Paul Hinge, chairman of a Mid Wales health watchdog, Ceredigion Community Health Council, says the ambulance service is "stretched" and restructuring processes mean hospitals have fewer beds available.
Health expert Marcus Longley warned that changes to the NHS in Wales, with fewer major A&E departments, could make the pressure on ambulances transferring patients worse, as response distances and times are increased.
Professor Longley said, though, that current problems lie within the system more broadly, and "the health service needs to get ahead of the problem, rather than just forever scrambling to catch up with it."
Abertawe Bro Morgannwg University Health Board says many of the people it has been treating have cardiac problems or have suffered a stroke. Many are over the age of 85.
The health board says it has brought in extra staff, and put on extra beds, to deal to with its A&E departments being exceptionally busy.
It says most routine operations have been postponed.
The Health Minister Lesley Griffiths said it is worth noting that exceptional pressure on A&E departments is "not a Wales-only problem", but is also happening in England.
"The public have an important part to play at this challenging time for emergency care services by using the most appropriate healthcare service to their needs and thinking before attending the Accident and Emergency Department or dialling 999."
"NHS staff continue to work extremely hard to care for patients during this period of pressure on hospital and emergency services, and my officials will continue to monitor the situation closely.”
Hywel Dda University Health Board says the number of people going to accident and emergency departments has increased at all of its hospitals this month, compared to last month.
It says some planned surgery has been postponed, so resources can be redeployed to A&E units, but it is working to ensure patients are not delayed in moving out of hospital and into more appropriate care.
The Welsh Ambulance Service says it is "very concerned at the handover delays that have been experienced recently".
It is "concerned that pressure across all hospitals in Wales has a direct impact on the ambulance response that is able to be provided to patients who call 999 for our help."
"Ambulance crews continue to provide clinical care for patients as they wait to be admitted into hospital and we provide ambulance clinicians, where possible, to care for patients in emergency departments to support the nursing and medical staff in hospitals."
The Welsh Government has urged patients to "think before attending the Emergency Department or dialling 999."
People with minor injuries or illnesses are being asked to consider other options, to reduce pressure on A&E departments:
- Self care: Keep a medical cupboard well-stocked, and rest at home
- Advice: NHS Direct Wales can help with health questions and help find local services. The helpline is 0845 46 47 and the website www.nhsdirect.wales.nhs.uk
- Community support: A pharmacist can provide expert advice, and provide medicine without an appointment
- Routine care: An appointment with your local GP when it's not an emergency
- Urgent care: If you need urgent healthcare, phone your GP surgery or out of hours service - for urgent dental care contact the NHS Direct Wales Dental Helpline on 0845 46 47
- Emergencies: Call 999 and ask for the ambulance service for serious emergencies, or go to an A&E department
The Welsh Government says there has been "a significant increase in emergency pressures during the last week."
It says some staff have been redeployed to help out in A&E departments.