Media playback is unsupported on your device Media caption Staff at Kibagabaga Hospital in Rwanda have developed their own version of the checklist

Making a series of simple checks such as ensuring that the correct patient is on the table and operating on the right part of the body, could help surgical teams save almost half a million lives a year across the world.

Patients have died when surgeons have removed the wrong organ, left instruments inside the body, or even operated on the wrong patient.

In 2008 the World Health Organization launched the Surgical Safety Checklist to counter human errors like these. Studies showed it was so effective in reducing complications that many hospitals quickly adopted it.

But although it was developed as a global tool, it has proved harder to roll out in poorer countries.

The Lifebox Foundation is training staff in one Rwandan hospital how to use the checklist, and hope to roll out the training to the rest of the country's 45 hospitals.

So what are the questions that could save your life?

1. Are you operating on the right patient?

Image caption Making sure the right patient is on the operating table is on the checklist twice

Incredible as it sounds, surgical teams don't always operate on the right patient, with an estimated 200-300 'wrong-person' operations taking place in the USA each year.

Checking the right person is on the operating table is so critical that it is on the list twice: once before the patient goes under anaesthetic and again before the incision is made.

If you create a 'tickbox culture' it doesn't necessarily get introduced in the right spirit Dr Iain Wilson, Consultant anaesthetist and Lifebox trustee

A UK hospital trust recently performed eye surgery on the wrong patient, despite the Surgical Safety Checklist being compulsory in UK hospitals since 2010.

It's not enough just to have the checklist to hand. The questions seem simple but using the list properly means really thinking each step through, says Dr Iain Wilson, a consultant anaesthetist who was involved in the development of the checklist.

"If you create a 'tickbox culture' it doesn't necessarily get introduced in the right spirit. It's a problem if you move the focus from the patient to the procedure."

2. Are you performing the right operation?

Image caption Checking the right operation is being performed can save a lot of time and distress

This is another double-check on the list.

'Wrong-site' operations are, not surprisingly, more common when there's a choice of left or right.

In a case where a man died when his only healthy kidney was removed, the surgeon said he studied the X-ray the wrong way round before the operation.

In Rwanda, where very few hospitals currently use the checklist, an elderly man went in for an operation for his fractured right hip. He woke up some time later to be told they had put the screw in the the wrong side and would have to start all over again the next day.

3. Do you know the name and job of everyone on the team?

Image caption Team introductions help everyone understand what they are doing

This is something surgical teams under time pressure might balk at: why do they need to introduce each other?

But group introductions not only let everyone know each other's role in the operation, they also encourage people to speak up later on in the operation, says consultant paediatric anaesthetist Dr Isabeau Walker.

"There's often someone who's noticed something that's not quite right. If that person's been introduced and they've got a voice, they're much more inclined to speak up."

4. Has the anaesthetic machine been checked?

Image caption Well-functioning equipment dramatically reduces deaths from anaesthesia

Although the checklist itself only takes a few minutes to run through, it refers to inspections that should have already taken place, like thorough machine checks.

This is especially important in developing countries where an estimated 40% of healthcare equipment is out of action, compared with less than 1% in high-income countries.

Modern techniques and monitoring have seen deaths from anaesthesia fall to 1 in 200,000 in the developed world.

But in Togo the risk of anaesthesia mortality is as high as 1 in 133, according to a study from 2005, and the vast majority of the deaths were considered to be avoidable.

5. Are the patient's oxygen levels being monitored?

Image caption Pulse oximeters, which measure blood levels, are essential for safe surgery

Oxygen levels in the patient's blood can be monitored by a pulse oximeter, a device which clips onto a finger or earlobe and sounds an alarm if the level drops.

While they are acknowledged as a standard safety device and are ubiquitous in Western operating theatres, 70% of operating theatres in Sub-Saharan Africa work without them.

It is the only item on the checklist that refers to new technology not widely available throughout the world.

To address this 'pulse oximetry gap", the Lifebox Foundation distributes pulse oximeters cheaply or even for free to lower income countries.

In the Rwandan project, pulse oximeter distribution goes hand in hand with Surgical Safety List training.

6. Have you removed all instruments from the patient?

Image caption One of the last steps on the checklist is to count all instruments, sponges and needles

A woman in Uganda died when a 12in mop was left in her body after a caesarean section. A mop is a large swab often used instead of suction in low-resource hospitals. By the time the mistake was discovered, the mop had completely embedded itself in the woman's intestines.

There are three stages to the checklist: "sign in", checks carried out before the patient goes under anaesthesia; "time out", before the first incision is made; and "sign out", before the patient leaves theatre.

One of the last checks before the patient leaves is a complete count of all instruments, sponges and needles - aimed at ensuring those kinds of life-and-death mistakes do not happen.