OAG Board of Directors
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AnesthesiologistEric Bean, MD, MS
Chair -
AnesthesiologistMelissa Welker, MD, MPH
Chair Elect -
AnesthesiologistNikki Jaworski, MD
Treasurer -
AnesthesiologistAri Tallen, MD
Secretary -
AnesthesiologistMurtaza Diwan, MD
Board Member -
AnesthesiologistShane Lee, MD
Board Member -
AnesthesiologistMichelle Smith, MD
Board Member
Clinical Leaders
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AnesthesiologistAndrew Neice, MD
Chief Medical Officer -
AnesthesiologistRahul Raghavan, MD
Clinical Quality Director -
AnesthesiologistOmar Halawa, MD
ASC Medical Director -
AnesthesiologistLuke Parr, MD
Critical Care Medical Director -
AnesthesiologistAbbie Tirrell, MD
Physician Billing Compliance Officer -
CRNATyler Berch, CRNA
Chief CRNA -
CRNADominique Irigoin, CRNA
Lead CRNA at Legacy Good Samaritan Medical Center
Corporate Leadership
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Lorissa Addabbo
Chief Executive OfficerAs Chief Executive Officer, Lorissa oversees the business, administrative and financial operations of the corporation. Her staff addresses compliance, contracting with hospitals and ambulatory surgery centers, insurance reimbursement negotiation, physician & CRNA recruitment, scheduling, credentialing and information technology.
Lorissa brings a wealth of expertise and leadership to OAG. Most recently, she served as Vice President of Anesthesia, Surgical Services, and Neuromuscular Service Lines at Salem Health, which informs her first-hand knowledge of OAG’s value and quality. During her tenure she realized that she prefers to work for independent practices, as she had done for seven years as the CEO of Hope Orthopedics. Her earlier leadership roles at Adventist Medical Center, Aldrich Advisors, and Salem Health round-out her extensive knowledge of the Pacific Northwest healthcare market.
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Fiona Williams
Chief Operations OfficerAs COO, Fiona is an integral member of the Executive Leadership Team at OAG. Fiona’s responsibilities include overseeing the daily operations of OAG’s clinical workforce across all health systems, managing operational policies, strategic planning for the organization, enhancing staffing efficiencies, implementing objectives for optimal practice management, and various other projects that support an integrated approach for organization-wide improvements to meet the dynamic needs of the healthcare system.
Fiona hails from Melbourne, Australia and graduated with a Bachelor of Health Science (Nursing) from Victoria University in 1993. Over the past 28 years she has specialized in Perioperative Nursing, completing a Graduate Certificate in Perioperative Nursing from Royal Melbourne Institute of Technology. Throughout her career she has worked in large public and private nonprofit health systems as a staff nurse, scrubbing/circulating in all specialties, before transitioning to leadership. Fiona progressed into more senior roles and attained a Diploma of Leadership and Management from Swinburne University of Technology.
In 2017, Fiona and her family relocated to Portland, Oregon and for the past 5 years, Fiona was the Senior Director of Surgical and Interventional Services at Legacy Emanuel/Randall Children’s Hospital, where she was responsible for strategic and operational oversight of 19 ORs and 5 Cath Labs.
In her spare time Fiona attempts to keep up with her two teenage sons, enjoying watching them play sport. Family summers are spent at Hood River or southern Oregon enjoying the kiteboarding scene, and winters are for snowmobiling the multitude of trails in the PNW or venturing further to Montana and Idaho.
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Micheal McCarthy
Human Resources DirectorMicheal joined OAG in 2016 as Human Resources Director. In his role, he is responsible for all recruitment activities, human resources and credentialing, employee relations, patient satisfaction surveys, performance reviews and leadership development.
Micheal has a Bachelor of Arts in Management and Organizational Leadership from George Fox University, and a Master of Science in Counseling Psychology from Lewis and Clark. He has more than 20 years of experience in Human Resources working with companies in retail, technology, healthcare, and most recently an international design firm.
Micheal and his wife have 2 great kids, and a feisty jack russell terrier. He enjoys the outdoors of the Pacific Northwest and is an avid trail runner.
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Siân Williams
Associate Director, Revenue Strategy and OperationsSiân overseas all area of payor contract management. She has over 20 years of experience in healthcare. She received her Bachelors from University of Oregon.
Siân joined OAG in 1993 and brings 14 years of experience managing payor contracting, negotiations, and analysis. Sian serves as billing liaison to our billing vendor, serves on various internal billing committees and is a non-voting member of Legacy Health Partner’s Finance and Contracting Committee. Prior to becoming OAG's Payer Contract Manager, Siân served in various roles ranging from Contracts Analyst, Contracts Administrator and Quality Assurance Administrator, overseeing risk management, credentialing and contract coordination.
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"Ren" Hongbao Ren
Finance DirectorRen is an experienced healthcare manager with over 20 years of experience overseeing all financial functions including accounting, budgeting/forecasting, financial proforma, cost/benefit analysis, business planning, patient cost accounting, benchmarking, physician comparison/reporting, labor productivity, and financial performance management at the hospital as well as at health system level.
Ren’s professional journey began as a CPA assistant at a small firm, where she later advanced to the role of senior financial analyst at US Bancorp. In 1997, she joined Legacy Heath, where she dedicated over 25 years to various aspects of healthcare finance. Ren culminated her tenure at Legacy Health as finance manager at Legacy Emanuel Medical Center.
As OAG’s Finance Director, she oversees the entire financial operations of the Corporation as determined by the policies of the Board and the CEO. The Finance Director oversees all financial functions including accounting, budget, credit, insurance, tax, financial audits, and treasury. Ren designs and coordinates a wide variety of accounting and statistical data and reports. She assists the CEO with establishing and maintaining banking relationships, vendor activities and relationships, and leading executive level finance projects.
