Deficits in postural control in individuals with COPD - emerging evidence for an important secondary impairment
© Novamedia srl 2010
Received: 11 June 2010
Accepted: 28 November 2010
Published: 20 December 2010
Emerging evidence suggests that individuals with COPD demonstrate reductions in balance control that may be associated with an increased fall risk. The purpose of this review is to: 1) provide a brief overview of balance control and its assessment; 2) review relevant literature describing balance impairment in individuals with COPD; and 3) highlight important areas for future research. The observation of balance deficits and an increased fall risk in patients with COPD suggests the need for including balance assessment and training for patients enrolled in pulmonary rehabilitation who may be vulnerable. Further studies are needed to determine which aspects of balance are affected and to examine the impact of interventions.
KeywordsCOPD falls postural control pulmonary rehabilitation
Deficit nel controllo posturale in soggetti affetti daBPCO – evidenza emergente di un importante dannosecondario
Un’evidenza emergente suggerisce che chi è affetto da BPCO mostra una riduzione nel controllo dell’equilibrio che si può associare ad un maggiore rischio di cadute. Scopo di questa rassegna è: 1) fornire una breve revisione del controllo dell’equilibrioe delle modalità di valutazione; 2) passare in rassegna la letteratura di maggior rilievo che descrive i deficit di equilibrio nei soggetti con BPCO; 3) sottolineare le aree peculiari per le ricerche future. L’osservazione di un deficit di equilibrioe di un maggior rischio di cadute nei pazienti con BPCO suggerisce la necessità di inserire la valutazione dell’equilibrio ed uno specifico training nei pazienti che vengono arruolati in un programma di riabilitazione respiratoria e che si dimostrinoa rischio. Ulteriori studi sono necessari per determinare quali aspetti dell’equilibrio siano affetti e per valutare l’impatto degli interventi.
KeywordsCOPD falls postural control pulmonary rehabilitation
Parole chiaveBPCO cadute controllo posturale riabilitazione respiratoria
Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder characterized by progressive airflow limitation . It is one of the most important causes of death in North America and Europe, and is projected to rank third in 2020 in the global burden of disease [2, 3]. While treatment of COPD has traditionally focused on lung function, systemic effects of the disease are gaining increased attention. Although reductions in peripheral muscle performance, functional mobility and exercise capacity have been well demonstrated [4, 5], emerging evidence suggests that individuals with COPD also demonstrate important deficits in balance control [6–11].
The ability to maintain balance is critical for mobility, avoidance of falls and functional independence in daily living. Balance impairment has been associated with an increased risk of falls and a resulting increase in mortality rate among older adults [12–14]. A large cross-sectional study reported that COPD was second only to osteoarthritis in its association with the number of falls in elderly women . In a recent prospective study, individuals with COPD were found to have a projected annual fall rate of 1.2 falls per person - a substantially higher rate than that previously reported for older adults (incidence rate of 0.24) [16, 17]. Furthermore, in this study fallers with COPD showed a greater decline in health-related quality of life scores after 6 months compared to non-fallers . Given the devastating consequences of falls in older adults, an understanding of the balance deficits present in individuals with COPD is essential to guide the development of balance training and fall prevention programs for this population. Therefore, the purpose of this article is to: 1) provide a brief overview of balance control and its assessment; 2) review relevant literature describing balance impairment in individuals with COPD; and 3) highlight important areas for future research.
Balance control and assessment
Successful maintenance of balance, or postural control, requires that the centre of mass (COM) be maintained within the limits of the base of support (BOS) . This is neither a simple nor a fixed task. Rather, the ability to stand upright on two limbs is an extremely complex skill that requires the integration of multiple somatosensory, neuromuscular, as well as central nervous system (CNS) inputs, which must be constantly updated and fine-tuned under an array of situations in everyday life . While the ability to maintain balance during stance is a formidable skill in and of itself, optimal postural control requires centrally initiated dynamic postural adjustments to be made prior to the initiation of voluntary movement (such as taking a step); this must also occur in response to external perturbations which threaten to move the COM outside the BOS and potentially cause a fall [18, 20]. Both static (maintaining equilibrium with minimal movement) and dynamic (maintaining equilibrium with moving BOS) postural control are essential to maintain stability and avoid falls .
Clinical balance assessment tools are directed to screen for general balance impairments, thereby predicting fall risk [21, 22]. For example, the Berg Balance Scale - a widely accepted and psychometrically robust clinical measure of balance for older adults - is a 14-item performance based test with predictive validity for determining fall risk [23, 24]. Activities such as transfers, reaching, turning around and single legged stance are graded on a scale that ranges from 0 (unable/unsafe) to 4 (independent/efficient/safe), with higher scores indicating greater balance control. Basic functional mobility tests, such as the Timed Up and Go, and measures of balance confidence are also often considered as part of a complete balance assessment as they have been shown to correlate well with standard balance scales and with risk of falls [22, 25]. These clinical tools are both discriminative and evaluative; they allow clinicians to identify which patients may benefit from balance retraining and to monitor change in response to interventions.
While functional balance tests are easy to perform and therefore suitable for daily clinical use, laboratory techniques such as electromyography, kinematics and kinetics, provide a continuous evaluation of postural control with a level of precision not accessible in observationally-based clinical assessments . The precision of measurement and closer approximation of the physiologic components engaged in the maintenance of stability are important advantages of including such measurements in a comprehensive evaluation of balance.
Balance impairment in COPD
Overview of Studies Evaluating Deficits in Postural Control in COPD
Grant et al. 1982 
203 patients with advanced hypoxemic COPD (PaO2 51 mm Hg), age 66 yrs; 74 controls, age 64 yrs.
Measures of coordination from Halstead-Reitan Test Battery including a tactual performance test and the tapping test.
Grooved pegboard test.
Impaired perceptual-motor integration, motor dexterity and coordination in COPD vs. controls.
Butcher et al. 2004 
30 COPD (FEV1 38% predicted), age 71 yrs; 21 controls, age 68 yrs.
Timed Up and Go Posturography Community Balance and Mobility Scale.
Deficits in functional balance and ks, coordination in COPD compared to controls. Increased sway for eyes open, moving platform test.
Eisner et al. 2008 
1,202 COPD (FEV1 62% predicted), age 58 yrs; 302 age, sex and race matched controls.
Standing balance task from Short Physical Performance Battery.
Functional Reach Test.
Poorer performance on standing balance task and functional reach in COPD vs. controls.
Chang et al. 2008 
19 COPD (FEV1 46% predicted), age 69 yrs.
Timed Up and Go and postural sway in quiet stance following a 6 MWT.
Static balance in semi-tandem stance with eyes closed impaired after a sub-maximal exercise test.
Beauchamp et al. 2009 
39 COPD (FEV1 42% predicted) age 71 yrs.
Berg Balance Scale Timed Up and Go (TUG) and History of Falls.
Worse balance performance on Berg and TUG compared to age-matched reference values.
Impaired balance in fallers vs. non-fallers with COPD.
Smith et al. 2010 
12 COPD (FEV1 33% predicted), age 65 yrs; 12 controls, age 64 yrs.
Center of pressure displacement using a force plate. Angular motion of hip and lumbar spine.
Tests repeated before and after an upper limb exercise task.
Reduced balance in mediolateral direction and increased hip motion in COPD vs. controls.
Roig et al. 
20 COPD (FEV1 47% predicted), age 72 yrs; 20 controls, age 68 yrs.
Postural sway and number of "falls" using the Sensory Organization Test (SOT) to assess balance on a moving force plate and visual surround system. Physical Activity Scale for the Elderly. Knee extensor muscle torque.
Reduced scores on the SOT and more frequent "falls" in COPD vs. controls.
No association between physical activity or muscle strength with balance deficits.
Two studies have considered the influence of fatigue on laboratory measures of static balance in patients with moderate to severe COPD. Chang and colleagues investigated static postural control following sub-maximal exercise in 19 COPD (FEV1 46% predicted) subjects . The authors reported that in the absence of visual input patients with COPD demonstrated impaired static postural control (i.e. increased sway) following a six-minute walk test. It was hypothesized that the increased postural sway following exercise was related to decreased peripheral muscle strength and endurance as well as to the increase in ventilation following exertion. Smith et al. compared postural sway as well as lumbar spine and hip movement in 12 people with severe COPD (FEV1 33% predicted) with 12 healthy controls, before and after participation in upper limb exercise. Those with COPD demonstrated increased mediolateral sway and angular motion of the hip compared to healthy controls. This finding has important implications, as mediolateral displacement is closely related to falls in older adults . This mediolateral displacement was reported to further increase after upper limb exercise, a finding attributed to the impact of trunk muscles on balance and respiration .
These studies suggest that deficits in balance constitute an important secondary impairment in individuals with COPD. Abnormal balance was identified from both clinical and laboratory measures in individuals with varying degrees of COPD severity. It is likely that the observed balance deficits may contribute to the increased risk of falling in this population.
Areas for future research
The underlying mechanisms for reduced postural control in individuals with COPD remain unclear. Many hypotheses have been proposed, including decreased levels of physical activity [6, 7], peripheral muscle weakness , altered trunk muscle mechanics , hypoxemia  and somatosensory deficits . These ideas present clinician investigators with exciting scientific opportunities. In addition, while there is increasing evidence that individuals with COPD exhibit impairments in postural control, a detailed assessment of the systems responsible for these deficits is lacking in the literature.
Effect of a Conventional Pulmonary Rehabilitation Program on Balance, Exercise Tolerance and Health-Related Quality of Life*
95% Confidence interval
46.9 ± 7.0
49.6 ± 5.7
2.8 ± 2.8
1.7 to 3.8
TUG score (sec)
15.7 ± 5.3
14.2 ± 4.5
-1.5 ± 2.4
-2.4 to -0.5
74.3 ± 17.0
79.1 ± 16.0
4.8 ± 15.4
-1.0 to 10.7
6 MWT distance (m)
303.4 ± 84.2
355.8 ± 92.0
52.5 ± 54.0
31.1 to 73.9
3.0 ± 1.1
4.6 ± 1.3
1.5 ± 1.4
1.0 to 2.1
3.8 ± 1.0
5.2 ± 0.9
1.4 ± 1.0
1.0 to 1.8
In summary, there is a growing body of evidence to suggest that balance impairments are of significant concern for individuals with COPD. These findings highlight the importance of an increased risk of falling in COPD and suggest the need for including a balance assessment for patients enrolled in pulmonary rehabilitation, with focused balance training for those at risk. Fall prevention strategies should also be taught as part of the patient education-self management program. An improved understanding of the mechanisms that underlie the observed balance deficits in COPD and the most effective interventions for improving balance will likely reduce the healthcare resource utilization associated with repeated falls as well as improve health related quality of life for our patients with COPD.
Conflict of interest statement
None of the authors has any conflict of interest to declare in relation to the subject matter of this manuscript.
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