On two occasions this year, it took an ambulance over an hour to arrive at a life-threatening emergency.
New figures also show that response-time targets aren't being met in up to 50 per cent of such cases across the country.
HIQA says ambulances should arrive at life-threatening emergencies in less than 19 minutes in 80 per cent of cases.
But new figures, released by the National Ambulance Service, show this isn't being met in almost all regions in Ireland.
In the first four months of this year, for non-cardiac cases, it was reached only 44 per cent of the time by Dublin Fire Brigade, the major provider of emergency ambulance cover in Dublin.
It was also met in only 52 per cent of these type of cases in the west and southeast.
There were response-times of over an hour in Kildare and Cork and one of 44 minutes in Leitrim - and three further calls of over 42 minutes for cardiac emergencies, in Tipperary, Monaghan and Wexford.
The HSE has not yet responded to requests for comment on the statistics.