People in north Wales who suffer from serious sleeping problems face a long wait before they can be treated.
Sleep apnoea affects about 1% of middle-aged men
The unit which helps patients with sleep apnoea - a condition which can cause sufferers to stop breathing for up to a minute when airflow to the lungs is restricted during sleep - is facing financial problems.
The department in Ysbyty Gwynedd was set up in 1995 for a small number of patients.
Over the last eight years demand for the services have increased, but funding levels have remained the same.
About 150 adults and children are being monitored and treated. Many have to sleep connected to machines which keep their throats open.
The services are under review
New patients have been told they will have to wait for treatment based on clinical need as determined by the consultant.
Gwynedd health board has said it is waiting the outcome of a review by Health Commission Wales, the body responsible for planning and commissioning specialist NHS services across Wales.
The board said it hoped the report would provide clear direction for all patients in Wales suffering from the consequences of sleep apnoea and other sleep disorders.
In a statement to BBC Wales on Thursday, chief executive Grace Lewis-Parry said the health board was awaiting the outcome of a UK-wide review of demands for the service.
"It is hoped this will provide clear direction for all patients in Wales suffering from the consequences of sleep apnoea and other sleep disorders," she said.
Sleep apnoea affects about 1% of middle-aged men in the UK.
It is linked with an increased risk of high blood pressure, heart attack, stroke and adult-onset diabetes.