Ventilatory variability (vVE) constitutes the dynamic and complex breath-to-breath oscillation of pulmonary ventilation. However, vVE has only recently been investigated in heart failure and chronic obstructive pulmonary disease (COPD) using the Poincaré approach. Briefly, the Poincaré analysis generates, through scatter plots, two pieces of information: called SD1 (standard deviation 1) and SD2 (standard deviation 2); SD1 is defined as the dispersion of data points perpendicular to the line of identity across the plot's centroid and is a short-term variability descriptor; SD2 describes the dispersion of points along the line of identity and reflects the long-term variability of the signal.

the present study aims to perform Poincaré analysis to distinguish vVE patterns between healthy controls and patients diagnosed with COPD, heart failure (HF) and heart failure with COPD during cardiopulmonary exercise testing (CPET).

Patients with COPD, heart failure, COPD + HF and healthy subjects participated in this research. Lung function was performed according to the recommendations of the American Thoracic Society/European Respiratory Society and adjusted to the Brazilian reference values. Standard echocardiography followed the recommendations of the American Echocardiography Society. A symptom-limited incremental CPET was performed on a cycle ergometer, with increments per minute of 5–10 W for patients and 10–15 W for healthy controls. Poincaré ́ analysis was used to calculate vVE using a custom R program (http://www.R-project.org), with breath-by-breath aliquots to obtain SD1 and SD2 values, normalized by the number of points in VE. All procedures were approved by the Local Ethics Committee (51596221.4.0000.5076).

Demographic and anthropometric data including age, height, weight and BMI were not significantly different between groups (P > 0.05). SD1 and SD1/SD2 for VE were significantly different for heart failure and heart failure-COPD compared to COPD and controls (P > 0.05). SD2 did not differ between groups (P>0.05). Surprisingly, COPD and controls shared very similar mean values for SD1, SD2, and SD1/SD2, and HF-COPD showed similar vVE to heart failure alone (P>0.05).

Our results demonstrated increased vVE in chronic heart failure applying the Poincaré approach.

Despite the small number of patients, our preliminary results support the measurement of vVE by the Poincaré ́ method as a promising tool in clinical physiology.