About Us

Our commitment
We are committed to providing comprehensive, compassionate and patient-focused care for all of our patients and their families. Our physicians, nurse practitioners, sleep technologists, and respiratory therapists continue to educate themselves in order to provide you with the most up-to-date treatment options and, our efficient, friendly and professional staff works hard to make every patient’s visit to Michigan Lung and Critical Care Specialists as hassle-free as possible.

Our staff
Our physicians have been members of the active staff at Genesys Regional Medical Center in Grand Blanc since 1992.

Gregory Streff, DO is the Program Director of the Pulmonary/Critical Care Fellowship program at Genesys Regional Medical Center. He is board-certified in Internal Medicine, Pulmonary/Critical Care, and Sleep Medicine, and is a fellow of the American College of Chest Physicians and of the American College of Osteopathic Internists and a fellow of the American Academy of Sleep Medicine.

Mark Rittenger, DO is board-certified in Internal Medicine, Pulmonary/Critical Care, and Sleep Medicine, and is a fellow of the American College of Chest Physicians, and a diplomate of the American Academy of Sleep Medicine.

Sleep disorder consultations with our physicians can be scheduled for patients at our Grand Blanc office. In addition, our physicians can order and interpret sleep studies for these area sleep labs:

Michigan Lung and Critical Care Specialists Sleep Lab
(Grand Blanc)
Lapeer Sleep Diagnostic Center (Lapeer)
West Flint Sleep Lab (Flint)


		Dr. Gregory Streff Dr. Mark Rittenger		Our commitment We are committed to providing comprehensive, compassionate and patient-focused care for all of our patients and their families. Our physicians, nurse practitioners, sleep technologists, and respiratory therapists continue to educate themselves in order to provide you with the most up-to-date treatment options and, our efficient, friendly and professional staff works hard to make every patient’s visit to Michigan Lung and Critical Care Specialists as hassle-free as possible. Our staff Our physicians have been members of the active staff at Genesys Regional Medical Center in Grand Blanc since 1992. Gregory Streff, DO is the Program Director of the Pulmonary/Critical Care Fellowship program at Genesys Regional Medical Center. He is board-certified in Internal Medicine, Pulmonary/Critical Care, and Sleep Medicine, and is a fellow of the American College of Chest Physicians and of the American College of Osteopathic Internists and a fellow of the American Academy of Sleep Medicine. Mark Rittenger, DO is board-certified in Internal Medicine, Pulmonary/Critical Care, and Sleep Medicine, and is a fellow of the American College of Chest Physicians, and a diplomate of the American Academy of Sleep Medicine. Sleep disorder consultations with our physicians can be scheduled for patients at our Grand Blanc office. In addition, our physicians can order and interpret sleep studies for these area sleep labs: Michigan Lung and Critical Care Specialists Sleep Lab (Grand Blanc) Lapeer Sleep Diagnostic Center (Lapeer) West Flint Sleep Lab (Flint)