PURPOSE: Although the measurement of pulmonary congestion can aid in the diagnosis of alterations in cardiac output, there have been few non-invasive devices to quantitate total intrathoracic fluid (TIF). New devices able to accurately measure thoracic impedance (Zo), as the inverse of TIF, should prove useful for both in- and out-patient cardiac assessment. Hypotheses: 1.Zo inversely correlates to the degree of intra-thoracic fluid volume observed on chest x-ray (CXR); i.e., higher Zo values = normal CXR; lower Zo values = wet CXR. 2.Zo does not correlate to subject Body Mass Index (BMI) since Zo reflects the degree of intra-thoracic fluid volume.
METHODS: We prospectively measured the Zo value of patients admitted to the MICU at our tertiary care university hospital, using a new non-invasive thoracic bioimpedance system (ZOE™, National Medical Testing, Inc.). The Zo was measured in triplicate and averaged. Each patient had a CXR on the same day as the Zo measurement. A single radiologist blinded to the Zo values interpreted the CXR, which was then categorized as either normal or wet. Statistical comparison of Zo and CXR category and between Zo and BMI was performed using MS Excel.
RESULTS: Nineteen (19) patients were studied. The CXR pulmonary vasculature was normal in 12 and wet in 7. The Zo values for the normal and for the wet CXR were 17.1 ± 1.60 and 21.62 ± 9.17 respectively. There was considerable overlap of Zo values between the two CXR categories. No correlation was noted between all Zo values and BMI.
CONCLUSION: Thoracic impedance (Zo) measured by ZOE™: 1.Does not correlate with CXR category of pulmonary vasculature (normal, wet) in our patient population; this does not support the Hypothesis. 2.Does not correlate to BMI; this does support the Hypothesis.
CLINICAL IMPLICATIONS: 1.The ZOE™, non-invasive thoracic bioimpedance system cannot replace the traditional chest X-ray to assess intra-thoracic fluid status in our patient population. 2.In the future, other new non-invasive thoracic bioimpedance systems will be tested in the same format as this evaluation.
DISCLOSURE: Puneet Garcha, None.