Physiological correlates of pulmonary function in children with cystic fibrosis.

RATIONALE: Although peak aerobic capacity (VO(2peak)) has been linked to outcome in patients with cystic fibrosis (CF), measuring is time consuming, and requires expensive equipment and expertise that is not readily available in all centers. Other fitness parameters such as peak anaerobic power, measures of power and strength may be simpler to deliver in the clinic. The relationship between these measures and established outcomes such as forced expiratory volume in one second (FEV(1)) and peak aerobic power (VO(2peak)) in CF remains unclear. Therefore we evaluated (a) aerobic fitness, (b) anaerobic fitness, and (c) upper and lower body muscle strength to determine their relationship to FEV(1) and VO(2peak) in children with CF. METHODS: Eighty-two patients (7-18 years) with CF (40 female) from the CF clinic at The Hospital for Sick Children in Toronto performed a maximal incremental cycling test to exhaustion. Anaerobic power (W) for 10 and 30 sec cycling trials as well as vertical jump (VJ) and hand grip strength (HG) were compared to FEV(1) and VO(2peak). RESULTS: Absolute VO(2peak) (R(2) = 0.16, P < 0.001), anaerobic power (R(2) = 0.21, P < 0.001), and hand grip strength (R(2) = 0.10, P = 0.003) were significantly correlated to lung function whereas measures of explosive lower body strength (VJ) were not. Anaerobic power (R(2) = 0.16, P = 0.001) and hand grip strength (R(2) = 0.08, P = 0.01) were related to VO(2peak). Vertical jump was correlated with VO(2peak) (R(2) = 0.29, P < 0.001) but not FEV(1). CONCLUSIONS: Simple fitness tests such as hand grip strength and anaerobic cycle tests may be useful indicators of lung health and fitness.

Longitudinal relationship between physical activity and lung health in patients with cystic fibrosis.

Exercise is beneficial for patients with cystic fibrosis (CF) but long-term effects of physical activity on lung function evolution are unknown. We evaluated the longitudinal relationship between changes in habitual physical activity (HPA) and rate of decline in lung function in patients with CF. We tracked HPA using the Habitual Activity Estimation Scale, forced expiratory volume in 1 s (FEV1) and Stage I exercise tests in 212 patients with CF over a 9-year period. Adjusting for sex, baseline age and FEV1, mucoid Pseudomonas aeruginosa and CF-related diabetes, mean ± sd FEV1 % predicted decreased by 1.63 ± 0.08% per year (p<0.0001) while mean ± sd HPA increased by 0.28 ± 0.03 h·day(-1) per year (p<0.0001) over the study period. A greater increase in HPA was associated with a slower rate of decline in FEV1 (r=0.19, p<0.0069). Dividing subjects into "high" and "low" activity (above or below the mean rate of change of activity, respectively), a steeper rate of FEV1 decline was observed for low (-1.90% per year) compared to high (-1.39% per year) (p=0.002). Increases in HPA are feasible despite progression of lung disease and are associated with a slower rate of decline in FEV1, highlighting the benefit of regular physical activity, and its positive impact on lung function in patients with CF.

Skeletal muscle metabolism in cystic fibrosis and primary ciliary dyskinesia.

Previous studies have reported differences in muscle function and metabolism between patients with cystic fibrosis (CF) and healthy controls (HC), but it is currently unknown whether these abnormalities are specific to CF or also seen in other airway diseases. In this study, we used magnetic resonance spectroscopy (MRS) during exercise to assess muscle metabolism in CF patients. Twenty patients with CF and 20 age, gender, and habitual activity-matched HCs and a respiratory disease comparison group with primary ciliary dyskinesia (PCD; n = 10) were studied. Phosphorus MRS (P-MRS) was used to characterize muscle bioenergetic metabolism at rest and after high-, moderate-, and low-intensity exercise. CF patients exhibited lower resting ATP/phosphocreatine (PCr) ratio and significantly higher end-exercise pH values compared with both HC and PCD patients. Both CF and PCD patients demonstrated significantly slower PCr recovery time constants after high-intensity exercise. Our results suggest that not only there are specific abnormalities of muscle metabolism in CF patients but also there is a nonspecific impact of respiratory disease on muscle function.

Exercise and physical activity in children with cystic fibrosis.

Regular exercise and habitual physical activity are important for patients with cystic fibrosis (CF). Research has demonstrated the benefits of aerobic, anaerobic, and strength exercise training programs for health and quality of life, however, the CF patient is faced with unique barriers and challenges to participation. Recently, increased levels of habitual physical activity have been shown to slow the decline in lung function in patients with CF, and regular participation in a variety of activities may result in greater adherence in the long term. Research is now available to justify the incorporation of exercise into the routine care of patients with CF. This paper provides the background and rationale for the implementation of exercise and habitual physical activity recommendations by the health care team. Education of health care providers regarding the importance of exercise and habitual physical activity for patients with CF is needed in order for exercise and physical activity to be incorporated as key components of clinical practice and into the lives of patients with CF.

Assessment of body composition in pediatric patients with cystic fibrosis.

RATIONALE: Cystic fibrosis (CF) leads to pathological changes in organs that express the cystic fibrosis transmembrane conductance regulator (CFTR), including secretory cells of the digestive tract and the pancreas. Maintaining nutritional sufficiency is challenging for CF patients and therefore accurate monitoring is important for their clinical management. PURPOSE: The objectives of this study were to evaluate the effectiveness of skinfold measurements as an accurate method for determining body composition (fat mass (FM) and lean body mass (LBM)) of this population, using dual-energy X-ray absorptiometry (DEXA) as a gold standard comparison and to determine the most accurate equation for this calculation in children with CF. METHODS: Fifty-five pediatric patients with CF participated in the study. FM and LBM calculated via four methods: Slaughter, Durnin, Durenberg (2-site and 4-site). The relationship between the methods and DEXA results were estimated by intraclass-correlation coefficient (ICC) and Bland and Altman analyses. RESULTS: The Slaughter method was the most accurate (ICC of 0.92 for FM and 0.99 for LBM) and displayed the least bias over the range of FM and LBM in CF patients. In addition, the results of Bland Altman analyses comparing each skinfold method to DEXA, revealed that the results were evenly distributed along the range of values for the Slaughter calculation, whereas the other three methods under and over estimated % fat results at the upper and lower ends of the range respectively. CONCLUSION: We therefore conclude that the Slaughter method may be used for body composition assessment of pediatric CF patients. This provides clinical teams with a simple, accurate and non-invasive method that can be used to monitor nutritional status in pediatric patients with CF.

Reliability and validity of the habitual activity estimation scale (HAES) in patients with cystic fibrosis.

PURPOSE: To understand potential benefits of exercise in the cystic fibrosis (CF) population, there needs to be accurate methods to quantify it. The Habitual Activity Estimation Scale (HAES) questionnaire has been shown to be a feasible tool to measure physical activity however the reliability and validity have yet to be determined in the CF population. METHODS: Fourteen (seven male, seven female) patients aged 16.2 +/- 4.2 years with CF participated in this study. Participants were clinically stable at the time of the study and participating in their habitual physical activity. To assess reliability, patients completed the HAES and a validated 3-day activity diary, and wore an ActiGraph Accelerometer for two consecutive weeks. Validity was assessed by comparing the activity results of each of the three instruments over a single week time period. RESULTS: ICC estimates of reliability for the HAES, diary, and accelerometer were 0.72 (P < 0.0001), 0.76 (P < 0.0001), 0.63 (P < 0.0001), respectively. Validity analysis indicated that there were significant relationships between the participants' activity results as estimated by the HAES, diary and accelerometer. Further, significant relationships were detected between activity measures when broken into morning, afternoon, or evening periods, and between measures from weekday or weekend days. There were also significant relationships among the three instruments when recording different activity levels (somewhat inactive, somewhat active, and very active). CONCLUSION: The findings of this study suggest that the HAES questionnaire is a reliable and valid instrument that can be used to assess activities of varying intensity in patients with CF.

Fetal response to maternal exercise in pregnancies with uteroplacental insufficiency.

OBJECTIVE: The purpose of this study was to determine the fetal response to submaximal maternal exercise at 22 to 26 weeks in pregnancies with abnormal uterine artery Doppler. STUDY DESIGN: This was a prospective comparison of singleton pregnancies with uteroplacental vascular insufficiency (UPVI) (mean uterine pulsatility index [PI] values >1.45 [n = 12]) and those with normal uterine artery Doppler (n = 23). Maternal and fetal cardiovascular responses to 5 minutes of steady state cycling at 10% and at 15% of predicted work rate maximum were studied. RESULTS: Umbilical artery Doppler deteriorated after exercise in patients with UPVI (pre PI 1.4 [0.35-2.14], post PI 1.64 [0.45-2.18]). Three (25%) had transient absent-end diastolic flow (AEDF) in umbilical artery, 2 of which developed early-onset intrauterine growth restriction (IUGR) with AEDF. Fetal cardiac output studies remained stable during the examinations. CONCLUSION: Submaximal steady state exercise had a transient deleterious effect in a subset of women with uteroplacental vascular insufficiency destined to develop early-onset IUGR.

Determination of maximal voluntary ventilation in children with cystic fibrosis.

Maximal voluntary ventilation (MVV) may be determined directly by the sprint method or calculated from pulmonary function data, using the functions MVV = forced expired volume in 1 sec (FEV(1)) x 35 or MVV = FEV(1) x 40. The purpose of this paper was to test the validity of the equation over a wide range of lung function in children. Cystic fibrosis (CF), a chronic lung disease where children typically have a wide range of pulmonary function, was chosen as the study requirement. Spirometric data from 332 children with CF who underwent pulmonary function testing between 1987-2000 were stratified according to disease severity, and box-plots comparing the ratio of MVV to FEV(1) for each category were generated. As results indicated that the equation underestimates true MVV proportionally to the degree of airflow limitation, a new function to predict MVV for this population was derived and tested. The new equation was derived using data from patients who were tested on odd-numbered days (group A). The validity of the new equation was then tested on the patients tested on even-numbered days (group B). To test its validity, the results were compared to the "gold standard" sprint values using a Bland and Altman plot. MVV was expressed as a function of FEV(1) and predicted FEV(1): MVV = 27.7(FEV(1)) + 8.8(PredFEV(1)) (R(2) = 0.98, P < 0.05). In this way, the accuracy of the new equation was confirmed. Whenever possible, we recommend MVV be determined by the sprint method in accordance with ATS guidelines. If this is not feasible, we recommend considering the new prediction equation.