Mandela "is not only revered, he is loved and profoundly admired by people all over the world, and the sense of letting go must be difficult for everyone involved," said Dr William Schaffner, an infectious disease specialist at Vanderbilt University.
In much of Africa, people are considered fortunate to live past age 60. For those who reach old age, death is still seen as sad, but friends and family typically celebrate with big parties to honor a life well-lived. Taking extraordinary measures to keep that person alive would be considered dishonorable, said Dr Sola Olopade, the Nigerian-born clinical director for the University of Chicago's Center for Global Health.
If such measures are being used for Mandela, many could consider it "quite painful," Olopade said, "because those are not the last memories you want to have for someone with such an exemplary life."
How Madiba is likely being treated
US doctors say Mandela's lung infection is most likely pneumonia, a very common cause of illness and death in the elderly.
The infection is usually caused by bacteria and causes lungs to fill with fluid or pus, making breathing difficult and often causing fever and weakness. Treatment includes antibiotics and extra oxygen, often from a mechanical ventilator.
An elderly person critically ill with pneumonia would typically be hospitalised in an intensive care unit and put on a mechanical ventilator, or breathing machine, said Dr J.P. Kress. He is director of the University of Chicago's medical intensive care unit's section on lung and critical care. Ventilators often require a breathing tube down the throat, and patients need to be sedated because of the discomfort.
These patients typically are hooked up to feeding tubes, intravenous fluids and all kinds of monitoring machines to check heart rate, blood pressure and other functions. For long stays, lying prone in a hospital bed, they have to be periodically moved into different positions to prevent bed sores; their arms and legs have to be exercised to fight muscle wasting.
Mandela has been hospitalised several times since December for a recurring lung infection, and he has had tuberculosis.
In a hospitalisation in March and April, doctors drained fluid from around his lungs, making it easier for him to breathe. He got care at home until he returned to the hospital on June 8.
For elderly patients hospitalised repeatedly with lung problems, the chances for recovery are often grim, Kress said.
"It's possible he's sitting in a chair asking, 'When am I going to get out of the hospital?' but that's very unlikely," he said.
Outlook usually poor
Patients so critically ill may have ups and downs, and small changes like needing a little less help from a ventilator may be seen as a sign of improvement even when the outlook remains poor, Kress said.
Schaffner said, "There are always little glimmers of hope. It's not a straight line down ... when you're so gravely ill."
Ada Levine faced end-of-life decisions with her mother, Maria Robles of Chicago. And it was difficult, even though her mother had made her wishes known. Robles died two weeks ago at age 75 after 12 years of heart failure and other problems that had her in and out of the hospital.
"It was not going to get better," Levine said. "You're hopeful. You believe in miracles and 'maybe.' At some point you realise there is no miracle, and you have to be strong and do the right thing."
Her mother did not want life support, but following that directive is easier said than done, Levine said.
"It's brutal, very difficult, hard, to watch this person decline and think now you're responsible for making their decisions."Loretta Downs, former president of the Chicago End-of-Life Care Coalition, said decisions about life support should turn around the patient's wishes.
"Very often it's not the person who's dying's choice," but the family's, she said. "Now that we can prolong dying, there's this whole question of are we prolonging dying versus prolonging living? It's not comfortable to be on life support."
AP Chief Medical Writer Marilynn Marchione in Milwaukee and Andrew Meldrum in Johannesburg contributed.