Experience with remote dielectric sensing (ReDS) for acute decompensated heart failure complicated by chronic obstructive pulmonary disease

Abstract

Remote dielectric sensing (ReDS) is a novel, non-invasive, miniature radar based, and vest testing system to quantify pulmonary edema. ReDS value can represent valuable additions to the fluid management in patients with congestive heart failure. We report a case of relatively lower ReDS value in spite of the obvious clinical volume overload and pulmonary congestion in a patient with acute heart failure and chronic obstructive pulmonary disease. Treatment for congestion to ameliorate his heart failure was accompanied by further decrease in ReDS value below normal ranges. Although ReDS technology is a promising modality to quantify the lung fluid amount, we might have to pay attention to some unique comorbidities including chronic obstructive pulmonary disease, which might attenuate electromagnetic waves and let ReDS values become inappropriately lower.

Learning objective

Remote dielectric sensing (ReDS) is a novel, non-invasive, miniature radar based, and vest testing system to detect pulmonary edema, which has a robust correlation with pulmonary fluid content in heart failure patients. However, the applicability of this modality in patients with a variety of comorbidities remains unknown. We should pay attention to unique comorbidities including chronic obstructive pulmonary disease, which might attenuate electromagnetic waves and let ReDS values become inappropriately lower.

Introduction

Remote dielectric sensing (ReDS, Sensible Medical Innovations Ltd., Netanya, Israel) is a novel, non-invasive, miniature radar based, and vest testing system to quantify the degree of pulmonary congestion, which has a robust correlation with pulmonary fluid content and a moderate association with pulmonary capillary wedge pressure in patients with congestive heart failure (HF) (Fig. 1) [1], [2], [3]. The vest can be worn over the clothing and the system provides the data of pulmonary fluid content within a minute. ReDS system is used as an adjunct modality in HF patients in various clinical settings, including home use, emergency department, and inpatient hospital wards, by guiding the adjusting of the doses of medications including diuretics according to the estimated pulmonary congestion [4], [5], [6].

Fig. 1.

Remote dielectric sensing system consisting of a monitor and a sensor unit.

However, the applicability of this modality in patients with a variety of comorbidities remains unknown. For example, the ReDS value is inappropriately decreased in cases of huge obesity, whereas the value might be inappropriately elevated in case of any occupied lesions including lung cancer. We here encountered a patient with comorbid chronic obstructive pulmonary disease (COPD) who had congestive HF.

Case report

We present a 71-year-old man with ischemic cardiomyopathy receiving cardiac resynchronization therapy with defibrillator (CRT—D) who was admitted to our hospital to treat his decompensated congestive HF.

Previous history

Five years previously, the patient had ventricular fibrillation due to ischemic cardiomyopathy. Coronary angiography showed chronic total occlusion of the right coronary artery, which was medically treated. Three years previously, he received implantation of CRT-D for worsening cardiac contractility and left bundle branch block. He continued smoking for over 50 years and was diagnosed with COPD. He was hospitalized for acute exacerbation of COPD three years previously. His forced expiratory volume in one second was 1.09 litter and percent predicted forced expiratory volume in one second was 39.2 %, which was complicated by severe airflow obstruction.

From one week previously, he suffered from sciatica and non-steroidal anti-inflammatory drugs were initiated. He gradually complained of dyspnea on exertion and bilateral leg edema, and was admitted to our institute's emergency room.

On admission

On admission, New York Heart Association functional class was IV. Body height was 162.7 cm and body weight was 41.1 kg (2 kg increase for a month). Blood pressure was 139/94 mmHg and pulse rate was 66 bpm. Oxygen saturation at room temperature was 98 %. Bilateral lung sound decreased and his heart sound showed gallop rhythm. Plasma B-type natriuretic peptide was 855 pg/mL. Of note, ReDS value displayed 24 %, which was approximately around the lower level of manufacture-proposed normal rage: between 20 % and 35 %.

His medication list was as follows: tiotropium olodaterol 10 μg inhaled daily, aspirin 100 mg, rosuvastatin 1.25 mg, imidapril 2.5 mg, carvedilol 20 mg, eplerenone 50 mg, furosemide 20 mg, and tolvaptan 7.5 mg.

Chest X-ray showed slight cardiomegaly and hyper-inflated lungs without bilateral pleural effusions (Fig. 2A). Electrocardiography showed pacing rhythm and low voltage in limbs. Transthoracic echocardiography showed left atrial diameter of 42 mm, left ventricular end-systolic diameter of 61 mm, and left ventricular ejection fraction of 29 %. Deceleration time was 168 msec and trans-mitral flow pattern was diastolic impaired. He had moderate functional mitral regurgitation due to tethering. Chest computed tomography displayed advanced destructive emphysema with vascular distortion without pleural effusion (Fig. 3).

Fig. 2.

Chest X-ray showing slight cardiomegaly and hyper-inflated lungs without bilateral pleural effusions on admission (A) and hyper-inflated lungs without cardiomegaly at discharge (B).

Fig. 3.

Chest computed tomography showing advanced destructive emphysema with vascular distortion.

In-hospital course

We assumed that he had systemic/pulmonary congestion to be treated, and we decided to treat his congestion despite relatively lower ReDS value. His congestive HF responded to the standard treatment, including oxygen supply and intermittent intravenous administration of furosemide. On day 14, his body weight decreased to 38.3 kg and plasma B-type natriuretic peptide improved down to 65 pg/mL. Of note, ReDS value decreased to 15 % (extremely below the lowest limit of 20 %).

In his follow-up chest X-ray before the index discharge, hyper-inflated lungs remained and the size of heart got smaller (Fig. 2B). Right heart catheterization showed pulmonary artery pressure of 33/14/22 mmHg, pulmonary capillary wedge pressure of 11 mmHg, and cardiac index of 2.03 L/min/m² using Fick's method. Sacubitril/valsartan and dapagliflozin were initiated. He was discharged on foot with New York Heart Association functional class II.

Database review

We retrospectively reviewed our ReDS database. Four patients with COPD trended to have lower ReDS values compared with 70 patients without COPD (25.5 % versus 28.5 %, p = 0.153 by Mann-Whitney U test).

Discussion

We here present a patient with COPD and congestive HF. ReDS value was inappropriately lower despite obvious signs of pulmonary congestion (approximately around the lower limit of the normal range of 20 %). Following the therapeutic intervention to the congestion, ReDS value further decreased to below the normal range (<20 %).

Pulmonary congestion is associated with HF symptoms including dyspnea on exertion, impaired exercise capacity, and mortality. Only a slight existence of residual pulmonary congestion at the index discharge is associated with poor clinical outcomes in patients hospitalized due to congestive HF [7], [8]. Nevertheless, there is no gold standard to accurately quantify the degree of pulmonary congestion thus far.

The validity of ReDS system was investigated by comparing it with other modalities in several studies. ReDS value had a moderate correlation with invasively measured pulmonary capillary wedge pressure and plasma B-type natriuretic peptide level [2]. Of note, we should understand the difference between “volume and pressure”. There was a robust correlation between ReDS value and the lung fluid percentage estimated by high-resolution computed tomography [1], [3]. The reliability of ReDS value was also investigated in another study. Both inter-rater and intra-rater reliability of ReDS values were sufficiently high [9]. Thus, ReDS system is an established technology to guide adjustment of medications including diuretics to treat patients with congestive HF.

However, in our patient, there was a discrepancy between ReDS value and other modalities. The patient had obvious systemic congestion and HF symptoms as well as elevated B-type natriuretic peptide level, whereas ReDS value was around the lower limit of the normal range.

Several comorbidities and clinical situations might affect the accuracy of ReDS value, whereas a scarcity of studies investigated it thus far. An extreme obesity is associated with inappropriately lower ReDS value due to the attenuation of electromagnetic waves. Any occupied lesions in the lung, including lung cancer, would inappropriately increase ReDS value. We confirmed that the vest was closely worn without any technical issues.

The impact of COPD on ReDS value remains unknown. Nevertheless, the existence of pulmonary emphysema might theoretically decrease the space of lung parenchyma, relatively decreasing ReDS value. Consistently, the percentage of lung fluid amount estimated by the computed tomography, which was measured at end-expiratory phase with full air in the lung, was relatively lower than ReDS value in the previous study [3]. Also, patients with COPD had relatively lower ReDS values compared with those without COPD in our database. Patchy emphysematous lesions in COPD may reduce the reproducibility of ReDS values. However, since ReDS value is measured by concentrically emitting energy between two sonars, it would have little impact upon the reproducibility of ReDS values.

Although further studies are warranted to validate our hypothesis, we should pay specific attention in interpreting ReDS value in patients with several unique comorbidities, including COPD, i.e. ReDS value might be inappropriately lower than the actual one in patients with COPD. Other modalities as well as patients' symptoms should be referenced to assess the degree of pulmonary congestion in such a cohort.

Ethics and funding

The use of ReDS system in our institute for the research purpose was approved by the Ethic Committee of the University of Toyama (MTK2020007) with written informed consent from the patient. We received no funding.

Declaration of competing interest

All of the authors have no COI to disclose and there has been no significant financial support for this work that could have influenced its outcome.