Ventilatory response to exercise and kinetics of oxygen recovery are similar in cardiac transplant recipients and patients with mild chronic heart failure.

BACKGROUND: Exercise capacity, assessed by cardiopulmonary exercise treadmill testing (CPET), does not return to normal following heart transplantation. This study evaluated the ventilatory response to exercise and the kinetics of oxygen (O(2)) recovery in heart transplant recipients (HTR) compared to healthy volunteers (HV) and heart failure patients. METHODS: Eighteen patients with end-stage heart failure (ESHF), 12 with mild heart failure (MHF) matched for peak oxygen consumption (Vo(2)) with the HTR, 12 HTR and 12 HV underwent CPET for measurements of peak Vo(2), Vo(2) at anaerobic threshold (AT), first-degree slope of Vo(2) decline during early recovery (Vo(2)/t-slope), time required for a 50% fall from peak Vo(2) (T(1/2) of Vo(2)) and the slopes of VE/Vco(2) and VE/Vo(2). RESULTS: The MHF and HTR groups had similar ventilatory responses to exercise and O(2) recovery kinetics. Peak Vo(2) (18.5 +/- 5.7 vs 9.4 +/- 0.9 ml/kg/min, p < 0.001), AT (13.8 +/- 4.8 vs 6.7 +/- 1.8 ml/kg/min, p < 0.001) and Vo(2)/t-slope (0.6 +/- 0.2 vs 0.3 +/- 0.2 liter/min/min, p = 0.055) were higher in the HTR than in the ESHF group. In contrast, HTR had lower VE/Vco(2)-slope (31.4 +/- 3.8 vs 39.2 +/- 9.9, p = 0.015) and T(1/2) Vo(2) (1.5 +/- 0.3 vs 2.4 +/- 1.1 minute, p = 0.014) than the ESHF group. Compared to HV, HTR had lower Vo(2) peak (18.5 +/- 5.7 vs 28.4 +/- 6.9 ml/kg/min, p < 0.001), AT (13.8 +/- 4.8 vs 19.8 +/- 4.5 ml/kg/min, p = 0.04), Vo(2)/t-slope (0.6 +/- 0.2 vs 1.0 +/- 0.4 liter/min/min, p = 0.005) and steeper VE/Vco(2) slope (31.4 +/- 3.8 vs 23.6 +/- 2.7, p = 0.062). Heart rate deceleration during recovery was significantly slower in HTR than in all other groups. CONCLUSIONS: Exercise intolerance and delayed O(2) recovery kinetics were only partially reversed after heart transplantation. This finding suggests that some of the pathophysiologic mechanisms of heart failure persist after heart transplantation.     

Skeletal muscle limits the exercise tolerance of renal transplant recipients: effects of a graded exercise training program

Sixteen renal transplant recipients were studied before and after they had participated in a 24-week exercise training program to determine (1) the nature of the factors explaining their impaired exercise tolerance, and (2) their adaptative responses to exercise training. During progressive treadmill exercise to exhaustion prior to training, renal transplant recipients stopped exercising at lower peak rates of oxygen consumption (VO2max) (29.0 +/- 7.8 47.9 +/- 9.1 mL O2.kg-1.min-1; P less than 0.001) and ventilation (55.9 +/- 13.2 v 124.0 +/- 22.2 L.min-1; P less than 0.0001), and at lower peak heart rates (169 +/- 22 v 196 +/- 9 beats.min-1; P less than 0.05) and peak blood lactate concentrations (5.0 +/- 2.1 v 11.5 +/- 4.0 mmol.L-1; P less than 0.001) than did controls. None showed a plateau in oxygen consumption with increasing workload. Exercise time to exhaustion was also significantly shorter in renal transplant recipients (9.5 +/- 1.8 v 16.0 +/- 1.3 min; P less than 0.0001). After training, exercise time to exhaustion (12.0 +/- 2.0 min; P less than 0.001), VO2max (37.5 +/- 4.8 mL O2.kg-1.min-1; P less than 0.05), maximum ventilation rate (68.5 +/- 14.0 L.min-1; P less than 0.05), peak blood lactate concentrations (7.8 +/- 1.8 mmol-L-1; P less than 0.001), and the rate of oxygen consumption at a blood lactate concentration of 2.0 mmol.L-1 (22.5 +/- 2.5 v 16.5 +/- 2.2 mL O2.kg-1.min-1; P less than 0.001) had all increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effectiveness of an upper extremity exercise device integrated with computer gaming for aerobic training in adolescents with spinal cord dysfunction

BACKGROUND/OBJECTIVE: To determine whether a new upper extremity exercise device integrated with a video game (GameCycle) requires sufficient metabolic demand and effort to induce an aerobic training effect and to explore the feasibility of using this system as an exercise modality in an exercise intervention. DESIGN: Pre-post intervention. SETTING: University-based research facility. SUBJECT POPULATION: A referred sample of 8 adolescent subjects with spina bifida (4 girls, 15.5 +/- 0.6 years; 4 boys, 17.5 +/- 0.9 years) was recruited to participate in the project. All subjects had some level of mobility impairment that did not allow them to participate in mainstream sports available to their nondisabled peers. Five subjects used a wheelchair full time, one used a wheelchair occasionally, but walked with forearm crutches, and 2 were fully ambulatory, but had impaired gait. MAIN OUTCOME MEASURES: Peak oxygen uptake, maximum work output, aerobic endurance, peak heart rate, rating of perceived exertion, and user satisfaction. RESULTS: Six of the 8 subjects were able to reach a Vo2 of at least 50% of their Vo2 reserve while using the GameCycle. Seven of the 8 subjects reached a heart rate of at least 50% of their heart rate reserve. One subject did not reach either 50% of Vo2 reserve or 50% of heart rate reserve. Seven of the 8 subjects increased their maximum work capability after training with the GameCycle at least 3 times per week for 16 weeks. Conclusions: The data suggest that the GameCycle seems to be adequate as an exercise device to improve oxygen uptake and maximum work capability in adolescents with lower extremity disability caused by spinal cord dysfunction. The subjects in this study reported that the video game component was enjoyable and provided a motivation to exercise.     

Functional significance of cardiac reinnervation in heart transplant recipients.

BACKGROUND: There is accumulating evidence of structural sympathetic reinnervation after human cardiac transplantation. However, the functional significance of reinnervation in terms of exercise capacity has not been established as yet; we therefore investigated the influence of reinnervation on cardiopulmonary exercise testing. METHODS: After orthotopic heart transplantation 35 patients (mean age, 49.1 +/- 8.4 years) underwent positron emission tomography with scintigraphically measured uptake of C11-hydroxyephedrine (HED), lung function testing, and cardiopulmonary exercise testing. Two groups were defined based on scintigraphic findings, indicating a denervated group (n = 15) with a HED uptake of 5.45%/min and a reinnervated group (n = 20) with a HED uptake of 10.59%/min. RESULTS: The two study groups did not show significant differences with regard to anthropometric data, number of rejection episodes, preoperative hemodynamics, and postoperative lung function data. The reinnervated group had a significant longer time interval from transplantation (1625 +/- 1069 versus 800 +/- 1316 days, p < .05). In transplant recipients with reinnervation, heart rate at maximum exercise (137 +/- 15 versus 120 +/- 20 beats/min, p = .012), peak oxygen uptake (21.0 +/- 4 versus 16.1 +/- 5 mL/min/kg, p = .006), peak oxygen pulse (12.4 +/- 2.9 versus 10.2 +/- 2.7 mL/min/beat, p = .031), and anaerobic threshold (11.2 +/- 1.8 versus 9.5 +/- 2.1 mL/min, p = .046) were significantly increased in comparison to denervated transplant recipients. Additionally, a decreased functional dead space ventilation (0.24 +/- 0.05 versus 0.30 +/- 0.05, p = .004) was observed in the reinnervated group. CONCLUSIONS: Our study results support the hypothesis that partial sympathetic reinnervation after cardiac transplantation is of functional significance. Sympathetic reinnervation enables an increased peak oxygen uptake. This is most probably due to partial restoration of the chronotropic and inotropic competence of the heart as well as an improved oxygen delivery to the exercising muscles and a reduced ventilation-perfusion mismatching.     

Exercise assessment in infants after cardiac transplantation

BACKGROUND: Few data describe exercise performance after cardiac transplantation during infancy. The aim of this study was to compare the cardiorespiratory response to exercise in healthy subjects with that of subjects who had undergone heart transplantation during infancy to treat hypoplastic left heart syndrome. METHODS: Subjects (24 heart transplant recipients and 25 healthy controls) exercised on a treadmill using pediatric ramp protocols. We measured heart rate (HR), blood pressure, and metabolic data. Median age at transplantation was 20 days (range, 4 to 97 days). Age of recipients at exercise testing was 9.7 +/- 2.3 years and in healthy subjects was 10.5 +/- 1.4 years (p=not significant [NS]). RESULTS: Exercise duration was similar in both groups (10.3 +/- 2.0 minutes in recipients vs 11.1 +/- 1.5 minutes in healthy subjects, (p=NS). Heart rate at rest was greater in recipients (94 +/- 15 beats per minute [bpm] vs 85 +/- 11 bpm, p=0.02). Peak HR also was less in the recipient group (158 +/- 15 bpm vs 189 +/- 12 bpm, p <0.001). Peak oxygen consumption was 14% less in the recipients (32.3 +/- 5.6 ml/kg/min vs 36.8 +/- 5.5 ml/kg/min, p <0.01). Ventilatory anaerobic threshold was decreased in recipients, 27.6 +/- 9.6 vs 32.8 +/- 6.0, p <0.05. Respiratory exchange ratio at peak exercise was equal in both groups (1.06 +/- 0.06 vs 1.06 +/- 0.08). Oxygen pulse index did not differ significantly, 5.5 +/- 1.1 ml/beat/m2 in recipients and 6.1 +/- 1.7 ml/beat/m2 in healthy subjects (p=NS). CONCLUSIONS: Overall, children who undergo cardiac transplantation in infancy have exercise capacities within the normal range. These recipients have a decreased heart rate reserve that may account for the differences in peak oxygen consumption when compared with healthy subjects.     

Exercise-related ventilatory abnormalities are more specific for functional impairment in chronic heart failure than reduction in peak exercise oxygen consumption.

BACKGROUND: Impaired functional capacity during exercise is used to assess need for transplantation in congestive heart failure patients, although impaired capacity is present in several chronic illnesses. The purpose of this study was to test the hypothesis that ventilatory abnormalities during exercise, rather than functional capacity, are specific to congestive heart failure patients. METHODS: We compared exercise-related gas exchange among a group of congestive heart failure patients and a group of patients who had chronic liver disease and normal cardiac function, matched for functional impairment, and a group of normal controls. RESULTS: Patients with congestive heart failure and patients with chronic liver disease experienced marked reduction in peak exercise oxygen consumption compared with normal controls (14.0 +/- 1.4 and 14.2 +/- 3.7 ml/kg/min, respectively, vs 25.8 +/- 5.6 ml/kg/min, p < 0.01). Minute ventilation at peak exercise was significantly higher in congestive heart failure subjects than in chronic liver disease patients (59.3 +/- 16.8 liter/min vs 41.4 +/- 14.2 liter/min, p < 0.05), although carbon dioxide production was similar (1,380 +/- 308 ml vs 1,180 +/- 389 ml, p = not significant), so that the ratio of minute ventilation to carbon dioxide production (ventilatory equivalent for carbon dioxide, an index of ventilatory drive) was significantly elevated in congestive heart failure subjects (43 +/- 9 vs 36 +/- 7, p < 0.05). CONCLUSIONS: Although functional impairment characterizes both congestive heart failure and chronic liver disease, only congestive heart failure patients exhibit exercise-related ventilatory abnormalities. Exercise-related ventilatory abnormalities may be more specific to the underlying pathophysiology of chronic heart failure and should be considered when evaluating patients for heart transplantation.     

Comparison of functional capacity in patients with end-stage heart failure following implantation of a left ventricular assist device versus heart transplantation: results of the experience with left ventricular assist device with exercise trial.

BACKGROUND: Use of a permanent left ventricular assist device (LVAD) has been proposed as an alternate treatment of patients with end-stage heart failure. The purpose of this study was to compare the functional capacity of patients following implantation of a LVAD vs heart transplant (HTx). METHODS: Eighteen patients from 6 centers who received an intracorporeal LVAD as a bridge to HTx underwent treadmill testing 1 to 3 months post-LVAD and again post-HTx. Baseline and peak measurements, including oxygen consumption, blood pressures, and respiratory rate were made during each treadmill test. RESULTS: Peak oxygen consumption was 14.5+/-3.9 ml/kg/minute post-LVAD and 17.5+/-5.0 ml/kg/minute post-HTx (p < .005). The percentage of the predicted peak oxygen consumption based on gender, weight, and age was 39.5%+/-5.5% post-LVAD and 47.7%+/-10.9% post-HTx (p < .005). Exercise duration was lower post-LVAD than post-HTx (10.3+/-4.2 minute vs 12.5+/-5.4 minute, p < .05). After LVAD implantation, peak total oxygen consumption correlated with peak LVAD rate and output. Eight patients reached an LVAD rate of 120 beats per minute (bpm) before the conclusion of exercise, the maximum rate for the outpatient electric device. The peak respiratory exchange ratio post-LVAD was 1.15+/-0.22 and post-HTx was 1.15+/-0.18, consistent with a good effort in both groups. CONCLUSIONS: Patients demonstrated a lower functional capacity post-LVAD than post-HTx. For some patients functional capacity post-LVAD may be improved by a higher maximum LVAD rate and output.     

Clinical predictors of exercise capacity 1 year after cardiac transplantation.

BACKGROUND: The exercise capacity of cardiac transplant recipients is reduced compared with normal controls. However, clinical variables predictive of post-transplant exercise capacity have not been well defined. The objective of the present study was to identify clinical features predictive of post-transplant exercise capacity. METHODS: Ninety-five cardiac transplant recipients underwent cardiopulmonary testing at 1 year after transplant. The exercise parameters were compared with both pre-transplant values and normal subjects. The relationships between exercise parameters and clinical characteristics were analyzed. RESULTS: Mean peak oxygen consumption (VO(2)) and exercise test duration at 1-year post-transplant improved significantly from 16.4 to 19.9 ml/kg/min and 5.5 to 7.6 minutes, respectively (p < 0.001), but were significantly lower than for normal controls (peak VO(2) 34.0 ml/kg/min; exercise duration 11.2 minutes; p < 0.001). Age- and gender-adjusted VO(2) was 54% of predicted. Pre-operative body weight correlated strongly with post-transplant weight (r = 0.80, p < 0.001). Significant recipient predictors of 1-year post-transplant peak VO(2) identified by multivariate regression analysis were age, male gender, body mass index, exercise peak heart rate and duration of post-operative intensive care. Donor variables did not contribute significantly to post-transplant peak VO(2). CONCLUSIONS: Peak VO(2) improved after cardiac transplantation but remained significantly impaired compared with normal subjects. In estimating the impact of cardiac transplantation on exercise capacity the most important pre-transplant factors to consider are age, gender and height and weight (or, alternatively, body mass index).     

Acute native lung hyperinflation is not associated with poor outcomes after single lung transplant for emphysema.

BACKGROUND: Single-lung transplantation for emphysema may be complicated by acute native lung hyperinflation (ANLH) with hemodynamic and ventilatory compromise. Some groups advocate the routine use of independent lung ventilation, double-lung transplant, or right-lung transplant with or without contralateral lung volume reduction surgery in high-risk patients. The goal of this study was to determine the incidence of ANLH and identify its potential predictors. METHODS: We reviewed 51 consecutive single-lung transplants for emphysema. Symptomatic ANLH was defined as mediastinal shift and diaphragmatic flattening on chest x-ray with hemodynamic or respiratory failure requiring cardiopressor agents or independent lung ventilation. Preoperative and postoperative physiologic and hemodynamic data were analyzed from both recipients and donors. RESULTS: Sixteen patients developed radiographic ANLH; 8 were symptomatic, 2 severely so. We could not identify high-risk patients before transplant by pulmonary function tests, predicted donor total lung capacity (TLC)/actual recipient TLC ratio, pulmonary artery pressures, or the side transplanted. There was a trend toward an increased incidence of symptomatic ANLH in patients with bullous emphysema on chest computed tomography, but this was accounted for primarily by patients with alpha1-antitrypsin deficiency (4/13 vs 4/38 with chronic obstructive pulmonary disease, P = 0.10). No patient required cardiopulmonary bypass or inhaled nitric oxide intraoperatively. Patients with acute native lung hyperinflation did not have increased reperfusion edema as measured by chest x-ray score or PaO2/F(I)O2 ratio. Compared to patients without ANLH, symptomatic patients had longer ventilator times (64.9+/-14.6 hours vs 40.4+/-3.9, P = 0.02, ANOVA) and longer lengths of stay (19.3+/-2.1 days vs 13.7+/-1.3, P = 0.07), but 30-day survival was 100%. Two symptomatic patients required independent lung ventilation or inhaled nitric oxide; the others were managed with decreased minute ventilation, early extubation, and cardiopressor agents. No patient required early lung volume reduction surgery or retransplantation. Acute native lung hyperinflation had no effect on FEV1 or 6-minute walk results at 1 year; survival at 1, 2, or 3 years; or the rate of acute rejection, infection, or bronchiolitis obliterans syndrome greater than grade 2. CONCLUSION: Acute native lung hyperinflation is common radiographically but is rarely clinically severe. Although there was a trend toward an increase in symptomatic ANLH in patients with bullous emphysema, a high-risk group could not be identified preoperatively. Our results do not support the routine use of bilateral lung transplant, the exclusive use of right single-lung transplant, simultaneous lung volume reduction surgery, or independent lung ventilation for patients with emphysema. Management strategies should be employed that limit overdistension of the native lung and lead to early extubation.     

Exercise tolerance of end-stage renal disease patients

The purpose of this study was to evaluate the exercise tolerance of end-stage renal disease patients, and to examine pulmonary function and blood lactate as its possible limiting factors. Ten end-stage renal disease patients (age 30 +/- 11) were tested at rest and in a subsequent graded treadmill test to exhaustion. Velocity was 4.8 km/h and the grade was incremented by 2.5% every 4 min. One minute of rest, used for blood sampling, separated successive stages. Pulmonary functions (FVC, FEV1) at rest were both 76% of predicted. Resting heart rate, systolic and diastolic blood pressures, and ventilatory equivalent values were higher than normal. At peak exercise, heart rate, oxygen uptake, oxygen pulse and blood lactic acid were lower than normally predicted for maximal exercise, while ventilatory equivalent and diastolic blood pressure were higher. Only six patients reached blood lactate levels beyond 4 mM.l-1 (onset of blood lactic acid), at which point they utilized 88 +/- 5% of their respective peak Vo2. The results suggest that the low exercise tolerance demonstrated in end-stage renal disease patients is not limited by the somewhat compromised pulmonary capacity or by excessive blood lactate levels.     

Isokinetic muscle strength predicts maximum exercise tolerance in renal patients on chronic hemodialysis

Patients with end-stage renal disease receiving chronic hemodialysis have impaired exercise tolerance. To distinguish between a central cardiorespiratory and a peripheral skeletal muscular origin for this fatigue, we measured exercise performance and peak oxygen consumption during a maximum exercise test in 10 patients receiving chronic hemodialysis. Skeletal muscle function was measured with an isokinetic cycle ergometer and a Cybex II isokinetic dynamometer. Peak rates of oxygen consumption (17.7 +/- 3.6 [mean +/- SD] mL O2/kg/min), blood lactate concentrations (3.4 +/- 0.9 mmol/L), peak heart rates (168 +/- 12 beats/min), and rates of ventilation (37.3 +/- 14.6 L/min) were low, but respiratory exchange ratios (1.1 +/- 0.1) were compatible with maximal effort. There was a significant correlation between isokinetic muscle strength and VO2 peak, exercise duration, peak ventilation, and peak blood lactate concentrations (P less than 0.05 to less than 0.001), but not between hemoglobin concentration, total blood hemoglobin content, or hematocrit and these variables. Therefore, in renal dialysis patients, isokinetic muscle strength is a better predictor of exercise capacity than are variables determining blood oxygen carrying capacity. This suggests that altered skeletal muscle function explains the impaired exercise tolerance of anemic patients with end-stage renal disease receiving chronic hemodialysis.     

Respiratory evaluation of patients on continuous ambulatory peritoneal dialysis prior to renal transplantation

BACKGROUND AND AIM: Pulmonary function tests (PFTs) and cardiopulmonary exercise tests (CPETs) are important in predicting preoperative pulmonary complications and mortality rate in potentially renal transplant recipients. There is no adequate clinical research aimed at learning the effect of empty and full status of the peritoneal cavity on PFTs and CPET for estimating decide PFTs and CPET timing in preoperative evaluation. The aim of this study was to investigate whether PFT and CPET results are altered in patients on continuous ambulatory peritoneal dialysis (CAPD) according to the presence of dialysis solution in the abdomen. SUBJECTS AND METHODS: 22 subjects were included (12 male, 10 female, mean age 29.64 +/- 8.29 years, CAPD duration, 37.35 +/- 7.15 months). Data were collected from each patient when the peritoneal cavity was filled with solution (full status) and again when the cavity had been drained (empty status). Forced expiratory volume in 1 s (FEV1), ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC), total lung capacity (TLC), and residual volume (RV) were calculated. Peak oxygen uptake (peak VO2) and exercise duration were determined by cardiopulmonary exercise testing. RESULTS: When the peritoneal cavity was empty, mean (+/- SD) values for the parameters tested were % predicted FEV1: 85 +/- 17%, %FEV1/FVC: 84 +/- 8%, % predicted TLC: 98 +/- 17%, % predicted RV: 108 +/- 25%, % predicted DLCO: 90 +/- 14%, peak VO2: 43 +/- 11 ml/kg/min, test duration: 6.8 +/- 1.6 min. When the peritoneal cavity was full, mean (+/- SD) values were % predicted FEV1: 86 +/- 17%, %FEV1/FVC: 83 +/- 7%, % predicted TLC: 91 +/- 14%, % predicted RV: 95 +/- 22%, % predicted DLCO: 87 +/- 16%, peak VO2: 42 +/- 8 ml/kg/min, test duration 6.5 +/- 1.7 min. % predicted FEV1, %FEV1/FVC, % predicted DLCO and peak VO2 were not statistically significant between the mean values at empty status versus those at full status (p < 0.05 for all). There were significant decreases between the mean values for % predicted TLC and % predicted RV at full status versus empty status (p < 0.002 for TLC, p < 0.001 for RV). No statistically significant correlation was found between PFTs and % change ratio of dialysate. CONCLUSION: FEV1, %FEV1/FVC, % predicted DLCO and CPET test results do not differ according to abdomen status in CAPD patients suggesting that the timing of PFT maneuver does not affect preoperative transplantation evaluation. Therefore, when evaluating the results of these tests prior to transplantation period, the presence of dialysis solution in the abdomen may be ignored.     

The 6-minute walk test does not reliably detect changes in functional capacity of patients awaiting cardiac transplantation.

BACKGROUND: Peak oxygen consumption (Vo(2)peak) is a strong independent predictor of prognosis in patients with severe chronic heart failure (CHF) and is used to guide optimal timing of transplantation. However, its assessment is relatively expensive and time-consuming and requires sophisticated equipment and highly trained personnel. The purpose of this study was to determine whether changes in 6-minute walk test (6WT) distance, a simple, inexpensive potential alternative measure of functional capacity, can predict changes in Vo(2)peak in patients with severe CHF. METHODS: Sixteen subjects (ejection fraction 23+/-2%, Vo(2)peak 16.2+/-1.1 ml kg (-1)min(-1)) underwent repeated 6WT and Vo(2)peak assessments that included familiarization and 4 serial measures, 6 weeks apart (baseline and at Weeks 6, 12 and 18). Analysis compared baseline performance with each subsequent testing occasion. RESULTS: At baseline, mean (+/-SE) VO(2)peak was 16.3+/-1.1 ml kg(-1) min(-1) and 6WT distance was 458+/-21 m. 6WT and Vo(2)peak were strongly correlated at all timepoints (average r=0.82; all p<0.05). However, mixed model analysis, assessing the capacity of the changes seen in 6WT to predict changes in Vo(2)peak, showed no statistical significance (F=0.11; p=0.74). CONCLUSIONS: The 6WT is commonly used to assess functional capacity in patients with heart failure. This study demonstrates that, despite a strong cross-sectional correlation with Vo(2)peak, changes in the 6WT are not a reliable predictor of changes in Vo(2)peak within patients. Therefore, the 6WT has limited utility as a serial measure to assess changes in the clinical status of patients with severe heart failure.     

Relationship of cardiac allograft size and pulmonary vascular resistance to long-term cardiopulmonary function.

The purpose of this study was to evaluate the long-term cardiopulmonary function of heart transplant patients who received disproportionately sized allografts for varying levels of pulmonary vascular resistance. Resting hemodynamics and oxygen uptake during exercise were recorded at 1 year after transplantation in 52 patients. No differences in resting heart rate, cardiac output, stroke volume, peak oxygen uptake during exercise, and exercise duration were found in recipients of undersized hearts (donor:recipient weight ratio [D:R] < 0.75), sized-matched hearts (D:R = 0.75 to 1.25), and oversized (D:R > 1.25) hearts. In a further analysis according to preoperative pulmonary vascular resistance, resting cardiac output (5.8 +/- 1.3 L/min) was normal, and peak exercise oxygen uptake (22.7 +/- 8.0 ml/kg/min) was mildly decreased in recipients of size-matched allografts with a pulmonary vascular resistance of less than 3 Wood units (size-matched hearts, with mild or no pulmonary vascular resistance). Of patients with moderate pulmonary hypertension (pulmonary vascular resistance > or = 3 Wood units), resting cardiac output was normal (5.1 +/- 0.6 L/min) in recipients of oversized hearts and was reduced (4.7 +/- 1.0 L/min) in recipients of sized-matched hearts (p < 0.05 versus recipients of size-matched hearts with pulmonary vascular resistance less than 3 Wood units).(ABSTRACT TRUNCATED AT 250 WORDS)     

Time course of physical reconditioning during exercise rehabilitation late after heart transplantation.

BACKGROUND: Exercise rehabilitation improves physical capacity in heart transplant recipients. The time course of physical reconditioning and skeletal muscle adaptation late after transplantation are unknown. METHODS: Twenty-one heart transplant recipients, at 5.2 +/- 2.1 years after transplantation, completed 1 year of an individually tailored home ergometer-training program (2.1 +/- 0.7 sessions weekly with matched heart rates, intensity at 10% below anaerobic threshold). We analyzed time course of physical reconditioning data for each home-training session (n = 2,396). Constant-load tests with consistent blood lactate concentrations were performed quarterly (n = 105) to estimate the time course of skeletal muscle adaptation. Nine heart transplant recipients served as a control group (CG). RESULTS: After 12 months, exercise capacity for matched heart rates (112 +/- 11 beats/min; CG, 114 +/- 8 beats/min) increased by 35% +/- 19% (from 43 +/- 14 to 58 +/- 18 W; p < 0.001; CG, 53 +/- 18 to 54 +/- 18 W); 24% of the increase was caused by improved skeletal muscle function and 11% by central functioning. Physical reconditioning showed its greatest increase within the first 3 months (+18%; p < 0.001); 50% of the increase consisted of better skeletal muscle or central functioning. Between the 4(th) and 12(th) months, exercise capacity increased continuously (+15%; p < 0.001), mainly because of better skeletal muscle functioning. CONCLUSIONS: The persistent improvement in exercise capacity along with consistent lactate concentrations during 12 months of training indicates that exercise training could counteract the negative side effects of immunosuppressive treatment on skeletal muscles. Even late after heart transplantation, physical training should be performed regularly to prevent the accelerated decrease in exercise capacity and in skeletal muscle function.     

A prediction model for estimating pulmonary oxygen uptake during the 6-minute walk test in organ transplant recipients

We developed a multivariate prediction equation for estimating the highest obtainable pulmonary oxygen uptake (VO2p) during the 6-minute walk test (6-MWT) in 54 organ transplant recipients: heart/heart-double-lung (n=14), kidney/kidney-pancreas (n=16), liver (n=14), double lung (n=8), bone marrow (n=2). They were of age, 48+/-12 years. Participants performed a 6-MWT during which expired gases were collected and analyzed with a portable metabolic system interfaced with a wireless heart rate monitor. The following variables significantly contributed to the model for predicting the highest obtainable 6-MWT VO2p: 6-MWT distance (m), age (years), gender (male=0, female=1), resting heart rate, peak heart rate, weight (kg), and transplant type (kidney/kidney-pancreas=1, other=0), where: VO2p=1.253+0.022 (6-MWT distance)+0.112 (age) -3.192 (gender) -0.104 (resting heart rate)+0.127 (peak 6-MWT heart rate)-0.084 (weight)+2.116 (transplant type). The explanatory variables in our final model accounted for 78% of the variance in 6-MWT VO2p. In conclusion, the addition of an easily estimated 6-MWT VO2p will provide added clinical information of functional capacity following an exercise rehabilitation intervention or during routine follow-up for organ transplant recipients.     

Assessing exercise performance after heart transplantation

OBJECTIVE: Heart transplantation improves the survival rate and quality of life in patients with severe symptoms of congestive heart failure and an ejection fraction of 20% or less. Despite marked symptomatic and clinical improvement in those who undergo heart transplantation, exercise capacity often remains reduced, and the factors limiting exercise performance during the post-transplantation period remain unclear. This study was performed to investigate the factors affecting exercise capacity in heart transplantation recipients. PATIENTS AND METHODS: Fourteen patients with cardiomyopathy were enrolled in this study. We measured peak exercise oxygen uptake (peak VO(2)) in seven patients (age range: 42 +/- 14 yr) 10-28 months after transplantation, in seven patients (age range: 33 +/- 18 yr) with dilated cardiomyopathy before heart transplantation, and in 14 healthy control subjects (age range: 44 +/- 12 yr). The left ventricular ejection fraction, Beck Depression Inventory score, Medical Outcome Health Survey Short Form-36 Questionnaire (SF-36) results, and immunosuppressive therapy administered were recorded in all patient groups. RESULTS: All patients in the post-transplantation group terminated exercise testing before the anaerobic threshold because of general fatigue. All heart transplantation recipients exhibited a left ventricular ejection fraction within the normal range (mean +/- SD = 57% +/- 2%). The peak VO(2) mean values were significantly different among the three groups (p = 0.001). There were statistically significant correlations between the peak VO(2) values and the Beck Depression Inventory scores (r = -0.637, p = 0.01), between the peak VO(2) values and bodily pain (r = 0.717, p = 0.006), between the peak VO(2) values and general health perceptions (r = 0.706, p = 0.007), and between peak VO(2) values and postoperative duration (r = 0.843, p = 0.03) in all patient groups. CONCLUSION: In the long-term treatment of heart transplant recipients, exercise training should be considered an important therapeutic tool that enables patients to achieve a good quality of life.     

Effectiveness of an Upper Extremity Exercise Device Integrated With Computer Gaming for Aerobic Training in Adolescents With Spinal Cord Dysfunction

Abstract

Background/Objective: To determine whether a new upper extremity exercise device integrated with a video game (GameCycle) requires sufficient metabolic demand and effort to induce an aerobic training effect and to explore the feasibility of using this system as an exercise modality in an exercise intervention.

Design: Pre-post intervention.

Setting: University-based research facility.

Subject Population: A referred sample of 8 adolescent subjects with spina bifida (4 girls, 15.5 ± 0.6 years; 4 boys, 1 7.5 ± 0.9 years) was recruited to participate in the project. All subjects had some level of mobility impairment that did not allow them to participate in mainstream sports available to their nondisabled peers. Five subjects used a wheelchair full time, one used a wheelchair occasionally, but walked with forearm crutches, and 2 were fully ambulatory, but had impaired gait.

Main Outcome Measures: Peak oxygen uptake, maximum work output, aerobic endurance, peak heart rate, rating of perceived exertion, and user satisfaction.

Results: Six of the 8 subjects were able to reach a Vo2 of at least 50% of their Vo2 reserve while using the GameCycle. Seven of the 8 subjects reached a heart rate of at least 50% of their heart rate reserve. One subject did not reach either 50% of Vo2 reserve or 50% of heart rate reserve. Seven of the 8 subjects increased their maximum work capability after training with the GameCycle at least 3 times per week for 16 weeks.

Conclusions: The data suggest that the GameCycle seems to be adequate as an exercise device to improve oxygen uptake and maximum work capability in adolescents with lower extremity disability caused by spinal cord dysfunction. The subjects in this study reported that the video game component was enjoyable and provided a motivation to exercise.     

Extracorporeal membrane oxygenation for neonatal respiratory failure. A report of 50 cases

From February 1985 through June 1987, 50 newborn infants in whom maximal ventilator therapy failed (80% predicted mortality) were treated with extracorporeal membrane oxygenation (ECMO) according to the following inclusion criteria: arterial oxygen tension less than 50 torr (alveolar-arterial oxygen gradient greater than 630 torr) for 2 hours or arterial oxygen tension less than 60 torr (alveolar-arterial oxygen gradient greater than 620 torr) for 8 hours. Criteria for exclusion from ECMO therapy included birth weight less than 2000 gm, gestational age less than 35 weeks, presence of intracranial hemorrhage, presence of other major congenital anomalies including cyanotic heart disease, and high levels of ventilatory support for more than 7 days. Mean birth weight was 3.28 +/- 0.56 kg, mean gestational age was 39.6 +/- 1.7 weeks, and mean age at the start of ECMO was 48.6 +/- 36.9 hours. Meconium aspiration, usually associated with persistent pulmonary hypertension, was the most common cause of pulmonary failure (62%). Mean pre-ECMO arterial oxygen tension during maximal ventilatory and pharmacologic support was 34.5 +/- 14.5 torr. Mean ventilatory support immediately before the institution of ECMO was as follows: peak inspiratory pressure 46.8 +/- 9.9 cm H2O, positive end-expiratory pressure 4.6 +/- 1.6 cm H2O, and intermittent mandatory ventilation rate 101.0 +/- 22.7 breaths/min with all patients receiving an inspired oxygen fraction of 1.0. Lung management to prevent pulmonary atelectasis during ECMO consisted of moderate levels of positive end-expiratory pressure (mean 10.3 +/- 2.6 cm H2O, range 8 to 14 in 94% of patients. Other mean ventilator parameters during ECMO were as follows: peak inspiratory pressure 22.8 +/- 1.6 cm H2O, intermittent mandatory ventilation rate 11.8 +/- 2.9, and inspired oxygen fraction 0.21. The overall long-term patient survival rate was 90%. Mean values for arterial blood gases and ventilator settings immediately after the discontinuation of ECMO were as follows: oxygen tension 78.4 +/- 22.1 torr, pH 7.39 +/- 0.10, carbon dioxide tension 37.4 +/- 10.7 torr, peak inspiratory pressure 25.2 +/- 3.9 cm H2O, positive end-expiratory pressure 5.6 +/- 1.2 cm H2O, and intermittent mandatory ventilation rate 41.3 +/- 12.6 with an inspired oxygen fraction of 0.42 +/- 0.17. Despite slightly higher levels of ventilator support (peak inspiratory pressure 46.8 versus 45.0 cm H2O, not significant) mean pre-ECMO oxygen tension was significantly lower than that reported from the National ECMO Registry (34.5 versus 42.0 torr, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)     

Thirteen-year experience in lung transplantation for emphysema

BACKGROUND: Emphysema is the most common indication for lung transplantation. Recipients include younger patients with genetically determined alpha-1 antitrypsin deficiency (AAD) and, more commonly, patients with chronic obstructive pulmonary disease (COPD). We analyzed the results of our single-institution series of lung transplants for emphysema to identify outcome differences and factors predicting mortality and morbidity in these two groups. METHODS: A retrospective analysis was undertaken of the 306 consecutive lung transplants for emphysema performed at our institution between 1988 and 2000 (220 COPD, 86 AAD). Follow-up was complete and averaged 3.7 years. RESULTS: The mean age of AAD recipients (49 +/- 6 years) was less than those with COPD (55 +/- 6 years; p < 0.001). Hospital mortality was 6.2%, with no difference between COPD and AAD, or between single-lung transplants and bilateral-lung transplants. Hospital mortality during the most recent 6 years was significantly lower (3.9% vs 9.5%, p = 0.044). Five-year survival was 58.6% +/- 3.5%, with no difference between COPD (56.8% +/- 4.4%) and AAD (60.5% +/- 5.8%). Five-year survival was better with bilateral-lung transplants (66.7% +/- 4.0%) than with single-lung transplants (44.9% +/- 6.0%, p < 0.005). Independent predictors of mortality by Cox analysis were single lung transplantation (relative hazard = 1.98, p < 0.001), and need for cardiopulmonary bypass during the transplant (relative hazard = 1.84, p = 0.038). CONCLUSIONS: AAD recipients, despite a younger age, do not achieve significantly superior survival results than those with COPD. Bilateral lung transplantation for emphysema results in better long-term survival. Accumulated experience and modifications in perioperative care over our 13-year series may explain recently improved early and long-term survival.