Calvary National public hospitals director Brenda Ainsworth accepted Mr Armistead's resignation on September 5.

His sudden departure came just a month after Ray Dennis resigned as chief executive after more than five years in the job.

Mr Dennis told The Canberra Times in August he had resigned to spend more time with his family.

The sudden departure of two of the hospital's senior executives comes amid speculation the hospital is under financial pressure.

Sources close to the health industry said the cost of delivering services had exceeded funds allocated to the hospital.

Ms Ainsworth said new leadership appointments would join Calvary's existing executive team to ensure the hospital "continues to deliver for the local community".

Karen Edwards will join Calvary Health Care in Bruce as interim chief executive from September 24 and will oversee the recruitment process for a new CFO.

"Karen has an extensive background in public hospitals in New South Wales as both CEO and director of nursing," Ms Ainsworth said.

"Calvary continues to achieve its activity targets, maintain the highest standards of patient safety and quality in care, and strengthen its role in public health and hospital services across the territory."

Calvary Hospital was contacted for comment on what precipitated Mr Armistead's resignation, whether he was forced to resign and if the hospital was under financial stress.