Remote dielectric sensing to detect pulmonary congestion in acute dyspnoeic patients: Reproducibility and the effect of pulmonary comorbidities.

Background: Remote Dielectric Sensing (ReDS) is a fast and non-invasive method that estimates lung fluid. We previously described moderate accuracies for ReDS to detect acute heart failure in consecutive patients. We hypothesise that unprecise ReDS values may stem from concomitant pulmonary diseases.

Purpose: To examine the ReDS reproducibility and the effect of pulmonary comorbidities on ReDS values in acute dyspnoeic patients.

Methods: This prospective observational study included 97 consecutive patients ≥50 years with acute dyspnoea. Upon admission, patients underwent low-dose chest computed tomography (CT), echocardiography and ReDS examination. ReDS is by default performed on the right hemithorax in sitting position. For reproducibility comparisons, we conducted additional ReDS measurements two centimetres above and below the default placement, and in sitting and supine position. Two blinded radiologists evaluated the CT scans for pulmonary congestion and pulmonary diseases.

Results: Comparing three ReDS measurements on the right hemithorax revealed coefficients of variations of 9.6 %, 8.2 %, and 8.3 %. For sitting versus supine comparison, the coefficient of variation was 9.5 % for the default ReDS placement. Patients with CT-verified pulmonary congestion had a coefficient of variation of 5.9 % in sitting versus supine comparison, while those without had 10.3 %. In multivariable regression, lower ReDS values were observed in patients with pneumonia (-1.81, p = 0.215, N = 51), emphysema (-5.44, p = 0.001, N = 26), and higher in fibrosis (5.58, p = 0.032, N = 8) and congestion (5.79, p = 0.002, N = 17), compared to those without.

Conclusion: ReDS values of lung fluid content and reproducibility were affected by pulmonary diseases. ReDS showed consistent reproducibility for patients with CT-verified pulmonary congestion.