Effects of Pseudomonas colonization on body composition and resting energy expenditure in children with cystic fibrosis

Nutritional outcomes in cystic fibrosis - are we doing enough?

Although outcome data for individuals with cystic fibrosis (CF) have shown consistent improvements throughout the twentieth century, more recent national registry data suggests that outcomes have reached a plateau. Median values for nutritional outcomes in CF currently cluster around the fiftieth centile for the normal population. These data suggest that up to half of CF patients have sub-optimal body mass index (BMI) which might have a significant adverse impact on their respiratory status. BMI might be underestimating the extent to which more important lean body mass might also be reduced. Nutritional decline is a particular problem during adolescence and commonly persists into early adult life. Current treatment strategies to optimize nutrition include the use of high energy diets, proton pump inhibitors and optimal use of enzyme preparations including higher strength preparations to decrease pill burden. Whilst these are all of potential benefit, poor adherence to nutritional care recommendations is probably the greatest impediment to future health improvement. More effective strategies to impact on treatment adherence are needed.

Nutrition and Lung Disease in Cystic Fibrosis

Among patients who have cystic fibrosis (CF), lung disease is a significant contributor to morbidity. From a clinical perspective, the link between malnutrition and lung dysfunction in CF is well established; however, the causal relationship remains unclear. Nutritional intervention for CF patients is predicated on the hypothesis that improved nutritional status improves pulmonary function. Which interventions will be of most value and have sustained gains is not completely clear from the available data. Taking into account that several factors condition the deficits that lead to malnutrition in CF, multidisciplinary interventions are likely to give the best results. More research is needed to better dissect the nutritional factors involved in lung disease and to identify effective and safe interventions through systematic controlled trials.

Comparison of methods of assessment of renal function in cystic fibrosis (CF) patients

Renal failure is increasingly being recognised in CF patients, usually as a consequence of long-term nephrotoxic therapy. There is a need for a simple method of assessment of renal function in this patient group. We compared measured creatinine clearance from validated timed urine collections (the generally accepted practical test of glomerular filtration) with 10 formulae used to estimate creatinine clearance in a group of 74 CF adult patients and 29 matched normal controls. Compared to direct measurement, formulae gave a range of values (95% CI for mean bias -13 to +27.9 ml/min). Even those with the best correlation (r=0.7) gave wide error ranges (limits of agreement: -42.3 to 45.9 ml/min). The most commonly used formulae (Cockroft-Gault [CGF] and abbreviated Modification of Diet in Renal Disease [aMDRD]) were not superior to most other formulae tested. Both CGF and aMDRD-derived estimates compared less favourably in CF patients than controls (mean bias: 9.7 vs 3.4 ml/min (p<0.05) and 4.9 vs 1.4 (p<0.05) respectively; 78% vs 95% (p<0.01) and 77% vs 97% (p<0.01) of estimates within 33% of measurement respectively). In particular, both CGF and aMDRD grossly overestimated renal function (mean bias 18.3 and 15.8 ml/min respectively, p<0.001) in CF patients with reduced creatinine clearance (<80 ml/min). CGF, aMDRD and other formulae cannot be used to reliably assess renal function in CF patients, since they will fail to detect those with renal impairment. Some form of carefully supervised direct measurement is still required.

Decreased lung function in female but not male subjects with established cystic fibrosis-related diabetes

OBJECTIVE

Although cystic fibrosis-related diabetes (CFRD) is associated with decreased lung function, sex is not known to influence CFRD. However, compared with male subjects with cystic fibrosis, female subjects with cystic fibrosis have increased morbidity. This study examines the association between female subjects with CFRD and poor lung function relative to male subjects using the percent predicted forced expiratory volume in 1 s (FEV(1)) as a surrogate measure of morbidity.

RESEARCH DESIGN AND METHODS

We compared 323 patients with established CFRD with 489 cystic fibrosis control subjects with normal glucose tolerance (NGT) listed in the U.K. Cystic Fibrosis Database. Patients stratified by sex and chronic Pseudomonas aeruginosa infection were compared using binary logistic regression, and patients with new CFRD diagnoses were compared prospectively for the year 2002.

RESULTS

CFRD in female subjects (but not male subjects) without chronic P. aeruginosa infection had a 20% lower percent predicted FEV(1) compared with control subjects with NGT (95% CI -11.7 to -27.7; P < 0.0001). Genotype, age, treatment center, age at diagnosis of cystic fibrosis, pregnancy, liver function, or dose of pancreatic enzyme replacement therapy did not confound this female disadvantage. Comparison of female subjects with newly diagnosed CFRD free of chronic P. aeruginosa infection with matched control subjects with NGT showed no FEV(1) disadvantage in the 1st year after CFRD diagnosis.

CONCLUSIONS

Only female subjects with CFRD have significantly decreased lung function compared with sex-matched NGT control subjects. The absence of poor lung function in the first 12 months after diagnosis of diabetes suggests that an opportunity may exist to intervene and possibly prevent a decline in lung function, which can be as much as 20% in female subjects with CFRD.

Energetic cost of physical activity in cystic fibrosis children during Pseudomonas aeruginosa pulmonary exacerbation

Chronic pulmonary infection by Pseudomonas aeruginosa is observed in 50% of patients with cystic fibrosis and requires the use of recurrent intravenous therapy. A decrease of resting energy expenditure (REE) and an increase of physical activity (PA) after intravenous anti-P. aeruginosa therapy (IVAT) is observed while total energy expenditure (TEE) does not change. A decrease in the energetic cost of physical activity (ECPA) could be hypothesized but has never been studied. Our aim was to assess the evolution of ECPA after home IVAT in both standardized condition at hospital and in free-living condition twice before and after IVAT. Sixteen CF patients (nine boys, seven girls) chronically colonized by P. aeruginosa with a mean age of 12.1+/-2.3 years (range 7.1-14.6) were studied before and after IVAT. Each patient passed throughout a visit in hospital: weight, height and fat-free mass were measured. Then, energy expenditure (EE) measured by indirect calorimetry and heart rate (HR) were simultaneously recorded at different levels of PA: REE, and at different intensity of physical activities on a cycloergometer using an incremental increase of the power brake force. Physical activity energy expenditure (PAEE) was computed in laboratory condition using PAEE=EE-BEE (basal energy expenditure). Linear regression between PAEE and power brake force was fitted for each patient before and after IVAT. ECPA in standardized conditions was compared at different range of power brake force using area under the curve (AUC). After coming back at home, 24 h TEE using the heart rate monitoring technique and PA by triaxial accelerometry were simultaneously measured in free-living condition for 24 h during a school day. ECPA in free-living conditions was compared by the ratio PAEE:PA where PAEE=DEE-REE (DEE=daily energy expenditure). After IVAT, median AUC between 60 and 90 W in standardized condition decreased significantly by -15.4% (median 14.9, range 8.8-30.3 vs. median 12.6, range 8.5-17.6; P<0.05, Wilcoxon rank test) while the decrease for lower range of power work load did not reach significance. Spearman correlation was significant between variations of forced expiratory volume in 1 s and variation of AUC at 30-60 W before and after IVAT in standardized condition. In free-living conditions, ratio PAEE/PA did not vary significantly (median 3.4, range 1.6-6.4 vs. median 2.8, range 1.4-4.8; NS). Our data demonstrate a decrease of ECPA after IVAT in standardized conditions for moderate level of PA (60-90 W), but not in free-living conditions. The decrease of ECPA was probably due to a decrease in the energetic cost of breathing after IVAT, that is particularly relevant to promote PA in CF patients.

Muscle Function and Resting Energy Expenditure in Female Athletes with Cystic Fibrosis

The pathophysiology of impaired exercise tolerance in patients with cystic fibrosis (CF) is not completely understood. The objective of this study was to compare exercise ability (at clinical and cellular levels) and resting energy expenditure in female athletes with CF compared with matched control subjects. Sixteen subjects and matched control subjects participated in the study. The girls with CF not only had a significantly greater resting energy expenditure (7.6% higher; p<0.05), their habitual daily activity was also significantly greater than that of control subjects (15% greater; p<0.01). Peak aerobic capacity was similar in both groups. However, peak anaerobic power was 20% less (p<0.05) in girls with CF. The 31P magnetic resonance spectroscopy studies demonstrated that there were no differences between the groups at rest, but at 25% total work output the girls with CF were less acidotic (CF, pH 6.99 [0.06]; control subjects, 6.90 [0.05]) and had a significantly lower inorganic phosphorus-to-phosphocreatine ratio (CF, 0.34 [0.07]; control subjects, 0.41 [0.08]). These differences continued to increase to maximal exercise. This study demonstrates that in spite of normal lung function and good nutritional status, females athletes with CF still had significant deficiencies in some measures of fitness and muscle metabolism compared with healthy athletes.

Impact of intravenous antibiotic therapy on total daily energy expenditure and physical activity in cystic fibrosis children with Pseudomonas aeruginosa pulmonary exacerbation

Resting energy expenditure (REE) increases during pulmonary exacerbation by Pseudomonas aeruginosa in cystic fibrosis (CF) patients, and decreases after i.v. anti-Pseudomonas aeruginosa antibiotic therapy (IVAT). However, the impact of IVAT on total energy expenditure (TEE) is unknown. The aim of this study was to assess the changes in TEE and its main components after IVAT administered at home. Body composition measured by skinfold thickness and bio-impedance analysis, energy intake (EI) assessed by a weekly diary, REE measured by indirect calorimetry (IC), TEE assessed by a technique using 24-h heart-rate monitoring method and physical activity (PA) monitored using an activity diary (AD) were assessed in 16 patients (9 boys and 7 girls) aged 12.1 +/- 2.3 y (range, 7.1-14.6 y), before and after 28 +/- 4 d including a 14-d IVAT course. After IVAT, weight increased significantly by 1.9% (32.1 +/- 7.5 versus 32.7 +/- 7.6 kg; p < 0.05), while fat mass and fat free mass increased non significantly. EI increased by 4.6% (10,797 +/- 3039 versus 11320 +/- 3074 kJ/d; p < 0.05). TEE was not affected by IVAT (7014 +/- 1929 versus 7081 +/- 1478 kJ/d) whereas REE decreased by 4.1% (5295 +/- 909 versus 5093 +/- 837 kJ/d; p < 0.05), resulting in 9.3% increase in PA assessed by AD converted to metabolic equivalent tasks (MET) (37.0 +/- 3.1 versus 40.7 +/- 4.5 MET; p < 0.05). The improvement in nutritional status after IVAT is not related to a decrease in TEE, but probably to an increase in EI and a decrease of REE after IVAT. After IVAT, the reduction in REE is probably compensated by an increase in PA in CF patients.

Resting energy expenditure and lung disease in cystic fibrosis

Optimal nutritional support is considered to be an integral part in the management of cystic fibrosis (CF). Several factors contribute to increased resting energy expenditure (REE), which itself can lead to energy imbalance and thus contribute to deterioration of the nutritional status. We aimed to assess the impact of lung parenchyma damage on REE and correlated these findings with forced expiratory volume in 1 s (FEV(1)). Twenty patients performed respiratory function testing (FEV(1)), pulmonary high-resolution computed tomography (HRCT) and assessment of REE with open circuit indirect calorimetry. HRCT was scored by using a modified Bhalla method. Mean HRCT score was 8.4 and mean REE value was 108.4% predicted vs. 96.5% predicted of 16 healthy subjects (P<0.01). There was a significant correlation between HRCT score and REE (P<0.01), HRCT score and FEV(1) (P<0.001) and REE and FEV(1) (P<0.05). The correlations demonstrate a close correlation between lung damage and elevated REE in people with CF. Prevention of negative energy balance is an important part in follow-up of patients with CF. Any increase in REE should raise suspicion of progress in lung impairment.