Differences in walking pattern during 6-min walk test between patients with COPD and healthy subjects

Multifaceted associations between walking performance, physical fitness, extremity function, health status, and depression in individuals with COPD

BACKGROUND/OBJECTIVE(S)

Chronic obstructive pulmonary disease (COPD) can precipitate a deterioration of an individual's physical performance and overall health. Evidence suggests that, along with pulmonary functions, several other factors are related to the significant impairment of walking performance in individuals with COPD. This study compared the depressive symptoms, health status, upper and lower extremity functions, and peak oxygen uptake (VO2peak) in a group of individuals with COPD based on walking performance using a cutoff distance of 350 m in the six-minute walking test (6MWT). The study also investigated the associations between these factors and walking performance.

MATERIALS AND METHODS

Participants performed the 6MWT according to the guidelines and were classified into high (>350 m; n = 40) or low (<350 m; n = 30) walking performance groups according to distance. The forced expiratory volume (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio were recorded. Participants completed the Patient Health Questionnaire-9 (PHQ-9), St. George's Respiratory Questionnaire (SGRQ), and the Upper and Lower Extremity Functional Index (UEFI/LEFI). Predicted VO2peak was measured using the Duke Activity Status Index (DASI).

RESULTS

Seventy participants with a mean age of 63 ± 11 years (20% female) were enrolled in this study. Patients with high walking performance demonstrated significantly better health status than those with low walking performance (SGRQ: 49 ± 25 vs. 56 ± 21, p = 0.03). Participants with low walking performance had lower predicted VO2peak compared to their higher performing counterparts (p = 0.002). The overall model was significant (F(8, 61) = 7.48, p = 0.0006), with PHQ-9, SGRQ, UEFI/LEFI, VO2peak, and FEV1/FVC explaining approximately 49.5% of the variance in the 6MWT distance.

CONCLUSION

This study shed light on the association of depressive symptoms, health status, extremity function, and VO2peak with walking performance, providing valuable insights that may impact the management and care of individuals with COPD.

Combining Different Wearable Devices to Assess Gait Speed in Real-World Settings

Assessing mobility in daily life can provide significant insights into several clinical conditions, such as Chronic Obstructive Pulmonary Disease (COPD). In this paper, we present a comprehensive analysis of wearable devices' performance in gait speed estimation and explore optimal device combinations for everyday use. Using data collected from smartphones, smartwatches, and smart shoes, we evaluated the individual capabilities of each device and explored their synergistic effects when combined, thereby accommodating the preferences and possibilities of individuals for wearing different types of devices. Our study involved 20 healthy subjects performing a modified Six-Minute Walking Test (6MWT) under various conditions. The results revealed only little performance differences among devices, with the combination of smartwatches and smart shoes exhibiting superior estimation accuracy. Particularly, smartwatches captured additional health-related information and demonstrated enhanced accuracy when paired with other devices. Surprisingly, wearing all devices concurrently did not yield optimal results, suggesting a potential redundancy in feature extraction. Feature importance analysis highlighted key variables contributing to gait speed estimation, providing valuable insights for model refinement.

Gait differences between COPD and healthy controls: systematic review and meta-analysis

BACKGROUND

Despite the importance of gait as a determinant of falls, disability and mortality in older people, understanding of gait impairment in COPD is limited. This study aimed to identify differences in gait characteristics during supervised walking tests between people with COPD and healthy controls.

METHODS

We searched 11 electronic databases, supplemented by Google Scholar searches and manual collation of references, in November 2019 and updated the search in July 2021. Record screening and information extraction were performed independently by one reviewer and checked for accuracy by a second. Meta-analyses were performed in studies not considered at a high risk of bias.

RESULTS

Searches yielded 21 085 unique records, of which 25 were included in the systematic review (including 1015 people with COPD and 2229 healthy controls). Gait speed was assessed in 17 studies (usual speed: 12; fast speed: three; both speeds: two), step length in nine, step duration in seven, cadence in six, and step width in five. Five studies were considered at a high risk of bias. Low-quality evidence indicated that people with COPD walk more slowly than healthy controls at their usual speed (mean difference (MD) -19 cm·s-1, 95% CI -28 to -11 cm·s-1) and at a fast speed (MD -30 cm·s-1, 95% CI -47 to -13 cm·s-1). Alterations in other gait characteristics were not statistically significant.

CONCLUSION

Low-quality evidence shows that people with COPD walk more slowly than healthy controls, which could contribute to an increased falls risk. The evidence for alterations in spatial and temporal components of gait was inconclusive. Gait impairment appears to be an important but understudied area in COPD.

Alterations in stride-to-stride fluctuations in patients with chronic obstructive pulmonary disease during a self-paced treadmill 6-minute walk test

Evaluating variability and stability using measures for nonlinear dynamics may provide additional insight into the structure of the locomotor system, reflecting the neuromuscular system's organization of gait. This is in particular of interest when this system is affected by a respiratory disease and it's extrapulmonary manifestations. This study assessed stride-to-stride fluctuations and gait stability in patients with chronic obstructive pulmonary disease (COPD) during a self-paced, treadmill 6-minute walk test (6MWT) and its association with clinical outcomes. In this cross-sectional study, eighty patients with COPD (age 62±7y; forced expiratory volume in first second 56±19%predicted) and 39 healthy older adults (62±7y) were analyzed. Gait parameters including stride-to-stride fluctuations (coefficient of variation (CoV), predictability (sample entropy) and stability (Local Divergence Exponent (LDE)) were calculated over spatiotemporal parameters and center of mass velocity. Independent t-test, Mann-Whitney U test and ANCOVA analyses were conducted. Correlations were calculated between gait parameters, functional mobility using Timed Up and Go Test, and quadriceps muscle strength using dynamometry. Patients walked slower than healthy older adults. After correction for Speed, patients demonstrated increased CoV in stride length (F(1,116) = 5.658, p = 0.019), and increased stride length predictability (F(1,116) = 3.959, p = 0.049). Moderate correlations were found between mediolateral center of mass velocity LDE and normalized maximum peak torque (ρ = -0.549). This study showed that patients with COPD demonstrate alterations in stride length fluctuations even when adjusted for walking speed, highlighting the potential of nonlinear measures to detect alterations in gait function in patients with COPD. Association with clinical outcomes were moderate to weak, indicating that these clinical test are less discriminative for gait alterations.

Real-world walking cadence in people with COPD

Introduction

The clinical validity of real-world walking cadence in people with COPD is unsettled. Our objective was to assess the levels, variability and association with clinically relevant COPD characteristics and outcomes of real-world walking cadence.

Methods

We assessed walking cadence (steps per minute during walking bouts longer than 10 s) from 7 days' accelerometer data in 593 individuals with COPD from five European countries, and clinical and functional characteristics from validated questionnaires and standardised tests. Severe exacerbations during a 12-month follow-up were recorded from patient reports and medical registries.

Results

Participants were mostly male (80%) and had mean±sd age of 68±8 years, post-bronchodilator forced expiratory volume in 1 s (FEV1) of 57±19% predicted and walked 6880±3926 steps·day-1. Mean walking cadence was 88±9 steps·min-1, followed a normal distribution and was highly stable within-person (intraclass correlation coefficient 0.92, 95% CI 0.90-0.93). After adjusting for age, sex, height and number of walking bouts in fractional polynomial or linear regressions, walking cadence was positively associated with FEV1, 6-min walk distance, physical activity (steps·day-1, time in moderate-to-vigorous physical activity, vector magnitude units, walking time, intensity during locomotion), physical activity experience and health-related quality of life and negatively associated with breathlessness and depression (all p<0.05). These associations remained after further adjustment for daily steps. In negative binomial regression adjusted for multiple confounders, walking cadence related to lower number of severe exacerbations during follow-up (incidence rate ratio 0.94 per step·min-1, 95% CI 0.91-0.99, p=0.009).

Conclusions

Higher real-world walking cadence is associated with better COPD status and lower severe exacerbations risk, which makes it attractive as a future prognostic marker and clinical outcome.

Determinants and reference values of the 6-min walk distance in the general population-results of the population-based STAAB cohort study

AIMS

The 6-min walk test is an inexpensive, safe, and easy tool to assess functional capacity in patients with cardiopulmonary diseases including heart failure (HF). There is a lack of reference values, which are a prerequisite for the interpretation of test results in patients. Furthermore, determinants independent of the respective disease need to be considered when interpreting the 6-min walk distance (6MWD).

METHODS

The prospective Characteristics and Course of Heart Failure Stages A-B and Determinants of Progression (STAAB) cohort study investigates a representative sample of residents of the City of Würzburg, Germany, aged 30 to 79 years, without a history of HF. Participants underwent detailed clinical and echocardiographic phenotyping as well as a standardized assessment of the 6MWD using a 15-m hallway.

RESULTS

In a sample of 2762 participants (51% women, mean age 58 ± 11 years), we identified age and height, but not sex, as determinants of the 6MWD. While a worse metabolic profile showed a negative association with the 6MWD, a better systolic and diastolic function showed a positive association with 6MWD. From a subgroup of 681 individuals without any cardiovascular risk factors (60% women, mean age 52 ± 10 years), we computed age- and height-specific reference percentiles.

CONCLUSION

In a representative sample of the general population free from HF, we identified determinants of the 6MWD implying objective physical fitness associated with metabolic health as well as with cardiac structure and function. Furthermore, we derived reference percentiles applicable when using a 15-m hallway.

Tele-Assessment of Functional Capacity through the Six-Minute Walk Test in Patients with Diabetes Mellitus Type 2: Validity and Reliability of Repeated Measurements

A tele-assessed 6MWT (TL 6MWT) could be an alternative method of evaluating functional capacity in patients with diabetes mellitus type 2 (DM2). This study aimed to assess the validity and reliability of a TL 6MWT. The functional capacity of 28 patients with DM2 (75% men) aged 61 ± 13 years was evaluated twice via an indoor, center-based 6MWT (CB 6MWT) and twice outside each patient's home via a web-based platform TL 6MWT. The study showed a high statistically significant correlation between the CB and TL 6MWT (Pearson's r = 0.76, p < 0.001). Reliability testing showed no statistically significant differences in the distance covered (CB1: 492 ± 84 m and CB2: 506 ± 86 m versus TL1: 534 ± 87 m and TL2: 542 ± 93 m, respectively) and in the best distance of the TL 6MWT (545 ± 93 m) compared to the best CB distance (521 ± 83 m). Strong internal reliability for both the CB (intraclass correlation coefficient (ICC) = 0.93) and the TL 6MWT (ICC = 0.98) was found. The results indicate that a TL 6MWT performed outdoors can be a highly valid and reliable tool to assess functional capacity in patients with DM2. No learning effect between the TL and CB assessment was found, minimizing the need for repetition.

Impact of Psychological Factors on Functional Performance among Patients with Chronic Obstructive Pulmonary Disease

The role of anxiety and depression in functional performance during walking in patients with chronic obstructive pulmonary disease (COPD) is controversial. In this cross-sectional study, we aimed to assess the effects of anxiety, depression, and health-related quality of life (HRQOL) on the functional performance of this patient population. Seventy COPD patients aged 63 ± 11 years participated in the study. To measure their functional performance, the six-minute walk test (6MWT) was used. Anxiety and depression were assessed using two questionnaires: the Anxiety Inventory for Respiratory Disease (AIR) scale and the Hospital Anxiety and Depression Scale (HADS). The St. George’s Respiratory Questionnaire (SGRQ) was used to assess HRQOL. Based on their anxiety levels, the patients were divided into a no anxiety group and a high anxiety group. There were no significant differences between the two groups in terms of pulmonary function profile or smoking status. The mean AIR and HADS (depression) scores were high (12.78 ± 4.07 and 9.90 ± 3.41, respectively). More than one-third of the patients (46%) reported high anxiety levels (above the standard cutoff score of 8). The mean score of the aggregated HADS scale was significantly higher in the high anxiety group (20.87 ± 6.13) than in the no anxiety group (9.26 ± 4.72; p = 0.01). Patients with high anxiety had poorer functional performance (6MWT: 308.75 ± 120.16 m) and HRQOL (SGRQ: 56.54 ± 22.36) than patients with no anxiety (6MWT: 373.76 ± 106.56 m; SGRQ: 42.90 ± 24.76; p < 0.01). The final multivariate model explained 33% of the variance in functional performance after controlling for COPD severity (F = 8.97). The results suggest that anxiety, depression, and poor health status are significantly associated with poor functional performance. This study highlights the need to screen patients with COPD at all stages for anxiety and depression.

Clinical assessment of balance and functional impairments in people with stable chronic obstructive pulmonary disease: a systematic review and meta-analysis

The objective of this study was to compare the balance and functional capacity between stable chronic obstructive pulmonary disease (COPD) patients versus healthy controls using clinical tests. A comprehensive search of PubMed/MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL), Embase and Web of Science was conducted from inception to 21 January 2022. Studies reporting the association between COPD status and balance or functional capacity using clinical tests were included. Two independent reviewers examined the titles and abstracts, extracted the data using a standardised form, and assessed the risk of bias of the included articles. A total of 27 studies with 2420 individuals with stable COPD were included. Overall, the risk of bias in the included studies was low to moderate. The meta-analysis showed a higher history of falls in individuals with COPD (odds ratio 1.59, 95% CI 1.25-2.02). Furthermore, an overall effect in favour of the healthy controls was observed in the Timed Up and Go (mean difference: 2.61 s, 95% CI 1.79-3.43), Berg Balance Scale (mean difference: -6.57 points, 95% CI -8.31 to -4.83), static balance tests (standardised mean difference: -1.36, 95% CI -2.10 to -0.62) and the 6-min walk test (mean difference: -148.21 m, 95% CI -219.37 to -77.39). In conclusion, individuals with stable COPD have worse balance and functional capacity compared to healthy controls. These results may guide clinicians to elaborate on therapeutic strategies focused on screening of balance and functional impairments. This is in addition to generating rehabilitation guidelines aimed at reducing the risk of falling in people with COPD.

Pulmonary and physical function limitations in aging men with and without HIV from the Multicenter AIDS Cohort Study (MACS)

PURPOSE

We examined the associations between pulmonary impairments and physical function and whether age, HIV serostatus, or smoking modified these relationships.

METHODS

Using Multicenter AIDS Cohort Study data, we examined associations between pulmonary function (diffusing capacity for carbon monoxide [DLCO], one-second forced expiratory volume [FEV1]) and subsequent physical outcomes (gait speed, grip strength, frailty [non-frail, pre-frail, frail]) using mixed models.

RESULTS

Of 1,048 men, 55% were living with HIV, median age was 57(IQR=48,64) and median cumulative pack-years was 1.2(IQR = 0,18.1); 33% and 13% had impaired DLCO and FEV1(<80% predicted), respectively. Participants with impaired DLCO had 3.5 kg (95%CI: -4.6, -2.4) weaker grip strength, 0.04 m/sec (95%CI: -0.06, -0.02) slower gait speed and 4.44-fold (95%CI: 1.81, 10.93) greater odds of frailty compared to participants with normal DLCO. Participants with impaired FEV1 had 3.1 kg (95%CI: -4.8, -1.4) weaker grip strength, similar gait speed (-0.001 m/sec [95%CI: -0.04, 0.03]) and 5.72-fold (95%CI: 1.90, 17.19) greater odds of frailty compared to participants with normal FEV1. Age, but not smoking or HIV, significantly modified the DLCO effect on gait speed and grip strength.

CONCLUSIONS

Pulmonary impairment and decreased physical function were associated. Preserving pulmonary function may help preserve physical function in aging men with and without HIV.

Cardiac Effort to Compare Clinic and Remote 6-Minute Walk Testing in Pulmonary Arterial Hypertension

BACKGROUND

The SARS-CoV-2 pandemic has limited objective physiologic assessments. A standardized remote alternative is not currently available. "Cardiac effort" (CE), that is, the total number of heart beats divided by the 6-min walk test (6MWT) distance (beats/m), has improved reproducibility in the 6MWT and correlated with right ventricular function in pulmonary arterial hypertension.

RESEARCH QUESTION

Can a chest-based accelerometer estimate 6MWT distance remotely? Is remote cardiac effort more reproducible than 6MWT distance when compared with clinic assessment?

STUDY DESIGN AND METHODS

This was a single-center, prospective observational study, with institutional review board approval, completed between October 2020 and April 2021. Group 1 subjects with pulmonary arterial hypertension, receiving stable therapy for > 90 days, completed four to six total 6MWTs during a 2-week period to assess reproducibility. The first and last 6MWTs were performed in the clinic; two to four remote 6MWTs were completed at each participant's discretion. Masks were not worn. BioStamp nPoint sensors (MC10) were worn on the chest to measure heart rate and accelerometry. Two blinded readers counted laps, using accelerometry data obtained on the clinic or user-defined course. Averages of clinic variables and remote variables were used for Wilcoxon matched-pairs signed rank tests, Bland-Altman plots, or Spearman correlation coefficients.

RESULTS

Estimated 6MWT distance, using the MC10, correlated strongly with directly measured 6MWT distance (r = 0.99; P < .0001; in 20 subjects). Remote 6MWT distances were shorter than clinic 6MWT distances: 405 m (330-464 m) vs 389 m (312-430 m) (P = .002). There was no difference between in-clinic and remote CE: 1.75 beats/m (1.48-2.20 beats/m) vs 1.86 beats/m (1.57-2.14 beats/m) (P = .14).

INTERPRETATION

Remote 6MWT was feasible on a user-defined course; 6MWT distance was shorter than clinic distance. CE calculated by chest heart rate and accelerometer-estimated distance provides a reproducible remote assessment of exercise tolerance, comparable to the clinic-measured value.

Urban environment and physical activity and capacity in patients with chronic obstructive pulmonary disease

BACKGROUND

Physical activity and exercise capacity are key prognostic factors in chronic obstructive pulmonary disease (COPD) but their environmental determinants are unknown.

OBJECTIVES

To test the association between urban environment and objective physical activity, physical activity experience and exercise capacity in COPD.

METHODS

We studied 404 patients with mild-to-very severe COPD from a multi-city study in Catalonia, Spain. We measured objective physical activity (step count and sedentary time) by the Dynaport MoveMonitor, physical activity experience (difficulty with physical activity) by the Clinical visit-PROactive (C-PPAC) instrument, and exercise capacity by the 6-min walk distance (6MWD). We estimated individually (geocoded to the residential address) population density, pedestrian street length, slope of terrain, and long-term (i.e., annual) exposure to road traffic noise, nitrogen dioxide (NO₂) and particulate matter (PM_2.5). We built single- and multi-exposure mixed-effects linear regressions with a random intercept for city, adjusting for confounders.

RESULTS

Patients were 85% male, had mean (SD) age 69 (9) years and walked 7524 (4045) steps/day. In multi-exposure models, higher population density was associated with fewer steps, more sedentary time and worse exercise capacity (-507 [95% CI: 1135, 121] steps, +0.2 [0.0, 0.4] h/day and -13 [-25, 0] m per IQR). Pedestrian street length related with more steps and less sedentary time (156 [9, 304] steps and -0.1 [-0.1, 0.0] h/day per IQR). Steeper slope was associated with better exercise capacity (15 [3, 27] m per IQR). Higher NO₂ levels related with more sedentary time and more difficulty in physical activity. PM_2.5 and noise were not associated with physical activity or exercise capacity.

DISCUSSION

Population density, pedestrian street length, slope and NO₂ exposure relate to physical activity and capacity of COPD patients living in highly populated areas. These findings support the consideration of neighbourhood environmental factors during COPD management and the attention to patients with chronic diseases when developing urban and transport planning policies.

Updated Perspectives on the Role of Biomechanics in COPD: Considerations for the Clinician

Patients with chronic obstructive pulmonary disease (COPD) demonstrate extra-pulmonary functional decline such as an increased prevalence of falls. Biomechanics offers insight into functional decline by examining mechanics of abnormal movement patterns. This review discusses biomechanics of functional outcomes, muscle mechanics, and breathing mechanics in patients with COPD as well as future directions and clinical perspectives. Patients with COPD demonstrate changes in their postural sway during quiet standing compared to controls, and these deficits are exacerbated when sensory information (eg, eyes closed) is manipulated. If standing balance is disrupted with a perturbation, patients with COPD are slower to return to baseline and their muscle activity is differential from controls. When walking, patients with COPD appear to adopt a gait pattern that may increase stability (eg, shorter and wider steps, decreased gait speed) in addition to altered gait variability. Biomechanical muscle mechanics (ie, tension, extensibility, elasticity, and irritability) alterations with COPD are not well documented, with relatively few articles investigating these properties. On the other hand, dyssynchronous motion of the abdomen and rib cage while breathing is well documented in patients with COPD. Newer biomechanical technologies have allowed for estimation of regional, compartmental, lung volumes during activity such as exercise, as well as respiratory muscle activation during breathing. Future directions of biomechanical analyses in COPD are trending toward wearable sensors, big data, and cloud computing. Each of these offers unique opportunities as well as challenges. Advanced analytics of sensor data can offer insight into the health of a system by quantifying complexity or fluctuations in patterns of movement, as healthy systems demonstrate flexibility and are thus adaptable to changing conditions. Biomechanics may offer clinical utility in prediction of 30-day readmissions, identifying disease severity, and patient monitoring. Biomechanics is complementary to other assessments, capturing what patients do, as well as their capability.

Technologies for the Instrumental Evaluation of Physical Function in Persons Affected by Chronic Obstructive Pulmonary Disease: A Systematic Review

Several systems, sensors, and devices are now available for the instrumental evaluation of physical function in persons with Chronic Obstructive Pulmonary Disease (COPD). We aimed to systematically review the literature about such technologies. The literature search was conducted in all major scientific databases, including articles published between January 2001 and April 2022. Studies reporting measures derived from the instrumental assessment of physical function in individuals with COPD were included and were divided into application and validation studies. The quality of validation studies was assessed with the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) risk of bias tool. From 8752 articles retrieved, 21 application and 4 validation studies were included in the systematic review. Most application studies employed accelerometers, gait analysis systems, instrumented mattresses, or force plates to evaluate walking. Surface electro-myography or near-infrared spectroscopy were employed in four studies. Validation studies were heterogeneous and presented a risk of bias ranging from inadequate to doubtful. A variety of data regarding physical function can be retrieved from technologies used in COPD studies. However, a general lack of standardization and limitations in study design and sample size hinder the implementation of the instrumental evaluation of function in clinical practice.

Impairment and characteristics of postural control sub-components in people with COPD: a scoping review

Purpose: Impairment of postural control is common in people with COPD. However, the precise characteristics of this alteration are not clearly known. The "Systems Framework for Postural Control" which define postural control sub-components, represents an interesting tool to explore this field. The main aim of this review was to identify which postural control sub-components are impaired in people with COPD and to summarise characteristics for each sub-component. A secondary aim was to precise the relation between postural control and activities of daily living (ADL).Materials and methods: A scoping review was conducted, according to the JBI methodology. Medline, Cochrane Library, Scielo, Google Scholar, OpenGrey, and HAL were searched from inception to May 2022. The search was performed in English and French.Results: Eighty-nine articles were included. There was evidence of a potential impairment for most of the postural control sub-components. Characteristics of every sub-component alteration were heterogeneous. Reduced postural control could be associated with difficulties in ADL.Conclusions: People with COPD may have impairment in a wide range of postural control sub-components. Further research is needed to clarify if a common pattern of modification exits for this alteration and to precise the link with ADL.Implications for rehabilitationImpairment of postural control is a common extra-respiratory manifestation in people with COPD and so clinicians must include it in their clinical reasoning.Numerous postural control sub-components could be altered in people with COPD, suggesting that postural control assessment must be holistic.This scoping review shows that characteristics of postural control impairment are varied and that there may be no common pattern at the COPD population level.The relationship between impaired postural control and activities of daily living remains unclear, but clinicians should be alert to potential negative interactions between these two areas.

A pilot study on the feasibility and effectiveness of treadmill-based perturbations for assessing and improving walking stability in chronic obstructive pulmonary disease

BACKGROUND

Falls risk is elevated in chronic obstructive pulmonary disease (COPD). However, there is a lack of evidence regarding the contributing factors. Here, we examined the feasibility of, and initial responses to, large walking perturbations in COPD, as well as the adaptation potential of people with COPD to repeated walking perturbations that might indicate potential for perturbation-based balance training in COPD.

METHODS

12 participants with COPD undergoing inpatient pulmonary rehabilitation and 12 age-gender-matched healthy control participants walked on an instrumented treadmill and experienced repeated treadmill-belt acceleration perturbations (leading to a forward balance loss). Three-dimensional motion capture was used to quantify the stability of participants body position during perturbed walking. Feasibility, stability following the initial perturbations and adaptation to repeated perturbations were assessed.

FINDINGS

Using perturbations in this manner was feasible in this population (no harness assists and participants completed the minimum number of perturbations). No clear, specific deficit in reactive walking stability in COPD was found (no significant effects of participant group on stability or recovery step outcomes). There were mixed results for the adaptability outcomes which overall indicated some adaptability to repeated perturbations, but not to the same extent as the healthy control participants.

INTERPRETATION

Treadmill-based perturbations during walking are feasible in COPD. COPD does not appear to result in significant deficits in stability following sudden perturbations and patients do demonstrate some adaptability to repeated perturbations. Perturbation-based balance training may be considered for fall prevention in research and practice in people with COPD.

Impact of chronic obstructive pulmonary disease on passive viscoelastic components of the musculoarticular system

Chronic obstructive pulmonary disease (COPD) produces skeletal muscle atrophy and weakness, leading to impairments of exercise performance. The mechanical work needed for movement execution is also provided by the passive tension developed by musculoarticular connective tissue. To verify whether COPD affects this component, the passive viscoelastic properties of the knee joint were evaluated in 11 patients with COPD and in 11 healthy individuals. The levels of stiffness and viscosity were assessed by means of the pendulum test, consisting in a series of passive leg oscillations. In addition, to explore the contribution of passive tension in the mechanical output of a simple motor task, voluntary leg flexion-extension movements were performed. Patients with COPD showed a statistically significant reduction in stiffness and viscosity compared to controls. Voluntary execution of flexion-extension movements revealed that the electromyographic activity of the Rectus Femoris and Biceps Femoris was lower in patients than in controls, and the low viscoelastic tension in the patients conditioned the performance of active movements. These results provide novel insights on the mechanism responsible for the movement impairments associated with COPD.

Consensus based framework for digital mobility monitoring

Digital mobility assessment using wearable sensor systems has the potential to capture walking performance in a patient's natural environment. It enables monitoring of health status and disease progression and evaluation of interventions in real-world situations. In contrast to laboratory settings, real-world walking occurs in non-conventional environments and under unconstrained and uncontrolled conditions. Despite the general understanding, there is a lack of agreed definitions about what constitutes real-world walking, impeding the comparison and interpretation of the acquired data across systems and studies. The goal of this study was to obtain expert-based consensus on specific aspects of real-world walking and to provide respective definitions in a common terminological framework. An adapted Delphi method was used to obtain agreed definitions related to real-world walking. In an online survey, 162 participants from a panel of academic, clinical and industrial experts with experience in the field of gait analysis were asked for agreement on previously specified definitions. Descriptive statistics was used to evaluate whether consent (> 75% agreement as defined a priori) was reached. Of 162 experts invited to participate, 51 completed all rounds (31.5% response rate). We obtained consensus on all definitions ("Walking" > 90%, "Purposeful" > 75%, "Real-world" > 90%, "Walking bout" > 80%, "Walking speed" > 75%, "Turning" > 90% agreement) after two rounds. The identification of a consented set of real-world walking definitions has important implications for the development of assessment and analysis protocols, as well as for the reporting and comparison of digital mobility outcomes across studies and systems. The definitions will serve as a common framework for implementing digital and mobile technologies for gait assessment and are an important link for the transition from supervised to unsupervised gait assessment.

Acceleration Gait Measures as Proxies for Motor Skill of Walking: A Narrative Review

In adults 65 years or older, falls or other neuromotor dysfunctions are often framed as walking-related declines in motor skill; the frequent occurrence of such decline in walking-related motor skill motivates the need for an improved understanding of the motor skill of walking. Simple gait measurements, such as speed, do not provide adequate information about the quality of the body motion's translation during walking. Gait measures from accelerometers can enrich measurements of walking and motor performance. This review article will categorize the aspects of the motor skill of walking and review how trunk-acceleration gait measures during walking can be mapped to motor skill aspects, satisfying a clinical need to understand how well accelerometer measures assess gait. We will clarify how to leverage more complicated acceleration measures to make accurate motor skill decline predictions, thus furthering fall research in older adults.

Kinematic evaluation of patients with chronic obstructive pulmonary disease during the 6-min walk test

BACKGROUND

A better understanding of gait kinematics during the 6-min walk test (6MWT) may facilitate the development of rehabilitation strategies for patients with chronic obstructive pulmonary disease (COPD).

AIM

To evaluate gait kinematics during the 6MWT in patients with COPD.

METHOD

Thirty-six patients with COPD and 19 healthy controls underwent a full-body kinematic analysis during the 6MWT. Data were collected using a system with four infrared cameras to capture the movement of a spherical marker covered with retroreflective tape attached to a helmet worn during the test.

RESULTS

The walking distances measured by the assessor and by kinematics analysis were lower in the group of patients (P = 0.036 and P = 0.013, respectively). Moreover, the walking distances measured by kinematics analysis were greater than those measured by the assessor for both groups (P < 0.001). In the kinematics analysis of the complete test, the mean and maximum speeds were higher for the controls than for the patients (P = 0.007 and P = 0.044, respectively). In the half-turn analysis, acceleration, speed, and deceleration peaks (maximal absolute values) were lower for the patients than for the controls (P = 0.002, P = 0.012 and P = 0.006, respectively).

CONCLUSIONS

Patients with COPD show worse functional capacity due to lower gait speed and acceleration-deceleration peaks after turnings as compared to healthy individuals during the 6MWT. Assessors can accurately predict the 6MWD measured by kinematics, though they underestimate this distance.

A Cross-Sectional Study on Balance Deficits and Gait Deviations in COPD Patients

Background

The gait abnormalities were linked to the balance deficits in the previous studies. However, the deviations in the gait parameters in COPD are currently not known. The study aims to compare gait parameters, static and dynamic balance, and risk of falls in COPD with those in non-COPD individuals.

Method

Fourty-two patients with COPD aged 45 years and gender-matched control subjects were included in the study. Gait parameters were assessed by Win-Track gait analyzer, the static balance was assessed by posturography, and the dynamic balance was assessed by the time up and go test. The fear of falls was assessed by Falls Efficacy Scale.

Results

COPD individuals had decreased static and dynamic balance as assessed by posturography (p < 0.05) and TUG (p < 0.01), respectively. A significant difference in swing duration (p=0.004) and also increased risk of falls (p < 0.01) was observed in COPD patients as compared to non-COPD individuals.

Conclusion

COPD individuals have increased swing duration, reduced static and dynamic balance, and increased fear of falls as compared to non-COPD individuals.

Development and Pilot Study of an iOS Smartphone Application for Perioperative Functional Capacity Assessment

BACKGROUND

Functional capacity assessment plays a core role in the preoperative evaluation. The Duke Activity Status Index (DASI) and the 6-minute walk test (6MWT) are 2 methods that have demonstrated the ability to evaluate functional capacity and predict perioperative outcomes. Smartphones offer a novel method to facilitate functional capacity assessment as they can easily administer a survey and accelerometers can track patient activity during a 6MWT. We developed a smartphone application to administer a 6MWT and DASI survey and performed a pilot study to evaluate the accuracy of a smartphone-based functional capacity tool in our Anesthesia and Perioperative Medicine Clinic.

METHODS

Using the Apple ResearchKit software platform, we developed an application that administers a DASI survey and 6MWT on an iOS smartphone. The DASI was presented to the patient 1 question on the screen at a time and the application calculated the DASI score and estimated peak oxygen uptake (VO2). The 6MWT used the CMPedometer class from Apple's core motion facility to retrieve accelerometer data collected from the device's motion coprocessor to estimate steps walked. Smartphone estimated steps were compared to a research-grade pedometer using the intraclass correlation coefficient (ICC). Distance walked was directly measured during the 6MWT and we performed a multivariable linear regression with biometric variables to create a distance estimation algorithm to estimate distance walked from the number of steps recorded by the application.

RESULTS

Seventy-eight patients were enrolled in the study and completed the protocol. Steps measured by the smartphone application as compared to the pedometer demonstrated moderate agreement with an ICC (95% CI) of 0.87 (0.79-0.92; P = .0001). The variables in the distance estimation algorithm included (β coefficient [slope], 95% CI) steps walked (0.43, 0.29-0.57; P < .001), stride length (0.38, 0.22-0.53; P < .001), age in years (-1.90, -3.06 to -0.75; P = .002), and body mass index (-2.59, -5.13 to -0.06; P = .045). The overall model fit was R = 0.72, which indicates a moderate level of goodness of fit and explains 72% of the variation of distance walked during a 6MWT.

CONCLUSIONS

Our pilot study demonstrated that a smartphone-based functional capacity assessment is feasible using the DASI and 6MWT. The DASI was easily completed by patients and the application clearly presented the results of the DASI to providers. Our application measured steps walked during a 6MWT moderately well in a preoperative patient population; however, future studies are needed to improve the smartphone application's step-counting accuracy and distance estimation algorithm.

Respiratory rehabilitation techniques used for the treatment of COPD patients

Introduction. Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality throughout the world. At present, the pharmacological therapy is not enough for a patient with COPD in regard to heath status and exercise tolerance. It requires additional therapies aimed to improve the quality of life, delay the lung function decline, increase exercise capacity, and reduce the respiratory symptoms and the number of exacerbations. Pulmonary rehabilitation program (PRP) has been shown to improve respiratory muscle, to optimize functional, psychosocial, behavioral and nutritional status. The aim of the present study was to asses the impact of PRP on COPD patients, focusing on the clinical benefits of PRP, which may further provide to the patients a good support for change. Material and method. Sixty-seven patients with clinically stable COPD were enrolled in this prospective study, consisting in a 6-weeks of PRP. There were recorded demographic data, smoking and medical history, and abnormal findings at the physical examination. All patients completed CAT (COPD Assessment Test) questionnaire and dyspnea on Borg scale, they performed spirometry, and six minutes walking test (6MWT), before and after the completion of the rehabilitation program. Results and Discussions. After the 6-week period of PRP, a large proportion of patients presented higher values of spirometric parameters, although the change was no statistically significant. The impact of COPD on the patient’s health was significantly improved, 58.2% of patients registered < 10 points of CAT questionnaire after PRP (p<0.05). 75% of patients reported a 0-5 points of dyspnea on Borg scale comparing with 29% before the PRP (p=0.0147), and 56% a 0-5 points of fatigue while only 25% of patients had the same score before the rehabilitation programme (p=0,022). Only 8 patients (11.94% vs 31.34%, p<0.05) reported a SaO2 lower than 90% after the PRP. The 6MWD was longer than 250m at the end of the 6-weeks of PRP for 38 patients (56.7% vs 22.38%, p<0.05). Conclusions. The present study showed that a PRP added to pharmacological treatment had a beneficial role of increasing the patient’ health status and exercise tolerance for COPD patients.

Timed Up and Go and Six-Minute Walking Tests with Wearable Inertial Sensor: One Step Further for the Prediction of the Risk of Fall in Elderly Nursing Home People

Assessing the risk of fall in elderly people is a difficult challenge for clinicians. Since falls represent one of the first causes of death in such people, numerous clinical tests have been created and validated over the past 30 years to ascertain the risk of falls. More recently, the developments of low-cost motion capture sensors have facilitated observations of gait differences between fallers and nonfallers. The aim of this study is twofold. First, to design a method combining clinical tests and motion capture sensors in order to optimize the prediction of the risk of fall. Second to assess the ability of artificial intelligence to predict risk of fall from sensor raw data only. Seventy-three nursing home residents over the age of 65 underwent the Timed Up and Go (TUG) and six-minute walking tests equipped with a home-designed wearable Inertial Measurement Unit during two sets of measurements at a six-month interval. Observed falls during that interval enabled us to divide residents into two categories: fallers and nonfallers. We show that the TUG test results coupled to gait variability indicators, measured during a six-minute walking test, improve (from 68% to 76%) the accuracy of risk of fall’s prediction at six months. In addition, we show that an artificial intelligence algorithm trained on the sensor raw data of 57 participants reveals an accuracy of 75% on the remaining 16 participants.

Signatures of knee osteoarthritis in women in the temporal and fractal dynamics of human gait

BACKGROUND

Osteoarthritis of the knee is characterized by progressive cartilage deterioration causing pain and function loss. Symptoms develop late with limited disease-modifying opportunities. Osteoarthritis is a major cause of immobility, with a higher prevalence above 60 years. This age-related increase in prevalence is further amplified by the female gender. Imaging and biochemical analyses for detection of osteoarthritis of the knee are expensive and labor-intensive. Continuous movement tracking could aid in detecting onset and/or worsening of symptoms.

METHODS

We used portable technology to investigate kinematic differences in female patients with knee osteoarthritis, weight-matched healthy female volunteers and obese female patients with osteoarthritis of the knee. Knee osteoarthritis was established radiographically and corroborated using magnetic resonance imaging.

FINDINGS

The total amount, type and level of activity did not differ significantly between groups. The temporal activity pattern during the day was however significantly different with a bimodal signature in healthy volunteers only. Sequence analyses revealed more time to recuperate after dynamic activity in both patient groups. Analysis of walking bouts revealed significant differences in stride interval dynamics, indicative of gait naturalness, only in healthy volunteers. Temporal activity, sequence and walking patterns were independent of body weight.

INTERPRETATION

We thus provide for the first-time evidence of temporal specific kinematic signatures in amount and quality of movement also in stride interval dynamics between people with and without osteoarthritis of the knee independent of body weight. These findings could allow early and non-intrusive diagnosis of osteoarthritis enabling concordant treatment.

Wearable Inertial Sensors to Assess Gait during the 6-Minute Walk Test: A Systematic Review

Wearable sensors are becoming increasingly popular for complementing classical clinical assessments of gait deficits. The aim of this review is to examine the existing knowledge by systematically reviewing a large number of papers focusing on the use of wearable inertial sensors for the assessment of gait during the 6-minute walk test (6MWT), a widely recognized, simple, non-invasive, low-cost and reproducible exercise test. After a systematic search on PubMed and Scopus databases, two raters evaluated the quality of 28 full-text articles. Then, the available knowledge was summarized regarding study design, subjects enrolled (number of patients and pathological condition, if any, age, male/female ratio), sensor characteristics (type, number, sampling frequency, range) and body placement, 6MWT protocol and extracted parameters. Results were critically discussed to suggest future directions for the use of inertial sensor devices in the clinics.

Does the 6-minute walk test in hospitalized COPD patients exclusively correlate with lung function parameters or should psychological factors also be taken into account?

The 6-minute walk test is generally considered a standard test for the evaluation of short-term maximal physical performance. It has not been evaluated whether psychological factors, such as anxiety or depression, affect the performance or the results of the test. The main aim of this study was to investigate whether a correlation exists between psychological factors and the data from the 6-minute walking test. The study cohort consisted of 85 (♀ = 34 and ♂ = 51) 66 ± 10 (mean ± SD) year-old patients with chronic obstructive pulmonary disease (COPD) hospitalized for disease exacerbation. Forced Expiratory Volume in the first second (FEV₁) (% predicted) as predictor for lung function, as well as anxiety and depression symptoms assessed using the Hospital Anxiety and Depression Scale (HADS) as psychological predictors were collected. Bivariate correlations and hierarchical linear regression models were used to analyse the correlations. Walking distance was on average 260m ± 107m and ranged from 64m to 480m. HADS was negatively correlated with 6-min walking distance (r = 0.441, p = .0009, r = -.523, p = 00006). Hierarchical linear regression showed that FEV₁ alone explained 33%, and together with the psychological variables anxiety and depression explained 42% of the variance of results from the 6-minute walking test. These findings demonstrated that 11% of the data correlated with the psychological variables alone (p = .011). The effect size for lung function (f² = .717) and psychological variables (f² = .352) were high, whereas the socio-demographic variables sex, age, educational level and BMI could not explain any additional variance in our cohort. In conclusion, our study indicates that psychological factors such as symptoms of depression and anxiety are associated with lower physical functional performance in the 6-minute walking test. As such, these factors should also be assessed. Future research is needed to show if treatments of anxiety and depression can improve the walking distance in COPD patients.

Use of accelerometer-based activity monitoring in orthopaedics: benefits, impact and practical considerations

Studies of the effectiveness of orthopaedic interventions do not generally measure physical activity (PA). Applying accelerometer-based activity monitoring in orthopaedic studies will add relevant information to the generally examined physical function and pain assessment.Accelerometer-based activity monitoring is practically feasible in orthopaedic patient populations, since current day activity sensors have battery time and memory to measure continuously for several weeks without requiring technical expertise.The ongoing development in sensor technology has made it possible to combine functional tests with activity monitoring.For clinicians, the application of accelerometer-based activity monitoring can provide a measure of PA and can be used for clinical comparisons before and after interventions.In orthopaedic rehabilitation, accelerometer-based activity monitoring may be used to help patients reach their targets for PA and to coach patients towards a more active lifestyle through direct feedback. Cite this article: EFORT Open Rev 2019;4:678-685. DOI: 10.1302/2058-5241.4.180041.

An update on pulmonary rehabilitation techniques for patients with chronic obstructive pulmonary disease

Introduction: Pulmonary rehabilitation (PR) is one of the core components in the management of patients with chronic obstructive pulmonary disease (COPD). In order to achieve the maximal level of independence, autonomy, and functioning of the patient, targeted therapies and interventions based on the identification of physical, emotional and social traits need to be provided by a dedicated, interdisciplinary PR team.Areas covered: The review discusses cardiopulmonary exercise testing in the selection of different modes of training modalities. Neuromuscular electrical stimulation as well as gait assessment and training are discussed as well as add-on therapies as oxygen, noninvasive ventilator support or endoscopic lung volume reduction in selected patients. The potentials of pulsed inhaled nitric oxide in patients with underlying pulmonary hypertension is explored as well as nutritional support. The impact of sleep quality on outcomes of PR is reviewed.Expert opinion: Individualized, comprehensive intervention based on thorough assessment of physical, emotional, and social traits in COPD patients forms a continuous challenge for health-care professionals and PR organizations in order to dynamically implement and adapt these strategies based on dynamic, more optimal understanding of underlying pathophysiological mechanisms.

Chronic obstructive pulmonary disease patients increase medio-lateral stability and limit changes in antero-posterior stability to curb energy expenditure

BACKGROUND

A relationship exists between step width and energy expenditure, yet the contribution of dynamic stability to energy expenditure is not completely understood. Chronic obstructive pulmonary disease (COPD) patients' energy expenditure is increased due to airway obstruction. Further, they have a higher prevalence of falls and balance deficits compared to controls.

RESEARCH QUESTION

Is dynamic stability different between COPD patients and controls; and is the association between dynamic stability and energy expenditure different between groups?

METHODS

Seventeen COPD patients (64.3 ± 7.6years) and 23 controls (59.9 ± 6.6years) walked on a treadmill at three speeds: self-selected walking speed (SSWS), -20%SSWS, and +20%SSWS. Mean and variability (standard deviation) of the anterior-posterior (AP) and medio-lateral (ML) margins of stability (MOS) were compared between groups and speed conditions, while controlling for covariates. Additionally, their association to metabolic power was examined.

RESULTS

The association between stability and power did not significantly differ between groups. However, increased metabolic power was associated with decreased MOS AP mean (p < 0.0001), independent of speed. Increased MOS AP variability (p = 0.01) and increased SSWS (p's < 0.05) were associated with increased metabolic power. The MOS ML mean for COPD patients was greater than that of healthy patients (p = 0.02). MOS AP mean decreased as speed increased and differed by group (p = 0.048). For COPD patients, a plateau was observed at SSWS and did not decrease further at +20%SSWS compared to controls. MOS AP variability (p < 0.0001), MOS ML mean (p < 0.0001), and MOS ML variability (p = 0.003) decreased as speed increased and did not differ by group.

SIGNIFICANCE

Patients with COPD operate at the upper limit of their metabolic reserve due to an increased cost of breathing. To compensate for their lack of stability, they walked with larger margins of stability in the ML direction, instead of changing the stability margins in the AP direction, due to its association with energy expenditure.

Subjects With COPD Walk With Less Consistent Organization of Movement Patterns of the Lower Extremity

BACKGROUND

The inherent stride-to-stride fluctuations during walking are altered in the aging population and could provide insight into gait impairments and falls in patients with COPD. Stride-to-stride fluctuations are quantified two ways: variability of the fluctuations (eg, standard deviation), and movement patterns within the fluctuations. Our objective was to investigate stride-to-stride fluctuations by evaluating the variability and movement patterns of lower limb joints in subjects with COPD compared to subjects without COPD as control subjects.

METHODS

In this cross-sectional study, 22 subjects with COPD (age 63 ± 9 y; FEV₁ 54 ± 19% predicted) and 22 control subjects (age 62 ± 9 y; FEV₁ 95 ± 18% predicted) walked for 3 min on a treadmill while their gait was recorded. The amount of variability (ie, standard deviation and coefficient of variation) and movement patterns (ie, predictability and consistency in organization) were quantified for the range of motion and joint angle of the hip, knee, and ankle, at 3 walking speeds (ie, self-selected, fast, and slow). General linear mixed models were used for analysis.

RESULTS

Control subjects had more consistent organization of the hip and knee joint movement patterns compared to subjects with COPD (P = .02 and P = .02, respectively). Further, control subjects adapted to speed changes by demonstrating more consistent organization of movement patterns with faster speeds, whereas subjects with COPD did not. At the fast walking speed, subjects with COPD demonstrated less consistent organization of knee and hip joint movement patterns as compared to control subjects without COPD (P = .03 and P = .005, respectively). The amount of variability did not differ between groups.

CONCLUSIONS

Although subjects with COPD did not demonstrate decreased amount of variability, their hip and knee joint movement patterns were less consistent in organization during walking. Reduced consistency in organization of movement patterns may be a contributing factor to falls and mobility problems experienced by patients with COPD.

Effects of Pulmonary Rehabilitation on Gait Characteristics in Patients with COPD

Pulmonary rehabilitation (PR) improves lower-limb muscle function in patients with chronic obstructive pulmonary disease (COPD). However, it remains unclear whether patients improve gait characteristics, in particular stride-to-stride fluctuations that are associated with fall risks. This study aims to identify whether, and to what extent, PR affects positively gait characteristics in COPD. In this prospective observational study, 44 COPD patients (aged: 62 ± 7 years; Forced expiratory volume in 1 s 56 ± 20% predicted) performed self-paced, treadmill 6-min-walk tests (Gait Real-time Analysis Interactive Lab) before and after PR, while spatiotemporal parameters and center of mass position were recorded (100 Hz, Vicon Nexus). Standard deviation, coefficient of variation, predictability (sample entropy), and consistency in organization (local divergence exponent) were calculated. Sub-analysis was performed to identify gait differences between good and poor responders (<30 m change in a 6-min-walk distance). Patients demonstrated shorter stride times (p = 0.001) and improved lower-limb muscle function (p < 0.001) following PR. The good responders had a greater increase in stride length (p < 0.001) and a greater decrease in stride time (p < 0.001) compared to the poor responders. Current PR improved stride time in patients, while movement patterns within stride-to-stride fluctuations did not change. Training programs specifically targeting balance issues and gait function may be beneficial in improving gait characteristics in COPD.

New evaluation of trunk movement and balance during walking in COPD patients by a triaxial accelerometer

Background

Individuals with COPD may experience ambulatory difficulty due to both effort intolerance arising from respiratory dysfunction and impaired balance control during walking. However, the trunk movement during walking has not been evaluated or adjusted for patients with COPD. The Lissajous index (LI) visually and numerically evaluates the left–right symmetry of the trunk movement during walking and is useful in clinical practice. In COPD patients, the LI is used as an indicator of the left–right symmetry of the trunk during walking. Here, we used the LI to evaluate the symmetry of COPD patients based on bilateral differences in mediolateral and vertical accelerations, and we investigated the correlation between the patients’ symmetry evaluation results and their physical function.

Patients and methods

Sixteen stable COPD patients (all males; age 71.3±9.2 years) and 26 healthy control subjects (15 males; age 68.2±6.9 years) participated in this study. They performed the 10-minute walk test at a comfortable gait speed wearing a triaxial accelerometer, and we measured their trunk acceleration for the evaluation of symmetry. Motor functions were also evaluated in the patients with COPD.

Results

The average mediolateral bilateral difference and LI values of the COPD patients were significantly larger than those of the healthy subjects. The COPD patients’ LI values were significantly correlated with their static balance.

Conclusion

The LI measured using a triaxial accelerometer during walking is useful in balance assessments of patients with COPD.

COPD stands for complex obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) has extensively been reported as a complex disease affecting patients' health beyond the lungs with a variety of intra- and extrapulmonary components and considerable variability between individuals. This review discusses the assessment of this complexity and underlines the importance of transdisciplinary management programmes addressing the physical, emotional and social health of the individual patient.COPD management is challenging and requires advanced, sophisticated strategies meeting the patient's individual needs. Due to the heterogeneity and complexity of the disease leading to non-linear and consequently poorly predictable treatment responses, multidimensional patient profiling is crucial to identify the right COPD patient for the right treatment. Current methods are often restricted to general, well-known and commonly used assessments neglecting potentially relevant (interactions between) individual, unique "traits" to finally ensure personalised treatment. Dynamic, personalised and holistic approaches are needed to tackle this multifaceted disease and to ensure personalised medicine and value-based healthcare.

Impact of Chronic Obstructive Pulmonary Disease on Cognitive and Motor Performances in Dual-Task Walking

When two tasks are performed simultaneously, they compete for attentional resources, resulting in a performance decrement in one or both tasks. Patients with attention disorders have a reduced ability to perform several tasks simultaneously (e.g., talking while walking), which increases the fall risk and frailty. This study assessed the cognitive and motor performances of patients with COPD and healthy controls within a dual-task walking paradigm. A subobjective was to assess the impact of a pulmonary rehabilitation program on the dual-task performances in COPD. Twenty-five patients with COPD and 20 controls performed a cognitive task (subtraction) and a 15-m walking test separately (single-task; ST) and jointly (dual-task; DT). In addition, a subsample of 10 patients performed the same evaluations 5 weeks later after a pulmonary rehabilitation program following current recommendations. Cognitive and gait performances in ST showed no differences between patients with COPD and controls (all p > 0.05). However, COPD patients exhibited a greater increase in gait variability than controls in DT (4.07 ± 1.46% vs. 2.17 ± 0.7%, p < 0.001). The pulmonary rehabilitation program had no effect on the dual-task impairment for the subsample of patients (p = 0.87). This study provides evidence of insufficient attentional resources to successfully deal with DT in patients with COPD, and this was expressed through an exaggerated increase in gait variability in DT walking. Given the high risk of falls and disability associated with altered gait variability, dual-task training interventions should be considered in pulmonary rehabilitation programs.

Patients with Chronic Obstructive Pulmonary Disease Walk with Altered Step Time and Step Width Variability as Compared with Healthy Control Subjects

RATIONALE

Compared with control subjects, patients with chronic obstructive pulmonary disease (COPD) have an increased incidence of falls and demonstrate balance deficits and alterations in mediolateral trunk acceleration while walking. Measures of gait variability have been implicated as indicators of fall risk, fear of falling, and future falls.

OBJECTIVES

To investigate whether alterations in gait variability are found in patients with COPD as compared with healthy control subjects.

METHODS

Twenty patients with COPD (16 males; mean age, 63.6 ± 9.7 yr; FEV₁/FVC, 0.52 ± 0.12) and 20 control subjects (9 males; mean age, 62.5 ± 8.2 yr) walked for 3 minutes on a treadmill while their gait was recorded. The amount (SD and coefficient of variation) and structure of variability (sample entropy, a measure of regularity) were quantified for step length, time, and width at three walking speeds (self-selected and ±20% of self-selected speed). Generalized linear mixed models were used to compare dependent variables.

RESULTS

Patients with COPD demonstrated increased mean and SD step time across all speed conditions as compared with control subjects. They also walked with a narrower step width that increased with increasing speed, whereas the healthy control subjects walked with a wider step width that decreased as speed increased. Further, patients with COPD demonstrated less variability in step width, with decreased SD, compared with control subjects at all three speed conditions. No differences in regularity of gait patterns were found between groups.

CONCLUSIONS

Patients with COPD walk with increased duration of time between steps, and this timing is more variable than that of control subjects. They also walk with a narrower step width in which the variability of the step widths from step to step is decreased. Changes in these parameters have been related to increased risk of falling in aging research. This provides a mechanism that could explain the increased prevalence of falls in patients with COPD.

Gait analysis in patients with chronic obstructive pulmonary disease: a systematic review

BACKGROUND

Gait instability is a major fall-risk factor in patients with chronic obstructive pulmonary disease (COPD). Clinical gait analysis is a reliable tool to predict fall onsets. However, controversy still exists on gait impairments associated with COPD.

RESEARCH QUESTION

Thus, the aims of this review were to evaluate the current understanding of spatiotemporal, kinematic and kinetic gait features in patients with COPD.

METHODS

In line with PRISMA guidelines, a systematic literature search was performed throughout Web of Science, PubMed Medline, Scopus, PEDro and Scielo databases. We considered observational cross-sectional studies evaluating gait features in patients with COPD as their primary outcome. Risk of bias and applicability of these papers were assessed according to the QUADAS-2 tool.

RESULTS

Seven articles, cross-sectional studies published from 2011 to 2017, met the inclusion criteria. Sample size of patients with COPD ranged 14-196 (mean age range: 64-75 years). The main reported gait abnormalities were reduced step length and cadence, and altered variability of spatiotemporal parameters. Only subtle biomechanical changes were reported at the ankle level.

SIGNIFICANCE

A convincing mechanistic link between such gait impairments and falls in patients with COPD is still lacking. The paucity of studies, small sample sizes, gender and disease status pooling were the main risk of biases affecting the results uncertainty. Two research directions emerged: stricter cohorts characterization in terms of COPD phenotype and longitudinal studies. Quantitative assessment of gait would identify abnormalities and sensorimotor postural deficiencies that in turn may lead to better falling prevention strategies in COPD.

A Review on Accelerometry-Based Gait Analysis and Emerging Clinical Applications

Gait analysis continues to be an important technique for many clinical applications to diagnose and monitor certain diseases. Many mental and physical abnormalities cause measurable differences in a person's gait. Gait analysis has applications in sport, computer games, physical rehabilitation, clinical assessment, surveillance, human recognition, modeling, and many other fields. There are established methods using various sensors for gait analysis, of which accelerometers are one of the most often employed. Accelerometer sensors are generally more user friendly and less invasive. In this paper, we review research regarding accelerometer sensors used for gait analysis with particular focus on clinical applications. We provide a brief introduction to accelerometer theory followed by other popular sensing technologies. Commonly used gait phases and parameters are enumerated. The details of selecting the papers for review are provided. We also review several gait analysis software. Then we provide an extensive report of accelerometry-based gait analysis systems and applications, with additional emphasis on trunk accelerometry. We conclude this review with future research directions.

Population measurement for health systems

How can health systems make good use of digital medicine? For healthcare infrastructure, the answer is population measurement, monitoring people to compute status for clustering cohorts. In chronic care, most effective is measuring all the time, to track health status as it gradually changes. Passive monitors run in the background, without additional tasks to activate monitors, especially on mobile phones. At its core, a health system is a "sorting problem". Each patient entering the system must be effectively sorted into treatment cohorts. Health systems have three primary problems: Case Finding (which persons have which diagnoses), Risk Stratification (which persons are which status), and Care Routing (which persons need which treatments). The issue is then which measures can be continuously monitored at appropriate periodicity. The solutions of population measurement measure vital signs with passive monitors. These are input to predictive analytics to detect clinical values for providing care within health systems. For chronic care, complex vitals must be measured for overall status, such as oxygen saturation or gait speed. This enables healthcare infrastructure to support stratification, with persons placed into current levels of health status. Practical considerations for health systems influence implementation of new infrastructure. Case finding is more likely to be useful in urban settings, with barriers to entry based upon lower incomes. Care routing is more likely to be useful in rural settings, with barriers to entry based upon isolated geographies. Viable healthcare at acceptable quality and affordable cost is now possible for the range of geographies and incomes.

Spatiotemporal gait characteristics in patients with COPD during the Gait Real-time Analysis Interactive Lab-based 6-minute walk test

Background and aim

Overground gait assessment is limited by the analysis of multiple strides or both spatiotemporal gait characteristics, while fixed speed treadmill walking restricts natural gait speed variations. The Gait Real-time Analysis Interactive Lab (GRAIL)-based 6-minute walk test (6MWT) enables 3D motion analysis and self-paced treadmill walking, and could provide insight in gait alterations in patients with chronic obstructive pulmonary disease (COPD). The aim of this study is to compare spatiotemporal gait characteristics between patients with COPD and healthy elderly during the GRAIL-based 6MWT.

Materials and methods

Eighty COPD patients (60% male; 62±7 years; FEV₁:56±19% predicted) and 38 healthy elderly (63% male; 62±6 years; FEV₁:119±17% predicted) performed two GRAIL-based 6MWTs. Mean differences and coefficient of variation of spatiotemporal gait characteristics were calculated using the trial with the largest walk distance. Sub-analyses were conducted to account for walking speed differences between groups, and muscle strength and COPD severity within the patient group.

Results

COPD patients showed increased temporal gait characteristics, decreased stride and step lengths, and increased gait variability compared to healthy elderly (p<0.01). Stride length variability remained increased in COPD after correction for walking speed (MD:0.98%, CI:0.36–1.61, p = 0.003). Reduced quadriceps strength did not translate into altered gait characteristics, while COPD severity is associated with stride time (left MD:-0.02s, CI:-0.04–0.01, p = 0.003; right MD:-0.02s, CI:-0.04–0.01, p = 0.003).

Discussion

COPD patients performed the GRAIL-based 6MWT differently compared to healthy elderly. Further research should use other variability measures to investigate gait characteristics in COPD, to assess subtle alterations in gait and to enable development of rehabilitation strategies to improve gait, and possibly balance and fall risk in COPD. Other lower limb muscle groups should be considered when investigating gait alterations in COPD.

Conclusion

COPD patients have different gait characteristics compared to healthy elderly. Independent of walking speed, COPD patients demonstrate increased stride length variability during the GRAIL-based 6MWT compared to healthy elderly.

Gait abnormalities of COPD are not directly related to respiratory function

STUDY OBJECTIVE

To assess whether gait abnormalities in COPD depend on mere impairment of respiratory function.

METHODS

In 40 patients with COPD at different GOLD stages and 28 controls, we evaluated: forced expiratory volume in 1s (FEV1); partial pressure of oxygen; Mini-Mental State Examination (MMSE); dynamic balance through the Mini-BESTest (MBT); Timed Up and Go (TUG) test without and with dual task counting aloud back by three; 6-min walk test (6MWT); body sway during quiet stance (stabilometry); spatial-temporal variables of gait by a 4-m long sensorized walkway (baropodometry). Lower-limb muscle strength, tendon reflexes, and sensation were also clinically evaluated.

RESULTS

Muscle strength of proximal but not distal muscles was slightly reduced in patients, whereas reflexes and sensation were unaffected. FEV1, partial pressure of oxygen, MMSE, MBT, stabilometry, as well as baropodometry, were abnormal and unrelated to muscle weakness. The time taken to perform the TUG test was increased, and to a larger extent with than without dual task. At baropodometry, variability of step length was increased; abnormalities of gait variables were associated with larger body sway but not with FEV1 or hypoxemia. Gait speed at 6MWT was correlated with MBT score and with FEV1 as well as hypoxemia.

CONCLUSIONS

6MWT findings give a measure of gait disability linked to endurance-related respiratory failure. Gait at baropodometry is associated with impairment of balance, cognitive status and abnormal dual task performance. We suggest that central nervous lesions, presumably of vascular origin, are detrimental to balance and gait in COPD.

Predicting Pulmonary Function from Phone Sensors

Introduction:Smartphones are ubiquitous, but it is unknown what physiological functions can be monitored at clinical quality. Pulmonary function is a standard measure of health status for cardiopulmonary patients. We have shown phone sensors can accurately measure walking patterns. Here we show that improved classification models can accurately predict pulmonary function, with sole inputs being motion sensors from carried phones.

Subjects and Methods:Twenty-five cardiopulmonary patients performed 6-minute walk tests in pulmonary rehabilitation at a regional hospital. They carried smartphones running custom software recording phone motion. Each patient's pulmonary function was measured by spirometry. A universal model, based on support vector machine, then computed the category of function with input from signal processing features and patient demographic features.

Results:All but a few of every 10-second interval for every patient was correctly predicted. The trained model perfectly computed the GOLD (Global Initiative for Chronic Obstructive Lung Disease) level 1/2/3, which is a standard classification of pulmonary function. Each level was determined to have a characteristic motion, which could be recognized from the sensor features. In addition, longitudinal changes were detected for 10 patients with multiple walk tests, except for cases with clinical instability.

Conclusions:These results are encouraging toward clinical validation of passive monitors running continuously in the background, for patients in homes during daily activities. Initial testing indicates the same high accuracy as with active monitors, for patients in hospitals during walk tests. We expect patients can simply carry their phones during everyday living, while models support automatic prediction of pulmonary function for health monitoring.

Classification Models for Pulmonary Function using Motion Analysis from Phone Sensors

Smartphones are ubiquitous, but it is unknown what physiological functions can be monitored at clinical quality. Pulmonary function is a standard measure of health status for cardiopulmonary patients. We have shown phone sensors can accurately measure walking patterns. Here we show that improved classification models can accurately measure pulmonary function, with sole inputs being sensor data from carried phones. Twenty-four cardiopulmonary patients performed six minute walk tests in pulmonary rehabilitation at a regional hospital. They carried smartphones running custom software recording phone motion. For every patient, every ten-second interval was correctly computed. The trained model perfectly computed the GOLD level 1/2/3, which is a standard categorization of pulmonary function as measured by spirometry. These results are encouraging towards field trials with passive monitors always running in the background. We expect patients can simply carry their phones during daily living, while supporting automatic computation ofpulmonary function for health monitoring.

GaitKeeper: A System for Measuring Canine Gait

It is understood gait has the potential to be used as a window into neurodegenerative disorders, identify markers of subclinical pathology, inform diagnostic algorithms of disease progression and measure the efficacy of interventions. Dogs’ gaits are frequently assessed in a veterinary setting to detect signs of lameness. Despite this, a reliable, affordable and objective method to assess lameness in dogs is lacking. Most described canine lameness assessments are subjective, unvalidated and at high risk of bias. This means reliable, early detection of canine gait abnormalities is challenging, which may have detrimental implications for dogs’ welfare. In this paper, we draw from approaches and technologies used in human movement science and describe a system for objectively measuring temporal gait characteristics in dogs (step-time, swing-time, stance-time). Asymmetries and variabilities in these characteristics are of known clinical significance when assessing lameness but presently may only be assessed on coarse scales or under highly instrumented environments. The system consists an inertial measurement unit, containing a 3-axis accelerometer and gyroscope coupled with a standardized walking course. The measurement unit is attached to each leg of the dog under assessment before it is walked around the course. The data by the measurement unit is then processed to identify steps and subsequently, micro-gait characteristics. This method has been tested on a cohort of 19 healthy dogs of various breeds ranging in height from 34.2 cm to 84.9 cm. We report the system as capable of making precise step delineations with detections of initial and final contact times of foot-to-floor to a mean precision of 0.011 s and 0.048 s, respectively. Results are based on analysis of 12,678 foot falls and we report a sensitivity, positive predictive value and F-score of 0.81, 0.83 and 0.82 respectively. To investigate the effect of gait on system performance, the approach was tested in both walking and trotting with no significant performance deviation with 7249 steps reported for a walking gait and 4977 for a trotting gait. The number of steps reported for each leg were approximately equal and this consistency was true in both walking and trotting gaits. In the walking gait 1965, 1790, 1726 and 1768 steps were reported for the front left, front right, hind left and hind right legs respectively. 1361, 1250, 1176 and 1190 steps were reported for each of the four legs in the trotting gait. The proposed system is a pragmatic and precise solution for obtaining objective measurements of canine gait. With further development, it promises potential for a wide range of applications in both research and clinical practice.

Occurrence of Anxiety and Depression among Stable COPD Patients and its Impact on Functional Capability

INTRODUCTION

Anxiety and depression are important but often under-diagnosed co-morbid conditions in patients with Chronic Obstructive Pulmonary Disease (COPD) which may affect the functional capacity of the patients.

AIM

To find out the proportion of depression and anxiety among stable COPD patients using a validated questionnaire suitable for use in clinic and the factors affecting their reduced functional capability as assessed by six-minute walk test.

MATERIALS AND METHODS

This was a descriptive cross-sectional study. Seventy five patients diagnosed with stable COPD in outpatient Department of Pulmonary Medicine in a tertiary care hospital, satisfying all inclusion criteria, were included in the study. They were examined clinically, categorized as per Global Initiative for Chronic Obstructive Lung Disease (GOLD) severity assessment guideline and interviewed by designated interviewer using validated questionnaire for depression (Hamilton depression rating scale, HAM-D) and anxiety (State Trait Anxiety Inventory, STAI). The functional exercise capacity of the patient was assessed by six-minute walk test. Statistical analysis was performed using Minitab software (version16.1).

RESULTS

Among 75 stable COPD patients (68 male, 7 female), majority (32 out of 75) had both depression and anxiety, while only anxiety or depression was present in 9 each. The patients with depression had no significant difference in six-minute walk distance, change in heart rate and respiratory rate (p = 0.4186, 0.219 and 0.41 respectively) as compared to those without depression, but were found to be more dyspnoeic at the end of the test (p= 0.003). There was also no significant difference in walk distance in patients with high STAI score as compared to those with low STAI score (p= 0.276).

CONCLUSION

Both anxiety and depression were present in majority of the stable COPD patients. The presence of these co-morbid conditions had no significant effect on the functional status of the patients in the form of reduced six-minute walk distance, though they were more symptomatic than those without these co-morbidities.

Mining Discriminative Patterns to Predict Health Status for Cardiopulmonary Patients

Smartphones are ubiquitous now, but it is still unclear what physiological functions they can monitor at clinical quality. Pulmonary function is a standard measure of health status for cardiopulmonary patients. We have shown that predictive models can accurately classify cardiopulmonary conditions from healthy status, as well as different severity levels within cardiopulmonary disease, the GOLD stages. Here we propose several universal models to monitor cardiopulmonary conditions, including DPClass, a novel learning approach we designed. We carefully prepare motion dataset covering status from GOLD 0 (healthy), GOLD 1 (mild), GOLD 2 (moderate), all the way to GOLD 3 (severe). Sixty-six subjects participate in this study. After de-identification, their walking data are applied to train the predictive models. The RBF-SVM model yields the highest accuracy while the DPClass model provides better interpretation of the model mechanisms. We not only provide promising solutions to monitor health status by simply carrying a smartphone, but also demonstrate how demographics influences predictive models of cardiopulmonary disease.

Predicting Transitions in Oxygen Saturation Using Phone Sensors

INTRODUCTION

Widespread availability of mobile devices is revolutionizing health monitoring. Smartphones are ubiquitous, but it is unknown what vital signs can be monitored with medical quality. Oxygen saturation is a standard measure of health status. We have shown phone sensors can accurately measure walking patterns.

SUBJECTS AND METHODS

Twenty cardiopulmonary patients performed 6-min walk tests in pulmonary rehabilitation at a regional hospital. They wore pulse oximeters and carried smartphones running our MoveSense software, which continuously recorded saturation and motion. Continuous saturation defined categories corresponding to status levels, including transitions. Continuous motion was used to compute spatiotemporal gait parameters from sensor data. Our existing gait model was then trained with these data and used to predict transitions in oxygen saturation. For walking variation, 10-s windows are units for classifying into status categories.

RESULTS

Oxygen saturation clustered into three categories, corresponding to pulmonary function Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 and GOLD 2, with a Transition category where saturation varied around the mean rather than remaining steady with low standard deviation. This category indicates patients who are not clinically stable. The gait model predicted status during each measured window of free walking, with 100% accuracy for the 20 subjects, based on majority voting.

CONCLUSIONS

Continuous recording of oxygen saturation can predict cardiopulmonary status, including patients in transition between status levels. Gait models using phone sensors can accurately predict these saturation categories from walking motion. This suggests medical devices for predicting clinical stability from passive monitoring using carried smartphones.

Can Commercially Available Pedometers Be Used For Physical Activity Monitoring In Patients With COPD Following Exacerbations?

BACKGROUND

Commercially available pedometers have been used as tools to measure endpoints in studies evaluating physical activity promotion programs. However, their accuracy in patients recovering from COPD exacerbations is unknown. The objectives of this study were to 1) assess the relative accuracy of different commercially available pedometers in healthy volunteers and 2) evaluate the accuracy of the top-performing commercially available pedometer in patients recovering from COPD exacerbations following hospital discharge.

METHODS

Twelve healthy volunteers wore 2 pedometers, 2 smartphones with pedometer apps and an accelerometer for 15 minutes of indoor activity. The top-performing device in healthy volunteers was evaluated in 4 patients recovering from COPD exacerbations following hospital discharge during 6 minutes of walking performed at home. Bland-Altman plots were employed to evaluate accuracy of each device compared with direct observation (the reference standard).

RESULTS

In healthy volunteers, the mean percent error compared to direct observation of the various devices ranged from -49% to +1%. The mean percent error [95% confidence interval (CI)] of the top-performing device in healthy volunteers, the Fitbit Zip^®, was +1% [-33 to +35%], significantly lower than that of the accelerometer (-13% [-56 to +29%], p=0.01). The mean percent error [95% CI] for the Fitbit Zip^® in patients recovering from COPD exacerbations was -3% [-7 to +12%].

CONCLUSIONS

The accuracy of commercially available pedometers in healthy volunteers is highly variable. The top-performing pedometer in our study, the Fitbit Zip,^® accurately measures step counts in both healthy volunteers and patients recovering from COPD exacerbations.