Reed Humphrey

Virginia Commonwealth University, Richmond, VA, United States

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Publications (18)32.64 Total impact

  • Circulation 01/2012; 125(10):1321-9. · 15.20 Impact Factor
  • Ross Arena, Reed Humphrey, Mary Ann Peberdy
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    ABSTRACT: The minute ventilation-carbon dioxide production (VE/VCO2) slope, obtained during exercise testing, possesses prognostic value in heart failure (HF). The VE-VCO2 relationship is generally linear thereby hypothetically producing similar slope values regardless of the exercise-test time interval used for calculation. This study assesses the ability of the VE/VCO2 slope, calculated at different time intervals throughout a progressive exercise test, to predict 1-year cardiac-related hospitalization and mortality in subjects with HF. Seventy-two subjects underwent symptom-limited exercise testing with ventilatory expired gas analysis. Mean age and left ventricular ejection fraction for 44 male and 28 female subjects were 51.2 years (+/-13.0) and 27.0% (+/-12.3) respectively. The VE/VCO2 slope was calculated from time 0 to 25, 50, 75 and 100% of exercise time and subsequently used to create five randomly selected VE/VCO2 slope categories. (The intraclass correlation coefficient found calculation of the VE/VCO2 slope, when divided into quartiles, to be a reliable measure (alpha=0.94, P<0.0001). Univariate Cox regression analysis revealed all VE/VCO2 slope categories (25-100% and random selections) were significant predictors of cardiac-related hospitalization and mortality over a 1-year period. Multivariate Cox regression analysis revealed all VE/VCO2 slope categories outperformed peak oxygen consumption (VO2) in predicting hospitalization and mortality at 1 year. Although the different classification schemes were not identical, these results suggest VE/VCO2 slope maintains prognostic significance regardless of exercise-test time interval. Calculation of VE/VCO2 slope may therefore still be valuable in subjects putting forth a sub-maximal effort while effort-dependent measures, such as peak VO2, are not.
    European Journal of Cardiovascular Prevention and Rehabilitation 01/2004; 10(6):463-8. · 2.63 Impact Factor
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    ABSTRACT: COMPARISON OF OXYGEN UPTAKE ON-KINETIC CALCULATIONS DURING SUBMAXIMAL EXERCISE. Ross Arena, Reed Humphrey, Mary Ann Peberdy, Michael Madigan. JEPonline. 2003;6(2):1-7. The mean response time (MRT) and time constant (TC) are two oxygen uptake (VO 2) on-kinetic calculations whose values are presumed to be interchangeable. This study tests the assumption of uniformity among different VO 2 on-kinetic calculations. Nineteen (13 male/6 female) apparently healthy subjects were recruited for this study. Mean age (±SD) for this group was 44.1±10.1 years. Subjects underwent a progressive exercise test and six-minute exercise session (1.6 m/hr, 3.0% grade) on separate days. Both breath-by-breath (bb) and 10-second averaged (avg) ventilatory expired gas data were used to produce four VO 2 on-kinetic calculations (MRT bb , MRT avg , TC bb , TC avg). There were statistically significant differences (p<0.05) between TC bb (17.6 s) and TC avg (22.7 s), MRT bb (22.9 s), and MRT avg (24.7 s). Comparisons amongst TC avg (22.7 s), MRT bb (22.9 s), and MRT avg (24.7 s) did not reach statistical significance (p>0.05). All VO 2 on-kinetic calculations were significantly correlated with peak VO 2 , age, and each other. These results indicate that all MRT and TC calculations may not be interchangeable. All VO 2 uptake on-kinetic expressions did, however, appear to represent aerobic capacity and were highly correlated with each other indicating that calculation method may not have an excessively negative impact.
    04/2003;
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    ABSTRACT: A significant discrepancy between measured oxygen consumption (VO(2)) (via ventilatory expired gas analysis) and estimated VO(2) (via the imposed workload) frequently is reported in the heart failure (HF) population during symptom-limited exercise testing. The purpose of this investigation was to examine the difference between measured and estimated VO(2) (VO(2) discrepancy) during a highly conservative ramping protocol. For this study, 28 subjects with compensated HF (20 men and 8 women; age, 51.1 +/- 14.6 years) and 19 healthy control subjects (age-, gender-, and activity-matched to an HF subgroup) underwent symptom-limited exercise testing (treadmill) with ventilatory expired gas analysis. Peak estimated and measured VO(2) values were significantly higher in the age-, gender-, and activity-matched control group than in the HF group, but the change in measured VO(2) per change in estimated VO(2) (Deltameasured/Deltaestimated VO(2) slope) and the VO(2) discrepancy did not reach statistical significance. Peak estimated VO(2) was a significant predictor of peak measured VO(2) in the overall HF group (R2 = 0.90; P <.001). Although estimated VO(2) is not considered a replacement for measured VO(2), these results indicate that a highly conservative exercise protocol may allow for a more accurate prediction of peak measured VO(2) via the estimated oxygen cost for a given workload in patients with compensated HF.
    Journal of Cardiopulmonary Rehabilitation 01/2003; 23(3):183-9.
  • Journal of Cardiopulmonary Rehabilitation 01/2003; 23(3):208-17.
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    ABSTRACT: The analysis of oxygen (O(2)) uptake on-kinetics during steady-rate is gaining interest in the heart failure (HF) population. The rate change in O(2) at the initiation of exercise can be assessed via nonlinear regression time constant (TC) or an algebraic equation (mean response time [MRT]). These calculations are presumed to be interchangeable, but research supporting this claim is limited. This investigation compares and contrasts two of the more commonly used O(2) uptake on-kinetic calculations. Twenty-eight subjects diagnosed with compensated HF and 19 age, sex, and activity-matched controls underwent a symptom-limited exercise test and a steady-rate exercise session (6 min). Peak O(2) uptake, O(2) uptake at ventilatory threshold, the O(2) uptake TC (TC), and the O(2) uptake mean response time (MRT) were calculated for each subject. O(2) uptake on-kinetics was significantly faster for the control group ( < 0.05) regardless of calculation method. There was a significant difference between the O(2) uptake TC and MRT for the HF group. All O(2) uptake on-kinetic calculations were significantly correlated with aerobic capacity. O(2) uptake TC and MRT values may not be interchangeable in the HF population. All O(2) uptake on-kinetic calculations did produce a significant difference between experimental and control groups and correlated with indicators of aerobic capacity. The 10-s O(2) uptake on-kinetic calculations may be preferable secondary to expired gas fluctuations associated with breath-by-breath measures. Further work is, however, needed to determine which averaged O(2) uptake on-kinetic expression is optimal given the significant difference between TC and MRT. A mechanism for this difference may be the oscillatory ventilatory expired gas pattern demonstrated by some patients with HF.
    Medicine &amp Science in Sports &amp Exercise 10/2002; 34(10):1563-9. · 4.48 Impact Factor
  • Ross Arena, Reed Humphrey
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    ABSTRACT: Several ventilatory expired gas measures obtained during exercise testing demonstrate prognostic value in the heart failure (HF) population. Comparison of prognostic efficacy between pertinent measures is sparse. The ability of various expressions of peak oxygen consumption (VO2), the relationship between minute ventilation (VE) and carbon dioxide production (VCO2), and the partial pressure of end-tidal carbon dioxide (P(ET)CO2) were assessed to determine which measure(s) best predicted cardiac-related hospitalization over a 1-year period in subjects diagnosed with HF. Univariate Cox regression analysis found that several expressions of peak VO 2, VE-VCO2 relationship, and P(ET)CO2 were significant predictors of hospitalization. Multivariate Cox regression analysis revealed that the VE/VCO2 slope significantly predicted hospitalization (chi2 = 29.1, P <.00001). Peak VO 2 and P(ET)CO2 did not provide additional predictive value. The prognostic superiority of the VE/VCO2 slope over peak VO2 may be a result of the latter measure's partial dependence on subject effort and skeletal muscle function.
    American heart journal 04/2002; 143(3):427-32. · 4.65 Impact Factor
  • R Arena, R Humphrey, M A Peberdy
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    ABSTRACT: Oxygen consumption (VO(2)) on-kinetics describes the rate change in oxygen uptake at the initiation of exercise. Several mathematical and graphical methods are used to assess VO(2) on-kinetics during constant-load or progressive exercise. VO(2) on-kinetics is prolonged in patients with heart failure (HF) compared with individuals who have normal cardiopulmonary function. Cardiac function has been implicated as one of the controlling mechanism for this observation. The contribution that pulmonary, vascular, and skeletal muscle function makes to delayed VO(2) on-kinetics in HF has yet to be determined. VO(2) on-kinetics also appears to have clinical value in HF, although evidence supporting this claim is limited. Questions about the controlling mechanism(s) and practical application of VO(2) on-kinetics in HF therefore remain unanswered. This report provides an overview of VO(2) on-kinetics assessment techniques, reviews research pertaining to the HF population, and provides direction for future investigations.
    Journal of Cardiac Failure 01/2002; 7(4):302-10. · 3.32 Impact Factor
  • Ross Arena, Reed Humphrey, Mary Ann Peberdy
    Journal of Cardiopulmonary Rehabilitation 01/2002; 22(2):93-5.
  • Ross Arena, Reed Humphrey, Mary Ann Peberdy
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    ABSTRACT: This study assessed the relationship between the Minnesota Living With Heart Failure Questionnaire (MLWHFQ) and key ventilatory expired gas measures during a symptom-limited exercise test in the heart failure (HF) population. Specifically, is there evidence to indicate that perceived quality of life (QOL) influences exercise performance independent of physiologic function in the HF population? Thirty-one subjects (21 male/10 female), diagnosed with compensated HF, underwent exercise testing and completed the MLWHFQ. Mean age and left ventricular ejection fraction were 52.8 years and 27.2%, respectively. Partial correlation, controlling for age and sex, assessed the relationship between MLWHFQ (overall and subscores) and key ventilatory expired gas measures. Intraclass correlation coefficient (ICC) analysis was used to determine reliability of the MLWHFQ. MLWHQ overall score (mean = 38.9, median = 36.0), physical subscore (mean = 14.8, median = 16.0), and psychosocial/symptomatology subscore (mean = 24.1, median = 19.0), were significantly correlated (P < or =.05) with peak oxygen consumption (VO2). The relationship between MLWHFQ and the minute ventilation-carbon dioxide production (VE/VCO2) slope was, however, not significant. ICC analysis revealed high reliability (0.95) for the MLWHFQ. The MLWHFQ demonstrates a significant relationship with peak VO2, a measure whose validity is dependent upon subject effort. VE/VCO2 slope, which is independent of subject effort and therefore potentially a better predictor of true physiologic function, does not appear to have a relationship with perceived QOL. These findings have implications for how the MLWHFQ is assessed, related to an exercise test, and used during clinical practice.
    Journal of Cardiopulmonary Rehabilitation 01/2002; 22(4):273-7.
  • R Humphrey, M N Bartels
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    ABSTRACT: In addition to patients with coronary artery disease, high-risk patients with severe congestive heart failure can benefit from rehabilitation. Traditionally, such patients were excluded from rehabilitation, but resistive exercise, higher-intensity programs, and interval training have now been safely conducted. Emerging data indicate that exercise training results in a number of improved physiologic and psychologic indices, including neural control, quality of life, exercise tolerance, ventricular function, skeletal muscle physiology, peripheral blood flow, and endothelial function. This review explores these beneficial outcomes through an assessment of therapeutic approaches, with special emphasis on the unique clinical characteristics of patients with congestive heart failure. OVERALL ARTICLE OBJECTIVE: To describe the benefits and the evolving role of cardiac rehabilitation for patients with congestive heart failure.
    Archives of Physical Medicine and Rehabilitation 04/2001; 82(3 Suppl 1):S76-81. · 2.36 Impact Factor
  • R McCall, R Humphrey
    Journal of Cardiopulmonary Rehabilitation 01/2001; 21(4):227-30.
  • R A. Arena, R Humphrey, M Peberdy
    Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2001; 33(5).
  • R Arena, R Humphrey
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    ABSTRACT: This study investigates the relationship between ventilatory expired gas and cardiac parameters measured during exercise testing in patients with heart failure. Twenty-five subjects (12 male, 13 female) diagnosed with compensated heart failure underwent symptom-limited exercise testing with ventilatory expired gas analysis. Metabolic and cardiac measures of interest were collected during testing. Mean peak oxygen consumption (VO2), minute ventilation/carbon dioxide production (VE/VCO2) slope, percentage of age predicted maximal heart rate achieved during exercise testing (%APMHR), and peak respiratory exchange ratio were 14.7 +/- 4.7 mL O2/kg/min-1, 33.8 +/- 9.8, 76% +/- 15%, and 1.1 +/- 0.11, respectively. The VE/VCO2 slope was significantly correlated with the following: %APMHR (r = -0.81, P < 0.001), peak VO2 (r = -0.83, P < 0.001), VO2 at ventilatory threshold (r = -0.70, P < 0.001), and the dead space to tidal volume ratio (VD/Vt) (r = 0.65, P < 0.001). The ability of peak VO2 and %APMHR to predict the VE/VCO2 slope was significant (r = 0.86, r2 = 0.72, P < 0.0001). This study demonstrates the importance of analyzing multiple exercise test parameters, including metabolic measures, in patients with heart failure.
    Journal of Cardiopulmonary Rehabilitation 01/2001; 21(3):130-4.
  • R. A. Arena, R. Humphrey, M. Peberdy
    Journal of Cardiopulmonary Rehabilitation. 01/2000; 20(5).
  • R Arena, R Humphrey, M A Peberdy
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    ABSTRACT: The safety and efficacy of exercise training in patients with congestive heart failure (CHF) is well established; however, the impact that exercise has on the subgroup of CHF patients awaiting heart transplant while on intravenous positive inotropic support remains largely unreported. This case study describes the safety and efficacy of exercise training in a patient awaiting heart transplant while on intravenous milrinone. Over a 1.2-year period, 246 exercise sessions were conducted with a total of 180.15 hours of aerobic exercise. During that time, the patient experienced only one hypotensive episode during exercise and had no other adverse events. The patient demonstrated a 38% increase in aerobic exercise time and a 34% increase in sustainable exercise workload. Research is needed to demonstrate the positive impact of exercise training on this subgroup of CHF patients.
    Journal of Cardiopulmonary Rehabilitation 01/2000; 20(4):259-61.
  • R Humphrey
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    ABSTRACT: LVAD use in the heart failure population is increasing and allows severely impaired patients an opportunity for exercise rehabilitation before cardiac transplantation. Although the LVAD provides nearly all of the cardiac output at rest, the native left ventricle contributes a modest amount during exercise, with the LVAD capable of providing a mechanical cardiac output of 10 L/min or greater. Given the parameters of the LVAD, exercise training responses should yield greater changes in submaximal exercise tolerance rather than changes in peak oxygen consumption. Heart rate and LVAD rate are driven by separate mechanisms but increase similarly during exercise. Blood pressure responses are somewhat variable early post LVAD implantation but normalize. Ratings of perceived exertion appear to be reliable and useful in this population. Evidence to date suggests that early mobilization and progressive exercise training in this population is safe and improves the transplantation experience. Although central contributions to oxygen consumption are limited by the inherent mechanical parameters of the LVAD, adequate cardiac output is provided for routine physical activities and moderate exercise training while the patient awaits transplantation.
    Journal of Cardiopulmonary Rehabilitation 01/1997; 17(2):73-5.
  • R Arena, R Humphrey, R McCall
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    ABSTRACT: The use of LVADs as a bridge to heart transplantation is increasing steadily as more surgical centers add this effective strategy for end-stage heart failure patients. Fundamental exercise physiology in the presence of LVADs has been described previously, and data is available that supports the safety and efficacy of exercise in this population. Variants to the expected exercise response that may be secondary to LVAD implantation, such as the pulmonary restrictive pattern that developed in the patient described in this case study, may occur. Clinicians should consider assessment and monitoring of pulmonary function in this patient population, especially in patients with exercise-induced dyspnea and perhaps patients with pre-existing pulmonary limitation.
    Journal of Cardiopulmonary Rehabilitation 19(6):344-6.

Publication Stats

179 Citations
32.64 Total Impact Points

Institutions

  • 1997–2004
    • Virginia Commonwealth University
      • Department of Physical Therapy
      Richmond, VA, United States
  • 2003
    • University of Alberta
      • Faculty of Rehabilitation Medicine
      Edmonton, Alberta, Canada
  • 2002
    • CUNY Graduate Center
      New York City, New York, United States