A Capital Coast District Health Board review team made a number of recommendations, including always using an ultrasound before the procedure.
Coroner Smith noted in his conclusion that he hoped a dedicated ultrasound machine was now available.
CCDHB deputy chief medical officer Grant Pidgeon "unreservedly apologised" to Mrs Sheehan's family.
"Capital and Coast DHB fully accepts its responsibility for providing safe health care. Any incident which involves a patient suffering harm or death while in our care is one event too many."
An internal review found that the decision to treat Mrs Sheehan by attempting to drain the fluid was reasonable and took into account her history, Dr Pidgeon said.
"Following this incident the training of registrars undertaking this procedure has been enhanced, and the importance of pre-procedure ultrasound marking has been stressed.
"These teachings are now part of a regular in-service programme."
The respiratory team also had a dedicated ultrasound machine that was routinely used, he said.