Ventilatory inefficiency during graded exercise in COPD: A pragmatic approach

• Published in: Clinical physiology and functional imaging 2021-01, Vol.41 (1), p.103-109
• Main Authors: Muller, Paulo T., Saraiva, Erlandson F.
• Format: Article
• Language: English
• Subjects: Airway management; Carbon dioxide; Chronic obstructive pulmonary disease; Efficiency; Exercise Test - methods; Exercise Tolerance - physiology; Female; Humans; Lung - physiopathology; Lung diseases; Male; Mechanical ventilation; Middle Aged; Obstructive lung disease; Pulmonary Disease, Chronic Obstructive - physiopathology; Respiratory function; Smoking; Ventilation
• ISSN: 1475-0961; 1475-097X
• DOI: 10.1111/cpf.12674

Background/Objective The current approach to measuring ventilatory (in)efficiency (V′E‐V′CO2 slope, nadir and intercept) presents critical drawbacks in the evaluation of COPD subjects, owing mainly to mechanical ventilatory constraints. Thus, we aimed to compare the current approach with a new method we have developed for ventilatory efficiency calculation. Methods The new procedure was based on measuring the amount of CO2 cleared by the lungs (V′CO2, L/min) plotted against a predefined range of increase in minute ventilation (V′E) (ten‐fold increase based on semilog scale) during incremental exercise to symptom‐limited maximum tolerance. This value was compared to a hypothetical predicted maximum CO2 output at the predicted maximal voluntary ventilation, defining ventilatory efficiency (ηV′E, %). The results were used to compare 30 subjects with COPD (II‐IV Global Initiative for Chronic Obstructive Lung Disease, GOLD) and 10 non‐COPD smokers, to establish the best discriminative physiological variable for disease severity through logistic multinomial regression. Results The new approach was more sensitive to progressive deterioration of airway obstruction, resulting in worse ηV′E as lung function worsens throughout the GOLD panel (ηV′E (%), p