Comparison of bioimpedance spectroscopy and the Watson formula for measuring body volume in patients on peritoneal dialysis

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• 作者：Gonzalo Martí ; nez Ferná ; ndez^a ; Agustí ; n Ortega Cerrato^a ; Lourdes de la Vara Iniesta^a ; Eva Oliver Galera^b ; Carmen Gó ; mez Roldá ; n^a ; Juan Pé ; rez Martí ; nez^a ; ^{gonzalomfer@hotmail.com" class="auth_mail" title="E-mail the corresponding author} ; ^{drjuanpm@gmail.com" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Peritoneal dialysis ; Bioimpedance spectroscopy ; Watson formula ; Total body volume
• 刊名：Nefrología (English Edition)
• 出版年：2016
• 出版时间：January-February 2016
• 年：2016
• 卷：36
• 期：1
• 页码：57-62
• 全文大小：524 K

文摘

Knowing total body volume (V) is crucial in patients on peritoneal dialysis (PD). It is usually calculated by the Watson anthropometric formula, although the use of bioimpedance spectroscopy (BIS) is becoming increasingly widespread. Measuring V with both methods can at times produce quite different results.

Objective

We aimed to identify differences between the 2 forms of measuring volume in a PD unit and determine which clinical factors are associated with these differences.

Methods

Ours is an observational study of 74 patients on PD. We measured V using BIS (Vbis) and the Watson formula (Vw); 271 measurements were made with each method. We calculated the difference between Vbis and Vw in each patient and classified them into 2 groups: Difference between volumes ≥10% or <10% Vbis. We assessed the presence of several clinical parameters in our patients.

We assessed whether there were any differences between Vbis and Vw (Student t-test). We determined whether there was any association between the difference in volumes and the presence of the clinical parameters analyzed (chi square test).

Results

V was 2.15 l higher measured by the Watson formula than with BIS (p < 0.01). In 58.67% of the measurements, the difference between Vbis and Vw was ≥10%.

Significant differences were found when comparing the presence of difference between volumes and the presence or not of diabetes mellitus (DM) (p = 0.03), hypertension (HTN) (p = 0.036), hypoalbuminemia (p < 0.01), hypoprealbuminemia (p < 0.01), low phase angle at 50 Hz (p < 0.01), high C reactive protein (p < 0.01), obesity (p = 0.027), E/I ratio (ratio between extracellular and intracellular water) ≥1 (p < 0.01) and residual diuresis (p = 0.029).

Conclusions

There are significant differences in the V of PD Unit patients when obtained by Watson formula or by BIS. A difference between the measurements is associated with the presence of DM, HTN, hypoalbuminaemia, obesity, malnutrition, inflammation, E/I ratio ≥1 and the absence of residual diuresis.