Lung fluid content during 6MWT in patients with COPD with and without comorbid heart failure

BACKGROUND

Impact of lung fluid content changing during exercise has not been investigated in chronic obstructive pulmonary disease (COPD). Using a novel point-of-care measurement system (remote dielectric sensing (ReDS) system), we aimed to investigate changes in lung fluid content before and after 6-minute walk test (6MWT); especially, differences between patients with and without comorbid heart failure (HF) were evaluated.

METHODS

From June 2021 to July 2022, patients with COPD referred for 6MWT were prospectively enrolled. Measurements of lung fluid content by ReDS were conducted before and after 6MWT. Data on demographics, exacerbation history, spirometry and 6MWT were collected. Patients were also assessed for comorbid HF by cardiovascular evaluation. The main variables of interest were pre-6MWT ReDS, post-6MWT ReDS and post-pre ∆ReDS.

RESULTS

In total, 133 patients with COPD were included. Comparisons between patients with COPD with and without HF indicated similar pre-6MWT ReDS (26.9%±5.9% vs 26.5%±4.7%; p=0.751), but a significant difference in post-6MWT ReDS (29.7%±6.3% vs 25.7%±5.3%; p=0.002). Patients with COPD without HF exhibited a significant decrease in post-6MWT ReDS (from 26.5% to 25.7%; paired t-test p=0.001); conversely, those with HF displayed a remarkable increase in post-6MWT ReDS (from 26.9% to 29.7%; paired t-test p<0.001). Receiver operating characteristic curve analysis showed an area under the curve of 0.82 (95% CI 0.71 to 0.93) for post-pre ∆ReDS in differentiating between patients with COPD with and without HF.

CONCLUSIONS

Dynamic changes in lung fluid content prior to and following 6MWT significantly differed between patients with COPD with and without HF. Measurements of lung fluid content by ReDS during exercise testing may be of merit to identify patients with COPD with unrecognised HF.

Noninvasive assessment of pulmonary congestion in heart failure: Need of the hour

Early pulmonary congestion detection and surveillance in acute heart failure patients can prevent decompensation, minimize hospitalizations, and improve prognosis. In India, the warm and wet types of HF are still the most common types and residual congestion at discharge is still a significant concern. Thus, there is an urgent need for a reliable and sensitive means of identifying residual and subclinical congestion. Two such monitoring systems are available and approved by US FDA. These include CardioMEMS HF System (Abbott, Sylmar, California) and ReDS System (Sensible Medical Innovations, Ltd., Nanya, Israel). CardioMEMS is a wireless pressure-sensitive implantable device, while ReDS is a wearable noninvasive device for measurement of the lung fluid and hence direct detection of PC. This review discusses the role of noninvasive assessment in PC monitoring in patients with heart failure and its implications from an Indian perspective.

Clinical implications of remote dielectric sensing system to estimate lung fluid levels

The reduction of pulmonary congestion is an essential clinical target in the management of chronic heart failure. This proves to be challenging given the lack of a gold standard method to quantify the degree of pulmonary congestion both quickly and non-invasively. Remote dielectric sensing (ReDS) is a non-invasive electromagnetic energy-based technology to quantify lung fluid levels as a percentage within minutes. This technique, due to its high negative predictive value, may be a useful tool particularly to rule out primarily cardiac causes of dyspnea in ambulatory patients when the values are normal. Further studies are warranted to establish ReDS-guided management of congestive heart failure patients.