A 90-year-old patient spent 45 hours sitting on a chair before being transferred to a hospital bed, the INMO has said.
It said there were 803 admitted patients waiting for a hospital bed this morning, with concern over the age profile of patients on trolleys or chairs in hospitals around the country.
The hospital worst affected is University Hospital Limerick with 127 patients waiting for a bed. There were 90 waiting at Cork University Hospital and 63 at St Vincent's University Hospital in Dublin and 60 at University Hospital Galway.
INMO General Secretary Phil Ní Sheaghdha said it is distressing that older patients are being treated on trolleys, chairs and other inappropriate spaces for long periods.
She said that in many hospitals, unfilled rosters "are becoming the norm rather than the exception, creating increasingly unsafe conditions for both nurses and patients".
Ms Ní Sheaghdha said: "The continued use of trolleys and reliance on surge capacity mean that too many nurses are routinely working short-staffed."
The HSE TrolleyGar figures put the number of patients on trolleys in emergency departments and wards across the country at 531.
