Assessment of respiratory compensation phase during graded exercise in patients with chronic heart failure.

Clinic of Cardiology, Medical University, Plovdiv, Bulgaria.
Folia medica 01/2007; 49(3-4):26-31.
Source: PubMed

ABSTRACT The VE-VO2 relationship during graded exercise has an inflection point beyond the ventilatory anaerobic threshold (VAT) termed the respiratory compensation point (RCP). Metabolic variables analyzed at the level of VAT and RCP may contribute to the better understanding of such limiting symptoms in chronic heart failure (CHF) patients as dyspnea and early fatigue. The AIM of the present study was to analyze the RCP during symptom limited ramp exercise testing in CHF patients.
Forty six CHF patients (II and III NYHA functional class; age = 51 +/- 9 years, LVEF% = 35% +/- 6%; mean +/- SD) and 20 matched controls performed graded cardiopulmonary exercise test on a cycle ergometer.
The duration and productivity of RCP (delta(x) = peak(x) - VAT(x)) in patients were significantly (p < 0.001) reduced compared to healthy subjects: delta duration = 3.0 +/- 1.2 vs 4.3 +/- 1.5 min, delta watts = 24.3 +/- 11.5 vs. 39.4 +/- 11.5, delta VO2/kg ( x min-1) = 3.8 +/- 1.3 vs 8.8 +/- 2.3. An important characteristic of this phase was the higher subjective cost of physical effort assessed by Borg scale and Watts/Borg ratio (Borg peak = 9.9 +/- 0.4 vs. 6.0 +/- 1.2; p < 0.001, Watts/Borg peak = 9.2 +/- 2.3 vs 23.9 +/- 6.4, p < 0.001). The relative hyperventilation of patients on the basis of the watt exercise can be seen in the values of derivative index V (ml x min-1 x watt-1) 478 +/- 59 vs 568 +/- 118; (p < 0.001) in controls and patients, respectively.
The impaired efficiency of oxygen delivery systems in patients with CHF is what causes the appearance of early limiting symptoms. Duration and productivity of respiratory compensation phase in CHF patients are considerably reduced compared to controls.

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    • "An incremental exercise protocol allows for the determination of the gas exchange threshold (GET) and respiratory compensation point (RCP) in healthy and patient populations (Beaver et al., 1986; Bergstrom et al., 2013; Dekerle et al., 2003; Green et al., 2003; Oshima et al., 1997; Tanehata et al., 1999; Tokmakova et al., 2007; Whipp and Ward, 2009; Whipp et al., 1986). The GET is a noninvasive estimate of the lactate threshold and is the point at which CO 2 production ( ˙ V CO 2 ) increases disproportionately to oxygen uptake ( ˙ V O 2 ) along with an increase in minute ventilation ( ˙ V E ) relative to ˙ V O 2 , while ˙ V E / ˙ V CO 2 remains constant (Beaver et al., 1986; Whipp et al., 1986). "
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    ABSTRACT: It is not known if the respiratory compensation point (RCP) is a distinct work rate (Watts (W)) or metabolic rate [Formula: see text] and if the RCP is mechanistically related to critical power (CP). To examine these relationships, 10 collegiate men athletes performed cycling incremental and constant-power tests at 60 and 100rpm to determine RCP and CP. RCP work rate was significantly (p≤0.05) lower for 100 than 60rpm (197±24W vs. 222±24W), while RCP [Formula: see text] was not significantly different (3.00±0.33lmin(-1) vs. 3.12±0.41lmin(-1)). CP at 60rpm (214±51W; [Formula: see text] : 3.01±0.69lmin(-1)) and 100rpm (196±46W; [Formula: see text] : 2.95±0.54lmin(-1)) were not significantly different from RCP. However, RCP and CP were not significantly correlated. These findings demonstrate that RCP represents a distinct metabolic rate, which can be achieved at different power outputs, but that RCP and CP are not equivalent parameters and should not, therefore, be used synonymously. Copyright © 2014. Published by Elsevier B.V.
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    ABSTRACT: Abstract It has previously been suggested that the respiratory compensation point (RCP) and critical speed (CS) parameters are equivalent and, therefore, like CS, RCP demarcates the boundary between the heavy- and severe-intensity domains. However, these findings are equivocal and therefore must be interpreted cautiously. Thus, we examined the relationship between CS and RCP across a wide range of subject fitness levels, in an attempt to determine if CS and RCP are equivalent. Forty men and 30 women (age: 23.2 ± 2.5 year, height: 174 ± 10 cm, body mass: 74.1 ± 15.7 kg) completed an incremental and four constant-speed protocols on a treadmill. RCP was determined as the point at which the minute ventilation increased disproportionately to CO2 production and the end-tidal CO2 partial pressure began to decrease. CS was determined from the constant-speed protocols using the linearized 1·time(-1) model. CS and RCP, expressed as speed or metabolic rate, were not significantly different (11.7 ± 2.3 km·h(-1) vs. 11.5 ± 2.3 km·h(-1), p = 0.208; 2.88 ± 0.80 l·min(-1) vs. 2.83 ± 0.72 l·min(-1), p = 0.293) and were significantly correlated (r(2) = 0.52, p < 0.0001; r(2) = 0.74, p < 0.0001, respectively). However, there was a high degree of variability between the parameters. The findings of the current study indicate that, while on average CS and RCP were not different, the high degree of variability between these parameters does not permit accurate estimation of one from the other variable and suggests that these parameters may not be physiologically equivalent.
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