Cardiopulmonary Exercise Test Using Arm Ergometry in Children With Spina Bifida: A Prediction Model for VO2 peak

Tuijtelaars J, Leonardi-Figuiredo MM, Crescêncio JC, et al. Cardiopulmonary Exercise test using arm ergometry in children with spina bifida: A prediction model for VO2Peak. Pediatric Physical Therapy. 2019;31(2):185-190. doi:10.1097/pep.0000000000000590

Link to Original Article: https://journals.lww.com/pedpt/fulltext/2019/04000/cardiopulmonary_exercise_test_using_arm_ergometry.15.aspx

Key Points

- The aim of the study was to develop a prediction model for peak oxygen uptake (VO2 peak) in children with spina bifida (SB) using a graded arm crank test.

- Data from 26 participants with SB were used to develop the prediction model, and an unrelated data set of participants with SB was used for validation.

- The developed equation to predict VO2 peak in participants with SB was VO2 peak (mL/min) = 194 + 18 x peak workload - 110 x sex (with sex defined as 0 for boys and 1 for girls).

- The prediction model showed a nonsignificant mean difference between the measured and predicted values of VO2 peak, as well as excellent agreement between the values.

- The model explained 93% of the variance in VO2 peak and showed promising results, but further validation using the same protocol is needed before implementation in clinical practice.

- The study highlights the importance of cardiopulmonary exercise testing in evaluating aerobic fitness and suggests that peak work rate in an arm crank test can be a good predictor of VO2 peak in children with SB.

Introduction

Spina bifida is a congenital disorder that results in neural tube defects and can cause deficits in muscle function, sensory function, and cognition. Individuals with spina bifida have poor aerobic fitness, making them more susceptible to secondary impairments like obesity, type 2 diabetes, and cardiovascular disease. Exercise testing, specifically cardiopulmonary exercise testing (CPET), is widely used to evaluate aerobic fitness, but it is expensive and impractical for clinical use. This study aims to develop and validate a prediction model for aerobic fitness in children with spina bifida using the graded arm crank test.

The graded arm crank test is an incremental protocol on an arm ergometer and has shown success in children with cerebral palsy. The researchers hypothesize that peak work rate (W peak) obtained during this test may be a good predictor of maximum oxygen uptake (VO2 peak), thus eliminating the need for expensive equipment. In addition to W peak, the study considers other factors such as age, sex, anthropometric measures, physical activity, level of the lesion, and the Hoffer classification.

The significance of this research lies in its potential to provide a feasible alternative to costly exercise testing methods. By utilizing the arm crank test, clinicians can assess aerobic fitness in children with spina bifida without the need for specialized equipment. This can help identify individuals at risk for secondary impairments and enable targeted interventions to prevent future health complications. Ultimately, the development and validation of a prediction model for VO2 peak using the graded arm crank test can contribute to improved clinical practice and better outcomes for children with spina bifida.

Methods

Participants

The study recruited 31 participants between the ages of 8 and 16 who had been diagnosed with spina bifida (SB) and were receiving treatment at the Infant Neurological Walking at Clinical Hospital in Ribeirão Preto, Brazil. All participants were required to have medical permission from their neurologist to participate in a maximal exercise test and had to be able to understand simple instructions. Participants were excluded if they had experienced any bone fractures in their upper limbs within the past year. Informed consent was obtained from all participants and their parents. Participants were also required to avoid intense exercise at least 24 hours prior to taking part in the exercise program and had to maintain a normal diet. To assess the level of lesion, each participant was assigned a classification based on the American Spinal Injury Association, which included four different levels: sacral, low lumbar, high lumbar, and thoracic. The walking level of each participant was also determined using the classification system developed by Hoffer et al and adapted by Schoenmakers et al. This included categories such as normal walking, community walking, household walking, therapeutic walking, and nonwalking. These classifications were important for categorizing and analyzing the data in order to understand the relationship between different factors and predicted aerobic fitness levels in children with spina bifida.

Anthropometrics

The study assessed the participants anthropometrics by placing the participants on an electronic anthropometric scale without shoes. The participants who were wheelchair dependent was assessed by subtracting total weight to the wheelchair weight. The study assessed the body height of each participant by measuring the arm span and estimating the height. For participants with sacral and low lumbar lesion, arm span width was adjusted by 0.90. For participants with high lumbar and thoracic lesion, arm span width was adjusted by 0.95.

Body Composition

The study utilized bioelectrical impedance (Biodynamics 450) to assess body composition. Prior to the measurement, participants were instructed to minimize liquid intake and empty their bladders. The measurement was performed with the participant lying in the supine position, with their hands and feet placed away from the body. Electrodes were then placed on the right foot and hand, after cleaning the skin with alcohol. Specifically, on the foot, the distal electrode was positioned at the base of the second toe, while the proximal electrode was placed between the medial and lateral malleoli. On the hand, the distal electrode was placed at the base of the third finger, and the proximal electrode was positioned at the wrist near the styloid process. This method allowed for the determination of body composition parameters such as lean mass, fat mass, and percentage of body fat. By employing bioelectrical impedance, the researchers were able to obtain objective measurements of body composition, which is essential for understanding the effects of spina bifida on body composition and for monitoring changes in body composition over time. This information is crucial for clinical practice, as it aids in the development of targeted interventions to improve the health and well-being of children with spina bifida. Additionally, the use of bioelectrical impedance is a cost-effective and non-invasive alternative to more expensive and complex exercise testing methods, making it a feasible option for assessing body composition in this population.

Physical Activity

The study utilized the Physical Activity Questionnaire for Children (PAQ-C) to assess the level of physical activity in the participants. The questionnaire is a valid tool for evaluating the general physical activity levels of Brazilian youth based on activities performed within the past 7 days. Each participant's physical activity level was classified into categories including extremely sedentary, sedentary, moderate activity levels, active, and high activity levels. To make the questionnaire applicable to wheelchair users, the first part of the questionnaire was modified. This section listed different types of activities performed by the participants, but some activities were not feasible for this population and were therefore removed from the list. This adaptation ensured that the questionnaire accurately captured the physical activity levels of the participants with spina bifida. The assessment of physical activity in this study is significant as it provides insight into the level of activity among children with spina bifida and enables the development of appropriate intervention strategies. Understanding the physical activity levels in this population is crucial for promoting their overall health and well-being. Additionally, the adaptation of the questionnaire for wheelchair users highlights the importance of incorporating inclusive measurement tools for accurate and comprehensive assessment of physical activity.

Cardiopulmonary Exercise Test

The study aimed to develop and validate a prediction model for VO2 peak in children with spina bifida using the graded arm crank test. The test was performed using an electromagnetically braked arm cranking ergometer with respiratory gas analysis. The protocol consisted of a warm-up phase, a load phase with increasing resistance, and a recovery phase. The test was stopped when participants could not maintain the required pace. Maximal effort was determined using objective criteria such as respiratory exchange ratio and heart rate, as well as subjective criteria such as unsteady arm cranking and unwillingness to continue. The findings suggest that the arm crank test is a feasible alternative to costly exercise testing methods for assessing aerobic fitness in children with spina bifida. The study considered various factors, including W peak, HR peak, age, sex, anthropometric measures, physical activity, level of the lesion, and the Hoffer classification, to determine the best predictor of aerobic fitness in this population. This research has important implications for clinical practice as it provides a reliable and cost-effective method for assessing aerobic fitness in children with spina bifida. By identifying the best predictor of VO2 peak, healthcare professionals can better tailor interventions to improve the aerobic capacity of these individuals, ultimately enhancing their overall health and well-being.

Data Analysis

The study aimed to develop and validate a prediction model for VO2 peak in children with spina bifida using the graded arm crank test. The researchers considered various factors, including W peak, HR peak, age, sex, anthropometric measures, physical activity, level of the lesion, and the Hoffer classification, to determine the best predictor of aerobic fitness in this population. Peak values of the CPET parameters were calculated as the mean over the final 30 seconds of the test, and scatterplots were used to check linearity of relationships with VO2 peak. Stepwise univariate linear regression analyses were performed to identify significant predictors, and the absolute or relative value of VO2 peak that had the best linearity was used as the dependent variable in the prediction model. The standard error of the estimate (SEE) was used as the accuracy measure for the developed prediction model. To validate the model, data from 13 participants with spina bifida were used, and tests were conducted to assess the significance and agreement between measured and predicted values of VO2 peak. The Shapiro-Wilk test was used to check for data normality, and paired-samples t-tests or Wilcoxon signed-rank tests were used accordingly. The intraclass correlation coefficient (ICC) model 2.1.A was calculated for reliability, with values above 0.7 considered acceptable or higher. A Bland-Altman plot was used to visually interpret the agreement between measured and predicted values. An α of .05 was used for significance in all analyses. This research is significant for clinical practice as it provides a potentially valuable tool for predicting aerobic fitness in children with spina bifida, using a cost-effective and feasible arm crank test instead of more expensive exercise testing methods.

Results

Participants

Out of 31 participants with SB, 5 participants were excluded due to no meeting both subjective and objective criteria for maximal exercise testing.

Prediction Model

The research study aimed to develop and validate a prediction model for VO2 peak in children with spina bifida using the graded arm crank test. Data from 26 participants were used to develop the model. The study found that VO2 peakabs could be better predicted by independent variables than VO2 peakrel, leading to the development of a prediction model for VO2 peakabs. Linear regression analysis showed that W peak was the main independent variable significantly correlated with VO2 peakabs.

In the multiple regression analysis, variables strongly and significantly correlated with VO2 peak were included. Due to multicollinearity, only W peak, sex, fat-free mass, PAQ-C score, level of the lesion, walking level, and body mass index were included in the model. By incorporating W peak and sex, the prediction model could explain 93% of the variance in VO2 peakabs.

The derived equation for predicting VO2 peak abs was VO2 peak (mL/min) = 194 + 18 × peak workload -110 × sex (0 for boys, 1 for girls). The standard error of estimation (SEE) was determined to be 96 mL/min.

The significance of this research lies in its potential application in clinical practice. The prediction model allows clinicians to estimate VO2 peak in children with spina bifida using the arm crank test, which is a feasible alternative to costly exercise testing methods. By incorporating factors such as W peak and sex, the model provides a reliable and practical tool for assessing aerobic fitness in this population. This can aid in individualizing exercise programs, monitoring progress, and promoting optimal health outcomes for children with spina bifida.

Validation of the Model

The researchers validated their prediction model for VO2 peak in children with spina bifida using data from participants collected in a previous study. They excluded four individuals who did not meet the criteria for maximal effort, resulting in a sample size of nine participants. The predicted VO2 peakabs value was calculated using the model and showed no significant difference from the measured VO2 peakabs value. The intraclass correlation coefficient (ICC) between the predicted and measured values of VO2 peakabs was 0.954, indicating an excellent correlation. Bland-Altman analysis showed a mean difference between the measured and predicted values of VO2 peak of -921 mL/min, which was not significantly different from zero. The limits of agreement were 4036 and 2236 mL/min. The Bland-Altman plot displayed more variables below the zero line, indicating that the predicted VO2 peakabs value was higher than the measured value. Overall, the model demonstrated good accuracy and reliability in predicting VO2 peakabs in children with spina bifida using the arm crank test. This research is significant for clinical practice as it provides a feasible alternative to costly exercise testing methods for assessing aerobic fitness in this population. Using the arm crank test can potentially improve accessibility and affordability of assessing aerobic fitness in children with spina bifida, leading to better management and intervention strategies.

Discussion

The aim of this study was to develop a prediction model for VO2 peak in children with spina bifida (SB) using variables obtained from a graded arm crank test. The study found a strong correlation between VO2 peak and Wpeak, suggesting that Wpeak could be used as an alternative when direct measurement of VO2 peak is not feasible. Comparison with a previous study using leg ergometry showed that the prediction model developed in this study had a smaller standard error of estimate (SEE), making it more accurate for predicting VO2 peak in children with SB. The arm crank test used in this study was adapted to be synchronous, minimizing the effect of different movements and making it more suitable for clinical populations. Another study using the Shuttle Ride Test (SRiT) as a field test found that a graded arm crank test in a laboratory setting was better suited for predicting VO 2peak in individuals who use wheelchairs. The prediction model developed in this study was validated using an independent dataset and showed a small mean difference between measured and predicted VO2 peak values, indicating good accuracy. The authors recommended further validation using a larger dataset before implementing the model in clinical practice.

Limitations

This study aimed to develop and validate a prediction model for VO2 peak in children with spina bifida using the graded arm crank test. The study included various factors such as W peak, HR peak, age, sex, anthropometric measures, physical activity, level of lesion, and Hoffer classification to determine the best predictor of aerobic fitness in this population. The results of the prediction model showed promise, although a larger sample size is needed for more accurate predictions. The study also highlighted a limitation related to the arm ergometer used, as it could only be partly adjusted in height, which may have influenced the results of the cardiopulmonary exercise test (CPET) for some children. In conclusion, this research is significant for clinical practice as it provides a feasible alternative, the arm crank test, for predicting VO2 peak in children with spina bifida. It offers benefits such as being more accessible and cost-effective compared to traditional exercise testing methods. To enhance the accuracy of the prediction model, future research should involve a larger sample size and address the limitation related to the arm ergometer by using adjustable equipment.

Opportunities for Future Research

1. Further validation of the developed prediction model for peak oxygen uptake (V̇O2 peak) in children with spina bifida (SB) using a larger independent dataset.

2. Comparison of the prediction model for V̇O2 peak in children with SB using arm ergometry with other existing prediction models using leg ergometry or field tests.

3. Assessment of the efficiency and feasibility of synchronous arm cranking in children with SB and its potential impact on V̇O2 peak measurements.

4. Investigation of the applicability and effectiveness of alternative outcome measures, such as peak work rate (Wpeak), in predicting V̇O2 peak in children with SB.

5. Evaluation of the prediction model for V̇O2 peak in a broader population of children with SB, including different levels of lesion and walking abilities.

6. Examination of the long-term implications of poor aerobic fitness and the potential benefits of early interventions to improve aerobic capacity in children with SB.