About Oxygen Concentrator Store

Updated: April 19, 2019

Our History and Who We Are

With more than 18 years of experience, Oxygen Concentrator Store from American Medical Sales and Rentals is one of the oldest and most experienced oxygen concentrator retailers in North America. AMSR is accredited by the Accreditation Commission for Health Care and holds a national BBB A+ rating.

Our Respiratory Specialists are fully trained on every product we carry and are available 7 days a week to answer any questions you have. Let our experts help you select the right device for you and your oxygen requirements.

Our Mission

Making Life with Oxygen Easier

Management Team

Jenny Hopkins AMSR Picture

Jenny Hopkins  CEO and Partner

  • Email Jenny Hopkins
  • Call Jenny Hopkins
  • 303-483-7156

Jenny is a managing partner at Crescendo Capital Partners and has been involved with AMSR since 2009. Her background includes more than 20 years of experience leading organizations for Hewlett Packard and Agilent Technologies. Outside of work Jenny enjoys golfing, skiing, and running.

Cindy George AMSR Picture

Cindy George  President

  • Email Cindy George
  • Call Cindy George
  • 303-483-7139

Cindy George brought her direct marketing prowess and sparkling personality to AMSR in October, 2013. Prior to that, she had spent almost 15 years in the direct response marketing industry, selling everything from computer learning, to nutraceuticals, to hopes and dreams. In her free time, Cindy revels in the wins and wallows in the losses of her home-state KC Cheifs and KU Jayhawks.

Shannon Walter AMSR Picture

Shannon Walter  Director of Operations

  • Email Shannon Walter
  • Call Shannon Walter
  • 303-483-7138

Shannon joined AMSR in February of 2012. Originally from North Carolina, she moved to Denver after college and began her first accounting job with Marriott Hotels. Shannon loves the fast pace of a smaller business and the opportunity to always be improving.

Scott Ridl AMSR Picture

Scott Ridl  Web Manager

  • Email Scott Ridl
  • Call Scott Ridl
  • 303-483-7155

Scott joined AMSR in 2008 and has over 10 years of experience as a web manager. He graduated from The Art Institute with a degree in Web Design & Interactive Media. He enjoys hiking, biking and playing guitar in his free time.

Marissa Ganje AMSR Picture

Marissa Ganje  Warehouse Manager

  • Email Marissa Ganje
  • Call Marissa Ganje
  • 303-483-7159

Marissa joined AMSR in 2012. She recently graduated from the University of Colorado at Colorado Springs. She oversees our rental program as well as inventory and transactions.

Aaron Searls AMSR Picture

Aaron Searls Sales Manager

  • Email Aaron Searls
  • Call Aaron Searls
  • 303-483-7147

Aaron has been a dedicated member of the AMSR team since July 2014. Prior to that, he worked over 6 years in a fitness gym assisting with coaching, mentoring, and developing healthy living habits with people of all ages. Aaron loves rooting for the Colorado Avalanche and enjoys all things outdoors. He has a passion for helping others and is always looking to improve himself.

Stefani Cinto AMSR Picture

Stefani Cinto  Sales Manager

  • Email Stefani Cinto
  • Call Stefani Cinto
  • 303-483-7162

Stefani, moved to Colorado from Nashville, TN where she taught ballroom dance. Stefani joined the AMSR team in the Summer of 2017 and brings over 5 years of experience to her role. Outside of work, Stefani enjoys ballroom and salsa dancing, kickboxing, and running.


Maddie Hager AMSR Picture

Maddie Hager Process Engineer

  • Email Maddie Hager
  • Call Maddie Hager
  • 303-672-8001

Maddie joined AMSR at the start of 2016. She was originally from North Dakota and graduated from NDSU with a degree in Process Engineering. She spends her free time in the mountains and enjoys snowboarding, hiking, and camping.

Sergio Gonzalez AMSR Picture

Sergio Gonzalez  Customer Service Support Technician

  • Email Sergio Gonzalez
  • Call Sergio Gonzalez
  • 303-483-7152

Sergio, originally from Dallas, Texas, has over 4 years of experience in the customer support field. Outside of work he enjoys many of the outdoor activities that Colorado has to offer. He is also an avid MMA, baseball, and basketball fan.

Sales Team

Nick Vannatta AMSR Picture

Nick Vannatta  Lead Oxygen Specialist

  • Email Nick Vannatta
  • Call Nick Vannatta
  • 303-483-7158

Nick joined AMSR in 2007. He has been factory-trained by Respironics, DeVilbiss, Inogen, Invacare, and SeQual. He is also certified to repair select Respironics and SeQual products. Nick enjoys getting to know his customers, and they often ask for him by name.

Bret Bennett AMSR Picture

Bret Bennett Oxygen Specialist

  • Email Bret Bennett
  • Call Bret Bennett
  • 303-483-7163

Bret joined AMSR in 2012 and is factory trained by Sequal, Respironics, and Invacare. He says he has never had a more fulfilling job and loves to connect with people over the phone. Helping customers finding the best solution for them is his number one priority.

Sean Lowe AMSR Picture

Sean Lowe Oxygen Specialist

  • Email Sean Lowe
  • Call Sean Lowe
  • 303-483-7145

Sean is originally from Louisiana but was born in Colorado Springs. He has over 10 years of experience in medical sales and his favorite part of his job is listening to customers and being a solution provider for something as important as oxygen! Outside of work, Sean likes to watch sports, run, and is an avid golf player and fan.

Carlos Arroyave AMSR Picture

Carlos Arroyave Bilingual Oxygen Specialist

  • Email Carlos Arroyave
  • Call Carlos Arroyave
  • 303-483-7144

Carlos, originally from Miami, Florida, joined the AMSR team in the Winter of 2017 and brings over 10 years of experience to his role. Outside of work, Carlos enjoys doing anything outdoors!

Isaiah Tafoya AMSR Picture

Isaiah Tafoya  Oxygen Specialist

  • Email Isaiah Tafoya
  • Call Isaiah Tafoya
  • 303-483-7157

Isaiah, a Colorado native, studied business and played basketball at Adams State University. Go Grizzlies! Isaiah loves going the extra mile for his customers. Outside of work Isaiah loves anything sports related as he still plays in numerous basketball leagues. He loves spending time with his family and loves this beautiful Colorado state.


Linda Ganje AMSR Picture

Linda Ganje Rental Specialist

  • Email Linda Ganje
  • Call Linda Ganje
  • 303-483-7154

Linda joined AMSR in 2008 and has been factory trained by Sequal, Inogen, Respironics, Invacare, AirSep, Inova Labs and DeVilbiss. She enjoys educating people about the various oxygen concentrator options and assisting them in selecting the products that best fit their needs. She loves to see the joy and the freedom that oxygen concentrators bring to their lives.

Joshua D’Estrada AMSR Picture

Joshua D’Estrada Rental Specialist

  • Email Joshua D’Estrada
  • Call Joshua D’Estrada
  • 303-483-7164

Joshua, a Colorado native, attended Metropolitan State University and has over 14 years of experience in both sales and the customer experience. Outside of work, Joshua enjoys music and golfing.

Buy Backs

Kristina Maynard  AMSR Picture

Kristina Maynard  Buy Back Specialist

  • Email Kristina Maynard
  • Call Kristina Maynard
  • 303-483-7137

Kristina joined AMSR in September of 2015, choosing to relocate to Colorado from the West Coast. Thrilled to contribute to a locally owned company that dedicates itself to being preeminent in our industry. Outside the office, Kristina enjoys music, jewelry and vintage cars.

Shipping & Receiving

Bryn McGary AMSR Picture

Bryn McGary Warehouse Technician

  • Email Bryn McGary
  • Call Bryn McGary
  • 303-799-0013

Bryn moved from Arcadia California to Colorado in 1991 and has over 8 years of experience in the shipping and receiving field. Outside of work she enjoys hiking, camping, and spending time with her family, friends, and 8 year old Rottweiler Basset Hound, Mara.