Limiting factors in peak oxygen uptake and the relationship with functional ambulation in ambulating children with Spina Bifida

Abstract

The objective of this study is to interpret the outcomes of peak oxygen uptake (VO 2peak ) in children with SB and explore the relationship between VO 2peak and functional ambulation using retrospective cross-sectional study. Twenty-three ambulating children with SB participated at Wilhelmina's Children's Hospital Utrecht, the Netherlands. VO 2peak was measured during a graded treadmill-test. Eschenbacher's and Maninna's algorithm was used to determine limiting factors in reaching low VO 2peak values. Energy expenditure during locomotion (both O 2 rate and O 2 cost) and percentage of VO 2peak and HR peak were determined during a 6-min walking test (6MWT). Differences between community and normal ambulators were analyzed. VO 2peak , VO 2peak /kg, HR peak , RER peak and VE peak were significantly lower compared to reference values, with significant differences between normal and community ambulators. Limiting factors according to the algorithm were mostly ''muscular and/or deconditioning'' (47%) and ventilatory ''gasexchange'' (35%). Distance walked during 6MWT was 48.5% of predicted distance. Both O 2 rate and O 2 cost were high with significant differences between normal and community ambulators [17.6 vs. 21.9 ml/(kg min) and 0.27 vs 0.43 ml/ (kg m)]. Also %HR peak and %VO 2peak were significantly higher in community ambulators when compared to normal ambulators (resp. 97.6 vs. 75% and 90.2 vs. 55.9%). VO 2peak seems to be mostly limited by deconditioning and/ or muscular components and possible ventilatory factors. For both peak values and functional ambulation, community ambulators were significantly more impaired than normal ambulators. High energy expenditure, %VO 2peak and %HR peak reflect high level of strain during ambulation in the community ambulators. Future exercise testing in children with SB should include assessment of ventilatory reserve. Exercise training in ambulatory children should focus on increasing both VO 2peak and muscular endurance, as well as decreasing energy cost of locomotion.

Cardiopulmonary exercise testing in congenital heart disease: (contra)indications and interpretation

“…It is important that these features be considered when performing clinical exercise testing in children as well as while designing exercise programmes for young subjects. Values for children from De Groot et al 50 …”

“…50 These results are displayed in table 4. Although, the algorithm needs further validation in children, it can be helpful for the interpretation of CPET data in children with CHD.…”

Validation of the Actical and Actiheart monitor in ambulatory children with Spina Bifida

“…An overestimation was not expected because children with SB have a higher cost of locomotion [18][19][20]. Another factor might be the increased number of acticounts, as discussed earlier, in combination with an even more so increased HRAR during normal walking.…”

“…Interestingly, acticounts are lower in community ambulatory children. This is most likely explained by the fact that they ambulate a much shorter distance than do their peers who are considered normal ambulatory [20]. The concern about the Actical not being able to register different gait patterns seems to be irrelevant in thispopulation, as reflected by the in-creased acticounts during walking.…”

“…Higher levels of PAEE are associated with a pathological gait pattern due to muscle weakness in the lower extremities [18][19][20]. With different energy expenditure and locomotion patterns, the question is whether existing PAEE equations developed in healthy children are valid for ambulatory children with SB.…”