Prediction of peak oxygen uptake from cycle exercise test work level in heart failure patients >/=65 years of age.
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Biomedical subjects
P H Brubaker
Publications and source records attributed to P H Brubaker.
Reproducibility of cardiopulmonary exercise testing in elderly patients with congestive heart failure.
Elderly patients with congestive heart failure, including those with preserved systolic function, underwent maximal cardiopulmonary exercise testing. Maximal exercise oxygen consumption, exercise time, heart rate, respiratory exchange ratio, and ventilatory anaerobic threshold showed good reproducibility.
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Effects of cardioselective beta blockers on ventilation and gas exchange in patients with heart disease during ramp treadmill testing.
The effects of cardioselective beta blockade on ventilation and gas exchange were investigated in 12 male subjects with coronary artery disease during ramp treadmill testing. Patients were able to maintain much of their functional capacity as measured by oxygen consumption in the beta-blocked condition, and also maintained minute ventilation by increasing respiratory rate despite a decrease in tidal volume.
Adrenergic beta-Antagonists↗
Identification of the anaerobic threshold using double product in patients with coronary artery disease.
This study compared the ventilatory threshold with the double-product break point in 104 patients with cardiovascular disease during ramp treadmill testing. The high correlation (r = 0.81) between the double-product break point and the ventilatory threshold, even in patients taking beta blockers, suggests the former method is a viable noninvasive alternative for identifying the anaerobic threshold in patients with cardiovascular disease, particularly when expired gas analysis is not appropriate or available.
Adrenergic beta-Antagonists↗
Exercise-induced ventilatory abnormalities in orthotopic heart transplant patients.
STUDY OBJECTIVE: The purpose of this investigation was to compare multiple ventilatory responses of heart transplant patients (HTP) with normal subjects (NL) at rest, at absolute and relative submaximal exercise levels, and at peak exercise. DESIGN: Ten male HTP and 10 matched NL were tested under similar conditions on a treadmill with the use of an incremental protocol to symptom-limited maximal levels while breath-by-breath measurements of gas exchange and ventilation were obtained. RESULTS: At an absolute carbon dioxide (VCO2) level of 1 L.min-1, minute ventilation (VE) was significantly higher in HTP compared with NL (38.4 +/- 1.9 versus 29.3 +/- 0.9 L.min-1). However, when compared at similar relative levels (i.e., 40% and 60% of the peak oxygen consumption [VO2 peak]), VE was found to be significantly higher in NL compared with HTP (25.5 +/- 1.4 versus 21.2 +/- 1.0 L.min-1 at 40%; 39.9 +/- 3.1 versus 32.1 +/- 2.0 L.min-1 at 60%, respectively). The reduced VE was the result of a significantly lower tidal volume (VT) in HTP compared with NL at 40% (1.14 +/- 0.08 versus 1.33 +/- 0.05 L) and 60% (1.40 +/- 0.10 versus 1.85 +/- 0.06 L) of VO2 peak, since breathing frequency (BF) was not different between the groups at these levels. CONCLUSIONS: These data demonstrate that HTP have abnormal ventilatory responses to incremental exercise that are largely explained by a diminished VT response. While mechanical factors known to affect VT cannot be ignored, it is likely that the abnormal VT response of HTP during exercise is secondary to respiratory muscle weakness and may be due to hypoperfusion, long-term deconditioning, and/or the long-term use of corticosteriods.
Adult↗
Comparison of standard- and extended-length participation in cardiac rehabilitation on body composition, functional capacity, and blood lipids.
Participation in a standard-length outpatient cardiac rehabilitation program (CRP) for 3 months is known to result in positive changes in body composition, functional capacity, and blood lipids in patients with coronary artery disease. However, there has been little attempt to compare patients who remain active in a formal CRP for an extended length of >1 year with patients who exit after a standard length of 3 months. Consequently, 50 patients underwent a series of tests including a maximal graded exercise treadmill test, assessment of body composition, and fasting blood lipid analysis, at entry to CRP and after a follow-up period that ranged from 1 to 5 years. All patients participated in a standard multidisciplinary cardiac rehabilitation program for 3 months. Twenty-five patients discontinued participation after 3 months and received no other contact from the program staff until follow-up, whereas 25 patients remained active in the program until follow-up. After statistically adjusting for baseline differences between the groups, significant differences were observed between the extended- and standard-length groups at follow-up for body weight (177 vs 183 lbs), percent fat (22% vs 24%), METS (10.5 vs 8.4), high-density lipoprotein level cholesterol (44 vs 39 mg/dl), total cholesterol/high-density lipoprotein ratio (5.2 vs 6.1), and triglycerides (134 vs 204 mg/dl), respectively. No significant differences in the adjusted means were observed between the groups at follow-up for total cholesterol (209 vs 219 mg/dl) and low-density lipoprotein cholesterol (136 vs 138 mg/dl). Data from this study demonstrate the efficacy of extended participation in CRP on body composition, functional capacity, and blood lipids. Greater efforts need to be directed at retaining patients in low-cost, center-based maintenance programs and at extending monitoring of patients exiting standard length CRPs.
Adult↗
Estimation of VO2 in older individuals with osteoarthritis of the knee and cardiovascular disease.
The American College of Sports Medicine (ACSM) equation for estimating oxygen consumption (VO2) is often inappropriately applied to non-steady-state treadmill exercise. Therefore, it was the purpose of this investigation to develop an equation to estimate VO2 that could be applied to non-steady-state treadmill exercise in a population of patients with osteoarthritis of the knee, and to assess the generalizability of this equation for estimating VO2peak in patients with cardiovascular disease. Subjects for the investigation were 414 participants in the Fitness and Arthritis in Seniors Trial (FAST), and 362 patients with cardiovascular disease. Results from the FAST subjects showed that the ACSM equation was inappropriate for estimating VO2 during non-steady-state incremental treadmill walking. We developed the following equation (FAST) using speed and the interaction between speed and grade as the predictor variables during treadmill walking: VO2(ml.kg-1.min-1) = 0.0698 x speed(m.min-1) + 0.8147 x grade(%) x speed(m.min-1) + 7.533 ml.kg-1.min-1 The generalizability of the FAST equation for estimating VO2peak was evaluated in the patients with cardiovascular disease. The measured VO2peak of these patients was 23.7 +/- 0.3 ml.kg-1.min-1, whereas the VO2peak values estimated from the FAST equation and the ACSM equation were 24.1 +/- 0.3 and 33.2 +/- 0.5 ml.kg-1.min-1, respectively. No significant differences were found between the measured VO2peak and that estimated from the FAST equation. The VO2peak estimated from the ACSM equation was significantly greater than the measured VO2peak. These results suggest it is more appropriate to use the FAST equation rather than the ACSM equation to estimate VO2 in older patients with either osteoarthritis of the knee or cardiovascular disease.
Age Factors↗
Long-term (5-year) changes in HDL cholesterol in cardiac rehabilitation patients. Do sex differences exist?
BACKGROUND: It is unknown whether the benefits of a cardiac rehabilitation program on HDL cholesterol (HDL-C) are equally achieved in men and women. To study this, we compared changes in HDL-C and other lipids in a large group of men and women participating in a cardiac rehabilitation program for up to 5 years. METHODS AND RESULTS: We compared changes in HDL-C and other fasting lipids in 553 men and 166 women participating in a cardiac rehabilitation program at baseline and then annually for up to 5 years. Patients exercised 3 days a week at 70% to 85% of their maximum heart rate predetermined by a symptom-limited treadmill test. Aerobic capacity was estimated in metabolic equivalents (METs), and percent body fat was determined by skin-fold measurements. Baseline HDL-C, LDL cholesterol (LDL-C), and total cholesterol were significantly higher in women, whereas the ratio of total cholesterol to HDL-C was lower. Although both men and women showed an increase in HDL-C after 1 year (10% and 7%, respectively), only the women's level continued to increase over 5 years (20% versus 5% for men, P = .03). The sex difference in change in HDL-C remained after adjustment for age and smoking. A nonsignificant trend toward a greater change in HDL-C in women existed after adjustment for baseline percent body fat and estimated METs. The change in the ratio of total cholesterol to HDL-C was also more favorable in women, with a 38% decrease over 5 years compared with a 14% decrease in men (P = .01). Total cholesterol decreased by 20% in women and 8% in men (P = .001), whereas LDL-C dropped by 34% in women and 15% in men (P = .0001). There was no sex difference in change in triglycerides. CONCLUSIONS: Women with heart disease who participate in a cardiac rehabilitation program may achieve greater lipid benefits over longer periods of time than previously demonstrated in men.
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A comparison between aero and standard racing handlebars during prolonged exercise.
The use of aero style handlebars has gained popularity in triathlons and individual time trial events recently. The effect of using these handlebars has only been examined during short term exercise. It was the aim of this investigation to compare time to exhaustion and selected measures of ventilation, gas exchange and pulmonary function when using aero style handlebars versus standard racing style handlebars during long term exercise. Eleven well trained cyclists with a VO2max of 61.7 +/- 2.9 ml.kg-1.min-1 completed two continuous rides at 80 to 95 percent of their VO2max. Subjects rode at 80% of their VO2max for one hour and the work rate was increased by 5% of their VO2max every 15 min thereafter. The rides were completed with the subject riding his/her personal bicycle on a Velodyne trainer and differed in that during one ride the subjects rode with aero style handlebars and during the other they rode with standard racing style handlebars. During the ride with standard racing style handlebars, subjects rode with their hands on top of the bars or on the hoods of the brake levers. The subjects rode with the standard racing handlebars for 69.3 +/- 5.3 minutes as compared to 59.8 +/- 7.0 minutes with the aero style handlebars. This difference was not statistically significant. The average work rates when the cyclists terminated the exercise bouts with the aero and standard racing handlebars were 268.1 +/- 38.4 and 276.4 +/- 39.3 watts and were not significant from one another. Gas exchange and ventilatory parameters were measured every 15 min during the exercise bouts.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Relationship of lactate and ventilatory thresholds in cardiac transplant patients.
The ventilatory threshold (VT) has been suggested as a method for determining exercise training intensity in cardiac transplant patients (CTPs). Since the VT has not been validated against the more accepted marker of the anaerobic threshold, the lactate threshold (LT), in CTPs, the purpose of this investigation was to compare the VT to the LT within, as well as between, CTPs and normal subjects (NLs). Ten male orthotopic CTPs and 10 age, size, and gender matched NLs were exercised to symptom-limited maximal levels following incremental treadmill protocols. The VT was determined using the V-slope method, and the LT was identified using the log-log transformation method. The NLs and significantly higher absolute levels of VO2 at both the VT (1298.6 +/- 78.5 vs 919.0 +/- 57.2 ml.min-1) and LT (1561.1 +/- 144.2 vs 921.6 +/- 47.6 ml.min-1) compared with the CTPs. However, there was no significant difference in the relative VO2 (% peak) between CTPs and NLs at the VT (57.2 +/- 3.0 vs 49.0 +/- 3.5%) or LT (58.2 +/- 3.3 vs 58.5 +/- 4.9%), respectively. Within groups there was no significant difference between the VT and LT for either CTPs (919.0 +/- 57.2 vs 921.6 +/- 47.6 ml.min-1 or NLs (1298.6 +/- 78.5 vs 1561.1 +/- 144.2 ml.min-1). From the results of this investigation it appears that the VT may be used as an indicator of LT in CTPs and is within a range acceptable for clinical application.(ABSTRACT TRUNCATED AT 250 WORDS)
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Acute exercise: buffering psychosocial stress responses in women.
We evaluated the experimental hypothesis that an acute bout of aerobic exercise (AE) serves as a buffer to psychosocial stress responses in low to moderate physically fit women. Forty-eight (24 White, 24 Black) 25- to 40-year-old women participated in two counterbalanced experimental conditions: an attention control and a 40-min bout of AE at 70% heart rate (HR) reserve. The attention control and AE treatments were followed by (a) 30 min of quiet rest, (b) exposure to mental and interpersonal threat, and (c) 5 min of recovery. Blood pressure (BP) and HR were monitored at baseline, during the stressors, and throughout recovery. Self-reported distress was assessed before each stressor and upon completion of the recovery period. The results provided clear evidence that exercise dampens BP reactivity to psychosocial stress. Additionally, compared with the attention placebo control, AE reduced both the frequency and intensity of anxiety-related thoughts that occur in anticipation of interpersonal threat and challenge.
Adaptation, Psychological↗
The effects of testosterone on lipids and eicosanoids in cynomolgus monkeys.
The effect of testosterone administration on plasma lipoproteins and eicosanoids was studied in 24 male cynomolgus monkeys. We hypothesized that elevated plasma testosterone would unfavorably alter plasma lipids as well as thromboxane A2 (TxA2) and prostacyclin (PGI2), two eicosanoids that have been linked to the increased incidence of atherosclerosis, myocardial ischemia, and thrombosis. To test our hypothesis, half of the monkeys (N = 12) were subjected to 10 wk of testosterone treatment, whereas the remaining monkeys (N = 12) received a sesame oil vehicle. The plasma concentrations of thromboxane B2 (TxB2) and 6-keto-PGF1 alpha, the stable metabolites of TxA2 and PGI2, respectively, were determined. Additionally, assays were conducted on total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and triglycerides (TG). Distribution of the HDL subfraction protein was measured by gradient gel electrophoresis. All monkeys exhibited significant increases in TC (P less than 0.001) and low density lipoprotein cholesterol (LDL-C) (P less than 0.001); however, monkeys who received testosterone also displayed significant increases in TxB2 (P less than 0.03) and decreases in HDL-C (P less than 0.03) compared with control monkeys. There was a trend in the HDL-C subfraction data, indicating that testosterone treatment may be associated with a decrease in the larger HDL2b subfraction and a corresponding increase in HDL3c. These results demonstrate that exogenous testosterone adversely alters cardiovascular risk profiles by increasing TXB2 production and decreasing HDL-C. Athletes who use testosterone as an anabolic androgenic steroid may have an increased risk for coronary heart disease.
6-Ketoprostaglandin F1 alpha↗
Anabolic steroids and aggressive behavior in cynomolgus monkeys.
An animal model was employed to examine the effect of testosterone on aggressive behavior patterns. Ten cynomolgus monkeys were assigned to either an experimental or a control group and given biweekly injections; the experimental group received testosterone propionate, and the controls a sham solution. Prior to and upon the completion of an 8-week treatment period, behavioral observations were conducted. Although the administration of testosterone resulted in a significant increase in aggression, more important was the finding that changes in behavior were mediated by social status; that is, the incidence of both contact and noncontact aggression in dominant monkeys was far greater than the frequency of these behaviors in subordinate monkeys. These data are discussed in terms of the potential role of anabolic steroids as a risk factor in cardiovascular disease.
Aggression↗
The role of anabolic steroids on baseline and stress heart rate in cynomolgus monkeys.
This investigation examined the role of anabolic steroids on baseline heart rate (HR) and HR responses to the threat of capture in Macaca fascicularis. Ten cynomolgus monkeys were randomly assigned either to a steroid or to a sham control group. Steroid-treated animals were given testosterone injections biweekly for 10 weeks, whereas sham controls received injections of sesame oil on an identical schedule. Pretreatment and posttreatment HRs were evaluated to establish both baseline and acute-stress responses. Results revealed that animals given testosterone experienced a statistically significant increase in baseline HR when contrasted with the sham controls. No difference between the groups was detected in response to the threat of capture.
Animals↗
Exercise intolerance in congestive heart failure: a lesson in exercise physiology.
The current working hypothesis of exercise intolerance in patients with CHF indicates that an initial reduction in cardiac output, secondary to either systolic or diastolic dysfunction, results in a variety of complex and inter-related pathophysiologic alterations in the skeletal muscle, the vasculature, the pulmonary system, and several neurohumoral systems. These numerous compensatory mechanisms, although they work to preserve vital body functions, they ultimately result in exercise intolerance. Thus, the syndrome of CHF provides a unique opportunity to evaluate the role of several fundamental principles of exercise physiology.
Exercise Test↗
Validity of rating of perceived exertion during graded exercise testing in apparently healthy adults and cardiac patients.
PURPOSE: Recent exercise guidelines recommend a generalized rating of perceived exertion (RPE) range of 12 to 16 (15-point Borg scale) as the perceptual range associated with a physiological training effect. However, whether an individual who selects an RPE within the generalized range during an graded exercise test or exercise training, is actually within the correlated physiological range (50 to 85% maximum oxygen consumption [VO2max]) has not been studied in large samples of apparently healthy individuals or cardiac patients. The purpose of the present study was to assess the validity of the generalized RPE recommendations in a large heterogeneous group of apparently healthy subjects and cardiac patients. METHODS: Subjects included apparently healthy adults (N = 463) and cardiac patients (N = 217) who presented for a sign-symptom limited maximal graded exercise test (SSLMGXT). Ratings of perceived exertion associated with relative exercise intensities of 60 and 80% of maximal heart rate reserve (MHRR) and peak exercise were selected for analyses. RESULTS: Significant interindividual variability in RPE was observed at both relative exercise intensities (6 to 20 RPE range at 60% MHRR; 8 to 20 RPE range at 80% MHRR) for both populations. Thirty-nine percent of healthy subjects and 32% of cardiac patients reported an RPE outside an 11 to 14 range at 60% of MHRR, whereas 32% of healthy subjects and 52% of cardiac patients reported an RPE outside of a 14 to 17 range at 80% of MHRR. Peak RPE was higher for the apparently healthy subjects compared with the cardiac patients (18.8 +/- 1.2 versus 16.5 +/- 1.8; P < 0.01). CONCLUSIONS: These results challenge the applicability of the generalized RPE recommendations described in recent exercise guidelines under typical clinical exercise testing conditions. The basis for the generalized RPE recommendations warrant further investigation. Those who desire to use RPE as a marker of relative exercise intensity during SSLMGXT should take into consideration the large interindividual variability in these measures.
Adult↗
A home-based maintenance exercise program after center-based cardiac rehabilitation: effects on blood lipids, body composition, and functional capacity.
BACKGROUND: Previous research indicates that patients exiting a 12-week cardiac rehabilitation program (CRP) have difficulty maintaining an adequate exercise program. Thus, the authors' purpose was to determine if a home-based exercise program would enable patients to maintain/improve their blood lipids, body composition, and functional capacity after exiting the CRP. METHODS: Thirty-one patients exiting an initial 12-week CRP were assigned randomly to the home-based (HB) intervention or the standard care (SC) condition. After one home visit, the HB participants (n = 16) were contacted by telephone every other week by CRP staff and completed and returned weekly exercise logs. The SC participants (n = 15) had no contact with the CRP other than to schedule follow-up tests. A third group (n = 17), randomly selected from patients that elected to remain in the center-based CRP (CB) for the same duration, also were examined. All groups underwent exercise testing, fasting blood lipid analysis, and body composition assessment before starting CRP (0M), after 3 months (3M) in a standard CRP, and after 9 months (12M) in either HB, SC, or CB condition (12 months after starting CRP). RESULTS: Analysis of variance indicated that there were significant increases in metabolic equivalents and high-density lipoprotein, in all three groups, over time. However, analysis of covariance revealed no significant differences between the HB, SC, and CB groups at 12M for any variable. CONCLUSIONS: These data indicate that the HB program was as effective as the CB program at improving/maintaining functional capacity, blood lipids, and body weight/composition. The similar success of the SC group is likely due to their prior experience in CRP and knowledge of follow-up testing. Home-based maintenance program could be offered as a low-cost alternative to CB programs.
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