From the AECC (Spanish Cancer Association) website.
“Provision of health transport: favoring access to health care of the National Health System, to patients who, due to clinical impossibility, or geographical distance from the health center and previously justified, cannot access it. Patients may be accompanied when the age or clinical situation requires it. You can request this service through the Patient Care Office of your health center and / or through your referring doctor.”
Similar info on the Ministry of Health website as well.
“Access to health transport provision
Sick or injured persons are entitled to finance this benefit when they receive health care from the National Health System, in their own or concerted centers, and who, due to physical impossibility or other exclusively clinical causes, cannot use ordinary transportation to travel to a health center or your home after receiving the corresponding health care, in case the causes that justify your need persist. They can be accompanied when the patient’s age or clinical situation requires it.
When there is a third party obligated to pay, the corresponding health administration must proceed to claim the amount of the services performed.”