This study assessed the exercise tolerance and the cardiorespiratory responses to a training program by the six-minute walk test (6'WT) in children with congenital heart disease (CHD). Seventeen cardiac and 14 healthy children performed maximal cardiopulmonary exercise test (CPET) and 6'WT. Reliability of 6'WT was assessed in all subjects (test-retest) by Bland-Altman plots. Cardiac subjects were randomly divided in training (T-CHD) and control groups (C-CHD). T-CHD underwent an individualized training exercise at the ventilatory threshold (VT) intensity during 12 weeks. We found that the 6'WT is a reliable and reproducible test. CHD children walked a lower distance than healthy children before training (472.5 +/- 18.1 vs. 548.8 +/- 7.7 m, respectively, p < 0.001). Likewise, power output, oxygen uptake (V.O (2)), and heart rate (HR) at the maximum and the VT levels, were significantly lower in patients (p < 0.001). After training, a significant improvement of walking distance (WD) was shown in T-CHD (529.6 +/- 15.3 vs. 467.7 +/- 17.1 m, p < 0.001). The power output, VO2, HR, and V.E increased slightly (6 to 10 %, p > 0.05) at peak exercise and significantly at ventilatory threshold level (p < 0.05) in T-CHD. Significant relationships between WD and VO2max as well as VO2 at VT were founded (p < 0.05). We concluded that the 6'WT is a useful and reliable tool in the assessment and follow-up of functional capacity during rehabilitation program in children with CHD.

It is concluded that general physical training at submaximal intensity induces better aerobic fitness and improves respiratory muscle oxygenation in children with CHD.

Background: It is well known that severe lung impairment in cystic fibrosis (CF) may compromise respiratory muscle function at rest. Even though patients with CF and severe obstructive lung disease exhibit an abnormal breathing pattern during exercise (due to expiratory flow limitation), patients with CF and normal lung function reportedly have a normal breathing pattern. Objectives: The aim of the study was to assess the precise characteristics of the ventilatory pattern adopted during exercise by children with CF and mild to moderate lung disease. Methods: Nine children diagnosed as having mild to moderate CF and 9 healthy children with a similar age distribution participated in this study. Both groups performed a continuous incremental cycling protocol. Breathing and timing components were assessed during exercise. Results: Differences in the breathing pattern between children with CF and controls during exercise are illustrated in Hey plot which described a rapid shallow breathing pattern in children with CF. During exercise, children with CF showed a significantly lower mean inspiratory flow than healthy children (p < 0.001), whereas the mean expiratory flow was higher (p < 0.001). Children with CF also showed a significant increase in the end-tidal carbon dioxide pressure, which may indicate the emergence of hypercapnia. Conclusions: During exercise, children with CF (even those not suffering from advanced disease) showed signs of rapid, shallow breathing and an increase in the ventilatory response. This was essentially due to an increase in the mean inspiratory flow, which in turn suggests an expiratory flow limitation. The children were also predisposed to hypercapnia.

Resource use efficiency in Asian carp farming systems is analysed based on a survey of 2493 farms of nine countries. Multivariate classification of farms by intensity and diversity identified six farm types: four types of specialized aquaculture farms at different levels of intensity, and two types of integrated agriculture±aquaculture systems. Pondbased, specialized semi-extensive systems (using mainly inorganic fertilizers and feeds of off-farm origin), and integrated semi-intensive systems (using feeds and fertilizer of both on and off-farm origin) are by far the most common types, accounting for 59% and 27% of all farms respectively. Specialized semi-extensive systems also show the highest protein and nutrient (N and P) use efficiencies, and among the highest labour use efficiency. Super-intensive cage farms are less efficient in nutrient and labour use, but provide very high returns to land and capital investment. On average, the aquaculture components of integrated agriculture± aquaculture systems are less nutrient, land, and labour efficient than specialized semi-extensive systems. Integrated semi-extensive systems (using organic fertilizers of on-farm origin) are particularly inefficient across all indicators. Hence in practice, gains in overall resource use efficiency through onfarm integration with agricultural production are constrained by the relative inefficiency of the aquaculture subsystems on integrated farms. Although such systems can likely be improved, integration as such is not a panacea to increasing resource use efficiency. Wide variation in resource use efficiency within all systems indicates potential for substantial efficiency gains through improved management regardless of the fundamental choice of system.

The aim of this study was twofold: first, to determine the breathing strategies of children with cystic fibrosis (CF) during exercise, and secondly, to see if there was a correlation with lung function parameters. We determined the tension-time index of the inspiratory muscles (T(T0.1)) during exercise in nine children with CF, who were compared with nine healthy children with a similar age distribution. T(T0.1) was determined as followed T(T0.1) = P0.1/PImax . T(I)/T(TOT), where P0.1 is mouth occlusion pressure, PImax is maximal inspiratory pressure, and T(I)/T(TOT) is the duty cycle. CF children showed a significant decrease of their forced expiratory volume in 1 sec (FEV1), forced vital capacity (FCV), and FEV1/FVC, whereas the residual volume to total lung capacity ratio (RV/TLC) ratio and functional residual capacity (FRC) were significantly increased (P < 0.001). Children with CF showed mild malnutrition assessed by actual weight expressed by percentage of ideal weight for height, age, and gender (weight/height ratio; 82.3 +/- 3.6%). Children with CF showed a significant reduction in their PImax (69.3 +/- 4.2 vs. 93.8 +/- 7 cmH2O). We found a negative linear correlation between PImax and weight/height only in children with CF (r = 0.9, P < 0.001). During exercise, P(0.1), P0.1/PImax, and T(T0.1) were significantly higher, for a same percent maximal oxygen uptake in children with CF. On the contrary, T(I)/T(TOT) ratio was significantly lower in children with CF compared with healthy children. At maximal exercise, children with CF showed a T(T0.1) = 0.16 vs. 0.14 in healthy children (P < 0.001). We observed at maximal exercise that P0.1/PImax increased as FEV1/FVC decreased (r = -0.90, P < 0.001), and increased as RV/TLC increased (r = 0.92, P < 0.001) only in children with CF. Inversely, T(I)/T(TOT) decreased as FEV1/FVC decreased (r = 0.89, P < 0.001), and T(I)/T(TOT) decreased as RV/TLC increased (r = -0.94, P < 0.001). These results suggest that children with CF adopted a breathing strategy during exercise in limiting the increase of the duty cycle. Two determinants of this strategy were degrees of airway obstruction and hyperinflation.