In the previous posts, we determined how to estimate ideal body weight and frame size. In this post , we will review the same concepts though they will be tailored to individuals with amputations.
Determining IBW
In situations, where a person has an amputation , the ideal body weight(IBW) is not calculated similarly as for other persons instead segmental weights are utilized to approximate body weight measurements. In this regard, the adjusted body weight is obtained by using the total body weight percentage for individual parts obtained from (Osterkamp, L (1995). Current perspective on assessment of human body proportions of relevance to amputees. J Am Diet Assoc.) wherein:
The person’s IBW prior to amputation is identified, then the percentage of the amputated part is subtracted to obtain the adjusted IBW.
Example: Calculate the adjusted IBW for female patient 5’8’’ with below the elbow amputation of right arm and amputation of left arm.
IBW (female 5’8’’) – 150 lbs
Right below the elbow (forearm -1.6 %+ hand -0.7% = (-0.23%)
Left arm (-5%)
150 lbs-(0.23%+ (-5%)
5.23%×150
=142.16 lbs
Adjusted IBW- 142.16 lbs
Determining BMI
To determine the BMI for an amputee, the formula developed by Himes can be utilized as follows:
Formula for BMI in Amputees: WtE = WtO/(1-P)
Where:
Total body weight (TBW) also known as “WtE” – Estimated total body weight
“WtO” – Observed body weight (weight measurement after the amputation)
P – The percentage of the missing part(s)
Example: A below-the-knee amputation is 5.9%(0.059) of TBW. Observed body weight is 85 kgs.
WtE = 85 kgs/(1-0.059)
= 85 kgs/(0.941)
= 90.32 kgs
Height measurements can be obtained from current height if possible to obtain, height measurement before amputation or from the arm span or knee height method depending on the amputation done.
The (TBW) is then applied in the BMI formula along with height measurement to determine BMI.
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