PT  - JOURNAL ARTICLE
AU  - Susan A. Ward
TI  - Ventilation/carbon dioxide output relationships during exercise in health
AID  - 10.1183/16000617.0160-2020
DP  - 2021 Jun 30
TA  - European Respiratory Review
PG  - 200160
VI  - 30
IP  - 160
4099  - http://err.ersjournals.com/content/30/160/200160.short
4100  - http://err.ersjournals.com/content/30/160/200160.full
SO  - EUROPEAN RESPIRATORY REVIEW2021 Jun 30; 30
AB  - “Ventilatory efficiency” is widely used in cardiopulmonary exercise testing to make inferences regarding the normality (or otherwise) of the arterial CO2 tension (PaCO2) and physiological dead-space fraction of the breath (VD/VT) responses to rapid-incremental (or ramp) exercise. It is quantified as: 1) the slope of the linear region of the relationship between ventilation (V′E) and pulmonary CO2 output (V′CO2); and/or 2) the ventilatory equivalent for CO2 at the lactate threshold (V′E/V′CO2) or its minimum value (V′E/V′CO2min), which occurs soon after but before respiratory compensation. Although these indices are normally numerically similar, they are not equally robust. That is, high values for V′E/V′CO2 and V′E/V′CO2min provide a rigorous index of an elevated VD/VT when PaCO2 is known (or can be assumed) to be regulated. In contrast, a high V′E–V′CO2 slope on its own does not, as account has also to be taken of the associated normally positive and small V′E intercept. Interpretation is complicated by factors such as: the extent to which PaCO2 is actually regulated during rapid-incremental exercise (as is the case for steady-state moderate exercise); and whether V′E/V′CO2 or V′E/V′CO2min provide accurate reflections of the true asymptotic value of V′E/V′CO2, to which the V′E–V′CO2 slope approximates at very high work rates.The efficiency of CO2 clearance at the lungs in exercise is estimated from the relationship between ventilation and CO2 elimination rate. It is compromised in lung and cardiovascular disease, stressing breathing and shortness of breath, and therefore impairing exercise capacity. https://bit.ly/3gYY866