Lauro Bertulano, 46, Rebecca Jones, 31, and Natalie Jones, 42, failed to carry out blood glucose tests on patients, then faked the results.
The court heard they failed to check blood glucose levels multiples times at required every two hours.
All patients on the ward should have had a routine blood glucose check every two hours. One patient went 26 hours without being checked once.
All three nurses worked on the specialist stroke ward at Princess of Wales Hospital, where their patients are unable to regulate their own blood glucose levels.
The court heard that Rebecca Jones made 51 fake entries in patients notes, Bertulano made 26 and Jones made four.
Suspicions were raised in February 2013 when there were discrepancies between levels recorded in patients’ notes and readings taken by Rebecca Jones on the glucose meter.
Gareth Williams, whose mother Lilian’s records were falsified by all three of the defendants read a statement out in court. The family said they had been left “completely haunted and traumatised” by the treatment their mother experienced, despite repeated complaints to staff.
Paul Roberts, chief executive of the University Health Board, said he was confident that the practices uncovered in the investigation were “not widespread”.
All three of the defendants previously pleaded guilty to multiple charges of wilful neglect.
Sentencing, Judge Tom Crowther QC, said: “This was clear-eyed and calculated deception, the purpose of which was to make the defendants’ working time easier. There was also… a real risk to health, even if that risk happily did not materialize.”
Rebecca Jones was sentenced to eight months, Berulano to four months and Natalie Jones was given a 12-month community order.