Relation Between V˙E/V˙CO2 Slope and Maximum Phonation Time in Chronic Heart Failure Patients

This study aimed to determine the relation between the regression slope relating minute ventilation to carbon dioxide output (V˙E/V˙CO2 slope) and maximum phonation time (MPT), and the MPT required to attain a threshold value for V˙E/V˙CO2 slope of ≤34 in chronic heart failure (CHF) patients. This cross-sectional study enrolled 115 CHF patients (mean age, 54.5 years; men, 84.9%). V˙E/V˙CO2 slope was assessed during cardiopulmonary exercise testing (CPX). Thereafter, patients were divided into 2 groups according to exercise capacity: V˙E/V˙CO2 slope ≤34 (V˙E/V˙CO2 ≤34 group, n = 81) and V˙E/V˙CO2 slope >34 (V˙E/V˙CO2 >34 group, n = 34). For MPT measurements, all patients produced a sustained vowel/a:/ for as long as possible during respiratory effort from the seated position. All subjects showed significant negative correlation between V˙E/V˙CO2 slope and MPT (r = −0.51, P < 0.001). After adjustment for clinical characteristics, MPT was significantly higher in the V˙E/V˙CO2 ≤34 group vs V˙E/V˙CO2 >34 group (21.4 ± 6.4 vs 17.4 ± 4.3 s, F = 7.4, P = 0.007). The appropriate MPT cut-off value for identifying a V˙E/V˙CO2 slope ≤34 was 18.12 seconds. An MPT value of 18.12 seconds may be a useful target value for identifying CHF patients with a V˙E/V˙CO2 slope ≤34 and for risk management in these patients.