Skeletal muscle oxidative capacity, fiber type, and metabolites after lung transplantation

Postoperative conditions of rehabilitative interest in lung transplantation: a systematic review

Lung transplantation is an elective treatment option for end-stage respiratory diseases in which all medical therapy options have been exhausted. The current study aimed to identify updated information on the postoperative conditions that may impair rehabilitation after lung transplantation and to provide specific considerations of their clinical relevance during the recovery process. The present study is a systematic review conducted by searching three primary databases: the United States National Library of Medicine PubMed system, Scopus, and the Cochrane Library. The databases were searched for articles published from database inception until May 2024; at the end of the selection process, 27 documents were included in the final analysis. The retrieved material identified 19 conditions of rehabilitative interest that potentially affect the postoperative course: graft dysfunction, dysphagia, postsurgical pain, cognitive impairment, chronic lung allograft dysfunction-bronchiolitis obliterans syndrome, phrenic nerve injury, delayed extracorporeal membrane oxygenation weaning, airway clearance, refractory hypoxemia, mediastinitis, reduced oxidative capacity, sternal dehiscence, coronavirus disease 2019 (COVID-19), gastroparesis, ossification of the elbow, Takotsubo cardiomyopathy, airway dehiscence, recurrent pleural effusion, and scapular prolapse. Although some patients are not amenable to rehabilitation techniques, others can significantly improve with rehabilitation.

Orthostatic Hypotension and Concurrent Autonomic Dysfunction: A Novel Complication of Lung Transplantation

Background

Persistent orthostatic hypotension (OH) is a lesser-known complication of lung transplantation (LTx). In this retrospective case series, we describe the clinical manifestations, complications, and treatment of persistent OH in 13 LTx recipients.

Methods

We identified LTx recipients who underwent transplantation between March 1, 2018, and March 31, 2020, with persistent symptomatic OH and retrospectively queried the records for clinical information.

Results

Thirteen patients were included in the analysis, 9 (69%) had underlying pulmonary fibrosis, and 12 (92%) were male. The median age, height, and body mass index at LTx were 68 years, 70 inches, and 27 kg/m², respectively. Six (46%) patients were deceased at the time of chart abstraction with a median (IQR) posttransplant survival of 12.6 months (6, 21); the 7 remaining living patients were a median of 19.6 months (18, 32) posttransplant. Signs and symptoms of OH developed a median of 60 (7, 75) days after transplant. Patients were treated with pharmacological agents and underwent extensive physical therapy. Most patients required inpatient rehabilitation (n = 10, 77%), and patients commonly developed comorbid conditions including weight loss, renal insufficiency with eGFR <50 (n = 13, 100%), gastroparesis (n = 7, 54%), and tachycardia-bradycardia syndrome (n = 2, 15%). Falls were common (n = 10, 77%). The incidence of OH in LTx recipients at our center during the study period was 5.6% (13/234).

Conclusions

Persistent OH is a lesser-known complication of LTx that impacts posttransplant rehabilitation and may lead to comorbidities and shortened survival. In addition, most LTx recipients with OH at our center were tall, thin men with underlying pulmonary fibrosis, which may offer an opportunity to instate pretransplant OH screening of at-risk patients.

Does branched-chain amino acid supplementation improve pulmonary rehabilitation effect in COPD?

BACKGROUND

Muscle wasting is frequent in chronic obstructive lung disease (COPD) and associated with low branched-chain amino acids (BCAA). We hypothesized that BCAA supplementation could potentiate the effect of a pulmonary rehabilitation program (PRP) by inducing muscular change.

MATERIALS AND METHODS

Sixty COPD patients (GOLD 2-3) were involved in an ambulatory 4-week PRP either with BCAA oral daily supplementation or placebo daily supplementation in a randomized double-blind design. Maximal exercise test including quadriceps oxygenation measurements, functional exercise test, muscle strength, lung function tests, body composition, dyspnea and quality of life were assessed before and after PRP.

RESULTS

Fifty-four patients (64.9 ± 8.3 years) completed the protocol. In both groups, maximal exercise capacity, functional and muscle performances, quality of life and dyspnea were improved after 4-week PRP (p ≤ 0.01). Changes in muscle oxygenation during the maximal exercise and recovery period were not modified after 4-week PRP in BCAA group. Contrarily, in the placebo group the muscle oxygenation kinetic of recovery was slowed down after PRP.

CONCLUSION

This study demonstrated that a 4-week PRP with BCAA supplementation is not more beneficial than PRP alone for patients. A longer duration of supplementation or a more precise targeting of patients would need to be investigated to validate an effect on muscle recovery and to demonstrate other beneficial effects.

Addressing the changing rehabilitation needs of patients undergoing thoracic surgery

The rehabilitation needs of individuals undergoing thoracic surgery are changing, especially as surgical management is increasingly being offered to patients who are at risk of developing functional limitations during and after hospital discharge. In the past rehabilitative management of these patients was frequently limited to specific respiratory physiotherapy interventions in the immediate postoperative setting with the aim to prevent postoperative pulmonary complications. In the past two decades, this focus has shifted toward pulmonary rehabilitation interventions that aim to improve functional status of individuals, both in the pre- and (longer-term) postoperative period. While there is increased interest in (p)rehabilitation interventions the majority of thoracic surgery patients are however currently on their own with respect to progression of their exercise and physical activity regimens after they have been discharged from hospital. There are also no formal guidelines supporting the referral of these patients to outpatient rehabilitation programs. The current evidence regarding rehabilitation interventions initiated before, during, and after the hospitalization period will be briefly reviewed with special focus on patients undergoing surgery for lung cancer treatment and patients undergoing lung transplantation. More research will be necessary in the coming years to modify or change clinical rehabilitation practice beyond the acute admission phase in patients undergoing thoracic surgery. Tele rehabilitation or web-based activity counseling programs might also be interesting emerging alternatives in the (long-term) postoperative rehabilitative treatment of these patients.

Dyspnea, effort and muscle pain during exercise in lung transplant recipients: an analysis of their association with cardiopulmonary function parameters using machine learning

Background

Despite improvement in lung function, most lung transplant (LTx) recipients show an unexpectedly reduced exercise capacity that could be explained by persisting peripheral muscle dysfunction of multifactorial origin. We analyzed the course of symptoms, including dyspnea, muscle effort and muscle pain and its relation with cardiac and pulmonary function parameters during an incremental exercise testing.

Methods

Twenty-four bilateral LTx recipients were evaluated in an observational cross-sectional study. Recruited patients underwent incremental cardio-pulmonary exercise testing (CPET). Arterial blood gases at rest and peak exercise were measured. Dyspnea, muscle effort and muscle pain were scored according to the Borg modified scale. Potential associations between the severity of symptoms and exercise testing parameters were analyzed using a Forest-Tree Machine Learning approach, which accomplishes for a ratio between number of observations and number of screened variables less than unit.

Results

Dyspnea score was significantly associated with maximum power output (WR, watts), and minute ventilation (VE, L/min) at peak exercise. In a controlled subgroup analysis, dyspnea score was a limiting symptom only in LTx recipients who reached the higher levels of WR (≥ 101 watts) and V_E (≥ 53 L/min). Muscle effort score was significantly associated with breathing reserve as percent of maximal voluntary ventilation (BR%MVV). The lower the BR%MVV at peak exercise (< 32) the higher the muscle effort perception. Muscle pain score was significantly associated with VO₂ peak, arterial [HCO₃⁻] at rest, and V_E/VCO₂ slope. In a subgroup analysis, muscle pain was the limiting symptom in LTx recipients with a lower VO₂ peak (< 15 mL/Kg/min) and a higher V_E/VCO₂ slope (≥ 32).

Conclusions

The majority of our LTx recipients reported peripheral limitation as the prevalent reason for exercise termination. Muscle pain at peak exercise was strictly associated with basal and exercise-induced metabolic altered pathways. The onset of dyspnea (breathing effort) was associated with the intensity of ventilatory response to meet metabolic demands for increasing WR. Our study suggests that only an accurate assessment of symptoms combined with cardio-pulmonary parameters allows a correct interpretation of exercise limitation and a tailored exercise prescription. The role and mechanisms of muscle pain during exercise in LTx recipients requires further investigations.

The Efficacy of Outpatient Pulmonary Rehabilitation After Bilateral Lung Transplantation

PURPOSE

Pulmonary rehabilitation (PR) is advocated in the pre- and post-lung transplantation (LTx) periods. However, there is limited literature on the benefit of PR post-LTx. The aim of this study was to investigate the efficacy of an outpatient, multidisciplinary, comprehensive PR program in bilateral LTx recipients in the early period after LTx.

METHOD

Twenty-three LTx recipients were referred to the PR center. Change in incremental and endurance shuttle walk tests, hand and quadriceps strength, respiratory muscle strength (maximum inspiratory/expiratory pressure), dyspnea (Medical Research Council score), quality of life (St George's Respiratory Questionnaire, Chronic Respiratory Questionnaire), and psychological status (Hospital Anxiety Depression Scale) were compared pre- and post-PR.

RESULTS

Seventeen of 23 (74%) recipients completed PR, comprising 15 male and 2 female patients whose median age was 51 yr. The initiation of the program was 75 ± 15 d after LTx. The incremental shuttle walk test distance was predicted as 23% before PR and it increased to 36% after PR (P < .001); the endurance shuttle walk test distance also increased (P < .01). Significant improvement was seen in upper and lower extremity strength, and St George's Respiratory Questionnaire and Chronic Respiratory Questionnaire scores and Hospital Anxiety Depression Scale scores reflected less anxiety and depressive symptoms. Furthermore, body mass and fat-free mass indices, maximum inspiratory pressure, and maximum expiratory pressure improved significantly. There was no significant change in forced expiratory volume in the first second of expiration, forced vital capacity, or Medical Research Council scores.

CONCLUSION

This study demonstrated that patients who attended PR within 3 mo of bilateral LTx showed improvements in exercise capacity, respiratory muscle strength, quality of life, body composition, and psychological status.

The Utility of the Sit-to-Stand Test for Inpatients in the Acute Hospital Setting After Lung Transplantation

OBJECTIVE

Measurement of physical function is important to guide physical therapy for patients post-lung transplantation (LTx). The Sit-to-Stand (STS) test has proven utility in chronic disease, but psychometric properties post-LTx are unknown. The study aimed to assess reliability, validity, responsiveness, and feasibility of the 60-second STS post-LTx.

METHODS

This was a measurement study in 62 inpatients post-LTx (31 acute postoperative; 31 medical readmissions). Interrater reliability was assessed with 2 STS tests undertaken by different assessors at baseline. Known group validity was assessed by comparing STS repetitions in postoperative and medical groups. Content validity was assessed using comparisons to knee extensor and grip strength, measured with hand-held dynamometry. Criterion validity was assessed by comparison of STS repetitions and 6-minute walk distance postoperatively. Responsiveness was assessed using effect sizes over inpatient admission.

RESULTS

Median (interquartile range) age was 62 (56-67) years; time post-LTx was 5 (5-7) days postoperative and 696 (244-1849) days for medical readmissions. Interrater reliability was excellent (intraclass correlation coefficient type 2,1 = 0.96), with a mean learning effect of 2 repetitions. Repetitions were greater for medical at baseline (mean 18 vs 8). More STS repetitions were associated with greater knee extensor strength (postoperative r = 0.57; medical r = 0.47) and 6-minute walk distance (postoperative r = 0.68). Effect sizes were 0.94 and 0.09, with a floor effect of 23% and 3% at baseline (postoperative/medical) improving to 10% at discharge. Patients incapable of attempting a STS test were excluded, reducing generalizability to critical care. Physical rehabilitation was not standardized, possibly reducing responsiveness.

CONCLUSIONS

The 60-second STS demonstrated excellent interrater reliability and moderate validity and was responsive to change postoperatively.

IMPACT

The 60-second STS represents a safe, feasible functional performance tool for inpatients post-LTx. Two tests should be completed at each time point.

Frailty after lung transplantation is associated with impaired health-related quality of life and mortality

BACKGROUND

Lung transplantation and related medications are associated with pathobiological changes that can induce frailty, a state of decreased physiological reserve. Causes of persistent or emergent frailty after lung transplantation, and whether such transplant-related frailty is associated with key outcomes, are unknown.

METHODS

Frailty and health-related quality of life (HRQL) were prospectively measured repeatedly for up to 3 years after lung transplantation. Frailty, quantified by the Short Physical Performance Battery (SPPB), was tested as a time-dependent binary and continuous predictor. The association of transplant-related frailty with HRQL and mortality was evaluated using mixed effects and Cox regression models, respectively, adjusting for age, sex, ethnicity, diagnosis, and for body mass index and lung function as time-dependent covariates. We tested the association between measures of body composition, malnutrition, renal dysfunction and immunosuppressants on the development of frailty using mixed effects models with time-dependent predictors and lagged frailty outcomes.

RESULTS

Among 259 adults (56% male; mean age 55.9±12.3 years), transplant-related frailty was associated with lower HRQL. Frailty was also associated with a 2.5-fold higher mortality risk (HR 2.51; 95% CI 1.21 to 5.23). Further, each 1-point worsening in SPPB was associated, on average, with a 13% higher mortality risk (HR 1.13; 95% CI 1.04 to 1.23). Secondarily, we found that sarcopenia, underweight and obesity, malnutrition, and renal dysfunction were associated with the development of frailty after transplant.

CONCLUSIONS

Transplant-related frailty is associated with lower HRQL and higher mortality in lung recipients. Abnormal body composition, malnutrition and renal dysfunction may contribute to the development of frailty after transplant. Confirming the role of these potential contributors and developing interventions to mitigate frailty may improve lung transplant success.

Sarcopenia of the Psoas Muscles Is Associated With Poor Outcomes Following Lung Transplantation

BACKGROUND

Sarcopenia, a known component of frailty, defined by diminished cross-sectional area of the psoas muscles, is associated with poor outcomes after a range of surgical procedures. However, little is known of the relationship between sarcopenia of the psoas muscles (SPM) and long-term survival, decline in pulmonary function, and graft failure after lung transplantation.

METHODS

We reviewed patients who underwent primary lung transplantation at our institution from 2011 to 2014. Cross-sectional areas of the psoas muscles at the L4 vertebral level were measured using preoperative computed tomography. Gender-based cutoff values for sarcopenia were generated and validated. The primary outcomes were 1-, 2-, and 3-year all-cause mortality, forced expiratory volume in 1 second values, and graft function. Adjusted logistic regression and survival analysis was used to analyze outcomes.

RESULTS

Ninety-five patients were included in this study; 39 (41.1%) patients were considered sarcopenic. SPM was significantly associated with short-term and midterm mortality on multivariate analysis (1 year: odds ratio [OR], 8.7, p = 0.017; 2 years: OR, 12.7, p < 0.01; 3 years: OR, 13.4, p < 0.01). Survival analysis showed significantly decreased survival in sarcopenic patients at 3 years (35.9% versus 76.8%; p < 0.01). SPM is also associated with decreased forced expiratory volume in 1 second (coefficient, -17.3; p = 0.03). Adjusted Cox analysis showed an increased hazard for all-cause mortality (hazard ratio, 5.8, p < 0.01) and graft failure (hazard ratio, 14.7, p < 0.01) in sarcopenic patients.

CONCLUSIONS

This study demonstrates a significant association between SPM and death, pulmonary function, and graft failure in patients receiving a lung transplant. Determining SPM preoperatively may be a useful component of frailty assessment and a predictor of survival in this patient population.

Physical Activity, Sedentary Time, and Associated Factors in Recipients of Solid-Organ Transplantation

BACKGROUND

Short-term survival after solid-organ transplantation has substantially improved, and the focus has shifted to long-term survival, including the role of physical activity (PA). Knowledge about PA and sedentary time in recipients of solid-organ transplantation is limited, and identification of the levels and associated factors is necessary for intervention development.

OBJECTIVE

The objectives of this study were to investigate the level of PA and sedentary time in recipients of solid-organ transplantation and to identify factors associated with these behaviors.

DESIGN

The design consisted of a cross-sectional survey.

METHODS

Questionnaires on PA level, sedentary time, and potential associated factors were used for recipients of solid-organ transplantation (kidney, liver, lung, and heart [N = 656]). Multiple regression analyses with a variable selection procedure were used.

RESULTS

Fewer than 60% of the recipients fulfilled the PA guideline. Factors significantly associated with a lower level of PA included being a woman, younger age (nonlinear), not actively working or being retired, physical limitations, and low expectations and self-confidence. Factors significantly associated with less sedentary time included exercise self-efficacy and not actively working or being retired. Significantly associated with more sedentary time were a high education level, fear of negative effects, physical limitations, and the motivator "health and physical outcomes." The type of transplantation did not significantly influence either of the outcome measures.

LIMITATIONS

The design did not allow for causal inferences to be made. The studied associated factors were limited to individual and interpersonal factors. Self-reported measures of PA and sedentary time were used.

CONCLUSIONS

In intervention development directed at increasing the level of PA and reducing sedentary time in recipients of solid-organ transplantation, attention should be paid to physical limitations, fear of negative effects, low expectations and self-confidence, health and physical outcomes, and exercise self-efficacy.

Effects of aging and comorbidities on nutritional status and muscle dysfunction in patients with COPD

Chronic obstructive pulmonary disease (COPD) is a prevalent, complex and debilitating disease which imposes a formidable burden on patients and the healthcare system. The recognition that COPD is a multifaceted disease is not new, and increasing evidence have outlined the importance of its extra-pulmonary manifestations and its relation to other comorbid conditions in the clinical course of the disease and its societal cost. The relationship between aging, COPD and its comorbidities on skeletal muscle function and nutritional status is complex, multidirectional and incompletely understood. Despite this, the current body of knowledge allows the identification of various, seemingly partially independent factors related both to the normal aging process and to the independent deleterious effects of chronic diseases on muscle function and body composition. There is a dire need of studies evaluating the relative contribution of each of these factors, and their potential synergistic effects in patients with COPD and advanced age/comorbid conditions, in order to delineate the best course of therapeutic action in this increasingly prevalent population.

Longer Versus Shorter Duration of Supervised Rehabilitation After Lung Transplantation: A Randomized Trial

OBJECTIVE

To investigate the effects of a supervised longer- (14wk) versus shorter-duration (7wk) rehabilitation program after lung transplantation (LTX).

DESIGN

Randomized controlled trial.

SETTING

Outpatient rehabilitation gym setting.

PARTICIPANTS

Post-LTX patients aged ≥18 years (N=66; 33 women; mean age, 51±13y) who had undergone either single LTX or bilateral LTX.

INTERVENTION

Outpatient rehabilitation program consisting of thrice-weekly sessions with cardiovascular training on bike ergometer and treadmill plus upper and lower limb strength training.

MAIN OUTCOME MEASURES

Measures were taken at baseline, 7 weeks, 14 weeks, and 6 months by assessors who were blinded to group allocation. Functional exercise capacity was measured by the 6-minute walk test (6MWT). Strength of quadriceps and hamstrings was measured on an isokinetic dynamometer and recorded as average peak torque of 6 repetitions for both muscles. Quality of life (QOL) was assessed with the Medical Outcomes Study 36-Item Short-Form Health Survey.

RESULTS

Of the participants, 86% had bilateral LTX and 41% had primary diagnosis of chronic obstructive pulmonary disease. The 6MWT increased in both groups with no significant difference between groups at any time point (mean 6mo 6MWD: short, 590±85m vs long, 568±127m; P=0.5). Similarly, at 6 months, there was no difference between groups in quadriceps average peak torque (mean, 115±38Nm vs 114±40Nm, respectively; P=.59), hamstring average peak torque (57±18Nm vs 52±19Nm, respectively; P=.36), or mental or physical health domains of quality of life.

CONCLUSIONS

Shorter duration (7wk) of rehabilitation achieves comparable outcomes with 14 weeks of supervised rehabilitation for functional exercise capacity, lower limb strength, and quality of life at 6 months after LTX.

Perceived Barriers to and Facilitators of Physical Activity in Recipients of Solid Organ Transplantation, a Qualitative Study

Background

Sufficient physical activity is important for solid organ transplant recipients (heart, lung, liver, kidney). However, recipients do not meet the recommended amount or required type of physical activity. The perceived barriers to and facilitators of physical activity in this population are largely unknown.

Methods

Semi-structured in depth interviews were conducted with solid organ transplant recipients in order to explore experienced barriers and facilitators. Qualitative methodology with thematic line-by-line analysis was used for analysis, and derived themes were classified into personal and environmental factors.

Results

The most important indicated barriers were physical limitations, insufficient energy level, fear, and comorbidities. The most frequently mentioned facilitators included motivation, coping, consequences of (in)activity, routine/habit, goals/goal priority, and responsibility for the transplanted organ. Neutral factors acting as a barrier or facilitator were self-efficacy and expertise of personnel. A comparison of barriers and facilitators between transplant recipient groups yielded no overt differences.

Conclusion

Several personal and environmental factors were indicated that should be considered in intervention development to increase physical activity behavior in solid organ transplant recipients.

Magnetic stimulation supports muscle and nerve regeneration after trauma in mice

INTRODUCTION

Magnetic stimulation (MS) has the ability to induce muscle twitch and has long been proposed as a therapeutic modality for skeletal muscle diseases. However, the molecular mechanisms underlying its means of action have not been defined.

METHODS

Muscle regeneration after trauma was studied in a standard muscle injury mouse model. The influence of MS on the formation of motor units, posttrauma muscle/nerve regeneration, and vascularization was investigated.

RESULTS

We found that MS does not cause systemic or muscle damage but improves muscle regeneration by significantly minimizing the presence of inflammatory infiltrate and formation of scars after trauma. It avoids posttrauma muscle atrophy, induces muscle hypertrophy, and increases the metabolism and turnover of muscle. It triples the expression of muscle markers and significantly improves muscle functional recovery after trauma.

CONCLUSIONS

Our results indicate that MS supports muscle and nerve regeneration by activating muscle-nerve cross-talk and inducing the maturation of neuromuscular junctions.

Predicting 6-minute walking distance in recipients of lung transplantation: longitudinal study of 108 patients

BACKGROUND

Exercise capacity, muscle function, and physical activity levels remain reduced in recipients of lung transplantation. Factors associated with this deficiency in functional exercise capacity have not been studied longitudinally.

OBJECTIVE

The study aims were to analyze the longitudinal change in 6-minute walking distance and to identify factors contributing to this change.

DESIGN

This was a longitudinal historical cohort study.

METHODS

Data from patients who received a lung transplantation between March 2003 and March 2013 were analyzed for the change in 6-minute walking distance and contributing factors at screening, discharge, and 6 and 12 months after transplantation. Linear mixed-model and logistic regression analyses were performed with data on characteristics of patients, diagnosis, waiting list time, length of hospital stay, rejection, lung function, and peripheral muscle strength.

RESULTS

Data from 108 recipients were included. Factors predicting 6-minute walking distance were measurement moment, diagnosis, sex, quadriceps muscle and grip strength, forced expiratory volume in 1 second (percentage of predicted), and length of hospital stay. After transplantation, 6-minute walking distance increased considerably. This initial increase was not continued between 6 and 12 months. At 12 months after lung transplantation, 58.3% of recipients did not reach the cutoff point of 82% of the predicted 6-minute walking distance. Logistic regression demonstrated that discharge values for forced expiratory volume in 1 second and quadriceps or grip strength were predictive for reaching this criterion.

LIMITATIONS

Study limitations included lack of knowledge on the course of disease during the waiting list period, type and frequency of physical therapy after transplantation, and number of missing data points.

CONCLUSIONS

Peripheral muscle strength predicted 6-minute walking distance; this finding suggests that quadriceps strength training should be included in physical training to increase functional exercise capacity. Attention should be paid to further increasing 6-minute walking distance between 6 and 12 months after transplantation.

Rehabilitation in Patients before and after Lung Transplantation

Lung transplantation is an established treatment for patients with end-stage lung disease. It has been observed that despite near-normal lung function, exercise intolerance and reductions in quality of life (QOL) often persist up to years after transplantation. Several modifiable pre- and posttransplant factors are known to contribute to these persisting impairments. Physiological changes associated with severe and chronic lung disease, limb muscle dysfunction, inactivity/deconditioning, and nutritional depletion can affect exercise capacity and physical functioning in candidates for lung transplantation. After transplantation, extended hospital and intensive care unit stay, prolonged sedentary time, persisting inactivity, immunosuppressant medications and episodes of organ rejection may all impact lung recipients' recovery. Available evidence will be reviewed and content will be proposed (both evidence and experience based) for rehabilitation interventions prior to transplantation, during hospitalization after transplantation, and in both the immediate (≤12 months after hospital discharge) and long-term (>12 months after hospital discharge) posttransplant phase. Outpatient rehabilitation programs including supervised exercise training have been shown to be effective in improving limb muscle dysfunction, exercise capacity, and QOL both before and after transplantation if offered appropriately. Unmet research needs included the absence of sufficiently powered randomized controlled trials measuring the effects of rehabilitation interventions on crucial long-term outcomes such as sustained improvements in QOL, participation in daily activity, survival, incidence of morbidities and cost-effectiveness. Remotely monitored (telehealth) home-based exercise or pedometer-based walking interventions might be interesting alternatives to supervised outpatient rehabilitation interventions in the long-term posttransplant phase and warrant further investigation.

Functional capacity after pediatric liver transplantation: a pilot study

The prospective cross-sectional study investigated the 6MWT performance in pediatric group of liver transplant recipients (6-17 yr, median post-transplantation time of 22 months) and compared to the normal values obtained in healthy children as well as evaluated the reproducibility of the 6MWT. We analyzed the relationship between walked distance and the 6MWw, distance walked × body weight) with the anthropometric, clinical, and pulmonary functions. In post-transplanted group, the average walked distance was significantly shorter compared with control (687 ± 80 m vs. 511 ± 72 m, p < 0.001). The calculated ICC coefficient confirmed the reproducibility among tests. The Pearson correlation revealed that only walked distance in the 6MWT was moderately correlated with tidal volume. Conversely, the 6MWw was significantly correlated with age, weight, height, BMI, FVC, PEF rate, and volume expiratory. According to multiple regression analysis, age, VE and FVC factors explained 80% of the variance in the 6MWw. In conclusion, the pediatric liver transplant recipients' performance in the 6MWT is significantly lower than the values for healthy children of the same age. Notably, the 6MWw may provide relevant information, constituting an additional parameter in the determination of functional capacity.

Solid organ transplant recipients: clinical considerations in the application of exercise

Over 100 000 solid organ transplants are performed worldwide each year and this has a significant impact on physical function and quality of life. However, the capacity for exercise in solid-organ recipients is reduced. Regular physical activity improves most of the indices of fitness in these patients but, with few exceptions, they do not reach the values seen in healthy controls. The reason for the 40-60% reduction in maximal exercise capacity is not clear; the disease process, need for life long immunosuppression and sedentary lifestyle all contribute. The interaction between exercise and immunosuppressing medication merits research as does the specifics of the exercise prescription for these patients. This paper reviews important features of this rapidly expanding group of patients and suggests clinical considerations in the application of exercise in this population.

Pulmonary rehabilitation for respiratory disorders other than chronic obstructive pulmonary disease

Pulmonary rehabilitation (PR) is an important therapeutic intervention that should no longer be considered suitable only for patients with chronic obstructive pulmonary disease (COPD). A strong rationale exists for providing PR to persons with a broad range of respiratory disorders other than COPD. Evidence shows that PR for these patients is feasible, safe and effective. A disease-relevant approach should be undertaken, based on individual patients' needs. Further research is needed to better understand the optimal program content, duration and outcomes measures, to enable diverse patients to achieve maximal benefits of PR.

Sarcopenia in lung transplantation: a systematic review

Lung transplant candidates and recipients have significant impairments in skeletal muscle mass, strength and function--individual measures of sarcopenia. Skeletal muscle dysfunction has been observed in the pre-transplant and post-transplant period and could have an important effect on transplant outcomes. A systematic review was performed to characterize the techniques used to study sarcopenia and assess the level of impairment throughout the transplant process. Electronic databases were searched (inception to July 2013) for prospective studies measuring at least 1 element of sarcopenia (muscle mass, strength, or function) in lung transplant patients. Eighteen studies were included, and study quality was assessed using the Downs and Black scale. A variety of measurements were used to evaluate sarcopenia in 694 lung transplant patients. Muscle mass in 7 studies was assessed using bioelectrical impedance (n = 4), computed tomography or magnetic resonance imaging (n = 2), or skin folds (n = 1), and was significantly reduced. Quadriceps strength was examined in 14 studies with computerized dynamometer (n = 10) and hand-held dynamometer (n = 4). Quadriceps strength was reduced in the pre-transplant period (mean range, 49%-86% predicted; n = 455 patients), further reduced immediately after transplant (51%-72%, n = 126), and improved beyond 3 months after transplant (58%-101%, n = 164). Only 2 studies measured lower extremity function (sit-to-stand test). A multitude of measurement techniques have been used to assess individual measures of sarcopenia, with reduced muscle mass and quadriceps strength observed in the pre-transplant and post-transplant period. Further standardization of measurement techniques is needed to assess the clinical effect of sarcopenia in lung transplantation.

Patients' expectations and experiences of rehabilitation following lung transplantation

INTRODUCTION

Exercise rehabilitation is a key element of care following lung transplantation; however, little is known about the patients' experience of rehabilitation, or whether it meets the needs of this complex patient group. This qualitative study explored patients' expectations of a supervised exercise rehabilitation program following lung transplantation.

METHODS

Participants undertook two semi-structured interviews, one before and one after the rehabilitation program. Interviews were digitally recorded, and themes were developed using line-by-line iterative thematic analysis and grounded theory.

RESULTS

Eighteen adults (11 females) with mean age of 52 participated in a mean of 26 sessions of exercise training. Themes were (i) desire for normalcy including resuming family roles and performing everyday activities; (ii) the importance of rehabilitation as the mechanism for how this transformation occurred; (iii) the benefits of exercising in a group setting; and (iv) the limitations on rehabilitation that were imposed by comorbidities, either existing pre-transplant or occurring as a postoperative sequelae.

CONCLUSION

Post-transplant exercise rehabilitation was perceived as a highly valuable tool that assisted recipients to return to "normal life." Group exercise was motivational, offered peer support, and therefore was advantageous to assist patients to achieve their desired physical performance level following transplantation.

Exercise limitation following transplantation

Organ transplantation is one of the medical miracles or the 20th century. It has the capacity to substantially improve exercise performance and quality of life in patients who are severely limited with chronic organ failure. We focus on the most commonly performed solid-organ transplants and describe peak exercise performance following recovery from transplantation. Across all of the common transplants, evaluated significant reduction in VO2peak is seen (typically renal and liver 65%-80% with heart and/or lung 50%-60% of predicted). Those with the lowest VO2peak pretransplant have the lowest VO2peak posttransplant. Overall very few patients have a VO2peak in the normal range. Investigation of the cause of the reduction of VO2peak has identified many factors pre- and posttransplant that may contribute. These include organ-specific factors in the otherwise well-functioning allograft (e.g., chronotropic incompetence in heart transplantation) as well as allograft dysfunction itself (e.g., chronic lung allograft dysfunction). However, looking across all transplants, a pattern emerges. A low muscle mass with qualitative change in large exercising skeletal muscle groups is seen pretransplant. Many factor posttransplant aggravate these changes or prevent them recovering, especially calcineurin antagonist drugs which are key immunosuppressing agents. This results in the reduction of VO2peak despite restoration of near normal function of the initially failing organ system. As such organ transplantation has provided an experiment of nature that has focused our attention on an important confounder of chronic organ failure-skeletal muscle dysfunction.

An official American Thoracic Society/European Respiratory Society statement: key concepts and advances in pulmonary rehabilitation

BACKGROUND

Pulmonary rehabilitation is recognized as a core component of the management of individuals with chronic respiratory disease. Since the 2006 American Thoracic Society (ATS)/European Respiratory Society (ERS) Statement on Pulmonary Rehabilitation, there has been considerable growth in our knowledge of its efficacy and scope.

PURPOSE

The purpose of this Statement is to update the 2006 document, including a new definition of pulmonary rehabilitation and highlighting key concepts and major advances in the field.

METHODS

A multidisciplinary committee of experts representing the ATS Pulmonary Rehabilitation Assembly and the ERS Scientific Group 01.02, "Rehabilitation and Chronic Care," determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant clinical and scientific expertise. The final content of this Statement was agreed on by all members.

RESULTS

An updated definition of pulmonary rehabilitation is proposed. New data are presented on the science and application of pulmonary rehabilitation, including its effectiveness in acutely ill individuals with chronic obstructive pulmonary disease, and in individuals with other chronic respiratory diseases. The important role of pulmonary rehabilitation in chronic disease management is highlighted. In addition, the role of health behavior change in optimizing and maintaining benefits is discussed.

CONCLUSIONS

The considerable growth in the science and application of pulmonary rehabilitation since 2006 adds further support for its efficacy in a wide range of individuals with chronic respiratory disease.

Impaired exercise capacity after lung transplantation is related to delayed recovery of muscle strength

Lung transplant recipients report reduced exercise capacity despite satisfactory graft function. We analysed changes in lung function, six-min walk distance (6MWD), and quadriceps strength in the first 26-wk post-transplant and examined what factors predict 6MWD recovery. All lung transplant recipients at a single institution between June 2007 and January 2011 were considered for inclusion. Lung function, 6MWD, and quadriceps strength corrected for body weight (QS%) were recorded pre- and two-, six-, 13-, and 26-wk post-transplant. Fifty recipients, of mean (± SD) age 42 (± 13) yr, were studied. Mean FEV1 % and 6MWD improved from 26.4% to 88.9% and from 397 to 549 m at 26 wk, respectively (both p < 0.001). QS% declined in the first two wk but had improved to above pre-transplant levels by 26 wk (p = 0.027). On multivariate analysis (n = 35), lower pre-transplant exercise capacity and greater recovery in muscle strength explained most of the improvement in exercise capacity. Delayed recovery of exercise capacity after lung transplantation is unrelated to delay in improvement in graft function, but occurs secondary to the slow recovery of muscle strength. Our findings show that additional controlled trials are needed to better understand the influence of exercise rehabilitation on improvement in exercise capacity post-transplantation.

The influence of clinical course after lung transplantation on rehabilitation success

Pulmonary rehabilitation (PR) is a cornerstone of treatment following lung transplantation (LTx). The aim of this study was to observe the influence of a prolonged postsurgical clinical course on success of a 3-week inpatient PR. LTx recipients were divided according to their clinical course defined by their individual length of stay (LOS) in the transplant center (cohort 1: LOS >; cohort 2: ≤42 days). Peak work rate (PWR), maximum oxygen uptake (VO(2max) ), 6-min walk distance (6-MWD), vital capacity (VC), forced expiratory volume in one second (FEV1), physical activity of daily life (ADL), and health-related quality of life (HRQoL) measured using Short Form 36 questionnaire (SF36) were assessed at beginning and completion of PR. A total of 138 patients were included (LOS >42 days: 30; LOS ≤42 days: 108). At completion, physical functioning (VC, FEV1, PWR, VO(2max) , 6-MWD, ADL), and HRQoL (all SF36 domains) improved in each cohort (P < 0.05). No differences were found in between both cohorts in VC, FEV1, and ADL (n.s.), but in PWR, 6-MWD, and the SF36 domain 'physical functioning' (P < 0.05). A 3-week inpatient PR improves physical functioning despite prolonged hospitalization. HRQoL is close to normal. (ClinicalTrials.gov. identifier: NCT00759538).

Exercise training after lung transplantation improves participation in daily activity: a randomized controlled trial

The effects of exercise training after lung transplantation have not been studied in a randomized controlled trial so far. We investigated whether 3 months of supervised training, initiated immediately after hospital discharge, improve functional recovery and cardiovascular morbidity of patients up to 1 year after lung transplantation. Patients older than 40 years, who experienced an uncomplicated postoperative period, were eligible for this single blind, parallel group study. Sealed envelopes were used to randomly allocate patients to 3 months of exercise training (n = 21) or a control intervention (n = 19). Minutes of daily walking time (primary outcome), physical fitness, quality of life and cardiovascular morbidity were compared between groups adjusting for baseline assessments in a mixed models analysis. After 1 year daily walking time in the treated patients (n = 18) was 85 ± 27 min and in the control group (n = 16) 54 ± 30 min (adjusted difference 26 min [95%CI 8-45 min, p = 0.006]). Quadriceps force (p = 0.001), 6-minute walking distance (p = 0.002) and self-reported physical functioning (p = 0.039) were significantly higher in the intervention group. Average 24 h ambulatory blood pressures were significantly lower in the treated patients (p ≤ 0.01). Based on these results patients should be strongly encouraged to participate in an exercise training intervention after lung transplantation.

Hypoxia and muscle maintenance regulation: implications for chronic respiratory disease

PURPOSE OF REVIEW

Muscle wasting and impaired muscle oxidative metabolism are common extrapulmonary features of chronic respiratory failure (CRF) that significantly increase disease burden. This review aims to address the question whether hypoxia, an obvious consequence of this disease, actually plays a causal role in these muscle impairments.

RECENT FINDINGS

In experimental models, a causal role for hypoxia in muscle atrophy and metabolic impairments has clearly been shown. Although the hypoxia-inducible factors and nuclear factor kappa B are putative mediators of these hypoxia-induced alterations, their true involvement remains to be proven. Molecular signatures of disrupted regulation of muscle mass and oxidative metabolism observed in these experimental models also have been shown in muscles of patients suffering from CRF, suggestive of but not conclusive for a causal role of hypoxia. Therapies, including but not restricted to those aimed at alleviating hypoxia, have been shown to partially but not completely restore muscle mass and oxidative capacity in CRF patients, which may imply an additive effect of nutritional modulation of substrate metabolism.

SUMMARY

Although hypoxia clearly affects skeletal muscle maintenance, it remains to be confirmed whether and by which underlying molecular mechanisms hypoxia is causally involved in CRF-related muscle atrophy and impaired oxidative capacity.

Lung transplantation and lung volume reduction surgery

Since the publication of the last edition of the Handbook of Physiology, lung transplantation has become widely available, via specialized centers, for a variety of end-stage lung diseases. Lung volume reduction surgery, a procedure for emphysema first conceptualized in the 1950s, electrified the pulmonary medicine community when it was rediscovered in the 1990s. In parallel with their technical and clinical refinement, extensive investigation has explored the unique physiology of these procedures. In the case of lung transplantation, relevant issues include the discrepant mechanical function of the donor lungs and recipient thorax, the effects of surgical denervation, acute and chronic rejection, respiratory, chest wall, and limb muscle function, and response to exercise. For lung volume reduction surgery, there have been new insights into the counterintuitive observation that lung function in severe emphysema can be improved by resecting the most diseased portions of the lungs. For both procedures, insights from physiology have fed back to clinicians to refine patient selection and to scientists to design clinical trials. This section will first provide an overview of the clinical aspects of these procedures, including patient selection, surgical techniques, complications, and outcomes. It then reviews the extensive data on lung and muscle function following transplantation and its complications. Finally, it reviews the insights from the last 15 years on the mechanisms whereby removal of lung from an emphysema patient can improve the function of the lung left behind.

Effect of inpatient rehabilitation on quality of life and exercise capacity in long-term lung transplant survivors: a prospective, randomized study

BACKGROUND

The purpose of this study was to examine the effect of an inpatient rehabilitation program on health-related quality of life (HRQOL) and exercise capacity (EC) in long-term (>1 year after lung transplantation) survivors (LTSs) in comparison to a control group (CG).

METHODS

Sixty LTSs, 4.5 ± 3.2 years after lung transplantation (LTx), were randomly assigned to two equally sized groups that were stratified for gender and underlying disease. Thirty LTSs (age 49 ± 13 years, 13 male and 17 females, 19 double LTxs, 7 BOS Stage ≥ 1) attended an inpatient rehabilitation program (intervention group, IG) for 23 ± 5 days. The CG (age 50 ± 12 years, 13 males and 17 females, 20 double LTxs, 2 BOS Stage ≥ 1) received medical standard therapy (physiotherapy). Patients were evaluated by cardiopulmonary exercise testing, 6-minute walk test (6MWT), SF-36, SGRQ and the Quality of Life Profile for Chronic Diseases questionnaire before and after (18 ± 3 days) the program.

RESULTS

The groups were statistically indistinguishable in terms of clinical data. Each treatment group significantly improved their sub-maximal EC (6MWT: IG, 493 ± 90 m vs 538 ± 90 m, p < 0.001; CG, 490 ± 88 m vs 514 ± 89 m, p < 0.001) and maximal EC (VO(2peak): IG, 17.0 vs 18.5 ml/min/kg, p = 0.039; CG, 18.0 vs 19.5 ml/min/kg, p = 0.005), without reaching statistical significance between the groups. In both study groups, patients HRQOL tended to improve. Significant correlations were found between EC parameters and HRQOL scales.

CONCLUSIONS

Our data suggest that structured physical training may improve exercise tolerance in LTS. Our study results did not demonstrate a significant benefit of an inpatient over an outpatient exercise program.

Respiratory competent mitochondria in human ovarian and peritoneal cancer

Impaired respiration was proposed by Warburg to be responsible for aerobic glycolysis in cancer cells. However, intact mitochondria isolated from human ovarian and peritoneal cancer tissues exhibit substantive oxidative phosphorylating activities in terms of membrane potential, ATP biosynthesis and oxygen consumption. The specific activities of succinate, malate and glutamate dehydrogenases are comparable to reported values for human skeletal muscle, heart and liver but the rate of ATP production is one order of magnitude lower compared to human skeletal muscle. It was concluded that the TCA cycle is functional in these ovarian cancer tissues which contain OXPHOS competent mitochondria.

Exercise training after lung transplantation: a systematic review

BACKGROUND

Lung transplant recipients experience persistent impairments in exercise capacity and skeletal muscle function despite a vast improvement in lung function after transplantation. Exercise training may be beneficial in improving exercise capacity in lung transplant recipients. A systematic review was undertaken to examine the evidence for exercise training on functional outcomes in lung transplant recipients.

METHODS

Studies were identified by searching electronic databases and scanning reference lists. Only randomized controlled trials, controlled trials, and prospective cohorts were included in the review. Seven studies met the inclusion criteria. Study quality was assessed using the Physiotherapy Evidence Database, Jadad, and Downs scales.

RESULTS

The overall quality of studies was fair to moderate in assessing the effect of exercise training on maximal and functional exercise capacity, skeletal muscle function, and lumbar bone mineral density. Every study reported significant improvements in these outcomes. Some studies lacked randomization and/or a control group, so it was not possible to separate the effects of training with the natural recovery process after lung transplantation.

CONCLUSION

Some evidence was found to support that a period of structured exercise training could improve maximal and functional exercise capacity, skeletal muscle strength, and lumbar bone mineral density in lung transplant recipients. Further studies are needed to determine the potential for exercise training to optimize these functional outcomes and to develop optimal guidelines for exercise prescription in the lung transplant population.

Review series: Rehabilitation in non COPD: Mechanisms of exercise limitation and pulmonary rehabilitation for patients with pulmonary fibrosis/restrictive lung disease

The standard of care in the treatment of chronic lung disease includes pulmonary rehabilitation (PR). While evidence of the effectiveness of PR in chronic obstructive lung disease (COPD) is robust, that for pulmonary fibrosis and other non-fibrotic restrictive lung diseases is less extensive. However, PR has been shown to improve functional exercise capacity and health-related quality of life in non-COPD patients, primarily those with interstitial lung diseases. This review examines mechanisms of exercise limitation in non-COPD patients and discusses how they might affect both the application of and outcome measures of PR. We also review the assessment of exercise performance, dyspnea, and quality of life as well as special protocols, safety considerations, and special techniques in PR as applied to patients with pulmonary fibrosis or restrictive lung disease. At present, there are no evidence-based guidelines for PR in non-COPD patients whereas PR is firmly recommended in COPD management. More research is needed to strengthen the evidence for the use of PR in non-COPD patients. Meanwhile, the available data, summarized in this review, support the inclusion of PR in the management of all patients with chronic lung disease including pulmonary fibrosis and restrictive lung disease.

Exercise training before and after lung transplantation

The benefits of exercise training in individuals with chronic lung diseases such as chronic obstructive pulmonary disease, cystic fibrosis, and interstitial lung disease have been well documented. Although there is limited research available, it appears that exercise is safe and beneficial for people with severe end-stage chronic lung disease who are awaiting lung transplantation in addition to recipients of lung transplants. Evidence-based guidelines for exercise training in the pre- and post-lung transplantation phases have not yet been developed. However, by considering exercise guidelines for people with chronic lung disease and in older adults in light of the physiological changes that can occur either pre- or post-lung transplantation, a safe and appropriate exercise training program can be developed. Depending on the individual's exercise capacity and goals, the training program may include aerobic and resistance exercise, and flexibility and balance training. In the pre-transplant and acute post-transplant phases, the intensity of exercise is dictated primarily by symptom limitation and adequate rest, which is required between exercise bouts to allow for recovery. In the post-transplant phase, it is possible for lung transplant recipients to increase their exercise capacity and even participate in sports. Further research needs to be conducted to determine the optimal training guidelines and the long-term benefits of exercise, both in lung transplant candidates and recipients.

Transplantation in Chronic Obstructive Pulmonary Disease

Lung transplantation is a surgical option for patients who fail optimization of medical treatment for the severe symptoms that result from COPD. This review will discuss patient selection, transplant listing, and the surgical technique for transplantation in COPD. Furthermore, it will describe transplant outcomes and its effects on recipient survival, pulmonary function, exercise capacity, respiratory muscle function, and quality of life. The respective roles of transplantation and lung volume reduction surgery as therapies for advanced disease will be outlined.

Physical activity in daily life 1 year after lung transplantation

BACKGROUND

Reduced physical fitness has been reported to occur after lung transplantation. Pre- and post-transplant factors, including an inactive lifestyle, have been proposed as possible causes. However, daily physical activity has not been objectively assessed so far in lung recipients. The purpose of this study was to objectively measure daily physical activity in lung recipients.

METHODS

Twenty-two clinically stable patients with single (n = 7) and bilateral lung grafts (n = 15) underwent measurements of physical activity with activity monitors at least 12 months after surgery. Results were compared with findings from 22 healthy, age- and gender-matched control subjects.

RESULTS

Substantial and statistically significant differences in daily activity were observed. Steps, standing time and moderate-intensity activity of lung recipients were reduced by 42%, 29% and 66%, respectively, relative to controls. Daily sedentary time was increased by 30%. Daily steps correlated with self-reported physical functioning (r = 0.81), 6-minute walk distance (r = 0.68), quadriceps force (r = 0.66) and maximum workload (r = 0.63).

CONCLUSIONS

This study has shown for the first time that daily activity is substantially reduced after lung transplantation and related to measures of physical fitness and health-related quality of life. Future studies need to examine whether physical activity can be modified to improve functional recovery after lung transplantation.

Absolute quantification of phosphorus metabolite concentrations in human muscle in vivo by 31P MRS: a quantitative review

31P MRS offers a unique view of muscle metabolism in vivo, but correct quantification is important. Inter-study correlation of estimates of [Pi] and [phosphocreatine (PCr)] in a number of published studies suggest that the main technical problem in calibrated 31P MRS studies is the measurement of PCr and Pi signal intensities, rather than absolute quantification of [ATP]. For comparison, we discuss the few published biopsy studies of calf muscle and a selection of the many studies of quadriceps muscle. The ATP concentration is close to the value that we obtained in calf muscle in our own study, presented here, on four healthy subjects, by localised 31P MRS using a surface coil incorporating an internal reference and calibrated using an external phantom. However, the freeze-clamp biopsy PCr concentration is approximately 20% lower than the value obtained by 31P MRS, consistent with PCr breakdown by creatine kinase during freezing. Finally, we illustrate some consequences of uncertainty in resting [PCr] for analysis of mitochondrial function from PCr kinetics using a published 31P MRS study of exercise and recovery: the lower the assumed resting [PCr], the lower the absolute rate of oxidative ATP synthesis estimated from the PCr resynthesis rate; in addition, the lower the assumed resting [PCr], or the higher the assumed [total creatine], the higher the apparent resting [ADP], and therefore the more sigmoid the relationship between the rate of oxidative ATP synthesis and [ADP]. Correct quantification of resting metabolite concentrations is crucially important for this sort of analysis. Our own results ([PCr] = 33 +/- 2 mM, [Pi] = 4.5 +/- 0.2 mM, and [ATP] = 8.2 +/- 0.4 mM; mean +/- SEM) are close to the overall mean values of the 10 published studies on calf muscle by 'calibrated' 31P MRS (as in the present work), and of [PCr] and [Pi] in a representative selection of 'uncalibrated' 31P MRS studies (i.e. from measured PCr/ATP and Pi/ATP ratios, assuming a literature value for [ATP]).

Impaired Muscle Oxygen Metabolism in Uremic Children: Improved After Renal Transplantation

BACKGROUND

The purpose of this study is to clarify skeletal muscle oxidative metabolism in children with end-stage renal disease (ESRD) before and after renal transplantation.

METHODS

We examined muscle oxygenation and metabolism by using noninvasive near-infrared spectroscopy in 10 patients (age, 12.4 +/- 3.1 years) 1 week before and 4 weeks after renal transplantation and in 10 controls (age, 12.8 +/- 2.6 years) during submaximal hand-grip exercise using the flexor digitorum superficialis muscle. We used 2 indicators to evaluate muscle metabolism. The rate of initial decrease in hemoglobin/myoglobin deoxygenation during arterial occlusion after exercise relative to the value at rest (S2/S1) was used as an indicator of mitochondrial oxygen consumption, whereas recovery time (TR) after exercise was used as an indicator of oxygen delivery to the muscle and aerobic capacity.

RESULTS

S2/S1 and TR after exercise were significantly lower in patients before renal transplantation compared with the control group (P < 0.05). S2/S1 and TR after exercise improved significantly after renal transplantation (P < 0.01, P < 0.05) and were not significantly different from those of controls.

CONCLUSION

Oxidative metabolism in skeletal muscle during exercise is impaired in children with ESRD and recovers after renal transplantation.

Noninfectious Pulmonary Complications After Lung Transplantation

This article reviews several important noninfectious pulmonary complications that threaten survival, pulmonary function, and quality of life after lung transplantation. Topics reviewed include primary graft dysfunction (PGD), native lung hyperinflation, anastomotic complications, phrenic nerve injury, pleural complications, lung cancer, pulmonary toxicity associated with immunosuppressive medications, and exercise limitation.

Functional coupling of adenine nucleotide translocase and mitochondrial creatine kinase is enhanced after exercise training in lung transplant skeletal muscle

Mechanisms responsible for limitation of exercise capacity in lung transplant recipients (LR) and benefits gained by exercise training were studied. Mitochondrial respiration parameters, energy transfer, and cell structure were assessed in vastus lateralis biopsies using the permeabilized fiber technique with histochemical and morphometric measurements. Twelve male controls (C) and 12 LR performed exercise training over 12 wk. Before exercise training, there were strong correlations between exercise capacity (maximal O2 consumption and endurance time at 70% maximal power output) and cellular events, as assessed by percentage of type I fibers and apparent Km for exogenous ADP. Anticalcineurins were not involved in LR exercise limitation, since there were no differences in maximal mitochondrial rate of respiration before exercise training and no abnormalities in respiratory chain complexes compared with C. Training resulted in a significant increase in physiological parameters both at the cellular (apparent Km for exogenous ADP and stimulating effect of creatine) and integrated (maximal O2 consumption, power output at ventilatory threshold, maximal power output, and endurance time at 70% maximal power output) levels in LR and C. After the training period, improvements in maximal O2 consumption and in maximal mitochondrial rate of respiration were noted, as well as changes in endurance time and percentage of type I fibers. Because there were no changes in diameters and fiber types, baseline alteration of apparent Km for exogenous ADP and its improvement after training might be related to changes within the intracellular energetic units. After the training period, intracellular energetic units exhibited a higher control of mitochondrial respiration by creatine linked to a more efficient functional coupling adenine nucleotide translocase-mitochondrial creatine kinase, resulting in better exercise performances in C and LR.