Pope John Paul II is being fed through a nasal tube to aid his recovery from illness, the Vatican revealed this week.
The BBC News website looks at what the procedure the 84-year-old pontiff has had involves and what might happen next.
Why is the Pope being fed with a tube?
Alternative routes of feeding are considered when an individual is unable to meet their nutritional requirements orally.
This can be for a number of reasons - if a person has difficulty swallowing or is unable to eat or drink for a period of time and dietary supplements are not enough to avoid malnutrition and dehydration.
Feeding by nasogastric tube is the most common short-term method of getting food directly to a patient's stomach
Insertion involves passing a flexible plastic tube through the nostril, down the back of the throat and into the stomach
Procedure can be uncomfortable, but does not involve sedation or surgery
Liquid food is fed into the tube
The Pope recently had a tracheotomy - a tube into the windpipe - to help him breath. This can make swallowing more difficult.
Carole Anne McAtear, chairwoman of the British Dietetic Association's Parenteral and Enteral Nutrition Group, said: "Normally when you swallow, you close off your airway pipe to expand your oesophagus [food pipe] to allow you to swallow.
"So when you artificially hold open your trachea with a tube that limits the amount of movement you have in your oesophagus and can make swallowing more difficult.
"So he is probably not able to swallow very well at the moment."
The Vatican statement said that in order "to improve his calorific intake and promote an efficient recovery of his strength, nutrition via the positioning of a nasal-gastric tube has begun".
The Pope's Parkinson's disease might also make his swallowing more difficult, she said.
How does tube feeding work?
Enteral feeding means being fed with specially prepared liquid feeds through a tube into your stomach.
There are three main ways of doing this - via the nose with a nasogastric tube or directly through the abdominal wall into the stomach with a PEG (percutaneous endoscopic gastrostomy) tube or into the beginning of the small bowel with a JEJ (jejunostomy) tube.
The Pope has had a nasogastric tube.
Some people may need to take all their food and drink this way. While others can take some food by mouth and some fed through a tube.
The tubes can be removed at any time with no long term effects.
Which way is best?
That will depend on the individual's circumstances. Nasogastric tubes can be used for a person's life-time.
However, PEG tubes tend to be used for more long term feeding. This was the type of tube used in the case of the late Terri Schiavo, who was left with brain damage for years after a temporary event that starved her brain of oxygen.
Some patients prefer them on cosmetic grounds because they are discreet and can be hidden under clothing.
They are also used where obstruction of the upper gullet or respiratory tract makes passing a nasogastric tube difficult.
JEJ tubes are used when it is best to bypass the stomach completely. For example, when a person has had stomach or oesophageal surgery.
Are there ethical issues?
Yes. Each case has to be considered individually on its own merits and ethics and a decision made by the individual, their family and all of the healthcare professionals involved in their care.
Guidelines say enteral tube feeding should never be started without consideration of all related ethical issues and must be in a patient's best interests.
In some cases, tube feeding will not be deemed a suitable intervention.
Enteral tube feeding is considered to be a medical treatment in law. Starting, stopping, or withholding such treatment is therefore a medical decision which is always made taking the wishes of the patient into account, says the British Society of Gastroenterology.
Terri Schiavo's parents were locked in a legal battle with her legal guardian and husband Michael Schiavo for years before her recent death.
They opposed his wish to remove the feeding tube and let her die.
The US federal appeals court rejected a petition by the parents to have the feeding tube reinserted.
The US Supreme Court repeatedly refused to intervene.