracic Society.

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Mark Neagle, MD, FCCP

Mark Neagle, MD, FCCP is a Board-Certified Physician of Internal Medicine, Pulmonary Disease, Critical Care Medicine, and Sleep Medicine.

Dr. Neagle earned his Doctor of Medicine at the University of Chicago, Pritzker School of Medicine, in Chicago, IL.  He completed an Internship and Residency in Internal Medicine at the University of Washington Affiliated State Hospitals in Seattle, WA.  Dr. Neagle performed a Fellowship in Pulmonary, Critical Care, and Sleep Medicine at the University of Utah in Salt Lake City, UT.

Dr. Neagle is a member of the American College of Chest Physicians, Colorado Medical Society, Larimer County Medical Society, and Northern Colorado IPA.

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Richard Milchak, MD, FCCP

Richard Milchak, MD, FCCP is a Board-Certified Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.

Dr. Milchak earned his Doctor of Medicine at the University of Nevada, School of Medicine in Reno, NV.  He completed an Internship and Residency in Internal Medicine at the University of Arizona, University Medical Center.  Dr. Milchak performed a Fellowship in Pulmonary and Critical Care at the University of Iowa Hospitals and Clinics. 

Dr. Milchak is a member of the American Thoracic Society, American College of Chest Physicians, Society of Critical Care Medicine, Northern Colorado IPA, Colorado Medical Society, and Larimer County Medical Society.

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Carlos Vassaux, MD

Carlos Vassaux, MD is a Board-Certified Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.

Dr. Vassaux earned a Doctor of Medicine at Universidad Francisco Marroquin in Guatemala, Guatemala.  He completed an Internship and Residency in Internal Medicine at St. Elizabeth's Medical Center in Boston, MA.  He performed a Fellowship in Pulmonary and Critical Care at St. Elizabeth's Medical Center, as well.

Dr. Vassaux is a member of the American Thoracic Society, American College of Chest Physicians, Colorado Medical Society, Larimer County Medical Society, and Northern Colorado IPA. 

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Brent Peters, MD, FCCP

Brent Peters, MD, FCCP is a Board-Certified Physician of Internal Medicine, Pulmonary Disease, and Critical Care Medicine.

Dr. Peters earned his Doctor of Medicine at the University of Kansas, School of Medicine in Kansas City, KS.  He completed an Internship in Internal Medicine and Residency in Internal Medicine, serving as Chief Resident at the University of Kansas School of Medicine in Wichita, KS.  Dr. Peters performed a Fellowship in Pulmonary and Critical Care at the University of Iowa Hospitals and Clinics in Iowa City, IA.

Dr. Peters is a member of the American Thoracic Society, American College of Physicians, American College of Chest Physicians, Society of Critical Care Medicine, Northern Colorado IPA, Colorado Medical Society, and Larimer County Medical Society.

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Kirk DePriest, DO

Kirk DePriest, DO is a Doctor of Osteopathic Medicine who is Board-Certified in Internal Medicine and Pulmonary Disease. 

Dr. DePriest earned his Doctor of Osteopathic Medicine at Michigan State University College of Osteopathic Medicine in Lansing, Michigan.  He completed an Internship and Residency in Internal Medicine at the Oklahoma State University Health Sciences Center.  He performed a Fellowship in Pulmonary, Critical Care, and Interventional Pulmonology at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina.

Dr. DePriest is a member of the Northern Colorado IPA, Colorado Medical Society, Larimer County Medical Association, American Osteopathic Association, American College of Chest Physicians, American Thoracic Society, and Society of Critical Care Medicine.

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Anne Voorhes, PA-C

Anne grew up in Pierre, South Dakota.  She graduated from the University of South Dakota with a Master’s degree in Physician Assistant Studies in 2007.  Following graduation, she moved to the Twin Cities where she worked for a group that specialized in weight loss surgery.  She found her true calling, however, in sleep medicine.  After working at a pulmonary and sleep disorders clinic in Minneapolis for two years, she was ready to return to a smaller town.  She was drawn to Colorado by its mountains, weather, and variety of outdoor activities.  Outside of work, Anne enjoys biking, hiking, and fishing with her brother, who also lives in the area.

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