A Novel Method for Ventilatory Efficiency Assessment: Integrative Insights from Physiology to SHIP Normative Data

Background: Conventional ventilatory efficiency indices, like the minute ventilation (ν̇ E ) to carbon dioxide production (ν̇CO₂) slope (ν̇ E -□CO₂ slope or nadir), often inadequately capture ventilatory dynamics, particularly beyond the respiratory compensation point. This limits the comprehensive interpretation of exercise ventilatory cost. This study provides an extensive review of a novel technique for calculating ventilatory efficiency (ην̇E), derived from the semilogarithmic relationship between ν̇CO₂ and logν̇E, to establish a normalized physiological marker and precise reference values. Methods: Data from 1150 participants (52% women) from the Pomerania Health Study (SHIP) cohorts were analyzed. Participants underwent standardized incremental cardiopulmonary exercise tests (CPET). The ν̇CO₂–logν̇ E slope was calculated from the first ventilatory threshold (VT 1 ) to peak exercise. The ην̇ E was defined as the percentage ratio of the observed slope to a theoretical maximal slope, derived from predicted maximal voluntary ventilation and ideal CO₂ lung removal. Normative equations, adjusted for age, sex, and anthropometry, were derived using quantile regression. Results: The linearized ν̇CO₂–logν̇ E slope showed additional discriminatory power beyond VT 1 compared to the traditional ν̇ E -ν̇CO₂ slope. Median ην̇ E was 14.3% in women and 14.7% in men. While absolute ν̇CO₂–logν̇ E slopes decreased with age and were higher in men, ην̇ E modestly increased across the lifespan, suggesting compensatory ventilatory efficiency adaptation with aging. Sex-specific reference equations were derived. Conclusions: The proposed ην̇ E index is robust, physiologically grounded, and normalizes age-related changes, enhancing CPET interpretation. These normative reference equations, established from a large epidemiological sample, offer a refined, individualized framework for assessing ventilatory performance in health and disease. Publication History Article published online: 04 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany