Peak ventilation during treadmill cardiopulmonary exercise testing: applicability analysis of the FRIEND registry prediction equation in a Brazilian healthy sample
Authors: Milani M , Milani J G P O , Cipriano G F B , Cipriano Junior G 
Published: October 2022

Abstract

Background
Peak ventilation (VEpeak) measured by cardiopulmonary exercise testing (CPX) is a valuable clinical information, especially in patients with pulmonary diseases. Measured values can be compared to maximal voluntary ventilation or to predicted VEpeak calculated by nonexercise equations. However, the FRIEND Registry prediction equation has never been assessed for portability in a Brazilian population sample.

Purpose
To analyze the applicability of the FRIEND registry prediction equation for VEpeak during treadmill CPX in a Brazilian healthy sample.

Methods
Cross-sectional study of subjects assessed by CPX in the Brazilian Midwest region between January/2011 to March/2020. The inclusion criteria were CPX performed on treadmill in healthy individuals aged 20 years or older, and with respiratory exchange ratio ≥1.0. The exclusion criteria were any history of cardiovascular or pulmonary disease, presence of cardiovascular risk factors (such as hypertension, diabetes mellitus, current smoking, and obesity) and abnormalities on CPX. Measured VEpeak values were compared with predicted values calculated using age, sex, and height, according to the FRIEND Registry prediction equation. Variables were described as median and interquartile range. Statistical comparisons between measured and predicted VEpeak were performed using Spearman correlation test, Wilcoxon signed rank test, and Blant-Altman agreement analysis.

Results
During the study period 7,843 CPX were performed and included for study eligibility. After the inclusion and exclusion criteria were applied, 3,544 healthy individuals' assessments were included [1,574 females and 1,970 males, age 39 (33, 47) years]. The measured and predicted VEpeak were, respectively, 76.8 (66.7, 87.4) and 76.2 (68.5, 83.0) L min–1 in females, with significant difference (p=0.004). In males, the measured and predicted VEpeak were, respectively, 123.0 (107.3, 137.3) and 114.8 (107.5, 120.7) L min–1, also with statistical difference (p&lt;0.001). Correlations were significant (p&lt;0.001) for both sexes (r2=0.424 for females and .421 for males) (Figure 1). Average error was lower for females than males, with bias of 1.22 L min–1 (95% limits of agreement: - 26.95 to 29.39) in females and bias of 8.41 L min–1 (95% limits of agreement: −33.04 to 49.87) in males (Figure 2).

Conclusion
Measured VEpeak median values were greater than predicted median values for both sexes, with lower average error in females than in males. The significant average error in males limits the prediction equation applicability in the Brazilian population. Thus, the development of a new Brazilian prediction equation is necessary to better evaluate the variable response during CPX in Brazil.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).