Exercise ventilation (V′E) relative to carbon dioxide output (V′CO2) is particularly relevant to patients limited by the respiratory system, e.g. those with chronic obstructive pulmonary disease (COPD). High V′E−V′CO2 (poor ventilatory efficiency) has been found to be a key physiological abnormality in symptomatic patients with largely preserved forced expiratory volume in 1 s (FEV1). Establishing an association between high V′E−V′CO2 and exertional dyspnoea in mild COPD provides evidence that exercise intolerance is not a mere consequence of detraining. As the disease evolves, poor ventilatory efficiency might help explaining “out-of-proportion” breathlessness (to FEV1 impairment). Regardless, disease severity, cardiocirculatory co-morbidities such as heart failure and pulmonary hypertension have been found to increase V′E−V′CO2. In fact, a high V′E−V′CO2 has been found to be a powerful predictor of poor outcome in lung resection surgery. Moreover, a high V′E−V′CO2 has added value to resting lung hyperinflation in predicting all-cause and respiratory mortality across the spectrum of COPD severity. Documenting improved ventilatory efficiency after lung transplantation and lung volume reduction surgery provides objective evidence of treatment efficacy. Considering the usefulness of exercise ventilatory efficiency in different clinical scenarios, the V′E−V′CO2 relationship should be valued in the interpretation of cardiopulmonary exercise tests in patients with mild-to-end-stage COPD.
Ventilatory efficiency is a key measurement for the interpretation of cardiopulmonary exercise testing in COPD http://ow.ly/1nsY307pbz8
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Support statement: J.A. Neder has been funded by a New Clinician Scientist Program from the Southeastern Ontario Academic Medical Association (SEAMO), Canada. The funder had no role in the study design, data collection and analysis, or preparation of the manuscript.
Conflict of interest: None declared.
- Received October 17, 2016.
- Accepted December 12, 2016.
- Copyright ©ERS 2017