Cirrhosis associated with decreased survival and a 10-year lower median age at death of cystic fibrosis patients in the Netherlands.

BACKGROUND: Up to 10% of patients with Cystic Fibrosis develop cirrhotic CF-related liver disease with portal hypertension: CF cirrhosis (CFC). In a nationwide study, we aimed to determine the role of CFC on survival in the Netherlands between 1 and 1-2009 and1-1-2015. METHODS: We identified all CFC patients in the Netherlands, based on ultrasonographic liver nodularity and portal hypertension. A non-cirrhotic control group was obtained from the national Dutch CF patient registry. We compared groups with regards to baseline lung function and nutritional status and survival and age at death over a 6-year period. In case of death of CFC patients, the clinical reported cause was recorded. RESULTS: At baseline, we found no significant difference in lung function and nutritional status between the CFC patients (N = 95) and controls (N = 980). Both the 6-year survival rate (77 vs. 93%; P < .01) and the median age at death (27 vs. 37 years; P = .02) was significantly lower in CFC compared to controls. In the deceased CFC patients, the reported primary cause of death was pulmonary in 68% of cases, and liver failure related in 18% of cases. CONCLUSIONS: In the Netherlands, the presence of CFC is associated with a higher risk for early mortality and an approximately 10-year lower median age at death. This substantial poorer outcome of CFC patients was not reflected in a lower baseline lung function or a diminished nutritional status. However, in the case of mortality, the reported primary cause of death in CFC patients is predominantly pulmonary failure and not end-stage liver disease.

Determinants of functional independence and quality of life in children with spina bifida.

OBJECTIVE: To investigate determinants of functional independence and study which functional abilities were determinants for 'health-related quality of life' in children with myelomeningocele. DESIGN: Cross-sectional study by means of clinical assessment, 'disability' measurement and questionnaires. Uni- and multivariate logistic regression models were used to investigate factors that were determinants for these outcomes. Results were expressed as odds ratios (OR) and 95% confidence intervals (95% CI). SETTING: Outpatient spina bifida clinic at a university hospital. SUBJECTS: One hundred and twenty-two children with myelomeningocele. Mean age 7.9; range 1-18 years. MAIN MEASURES: Functional independence as measured by the Pediatric Evaluation of Disability Inventory (PEDI), and quality of life as measured by the Spina Bifida Health Related Quality of Life Questionnaire. RESULTS: Lesion level below L3 (OR 0.4, 95% CI 0.1-1.0), mental status of IQ > or =80 (OR 4.2, 95% CI 1.2-14.9), having no contractures in lower extremities (OR 3.4, 95% CI 1.3-8.8), and having normal strength of knee extensor muscles (OR 4.1, 95% CI 1.4-11.5) were most strongly associated with independence in self-care. Mental status (OR 16.1, 95% CI 2.8-93.9), having no contractures in lower extremities (OR 1.5, 95% CI 1.4-5.3), and normal strength in knee extensors (OR 11.0, 95% CI 1.3-97.0) were the most important determinants for independence in mobility. Concerning functional abilities, being independent with regard to mobility was the most important determinant for 'health-related quality of life' (OR 5.3, 95% CI 1.6-17.4). CONCLUSIONS: In children with myelomeningocele, good muscle strength, mental ability and being independent in mobility appeared to be much more important for daily life function and quality of life than other medical indicators of the disorder.

Spinal fusion in children with spina bifida: influence on ambulation level and functional abilities.

The aim of this study was to determine the influence of spinal fusion on ambulation and functional abilities in children with spina bifida for whom early mobilization was stimulated. Ten children (three males and seven females) with myelomeningocele were prospectively followed. Their mean age at operation was 9.3 years (standard deviation (SD): 2.4). Spinal curvature was measured according to Cobb. Pelvic obliquity and trunk decompensation were measured as well. The ambulation level was scored according to Hoffer, and functional abilities, as well as the amount of caregiver assistance, were documented using the Pediatric Evaluation of Disability Inventory. All patients were assessed before surgery and three times after surgery, with a total follow-up duration of 18 months after surgery. After spinal fusion, magnitude of primary curvature decreased significantly (p=0.002). Pelvic obliquity and trunk decompensation did not change. In spite of less immobilization as compared with other reported experiences, ambulation became difficult in three out of four patients who had been able to ambulate prior to surgery. Functional abilities and amount of caregiver assistance concerning self-care (especially regarding dressing upper and lower body, and self-catheterization) and mobility (especially regarding transfers) showed a nonsignificant trend to deterioration within the first 6 months after surgery, but recovered afterwards. From pre-surgery to 18 months after surgery, functional skills on self-care showed borderline improvement (p=0.07), whereas mobility did not (p=0.2). Mean scores on caregiver assistance improved significantly on self-care (p=0.03), and borderline on mobility (p=0.06), meaning that less caregiver assistance was needed compared with pre-surgery. The complication rate was high (80%). In conclusion, within the first 6 months after spinal fusion, more caregiver assistance is needed in self-care and mobility. It takes about 12 months to recover to pre-surgery level, while small improvement is seen afterwards. After spinal fusion, ambulation often becomes difficult, especially in exercise walkers. These findings are important for health-care professionals, in order to inform and prepare the patients and their parents properly for a planned spinal fusion.

Spina bifida at the sacral level: more than minor gait disturbances.

OBJECTIVE: To investigate functional outcome in two groups of children with sacral level paralysis: myelomeningocele (MMC) versus lipomyelomeningocele (LMMC). Additionally both groups were compared with each other and when possible with reference values. DESIGN: Cross-sectional study by means of (1) clinical assessment, and (2) disability measurement. SETTING: Spina bifida outpatient clinic at a university hospital in the Netherlands. SUBJECTS: Sample of 30 children with MMC and 14 with LMMC. Mean age (SD) 6.0 (4.9) and 8.4 (4.9) years respectively. MAIN MEASURES: Muscle strength, ambulation level, motor performance (Bayley Scales of Infant Development (BSID) and Movement Assessment Battery for Children), and the Pediatric Evaluation of Disability Inventory (PEDI). RESULTS: The majority of patients in both groups were normal ambulant, 14/21 (67%) in MMC and 9/14 (64%) in LMMC. Ambulation was strongly associated with muscle strength of hip abductors (odds ratio (OR): 13.5, 95% confidence interval (CI) 2.5-73.7), and ankle dorsal-flexor muscles (OR: 110, 95% CI 8.9-135.9). No significant differences were found in lesion and ambulation level. Muscle strength and motor performance were significantly lower in the MMC group than in the LMMC group (p < 0.05). PEDI scores were comparable in both groups. Most problems were noted in mobility skills and caregiver assistance in self-care, especially regarding bladder and bowel management. CONCLUSIONS: Gross motor and functional problems were seen in both groups. The MMC group showed more muscle weakness and motor problems. However, in both groups caregiver assistance was needed for a prolonged period, especially regarding bladder and bowel management. These findings need special attention, particularly in children who attend regular schools.

Long-term outcome of neurosurgical untethering on neurosegmental motor and ambulation levels.

The aim of this study was to determine the long-term outcome of neurosurgical untethering on neurosegmental motor level and ambulation level in children with tethered spinal cord syndrome. Forty-four children were operated on (17 males, 27 females; mean age at operation 6 years 2 months, SD 5 years). Sixteen patients had myelomeningocele, nine had lipomyelomeningocele, and 19 had other types of spinal dysraphism. Motor level and ambulation level were assessed pre- and three times postsurgery (mean duration of follow-up 7 years 1 month, SD 1 year 8 months). Deterioration of motor level was seen in five of 44 patients, 36 of 44 remained stable, while improvement was seen in three of 44 patients. Deterioration of ambulation level was seen in five of 44 patients, and remained stable in 26 of 44. Thirteen of 44 children were too young to ambulate at time of operation (< 2 years 6 months). Late deterioration of motor or ambulation level was only seen in (lipo) myelomeningocele patients. Deterioration of ambulatory status was strongly associated with obesity and retethering. Revision of the initial tethered cord release was performed in nine of 44 patients, mainly in those with lipomyelomeningocele.

Treatment of children with cystic fibrosis: central, local or both?

UNLABELLED: Owing to a lack of longitudinal studies, the effect of centralization of care on pulmonary function and survival remains unclear. Three different levels of involvement of centralized care in the treatment of paediatric cystic fibrosis patients were compared with regard to longitudinal pulmonary function and nutritional and microbiological status in a 3-y period, and the literature was reviewed on the possible advantages and disadvantages of centralized care. The study included 105 paediatric patients attending the Cystic Fibrosis Centre between January 1997 and January 2001. Twenty-three patients were treated by local paediatricians according to the protocol of the Centre and were seen only once a year at the Centre, for an annual check-up (local care). Forty-one patients were treated at the Centre only (centralized care). The remaining 41 patients were treated in close cooperation between the Centre and local hospitals, with patients visiting the doctors alternately (shared care). The mean annual changes in pulmonary function and body mass index from all patients, as well as a microbiological survey, were reviewed. No significant differences were found between the three groups for annual changes in FEV1, FVC and body mass index, nor did the review of microbial colonization show any significant differences between the groups. Because the groups in this study were relatively small, the results might have been influenced by lack of power. CONCLUSION: In this relatively small group, no differences in pulmonary function, nutritional status or microbiological colonization between the three levels of involvement of centralized care could be found. This could signify that local paediatricians have a special role in the care for patients with cystic fibrosis, in close cooperation with the specialists at the Centre.

Paediatric rehabilitation.

More and more researchers are questioning the theoretical and scientific foundations as well as the efficacy and effects of many physiotherapy interventions. The same applies for many of the neurophysiological based interventions that are being used in paediatric rehabilitation. Opinions and views regarding the development of motor behaviour of infants and children are significantly changing. Paediatric interventionists should consider bringing their interventions and focus of treatment into agreement with changed scientific knowledge. Moreover, for almost all other medical problems in childhood, paediatric rehabilitation has little to offer but mostly miniaturized forms of adult treatment. It not only means that we have to make a paradigm shift, but also are in the need of a broader view on paediatric rehabilitation as a specialized professional activity.

Osteogenesis imperfecta in childhood: perceived competence in relation to impairment and disability.

OBJECTIVES: To examine the perceived competence of children with different types of osteogenesis imperfecta (OI) and to investigate the possible relationships between their perceived competence and impairment parameters. DESIGN: Cross-sectional study. SETTING: National referral center (hospital) for the treatment of children with OI. PATIENTS: Forty children with OI (type I = 17; type III = 11; type IV = 12) with a mean age +/- standard deviation of 12.6 +/- 3.2 years. INTERVENTIONS: Measured joint range of motion (ROM) in the upper extremities (UEs), and lower extremities (LEs), muscle strength, functional skills, ambulation, and perceived competence. MAIN OUTCOME MEASURES: Joint ROM in UE and LE; muscle strength (using the manual muscle testing criteria of the Medical Research Council); functional skills using the Pediatric Evaluation of Disability Inventory in 3 domains (self-care, mobility, social function). Ambulation (according to Bleck and classified as nonwalking, therapy walking, household walking, neighborhood walking, community walking with or without the use of crutches), and perceived competence (using the Harter Self-Perception Profile for Children, which was cross-culturally validated for Dutch children). RESULTS: In children with type I, joint ROM and muscle strength were almost comparable to the healthy population. In children with type III, a severe decrease in joint ROM was measured, especially in the LEs, and muscle strength was severely decreased in the UEs and LEs. In children with type IV, joint ROM and muscle strength decreased, especially in the LEs. In all types, fairly to strongly positive perceived competence was measured except for fairly negative perceived competence in the athletic performance subscale in type I and a fairly negative perceived competence in the romance subscale in type III. No correlations were found between (1) joint ROM and athletic performance and physical appearance, (2) muscle strength and athletic performance or physical appearance, or (3) the functional skills, concerning self-care and mobility, with the subscales of the perceived competence. CONCLUSIONS: Although joint ROM, muscle strength, and functional and walking ability were related to the severity of the disease and differed significantly between the different types of OI, overall perceived competence in children with OI was fairly to strongly positive, without significant differences between the different types of OI.

Motor performance and disability in Dutch children with haemophilia: a comparison with their healthy peers.

We investigated whether haemophilic children who are on prophylactic therapy differ from their healthy peers in terms of motor performance and disability. Thirty-nine children, aged 4-12 years, with moderate (eight) and severe (31) haemophilia were included. Patients with severe haemophilia received primary prophylactic therapy that was individually tailored. The number of target joints, amount of swelling, range of motion, muscular strength and pain were measured, as well as motor skills and disability. The scores were compared to the normal population. No patients had target joints. Normal range of motion in all joints was seen in 97% (38/39) of the patients. Strength of elbow, knee, and ankle muscles were within the normal ranges. Ninety-five percent (37/39) of the patients had normal motor performance. Although 90% of our patients (35/39) had no disabilities in activities of daily living (ADL), 79% (31/39) of them reported that the disease impacted on their lives. Seventy-two percent (28/39) of the patients had pain, and in 21% (6/28) of them this was mainly caused by injections. Restrictions in sports or gymnastics were seen in 56% (22/39) of the patients. Those who indicated that they experienced pain and those who indicated restrictions in sports had a higher chance of experiencing disease impact compared to those who did not have these limitations. There were no significant differences between patients with moderate and severe haemophilia. In general, Dutch children with moderate or severe haemophilia are comparable with their healthy peers with regard to motor performance and ADL. However, a majority of the patients perceive an impact of their disease associated with pain and restrictions in sports.

Physiotherapy as an adjuvant to the surgical treatment of anterior chest wall deformities: a necessity? A prospective descriptive study in 21 patients.

PURPOSE: The authors postulated that physiotherapy as an adjuvant to the surgical treatment of anterior chest wall deformities is only indicated if specific abnormalities can be found that could be corrected by physiotherapy. The purpose of this study is to investigate whether such abnormalities can be found and to evaluate their course during a postoperative period of 18 months. METHODS: Twenty-one patients, 16 with pectus excavatum and 5 with pectus carinatum, were evaluated 6 weeks before and 6 weeks, 6 months, and 18 months after surgical correction. Postural impairments, spinal mobility and curvature, muscle strength, and muscle length were evaluated. RESULTS: Preoperatively, poor posture was seen in 10 patients, nonstructural scoliosis in 11, and abdominal muscle weakness in 4 patients. None of the patients had restriction of spinal mobility or shortened pectoral muscles. Six weeks after surgery, poor posture was seen in 9, nonstructural scoliosis in 11, and abdominal muscle weakness in 10 patients. The authors found a higher percentage of recovery for abdominal muscle weakness than for poor posture (90% versus 33%, respectively). CONCLUSIONS: The authors found preoperative postural impairments in 52% of their patients, in patients with pectus carinatum as well as in patients with pectus excavatum. In patients without postural impairments, physiotherapy is not necessary, with the exception of postoperative pulmonary care.

Osteogenesis imperfecta in childhood: prognosis for walking.

OBJECTIVES: We studied the predicted value of disease-related characteristics for the ability of children with osteogenesis imperfecta (OI) to walk. STUDY DESIGN: The severity of OI was classified according to Sillence. The parents were asked to report the age at which the child achieved motor milestones, the fracture incidence, and the age and localization of the first surgical intervention. The present main means of mobility was classified according to Bleck. RESULTS: There were 76 replies to the 98 questionnaires, of which 70 were included (type I, 41; type III, 11; type IV, 18). The type of OI was strongly associated with current walking ability, as was the presence of dentinogenesis imperfecta. Patients with type III and IV had a lower chance of ultimately walking compared with those with type I. Children with more than 2 intramedullary rods in the lower extremities had a reduced chance of walking than patients without rods. Rolling over before 8 months, unsupported sitting before 9 months, the ability to get in sitting position without support before 12 months, and the ability to get in a standing position without support before 12 months showed positive odds ratios. In Bleck > or = 4, multivariate analysis revealed that only the presence of rodding (yes/no) in the lower extremities had additional predictive value to the type of OI. The presence of dentinogenesis imperfecta and rodding (yes/no) had additional value in Bleck > or = 5. CONCLUSION: The type of OI is the single most important clinical indicator of the ultimate ability to walk. Information about motor development adds little. The early achievement of motor milestones contributes to the ability of independent walking when the type of OI is uncertain. Intramedullary rodding of the lower extremities is primarily related to the severity of the disease and in this way provides consequences for the ability to walk.

Osteogenesis imperfecta: profiles of motor development as assessed by a postal questionnaire.

UNLABELLED: This study was performed to achieve more detailed information regarding the age and sequence in the development of motor milestones in the different types of osteogenesis imperfecta (OI). The parents of 98 patients with a diagnosis of OI were sent a questionnaire regarding the age at which patients achieved motor milestones. All patients were attending the outpatient clinic for children with OI at the Wilhelmina Children's Hospital. The motor milestones were classified into static motor milestones and dynamic motor milestones and all data were checked with health care records. The age of development of motor milestones was compared to reference values of the healthy population. The severity of the disease was classified according to Sillence based on clinical, genetic and radiological data. The age of intramedullary rodding of the first nail in the lower and upper extremity and the localisation was noted. A total of 76 parents responded to the 98 questionnaires (78%). In OI type I, a delay exists in achieving motor milestones, comparable to the 95th percentile of the normal population. In type III, the development of all motor milestones was significantly delayed compared to types I and IV with a discrepancy between static and dynamic milestones. In OI type IV, a retardation in motor development developed after the milestone 'sitting without support' was achieved. Motor development in types I and IV was not influenced by intramedullary rodding of the lower extremities, since rodding was rarely performed before the milestone 'unsupported standing' was achieved. In type III, the influence of intramedullary rodding on the age of achieving motor milestones remains questionable. CONCLUSION: The severity of osteogenesis imperfecta has a large influence on the age and sequence in the development of motor milestones. No influence of intramedullary rodding of the lower extremities on motor development was found in osteogenesis imperfecta types I and IV, whereas the influence in type III remains questionable.

Skinfold measurements in children with cystic fibrosis: monitoring fat-free mass and exercise effects.

UNLABELLED: Monitoring fat free mass (FFM), an indicator of nutritional status and a predictor of exercise performance in children, is particularly important in patients with cystic fibrosis (CF). We assessed validity of the skinfold method for measuring FFM, and its changes with exercise training, in children with CF. A total of 14 children with moderately severe symptoms of CF (age 10-18 years) were followed longitudinally and measured three times, before (at 0 and 6 months) and after exercise training (at 12 months). Separately, single measurements were conducted in 12 children with mild symptoms of CF and in 13 healthy controls. FFM was calculated from four skinfold measurements, and compared with estimations from total body water measured with deuterium dilution. The FFM calculated from skinfolds was 1.7% (P < 0.05) and 3.3% (P < 0.005) higher than that estimated with deuterium oxide dilution in patients with CF and controls, respectively. Limits of agreement were similar in patients with moderate and mild symptoms and in controls. The measurements in patients with moderate symptoms showed similar bias and limits of agreement at 6 and 12 months as compared to 0 months. Changes in FFM measured with both methods were significantly correlated before exercise (r = 0.82, P < 0.0005), and after exercise training (r = 0. 60, P < 0.05). CONCLUSION: In children with cystic fibrosis, skinfold measurements are applicable to monitor fat free mass irrespective of clinical severity of the disease, and repeated measurements at intervals of 6 months are applicable to monitor changes in fat free mass during exercise training.

Outpatient exercise training in children with cystic fibrosis: physiological effects, perceived competence, and acceptability.

Exercise training is currently advocated as part of the treatment of patients with cystic fibrosis (CF). However, data are few that document physiologic benefits or changes in patients' perceptions of long-term training programs in children with CF. The aim of this study was to investigate the effects and acceptability of a home cycling program in children with CF. Fourteen patients (9 boys, 5 girls) with CF, mean (SD) age 14.1 (2.0) years, with mild to moderate impairment of lung function (forced expiratory volume in 1 s, mean (SD) 58.3 (16.3)% of predicted) were studied for 1 year. The first half of the study year was used to obtain baseline values at 0 and 6 months. During the second half of the year, a cycle program was carried out 5 times a week, for 20 min each day at a level of work that resulted in a heart rate of 140-160 beats/min. Once a week the cycle program was supervised by a physiotherapist. Measurements were repeated at 12 months. Effects of the exercise program were measured in terms of lung function, nutritional status, growth, muscle strength, exercise performance, perceived competence, and attitude towards the training program. Differences between the changes during the 6-month training period as compared to the 6-month control period were analyzed by multivariate statistics and nonparametric tests. Statistically significant differences (P < 0.05) between the two periods were found with respect to muscle strength of knee extensors and ankle dorsiflexors, and with respect to maximal oxygen consumption per kg body weight as well as per kg fat free mass. All changes were positive. No adverse effects were found. Perceived competence showed significant positive changes in feelings about physical appearance, general self-worth, and Total Perceived Competence Score. Scores concerning perceived acceptability of the program were significantly lower at the end of the training period; however, patients reported that they did want to continue with other sorts of training. We conclude that an exercise training program in the home can produce beneficial effects on oxygen consumption, muscle force, and perceived competence in children with CF. However, acceptability of the program was low, suggesting that long-term adherence would be poor, and hence, other sorts of training need to be identified.

Peripheral muscle weakness and exercise capacity in children with cystic fibrosis.

Exercise intolerance in cystic fibrosis (CF) is attributed to diminished nutritional and pulmonary function. We studied the pathophysiology of such intolerance in relation to muscle force and fat-free mass (FFM), in 15 children with moderately severe symptoms of CF (FEV1 < 80% predicted and/or weight for age < -1 SD of reference median), 13 children with mild symptoms of CF (FEV1 and weight above these thresholds), and 13 healthy controls. Cycle maximal workload (Wmax) and V O2max were assessed. Maximal peripheral muscle force was measured, and FFM was calculated from skinfolds. Patients with mild CF, as compared with matched controls, had lower values of Wmax per kilogram of FFM (3.9 +/- 0.5 versus 4.6 +/- 0.3 W/kg [mean +/- SD], respectively; difference = 0.7 [95% CI = 0.4 to 1.1]), and diminished maximal muscle force (2.7 +/- 0.4 kN versus 3.1 +/- 0.7 kN; difference = 0.44 [95% CI = 0.03 to 0.87]), but similar V O2max. Patients with moderate CF had lower FFM, muscle force, and exercise tolerance than did the other groups. Oxygen cost of work was elevated in both groups of CF patients. Muscle force showed a strong positive correlation with Wmax in patients and controls, with disproportionately lower regression slopes in the CF patients. In children with CF, muscle force is decreased and associated with diminished maximal work load, even in the absence of diminished pulmonary or nutritional status.

Maximal work capacity in relation to nutritional status in children with cystic fibrosis.

In children with cystic fibrosis, objective parameters of exercise tolerance are needed which are easy to measure in nonspecialized centres. We investigated maximal workload (W'max) in children with cystic fibrosis in relation to body weight and fat-free mass, and compared this with results for maximal oxygen consumption (V'O2,max). Fourteen patients with cystic fibrosis performed an incremental maximal exercise test on a bicycle ergometer. W'max, V'O2,max, body weight and fat-free mass were measured. W'max and V'O2,max were significantly correlated (r = 0.91; p < 0.001). Using standard deviation scores in relation to reference values, W'max and V'O2,max per kilogram body weight were significantly higher than uncorrected W'max and V'O2,max (mean difference (95% CI) 0.63 (0.24-1.01) and 0.91 (0.32-1.49) SD units, respectively). There was no such difference after correction for fat-free mass. Standardized V'O2,max was significantly higher than standardized W'max (mean difference (95% CI): 1.59 (1.14-2.04)), also after correction for body weight and fat-free mass. In children with mild-to-moderate cystic fibrosis, maximal workload per kilogram fat-free mass, but not per kilogram body weight, is a useful parameter to correct for diminished nutritional status. In these patients, maximal workload is consistently lower than maximal oxygen consumption. Taking into account this difference, maximal workload and maximal workload per kilogram fat-free mass can be used for follow-up of paediatric patients with cystic fibrosis in nonspecialized settings.

Reference values for maximum work capacity in relation to body composition in healthy Dutch children.

Exercise performance is associated with physical development. For sick children, there is a need for parameters reflecting exercise performance, which should be easy to measure and should take their nutritional state into account. The aim of this study was to investigate the relationship between maximum work-load (Wmax) and body weight (BW) as well as fat-free mass (FFM) in healthy children performing an incremental maximum exercise test on a bicycle ergometer, and to develop reference values for Wmax corrected for nutritional state. A random sample of 158 children (77 boys and 81 girls), aged 12-18 yrs, underwent an incremental maximum exercise test on a bicycle ergometer. BW and FFM were also measured. Correlation analysis showed a significant association (p < 0.001) between BW and Wmax (boys: r = 0.82; girls: r = 0.73), and between FFM and Wmax (boys: r = 0.89; girls: r = 0.79). Two-way analysis of variance showed a significant effect of gender on variance of Wmax/BW ratio as well as Wmax/FFM ratio. The influence of age was significant for Wmax/FFM (p = 0.003), but not for Wmax/BW. The maximum workload/body weight ratio and the maximum workload/fat-free mass ratio are useful parameters of work capacity in bicycle exercise testing in children. The reference values (mean, SD, median, and percentiles) for boys and girls aged 12-18 years can be used to predict workload corrected for body composition in healthy and sick children.

The six-minute walking test in children with cystic fibrosis: reliability and validity.

There is a need to judge general exercise tolerance in children with cystic fibrosis (CF) under normal daily activity conditions and -when more extensive testing is required-in an exercise laboratory in a specialized center. We investigated the reproducibility, validity, and criterion for a 6-minute walking test, which simulates normal childhood activities. In Part A, we evaluated the reproducibility of a 6-minute walking test in 23 children (12 girls and 11 boys; ages 11.1 +/- 2.2 years; range, 8.2 15.6 years) with mild symptoms of CF [forced expiratory volume in 1 second (FEV1) 94.4 +/- 16.5% of predicted values (range, 60.6-129.7); body weight Z-score -0.71 +/- 0.81 (range, -1.73-0.93)]. The subjects performed two standardized 6-minute walking tests with 1 week between tests. There was no significant difference between the two walking distances reached (737 +/- 85 versus 742 +/- 90 meters; P = 0.56), and there was a strong correlation between the two walking distances reached by the individuals (r = 0.90, P < 0.0001). In Part B, the validity of the walking test was evaluated in 15 children (6 girls and 9 boys; ages 14.5 +/- 2.0 years; range, 10.2-16.9 years) with moderate symptoms of CF [FEV1 = 58 +/- 16.0% of predicted values, (range, 41.1-89.4); RV/TLC ratio = 46.3 +/- 6.5% (range, 31.6-57.2); body weight Z-score: -1.29 +/- 0.60 (range, -2.20-0.14)]. They underwent standardized maximum incremental exercise testing on a cycle ergometer and a 6-minute walking test. Postexertional lactate values exceeded threshold values (as described in the literature) in all patients but one. Correlation analysis (Pearson) showed a significant correlation between the walking distance reached (WD = 697 +/- 104 meters), and the maximum workload (Wmax = 118 +/- 44 watt; r = 0.76, P < 0.001) or the maximum oxygen uptake (1,688 +/- 495 ml; r = 0.76, P < 0.001), the latter two being determined on a cycle ergometer, RV/TLC% showed a significant negative correlation (r = -0.72, P < 0.01) with WD. Stepwise multiple regression analysis showed a multiple regression coefficient of R = 0.84 (P < 0.001) for Wmax and RV/TLC % as the independent variables vs. WD as the dependent variable. We conclude that the 6-minute walking test is a valid and useful test in children with mild to moderate symptoms of CF to assess their exercise tolerance and endurance. Exercise test results correlated negatively with pulmonary hyperinflation expressed by the RV/TLC ratio.

Efficiency of oxidative work performance of skeletal muscle in patients with cystic fibrosis.

BACKGROUND: Exercise intolerance in patients with cystic fibrosis is commonly attributed to reduced pulmonary and nutritional status. The possible role of diminished efficiency of mitochondrial oxidative phosphorylation in relation to skeletal muscle performance was investigated in patients with cystic fibrosis. METHODS: In vivo synthesis of ATP in skeletal muscle during submaximal exercise was studied in eight patients with cystic fibrosis aged 12-17 years, and in 19 healthy control subjects aged 8-36 years. The intracellular pH and concentrations of phosphate compounds were calculated at four steady states from phosphorus-31 labelled nuclear magnetic resonance spectroscopy measurements in the forearm muscle during bulb squeezing in an exercise protocol. Normalised power output, expressed as percentage maximal voluntary contraction (Y, in %MVC), was related to the energy force of ATP hydrolysis (X = ln [ATP]/[ADP][Pi]). This relationship provides an in vivo measure of efficiency of oxidative work performance of skeletal muscle. RESULTS: During all workloads (but not at rest) intracellular pH was higher in the patients with cystic fibrosis than in the controls. The linear least square fit for Y = a-bX showed high correlations in both groups; the slope b was 19% lower in the patients than in the controls (11.8% v 14.5% MVC/ln M; 95% confidence interval for difference 0.3 to 5.0). CONCLUSIONS: In patients with cystic fibrosis oxidative work performance of skeletal muscle is reduced. This may be related to secondary pathophysiological changes in skeletal muscle in cystic fibrosis.