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Relation between VE/VCO2 slope and maximum phonation time in chronic heart failure patients
Kazuhiro P Izawa1, Satoshi Watanabe, Peter H Brubaker
1From the Graduate School of Health Sciences, Kobe University, Kobe, Japan (KPI); Department of Rehabilitation Medicine, St. Marianna University School of Medicine Hospital, Kawasaki, Japan (SW, ST, SM, TS); Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC, USA (PHB); Department of Physical Therapy, Tokushima Bunri University, Tokushima, Japan (YH); Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan (KO); Department of Rehabilitation, Visiting Nursing and Rehabilitation Network, Kawasaki, Japan (TS, YO); Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, Japan (KS, YJA); Division of Cardiology, St. Marianna University Toyoko Hospital, Kawasaki, Japan (NO); Division of Cardiology, St. Marianna University Yokohama-City Seibu Hospital, Yokohama, Japan (KO); and Department of Orthopedic Surgery, St. Marianna University School of Medicine, Kawasaki, Japan (HS).
Abstract:
This study aimed to determine the relation between the regression slope relating minute ventilation to carbon dioxide output (VE/VCO2 slope) and maximum phonation time (MPT), and the MPT required to attain a threshold value for VE/VCO2 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%). VE/VCO2 slope was assessed during cardiopulmonary exercise testing (CPX). Thereafter, patients were divided into 2 groups according to exercise capacity: VE/VCO2 slope ≤ 34 (VE/VCO2 ≤ 34 group, n = 81) and VE/VCO2 slope > 34 (VE/VCO2 > 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 VE/VCO2 slope and MPT (r = -0.51, P < 0.001). After adjustment for clinical characteristics, MPT was significantly higher in the VE/VCO2 ≤ 34 group vs VE/VCO2 > 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 VE/VCO2 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 VE/VCO2 slope ≤ 34 and for risk management in these patients.
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