Feasibility of Bioelectrical Impedance Spectroscopy Measurement before and after Thoracentesis

Abstract

Background. Bioelectrical impedance spectroscopy is applied to measure changes in tissue composition. The aim of this study was to evaluate its feasibility in measuring the fluid shift after thoracentesis in patients with pleural effusion. Methods. 45 participants (21 with pleural effusion and 24 healthy subjects) were included. Bioelectrical impedance was analyzed for “Transthoracic,” “Foot to Foot,” “Foot to Hand,” and “Hand to Hand” vectors in low and high frequency domain before and after thoracentesis. Healthy subjects were measured at a single time point. Results. The mean volume of removed pleural effusion was 1169 ± 513 mL. The “Foot to Foot,” “Hand to Hand,” and “Foot to Hand” vector indicated a trend for increased bioelectrical impedance after thoracentesis. Values for the low frequency domain in the “Transthoracic” vector increased significantly (P < 0.001). A moderate correlation was observed between the amount of removed fluid and impedance change in the low frequency domain using the “Foot to Hand” vector (r = −0.7). Conclusion. Bioelectrical impedance changes in correlation with the thoracic fluid level. It was feasible to monitor significant fluid shifts and loss after thoracentesis in the “Transthoracic” vector by means of bioelectrical impedance spectroscopy. The trial is registered with Registration Numbers IRB EK206/11 and NCT01778270.

Monitoring thoracic fluid content using bioelectrical impedance spectroscopy and Cole modeling

“…The expected effect of an extracellular fluid shift into the intracellular space while the total fluid volume remains constant, is an increase in , a decrease in , and an increase in K. Furthermore, K may also increase as a result of increased due to drainage of extracellular fluid from tissue. In HF patients, K increased from 0.57 to 0.63 and in pleural effusion patients from 0.57 to 0.62 [24,26]. The pleural effusion study included a separate control group of healthy subjects with K = 0.94, which is comparable to our results.…”

“…Previous studies have used Cole modeling for BIS measurements obtained with a transthoracic electrode configuration in the context of thoracic fluid accumulation [24,26]. Only a limited number of parameters were available for comparison with our results ( and ).…”

“…The study reported that an average weight loss of 1.6 kg during diuretic therapy was reflected into a transthoracic impedance change of : +25 % and : +10 % relative to the discharge ("dry") value. A study in patients with pleural effusion reported changes of : +10 % and : +2 % relative to the "dry" value for an average of 1.2 L of fluid removed from the thorax [24]. Pleural effusion consists mainly of extracellular fluid and is located below the lungs.…”

“…Based on the results reported by the two studies in HF and pleural drainage patients [26,24], we derived the ratio = / , which may be used as a measure of fluid distribution because the resistivity of intracellular and extracellular fluids is stable [39]. The expected effect of an extracellular fluid shift into the intracellular space while the total fluid volume remains constant, is an increase in , a decrease in , and an increase in K. Furthermore, K may also increase as a result of increased due to drainage of extracellular fluid from tissue.…”

“…Therefore, segmental bioimpedance measurements of the thorax have been suggested in order to maximize the sensitivity to changes in pulmonary fluid volumes [23]. Thoracic measurements have been shown to be sensitive to fluid loss after thoracentesis in patients with fluid accumulation below the lungs, in the pleural cavity [24,25]. Studies in HF patients with pulmonary edema, i.e.…”