Sweat lactate sensor for detecting anaerobic threshold in heart failure: a prospective clinical trial (LacS-001)
Authors: Katsumata Yoshinori , Muramoto Yuki , Ishida Noriyuki , Takemura Ryo , Nagashima Kengo , Ikoma Takenori , Kawamatsu Naoto , Araki Masaru , Goda Ayumi , Okawara Hiroki , Sawada Tomonori , Kawakubo Ichihara Yumiko , Hattori Osamu , Yamaoka Koki , Seki Yuta , Ryuzaki Toshinobu , Ikura Hidehiko , Nakashima Daisuke , Nagura Takeo , Nakamura Masaya , Sato Kazuki , Shiraishi Yasuyuki 
Published: August 2023

Background

The ventilatory threshold (VT), which requires an expensive analyzer and expertise in assessment, has not been widely and conveniently used in a clinical setting. This prospective clinical trial (LacS-001) aimed to investigate the safety of a lactate-monitoring sweat sensor, and the correlation between the lactate threshold in sweat (sLT) and the VT, to establish a simple method for determining the anaerobic threshold in patients with heart failure (HF).

Methods

We recruited 50 patients with HF and New York Heart Association functional classification I–II, with a median age of 63.5 years (interquartile range: 58.0–72.0 years). Incremental exercise tests were conducted, and changes in sweat lactate levels were monitored simultaneously. sLT was defined as the first steep increase in lactate levels from baseline and was evaluated by three independent investigators. The primary outcome measures were a correlation coefficient of 0.6 or greater between sLT and VT, the similarities as assessed by the Bland–Altman analysis, and the standard deviation of the difference between sLT and VT within 15 W.

Results

Among the 50 patients, a correlation coefficient of 0.651 (95% confidence interval, 0.391–0.815) was achieved in 32 cases. The difference between sLT and VT was −4.9±15.0 W, and no comparative error was noted in the Bland–Altman plot. No device-related adverse events were reported among the registered patients.

Conclusions

Our sweat lactate sensor provides a safe and accurate means of detecting VT in patients with HF in a clinical setting, thereby offering valuable additional information for treatment.

Clinical Perspective

What is new?

Successful real-time and continuous monitoring of sweat lactate levels with this experimental device during progressive exercise testing in patients with NYHA class I and II HF.

sLT determined by sweat lactate monitoring correlated strongly with VT, suggesting that VT can be detected with sufficient clinical accuracy.

Patients with intermediate sweat rates are good candidates for determining sLT.

Given the difficulties presented by the current methods for determining VT, the monitoring of lactate values in sweat by our sensors could be helpful for improving VT detection.

What are the clinical implications?

Our sweat lactate sensor provides a safe and accurate means of detecting ventilatory threshold (VT) in patients with heart failure in a clinical setting.

A correlation coefficient of 0.651 (95% confidence interval, 0.391–0.815) was achieved with −4.9±15.0 W as the difference between the lactate threshold in sweat and VT and no comparative error.

No device-related adverse events were reported among the registered patients.