Using RV/TLC to Determine Lung Reduction Procedure Efficacy, with Nathaniel Marchetti, DO

New research is shedding light on the potential utility of assessing changes in residual volume (RV)/total lung capacity (TLC) to determine the efficacy of lung reduction procedures in patients with emphysema and hyperinflation.

The data were presented at the American Thoracic Society (ATS) International Conference 2025 by Nathaniel Marchetti, DO, a professor of thoracic medicine and surgery at Lewis Katz School of Medicine at Temple University and medical director of the respiratory intensive care unit at Temple University Hospital, and suggest examining changes in RV/TLC may serve as a better physiological marker of improvement in patient outcomes than absolute RV following bronchoscopic lung volume reduction (BLVR).

“Currently, [RV] is the gold standard, so it's a good marker of improvement following lung reduction, no matter what the method is. In this case, we're looking at bronchoscopic lung volume reduction,” Marchetti explained to HCPLive. “However, it doesn't really account for what occurs. Because the residual volume decreases more than the total lung capacity, there's a resizing of the lung in relation to the chest wall.”

Patients with emphysema and hyperinflation have improved outcomes following lung reduction due to decreases in air-trapping that negatively impact lung, chest wall, respiratory muscle and cardiac function. While absolute reductions in RV are frequently used to evaluate the efficacy of these lung reduction procedures, changes in RV/TLC have been suggested to be a superior metric to indicate the adequacy of lung reduction in hyperinflated emphysematous patients.

In the present study, investigators reviewed data for 97 patients who underwent BLVR at Temple University Hospital from August 2018 to December 2023. Physiologic respiratory measures at baseline pre-BLVR were compared to data collected 6 months post-BLVR.

Among the cohort, 41% of patients were female and the mean age was 67.8±5.8 years. Investigators noted patients were severely obstructed (FEV1 0.82 ± 0.27L, 31.0±8.3% pred), hyperinflated (TLC, 7.2±1.3L, 121.8±16.3% pred), and air trapped (RV, 4.5±1.1L, 203.5±45.4% pred), and received one-way endobronchial valves for BLVR.

Post-BLVR, RV decreased by 310 mL in 74.2% of participants and RV/TLC decreased by 4% in 68.0% of participants. Investigators called attention to improvements in FEV1 (+0.19 ± 0.19), RV (-0.89 ± 0.93), RV/TLC (-8.4 ± 9.7), SGRQ (-24.5 ± 13.0), mMRC (-1.4 ± 0.83) and 6MWD (15.3 ± 74.8) 6 months following BLVR.

“For me, one thing that was very rewarding with this project and research was that this was a theory that was proposed by investigators 25 years ago and was very physiologically based, and it still holds true today,” Marchetti said. “I think that the take home message is that a reduction in RV/TLC is the most important parameter when you're looking at any therapy that's goal is to reduce lung volumes, and it should track best with what patients care about, which is symptoms.”

Editors’ note: Marchetti has relevant disclosures with the American Lung Association, NIH, AstraZeneca, and Sanofi.

Reference

Marchetti N, Thomas J, Patlakh N, et al. Reductions in RV vs. RV/TLC as a Measure of Success Following BLVR [abstract]. Am J Respir Crit Care Med 2025;211:A1017. https://doi.org/10.1164/ajrccm.2025.211.Abstracts.A1017