Down syndrome (DS), the trisomy of chromosome 21, is the most common chromosomal abnormality, occurring in 1 of 800 live births.1,2 Down syndrome includes a combination of birth defects, mental retardation, muscle hypotonicity, hypermobility of the joints or ligament laxity, light to moderate obesity, characteristic facial features, heart defects, increased infection, an underdeveloped respiratory and cardiovascular system, pulmonary impairments, visual and auditory problems, poor balance, perceptual difficulties, and other health problems.3,4
Children and adolescents with DS or other forms of intellectual disability seem to have reduced lung function and increased respiratory infections compared with healthy, age-matched controls.5 Children with DS have been reported to have upper and lower airway diseases and abnormalities.6,7 They have a higher incidence of respiratory infections, pneumonia and acute lung injury, and respiratory distress syndrome than children without DS. They are also at risk for restrictive pulmonary disease with decreased lung volumes and a weak cough because of generalized trunk and extremity weakness.8,9
The factors contributing to these problems include hypotonia; muscle weakness, particularly of abdominal and shoulder muscles; overweight or obesity; immune dysfunction; cardiac disease; large airway compression; small upper and lower airway volume; decreased numbers of alveoli; reduced lung surface area; tracheobronchomalacia; pulmonary hypoplasia; relative glossoptosis; increased secretions; nasal congestion; tonsils; and adenoids.10,11
Pulmonary problems are a primary cause of hospital admission and/or morbidity, particularly in young children with DS. These problems are underrecognized; most textbooks do not make reference to these problems and published research on these problems is lacking.12–14
The cardiovascular and respiratory systems work closely together to ensure sufficient amounts of oxygen are carried to organs. If lung volume or the amount of oxygen is reduced, removal of carbon dioxide may be deficient, therefore limiting available energy for physical activities.15,16
Poor physical activity and fitness resulting from the lower level of cardiopulmonary fitness and pulmonary problems have been reported several times in children with DS compared with peers who are healthy.17,18 This can affect their abilities to work and perform activities of daily living, worsen quality of life, and lead to a shortened life span.19,20
Medical personnel working with children with DS should focus on improving their pulmonary functions and preventing pulmonary infections. Early initiation of pulmonary therapy or exercise programs for restoration or maintenance of respiratory function should be provided. Pulmonary therapy for children with DS includes careful positioning to optimize ventilation and perfusion, postural drainage, percussion, vibration, and breathing exercises.11
Exercise programs should include strengthening and endurance exercise for primary and accessory respiratory muscles and strengthening exercise for abdominal and shoulder muscles.11,12 Although research evidence of weakness of neck and shoulder muscles of children with DS has never been published, it has been noted and recognized in clinical reports.21
Aerobic exercise is considered an important component of the pulmonary rehabilitation program to improve the patient's functional and physiological status. Aerobic exercise most commonly consists of track or treadmill walking, upright or recumbent cycling, rowing, stair stepping, elliptical trainer exercise, and arm ergometer training. A combined program of progressive resistance and aerobic exercise may have a larger effect on cardiovascular fitness than aerobic exercise alone in people with DS.22–25
Most pulmonary rehabilitation programs concentrate on lower extremity training using stationary cycle exercise, treadmill walking, or ground-based walking, but very few studies emphasizing strengthening exercises for upper extremities have been conducted.
Pulmonary function tests are objective, simple, feasible, quantifiable, and inexpensive measurements that can be used in a clinical setting to determine baseline respiratory function, detect pulmonary problems, and monitor gain from a physical rehabilitation program instead of invasive and expensive diagnostic methods such as chest x-ray, computerized topography, and bronchoscopy.26,27 Few investigations of pulmonary functions in children with DS have been published.12
The purposes of this study were to determine the effects of an aerobic training regimen for upper extremities, using a rowing ergometer, on the pulmonary functions in children DS and to compare its effectiveness with that of a chest physical therapy program.
Thirty-five children with DS, 19 boys and 16 girls, participated in this study. They were selected according to the following criteria: age between 8 and 12 years, able to walk independently, no associated congenital heart abnormalities nor musculoskeletal problems, not obese, no serious visual and/or auditory problems, and not participating in any sport activities.
The participants' IQs were previously determined on the Stanford-Binet Intelligence Scale administered by specialists, indicating they could understand and follow instructions. Medical clearance from the participant's physician was obtained before participating in this study.
They were recruited from the outpatient clinic, Faculty of Physical Therapy, Cairo University. Written consents and agreements were obtained from the children's parents for their participation in this study. This study was approved by the Department and the Faculty Internal Research Committee and Review Board.
The included children were assigned randomly into 2 study groups. Study group A received a chest physical therapy program, and study group B received an aerobic training regimen. The treatment programs for both study groups were conducted for 20 to 30 minutes, 3 times per week, for 12 successive weeks.
A third group (C) consisted of 20 children without DS who were healthy using the same inclusion criteria applied to the study groups. They were included in this study solely to measure the following pulmonary functions: vital capacity (VC), forced vital capacity (FVC), forced expiratory volume after 1 second (FEV1), and peak expiratory flow rate (PEFR) and were not subjected to any exercise programs. The posttreatment results in both study groups were matched with results from this healthy group.
Participating children were allocated randomly to the chest physical therapy group or rowing ergometer group. Randomization was performed simply by adding a specific identification number for each child. Figure 1 shows the recruitment process and the flow of participants through the study.
Materials and Procedures
A Zan-680 Ergospirometry system was used as a recording device for synchronous registration of breathing flow, respiration volumes as well as inspired and expired gases. It consists of a breath gas (O2 and CO2) analyzer, gas bottle, rubber mouthpiece, clips, mask, and computer unit that manipulate and analyze the measured parameters.
The ergospirometry system was used to measure the ventilatory functions of the participating children pre- and postapplication of treatment. The measured ventilatory parameters included VC to evaluate lung tissue dispensability; FVC to evaluates the airway resistance, lung size, and elastic properties of the lung; FEV1, the reference standard pulmonary function test as it relates closely to the development of obstructive lung disease; and lastly PEFR. All the measurements were done pretreatment and after 12 weeks, that is, posttreatment.
A weight and height scale was used to measure the children's weight (in kilogram) and height (in centimeter), as these data are necessary for calculations performed by the Zan-680 Ergospirometry system.
A rowing ergometer (Kettler Coach, 8 speeds, Henze Kettler GMPH and Co. D 59469. ENSE-PARSIT—Type 7985—made in Germany) was used for providing aerobic exercise training for the children. This rowing ergometer has 8 levels of resistance ranging from level 1, the least resistance, to level 8, the most resistance.
The participants in study group A received a chest physical therapy program including positioning, breathing exercises, and postural drainage in addition to incentive spirometer training. The participants in study group B received an aerobic training regimen using a rowing ergometer.
The rowing ergometer regimen used in this study was modified from Pitetti and Tan.28 The characteristics of the rowing ergometer regimen were as follows:
- The regimen consists of 3 phases, each phase lasted 4 weeks.
- The duration of rowing exercises in each session was 10 minutes for the first 4 weeks (phase 1) and increased by 5 minutes in each successive phase until the duration in the last phase (phase 3) was 20 minutes.
- A warm-up for 5 minutes before starting the procedures and a cool-down for 5 minutes after finishing the procedures were included.
- The warm-up and cool-down phases consisted of stretching exercises for upper and lower extremities and thoracic mobility exercises.
- After the warm-up period, the participants were instructed to exercise using the rowing ergometer equipment.
- The level of resistance in the first phase ranged from 1 to 2, progressed to 2 to 3 in the second phase until reaching 3 to 4 in the final phase.
- In each phase, every participant performed the rowing exercise on the basis of 2-minute work and 1-minute rest.
- The intensity of this training regimen was designed to exercise participants at target heart rates of 50% to 80% of their maximum heart rate calculated by the Karvonen method.29 The target heart rate was monitored using a polar heart rate monitor, recorded every minute, and averaged for each session. The intensity was increased as the exercise training program progressed (50%-60% in the first phase, 60%-70% in the second phase, and 70%-80% in the third phase).
- Throughout the exercise regimen, the researchers were present to ensure safety and to encourage the participants during the exercise session.
- Children's performance was below the threshold of pain and breathlessness.
During the performance of the rowing ergometer exercises the following procedures were followed:
- At the beginning of the program, each child was familiarized with the rowing ergometer and taught how to use this equipment.
- The amount of resistance on the flywheel was adjusted in each session according to the regimen phase.
- Each child was instructed to sit on the seat and gently ease it to the front of the machine and look forward as much as possible.
- The participant's feet were strapped into the foot plates, and the nylon straps were tightened around the top of his/her shoes.
- Then, each child was instructed to lean forward to grab the handlebar and extend his/her legs so that the seat was at the back of the slide.
- Once the legs were extended, the participant was instructed to lean back slightly and bring the handle all the way to his/her stomach.
- Then, the participant was instructed to begin rowing by extending his/her arms all the way forward, leaning forward, keeping his/her arms straight out. While keeping arms straight, he/she was asked to flatten his/her knees and then lean back slightly. The stroke finished by pulling his/her arms into his/her own chest.
- The process was repeated in a continuous motion.
- The display on the screen recorded how many meters each participant had rowed.
Figure 2 illustrates the rowing technique.
Means and standard deviations were calculated for each variable pre- and posttreatment for both study groups (A and B) and for the healthy group (C). For groups A and B, all mean values of recorded data were tested for significance by using a paired t test to compare pre- and posttreatment values within each group. Also, unpaired t tests were used to compare values pre- and posttreatment between groups. Comparisons among the 3 groups posttreatment were examined with a repeated-measures analysis of variance test and a least significant difference test. The α level for statistical significance was set at 0.05.
The results of this study, as illustrated in Table 1, showed no significant difference in the mean values of age, weight, and height of the participating children included in groups A and B. The means and standard deviations of demographic data and measures of ventilatory functions of the children who were healthy included in group C are presented in Table 2.
Table 3 includes the mean values of VC, FVC, FEV1, and PEFR pretreatment for groups A and B, which reveals no significant between group differences. As revealed in Tables 4 and 5, significant improvements were found in the mean values of all measured variables posttreatment for groups A and B.
Also, the findings of this study, as elucidated in Table 6, revealed no significant difference in the mean values of all measured variables when comparing the posttreatment results of both groups A and B. Finally, a comparison between the mean values of all measured variables for all groups A, B, and C posttreatment was reported in Table 7 and better values were recorded in group C than in the other groups.
Children with DS frequently have pulmonary problems, leading to a low level of performance of their activities of daily living and many other bad sequels. Unfortunately, these pulmonary problems may not receive sufficient attention from clinicians engaged in treating these children, while instead concentrating only on improving of their physical and intellectual capabilities.
Therefore, we believe finding other treatment techniques that could be effective in improving their pulmonary functions and minimizing or even preventing the serious consequences of these respiratory difficulties to be very important. Accordingly, this study was conducted to evaluate the effect of an aerobic training regimen using a rowing ergometer on the pulmonary functions in children with DS and to compare the effectiveness of that program with that of traditional chest physical therapy program.
The results of this study indicated that all participating children in groups A and B showed improved pulmonary functions of VC, FVC, FEV1, and PEFR toward the normal values recorded in group C. The significant improvements recorded immediately posttreatment in both groups A and B might be due to the provision of sufficient opportunities to practice the pulmonary therapy.
However, these posttreatment improvements were small and still far from the reference values for children who are healthy. This is evidenced by the significant difference registered in the mean values, for most measured variables, for children without DS when compared with posttreatment values for children in groups A and B. Therefore, these improvements may have little effects in the practical situation of these children and the actual effect size may have no clinical meaning.
Accordingly, clinicians may need to extend the duration of aerobic exercise programs or combine several programs of pulmonary rehabilitation together on the basis of the child's capacity. The results also indicate the need to search for other methods, tools, devices, and other rehabilitation programs to improve cardiopulmonary functions and fitness of children with DS.
The improvement recorded in group A posttreatment may be attributed to the application of the chest physical therapy program. It aimed to improve efficiency of ventilation by using positioning, postural drainage, percussion, and deep-breathing exercises using incentive spirometry. The chest physical therapy program helped participating children improve their pulmonary functions and circulation, and may have prevented infection of the lung by improving alveolar ventilation, venous return, and lymph drainage and decreasing dead space ventilation.30
Posttreatment improvement in group A may also have resulted from strengthening of respiratory muscles, which may be responsible for the improvement in the pulmonary functions, exercise capacity, and endurance, which also helps in the reduction of dyspnea and symptoms of breathlessness and maintaining positive pressure in the airways, especially through removal of excessive secretions.31,32 Positioning of children with DS in a way that could optimize both pulmonary and perfusive lung functions, enhance bronchial clearance of secretions, and facilitate oxygen transport may also have contributed to these results.33–34 Postural drainage, which is used frequently as a component of chest physical therapy and pulmonary rehabilitation programs, might be effective in mobilizing and clearing out secretions, may also prevent chest infections and allow more alveolar ventilation and improved pulmonary functions.35 Finally, the combination of chest physical therapy and incentive spirometer procedures may have contributed to the improved function in group A. This is in agreement with Karakoc et al36 who showed a significant improvement in ventilatory functions in patients with asthma during the application of the pulmonary rehabilitation program together with incentive spirometer training.
Several studies evaluated the effectiveness of the incentive spirometer on adult and elderly patients suffering from chronic pulmonary emphysema and chronic obstructive pulmonary disease, and they found incentive spirometry reduces the resistance to air flow by increasing lung volume, and improves deep diaphragmatic breathing and expansion of collapsed areas.30,37 Incentive spirometry also increases VC, FEV1, PEFR, and maximum voluntary ventilation.38 Tecklin39 also reported that the incentive spirometer gives visual feedback for diaphragmatic training.
The improvements in group B posttreatment might be due to the application of the rowing training program, a form of aerobic exercises, which could improve the ventilatory functions in children with DS.
The sedentary lifestyle of people with DS is believed to be among the main factors contributing to muscle weakness and hypotonia, higher prevalence of circulatory abnormalities, poor function of the pulmonary system, pulmonary abnormalities, and decreased levels of physical fitness.22,40,41 Reduced thoracic, abdominal, and shoulder muscle performance could contribute to poor lung function. Field tests consistently demonstrate that abdominal and thoracic muscle strength and endurance are reduced in children and adolescents with intellectual disability.42 Khalili and Elkins11 reported that exercise had a small but statistically significant effect on lung function in children with intellectual disability such as children with DS.
Aerobic exercise produces a training effect, improves ventilatory functions, and increases the capacity to use oxygen in several ways: by toning up muscles throughout the body, improving general circulation, lowering blood pressure, and reducing workload on the heart; strengthening muscles of respiration and thus reducing resistance to air flow, ultimately facilitating rapid flow of air in and out of the lungs; improving the strength and pumping efficiency of the heart, enabling more blood to be pumped with each stroke, resulting in improved ability to transport more oxygen rapidly from the lungs to the heart and to all parts of the body. These training effects further lead to an increase in the number of red blood cells and the amount of hemoglobin, making the blood a more efficient oxygen carrier. Therefore, aerobic exercises not only promote respiratory system improvement as chest physical therapy but also improve many other systems, which in turn improve the respiratory system.43
The result of this study concerning the general effect of aerobic exercises in improving of pulmonary functions is consistent with the work of Saudo et al,44 Harver et al,45 Tomohiro et al,46 Sutbeyaz et al,47 and Emiel.48 The positive effect of pulmonary rehabilitation and aerobic exercises on pulmonary functions and cardiopulmonary fitness, particularly for children with DS, has also been supported by Vicente-Rodriguez et al23 and Tylor et al.25
The findings of this study also coincide with the work of Khalili and Elkins11 who found that 8-week program of aerobic exercise could improve lung functions significantly in children with intellectual disability, and Ozmen and colleagues24 demonstrated a significant improvement in exercise capacity for 8- to 15-year-old children with intellectual disability who received a 10-week aerobic exercise regimen. Similar findings were proved by Rimmer et al,19 and Heller et al49 who reported the effectiveness of the exercise program on improving cardiopulmonary fitness and muscle strength in adults with DS.
On the other hand, Ordonez et al,50 who provided aerobic training for 22 male adolescents with DS for 12 weeks, found no cardiopulmonary effect although significant decreases in the percentage of fat mass, assessed by anthropometry, was found. In the same context, Varela et al,51 who conducted a 16-week rowing ergometer training regimen for 16 adolescents and young adults with DS, reported that even though they achieved higher levels of work performance, neither evidence of changes in body weight nor in cardiopulmonary responses was found either on the treadmill test or on the rowing test.
Biersteker and Bierteker52 reported that lung volumes were not affected by rowing activity in young, healthy adults, and Smith et al53 and Larson et al54 failed to support the effectiveness of aerobic exercise on pulmonary functions in adult patients with chronic obstructive pulmonary disease.
Aerobic training with a rowing ergometer could be helpful in improving pulmonary functions in children with DS and should be considered during their rehabilitation. Further study should be focused on the effectiveness of aerobic exercise programs using the upper extremities on pulmonary function of children of different ages and with different pathologies. Future studies are also recommended to determine which types of aerobic exercise programs are clinically worthwhile and to detect the ideal duration and intensity of the program that could be the most useful for improving pulmonary functions of children and adults with DS.
We extend our gratitude to the participating children and their parents without whose contributions this study would not have been accomplished. Special thanks are extended to Dr Ashraf Abdelaal, Assistant Professor of Physical Therapy, Cairo University, and Dr Alaa Abdulhafiz Khushhal, Lecturer of Physical Therapy, Umm Al Qura University, for their continuous support and encouragement.
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