Wong baker pain assessment tool is used in the patients who do not have appropriate cognitive level to use a number scale, like lay persons or children.
The patient then points out to face best represents how he/she is feeling at that point of time. The patient must be explained correlation between each face and its correlation with pain.
The Wong baker pain assessment tool depicts 6 faces from happy face to a crying grimace face.
The method was devised for the first time by a pediatric nurse consultant, Donna Wong, and a child life specialist, Connie Morain Baker.
Initially, the numbers 0-5 were used to quantify the pain, but using the numbers 0-2-4-6-8-10 is easier as it is more consistent with the numeric scale of 0-10.
The Wong baker pain assessment tool has indeed made the detection and grading of pain a lot easier especially in the pediatric population who some times have difficulty in communicating and the younger ones.
There are other pain assesment tools that have been developed, but the Wong baker pain assessment tool remains a easy and convenient option for the measurement of pain in small children.
For further reading you can visit the following:
http://en.wikipedia.org/wiki/Pain_scale
http://pain.about.com/od/testingdiagnosis/ig/pain-scales/Wong-Baker.htm