Early recovery of oxygen kinetics after submaximal exercise test predicts functional capacity in patients with chronic heart failure.
BACKGROUND
Oxygen (O2) uptake at peak exercise (VO2 peak) is an objective measurement of functional capacity in patients with chronic heart failure (CHF). The significance of recovery O2 kinetics parameters in predicting exercise capacity, and the parameters of submaximal exercise testing have not been thoroughly examined.


RESULTS
Thirty-six patients (mean age = 48+/-14 years) with CHF and New York Heart Association functional class I, II, or III, and eight healthy volunteers (mean age = 39+/-13 years) were studied with maximal and submaximal cardiopulmonary exercise testing (CPET). The first degree slope of O2 uptake decay during early recovery from maximal (VO2/t-slope), and submaximal exercise (VO2/t-slope)(sub), were calculated, along with VO2 half-time (T(1/2)VO2). Patients with CHF had a longer recovery of O2 uptake after exercise than healthy volunteers, expressed by a lower VO2/t-slope (0.616+/-0.317 vs. 0.956+/-0.347 l min(-1) min(-1), P=0.029) and greater T(1/2)VO2 (1.28+/-0.30 vs. 1.05+/-0.15 min, P = 0.005). VO2/t-slope correlated with the VO2 peak (r = 0.84, P<0.001), anaerobic threshold (r = 0.79, P<0.001), and T(1/2)VO2, a previously established estimate of recovery O2 kinetics (r = -0.59, P<0.001). (VO2/t-slope)(sub) was highly correlated with VO2/t-slope after maximal exercise (r=0.87, P<0.001), with the VO2 peak (r=0.87, P<0.001) and with T(1/2)VO2 after maximal exercise (r=-0.62, P<0.001). VO2/t-slope after maximal and submaximal exercise was reduced in patients with severe exercise intolerance (F=9.3, P<0.001 and F=12.8, P<0.001, respectively).


CONCLUSIONS
Early recovery O2 kinetics parameters after maximal and submaximal exercise correlate closely with established indices of exercise capacity in patients with CHF and in healthy volunteers. These findings support the use of early recovery O2 kinetics after submaximal exercise testing as an index of functional capacity in patients with CHF.
Nanas
S
S
Pulmonary & Critical Care Medicine Department, National and Kapodestrian University, Papadiamantopoulou 20, Athens 115 28, Greece. snanas@cc.uoa.gr
Nanas
J
J
Kassiotis
C
C
Nikolaou
C
C
Tsagalou
E
E
Sakellariou
D
D
Terovitis
I
I
Papazachou
O
O
Drakos
S
S
Papamichalopoulos
A
A
Roussos
C
C
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D002908:Chronic Disease; D005080:Exercise Test / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000378:metabolism* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology*; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism* / Q000493:pharmacokinetics*; D010101:Oxygen Consumption / Q000502:physiology; D011237:Predictive Value of Tests; D012123:Pulmonary Ventilation / Q000502:physiology; D020127:Recovery of Function / Q000502:physiology*
D010100:Oxygen