Association of daily physical activity volume and intensity with COPD severity

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.

Effects of Pedometer-Based Step-Feedback on Physical Activity of Severe COPD Patients

Purpose

This study investigated whether adding step-feedback (step-FB) from a pedometer to pulmonary rehabilitation (PR) programs could increase the physical activity (PA) of low-activity patients with severe chronic obstructive pulmonary disease (COPD).

Patients and Methods

We included low-activity patients with severe COPD (step-FB group: 14 patients; control group: 17 patients) who underwent PR for the first time. The usual PR program for patients with severe COPD consisted of two 8-week sessions (PR session 1: PR1, PR session 2: PR2). The step-FB group was provided a program with step-FB added to PR2 (PR2+step-FB). Furthermore, all patients were evaluated at pre-intervention (baseline), PR1, and PR2. The primary outcome of this study was the number of daily steps (steps) and energy expenditure from activity (energy expenditure), as measured by a pedometer. The secondary outcomes were dyspnea and exercise tolerance.

Results

In PR1, dyspnea, exercise tolerance, steps, and energy expenditure were significantly improved as compared to baseline, in both groups. During PR2, dyspnea and exercise tolerance were significantly improved as compared to PR1, in both groups. Steps and energy expenditure were significantly improved in the step-FB group, but not in the control group.

Conclusion

PR improved PA by improving physical function in severe COPD patients. Adding step-FB improved PA in severe COPD patients by presenting an activity goal for improving PA. Therefore, pedometer-based step-FB is a viable addition to PR and has the potential to improve PA continuously in these patients.

Cognitive behavioural therapy combined with physical activity behavioural modification strategies during pulmonary rehabilitation in patients with COPD

Introduction

Patients with COPD who exhibit elevated levels of anxiety and/or depression are typically less able to improve symptoms and physical activity levels following a programme of pulmonary rehabilitation (PR). The objective of the present study was to provide proof of concept that offering an intervention comprising cognitive behavioural therapy (CBT) alongside physical activity behavioural modification strategies (BPA) during PR is more effective in improving physical activity outcomes compared to PR and CBT alone.

Methods

32 patients with COPD (mean±sd forced expiratory volume in 1 s 42±14% predicted) were assigned 1:1 to receive PR+CBT+BPA or PR+CBT. BPA comprised motivational interviews, step-count monitoring, feedback using a pedometer and goal setting. Assessments included accelerometer-derived steps per day, movement intensity, 6-min walk distance (6MWD) and Hospital Anxiety and Depression Scale (HADS) scores.

Results

The magnitude of improvement across physical activity outcomes was greater for the PR+CBT+BPA compared to the PR+CBT intervention (by 829 steps per day (p=0.029) and by 80±39 vector magnitude units (p=0.042), respectively). Compared to PR and CBT alone, the PR+CBT+BPA intervention induced greater clinically meaningful improvements in HADS anxiety scores (by -2 units, 95% CI -4-1 units) and 6MWD (by 33±20 m).

Conclusions

Providing anxious and/or depressed patients with COPD with a combined intervention of CBT and BPA during PR presents more favourable improvements in physical activity outcome measures compared to CBT alone during PR.

Computed tomography-based body composition measures in COPD and their association with clinical outcomes: A systematic review

Background

Computed tomography (CT) is commonly utilized in chronic obstructive pulmonary disease (COPD) for lung cancer screening and emphysema characterization. Computed tomography-morphometric analysis of body composition (muscle mass and adiposity) has gained increased recognition as a marker of disease severity and prognosis. This systematic review aimed to describe the CT-methodology used to assess body composition and identify the association of body composition measures and disease severity, health-related quality of life (HRQL), cardiometabolic risk factors, respiratory exacerbations, and survival in patients with COPD.

Methods

Six databases were searched (inception-September 2021) for studies evaluating adult COPD patients using thoracic or abdominal CT-muscle or adiposity body composition measures. The systematic review was conducted in accordance with the PRISMA guidelines.

Results

Twenty eight articles were included with 15,431 COPD patients, across all GOLD stages with 77% males, age range (mean/median 59–78 years), and BMI range 19.8–29.3 kg/m². There was heterogeneity in assessment of muscle mass and adiposity using thoracic (n = 22) and abdominal (n = 8) CT-scans, capturing different muscle groups, anatomic locations, and adiposity compartments (visceral, subcutaneous, and epicardial). Low muscle mass and increased adiposity were associated with increased COPD severity measures (lung function, exercise capacity, dyspnea) and lower HRQL, but were not consistent across studies. Increased visceral adiposity (n = 6) was associated with cardiovascular disease or risk factors (hypertension, hyperlipidemia, and diabetes). Low muscle CSA was prognostic of respiratory exacerbations or mortality in three of six studies, whereas the relationship with increased intermuscular adiposity and greater mortality was only observed in one of three studies.

Conclusion

There was significant variability in CT-body composition measures. In several studies, low muscle mass was associated with increased disease severity and lower HRQL, whereas adiposity with cardiovascular disease/risk factors. Given the heterogeneity in body composition measures and clinical outcomes, the prognostic utility of CT-body composition in COPD requires further study.

The impact of low forced vital capacity on behavior restrictions in a population with airflow obstruction

Background

Recent studies have suggested that low forced vital capacity (FVC) is related to respiratory symptoms with various comorbid conditions that eventually lead to physical inactivity and may be applied to subjects with airflow obstruction (AO). Therefore, this study aimed to evaluate the association between low FVC and behavior restrictions in subjects with AO.

Methods

A cross-sectional study was performed using data from the Korea National Health and Nutrition Survey conducted between 2007 and 2015. Participants aged 40 to 79 years with spirometry-defined AO (pre-bronchodilator forced expiratory volume in one second/FVC <70%) were analyzed to evaluate the association between low FVC (defined as FVC <80% predicted) and behavior restrictions.

Results

A total of 3,345 participants with AO were included. The proportion of subjects with low FVC varied widely according to severity of airflow limitation (0.9%, 35.5%, and 85.1% in the mild, moderate, and severe-to-very-severe AO groups, respectively). Compared to the moderate AO group with normal FVC, those with low FVC were more likely to be older, to be never- or ex-smokers, to have larger waist size with higher body mass index, and to have comorbidities such as diabetes, hypertension, dyslipidemia, and osteoporosis. Low FVC was independently associated with behavior restrictions [adjusted prevalence ratio (aPR), 1.72; 95% confidence interval (CI), 1.43-2.06] among all participants with AO, and this was most prominent in those with moderate AO (aPR, 1.65; 95% CI, 1.27-2.13).

Conclusions

In subjects with moderate AO, low FVC was independently associated with behavior restrictions even after adjusting for confounding factors.

Factors influencing the physical activity in daily life of male patients with different levels of severity of chronic obstructive pulmonary disease

[Purpose] Physical activity influences the prognosis of chronic obstructive pulmonary disease and is influenced by exercise tolerance, and environmental, psychological, and many other factors, but the influence of these factors on physical activity levels in each stage of chronic obstructive pulmonary disease is unknown. This study aimed to clarify this matter. [Participants and Methods] Seventy-one male patients with chronic obstructive pulmonary disease (aged 72.2 ± 4.5 years) participated in this study. We compared physical activity levels (determined as daily steps), presence or absence of daily routine (e.g., housework or hobby), 6-minute walking distance, psychological factors (using the Hospital Anxiety and Depression Scale), and health-related quality of life (Physical and Mental component summary of the 36-item short-form health survey) between patients in different stages of chronic obstructive pulmonary disease. [Results] When examined at each stage of chronic obstructive pulmonary disease, physical activity levels correlated with the presence or absence of daily routine, 6-minute walking distance, and Physical component summary in all stages, but the scores in the anxiety and depression components of the Hospital Anxiety and Depression Scale and Mental component summary correlated only with stage 4. [Conclusion] Physical functioning was related to physical activity levels at any stage of chronic obstructive pulmonary disease, although psychological functioning was related to the progress of disease severity. The approach to promote an active lifestyle must be selected depending on the stage of chronic obstructive pulmonary disease.

Inhaled therapies in patients with moderate COPD in clinical practice: current thinking

COPD is a complex, heterogeneous condition. Even in the early clinical stages, COPD carries a significant burden, with breathlessness frequently leading to a reduction in exercise capacity and changes that correlate with long-term patient outcomes and mortality. Implementation of an effective management strategy is required to reduce symptoms, preserve lung function, quality of life, and exercise capacity, and prevent exacerbations. However, current clinical practice frequently differs from published guidelines on the management of COPD. This review focuses on the current scientific evidence and expert opinion on the management of moderate COPD: the symptoms arising from moderate airflow obstruction and the burden these symptoms impose, how physical activity can improve disease outcomes, the benefits of dual bronchodilation in COPD, and the limited evidence for the benefits of inhaled corticosteroids in this disease. We emphasize the importance of maximizing bronchodilation in COPD with inhaled dual-bronchodilator treatment, enhancing patient-related outcomes, and enabling the withdrawal of inhaled corticosteroids in COPD in well-defined patient groups.

Biobehavioral Prognostic Factors in Chronic Obstructive Pulmonary Disease: Results From the INSPIRE-II Trial

OBJECTIVE

To examine the prognostic value of select biobehavioral factors in patients with chronic obstructive pulmonary disease (COPD) in a secondary analysis of participants from the INSPIRE-II trial.

METHODS

Three hundred twenty-six outpatients with COPD underwent assessments of pulmonary function, physical activity, body mass index, inflammation, pulmonary symptoms, depression, and pulmonary quality of life and were followed up for up to 5.4 years for subsequent clinical events. The prognostic value of each biobehavioral factor, considered individually and combined, also was examined in the context of existing Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2011 risk stratification.

RESULTS

Sixty-nine individuals experienced a hospitalization or died over a mean follow-up period of 2.4 (interquartile range = 1.6) years. GOLD classification was associated with an increased risk of clinical events (hazard ratio [HR] = 2.72 [95% confidence interval = 1.63-4.54], per stage); 6-minute walk (HR = 0.50 [0.34-0.73] per 500 ft), total steps (HR = 0.82 [0.71-0.94] per 1000 steps), high-sensitivity C-reactive protein (HR = 1.44 [1.01-2.06] per 4.5 mg/l), depression (HR = 1.12 [1.01-1.25] per 4 points), and pulmonary quality of life (HR = 1.73 [1.14-2.63] per 25 points) were each predictive over and above the GOLD assessment. However, only GOLD group and 6-minute walk were predictive of all-cause mortality and COPD hospitalization when all biobehavioral variables were included together in a multivariable model.

CONCLUSIONS

Biobehavioral factors provide added prognostic information over and above measures of COPD severity in predicting adverse events in patients with COPD.

Six-minute-walk distance and accelerometry predict outcomes in chronic obstructive pulmonary disease independent of Global Initiative for Chronic Obstructive Lung Disease 2011 Group

RATIONALE

The 2011 combined Global Initiative for Chronic Obstructive Lung Disease (GOLD) assessment incorporates symptoms, exacerbation history, and spirometry in discriminating risk of exacerbations in patients with chronic obstructive pulmonary disease (COPD). Six-minute-walk distance (6MWD) and accelerometry also have been used to assess disease severity in COPD. The association between these measures and the risks of hospitalization and mortality in the context of GOLD 2011 is unknown.

OBJECTIVES

To describe changes in exercise tolerance and physical activity over time in patients with COPD and to test the hypothesis that lower baseline 6MWD or accelerometry step count is associated with increased risk of COPD-related hospitalization or all-cause mortality, independent of GOLD 2011 group.

METHODS

Physical function and medical outcomes were prospectively assessed in 326 patients with moderate to severe COPD in INSPIRE-II, a randomized controlled trial of a coping skills training intervention. Cox models were used to determine if GOLD 2011 group, 6MWD, or accelerometry steps were associated with risk of COPD-related hospitalization or all-cause mortality.

MEASUREMENTS AND MAIN RESULTS

Physical function declined over time in GOLD group D but remained stable in groups A, B, and C. GOLD classification was associated with time to death or first COPD-related hospitalization. Baseline 6MWD was more strongly associated with time to death or first COPD-related hospitalization (hazard ratio, 0.50 [95% confidence interval, 0.34, 0.73] per 150 m, P=0.0003) than GOLD 2011 classification. A similar relationship was observed for accelerometry steps (hazard ratio, 0.80 [95% confidence interval, 0.70, 0.92] per 1,000 steps, P=0.002).

CONCLUSIONS

Exercise tolerance and daily physical activity are important predictors of hospitalization and mortality in COPD, independent of GOLD 2011 classification. Physical function may represent a modifiable risk factor that warrants increased attention as a target for interventions to improve clinically meaningful outcomes in COPD.

Use of time in people with chronic obstructive pulmonary disease--a systematic review

“Physical inactivity” and “sedentary lifestyles” are phrases often used when describing lifestyles of people with chronic obstructive pulmonary disease (COPD). Evidence suggests activity types, independent of energy expenditure, influence health outcomes, so understanding patterns of time use is important, particularly in chronic disease. We aimed to identify reports of time use in people with COPD. Predefined search strategies were used with six electronic databases to identify individual activity reports (including frequencies and/or durations) in which community-dwelling people with COPD engaged. Eligible studies were assessed independently against predefined criteria and data were extracted by two reviewers. Data synthesis was achieved by aggregating activity reports into activity domains (sports/exercise, screen time, transport, quiet time, self-care, sociocultural, work/study, chores, and sleep). Twenty-six publications reported 37 specific daily activities. People with COPD were found to spend extended periods in sedentary behaviors (eg, standing [194 min/day]; sitting [359 min/day]; lying [88 min/day]), have limited engagement in physical activity (eg, walking [51 min/day]; exercising [1.2 episodes per week {ep/w}, 13 min/day]), have high health care needs (medical appointments [1.0 ep/w]), and experience difficulties associated with activities of daily living (eg, showering [2.5 ep/w, 60 minutes per episode]; preparing meals [4.7 ep/w]). Little data could be found describing how people with COPD use their time, and data synthesis was problematic because of variations in methodologies, population differences, and research emphases. Identified data largely referred to posture and were skewed according to country, assessment methods, and disease severity. Comparisons with age-matched population data showed people with COPD spent less time engaged in personal-care activities (self-care and sleeping) and chores than people in similar age groups. The incorporation of time-use outcomes in future research designs should be encouraged. Ideally, these tools should use consistent frameworks and comparable outcome measures in order to provide clearer descriptions of time use in chronic disease.

Association between peripheral muscle strength and daily physical activity in patients with COPD: a systematic literature review and meta-analysis

BACKGROUND

Patients with chronic obstructive pulmonary disease have skeletal muscle dysfunction and reduced daily physical activity (PA). Whether the reduction in quadriceps strength (QS) is directly linked to physical inactivity remains to be elucidated.

METHODS

A systematic review and a meta-analysis were conducted to determine the potential relationship between QS and the level of PA. The overall estimate of the correlation coefficient (r*) was calculated, and a subgroup analysis was conducted to analyze the association between QS and indices of PA separately.

RESULTS

A total of 8 studies were included in the meta-analysis. The overall association between QS and PA was low but highly significant (r * = 0.288, 95% CI = 0.180-0.389; P < .001). In the subgroup analysis, the association between QS and the number of steps per day was low (r = 0.260; 95% CI = 0.060-0.440) and the association between QS and the time spent walking was moderate (r = 0.418; 95% CI = 0.229-0.576).

CONCLUSIONS

Peripheral muscle strength is associated with PA as assessed by the number of steps per day and the time spent walking in patients with chronic obstructive pulmonary disease. The overall association between QS and PA was low to moderate and highly significant.

Factors associated with a low level of physical activity in patients with chronic obstructive pulmonary disease

BACKGROUND

Physical activity such as walking is strongly recommended for patients with chronic obstructive pulmonary disease (COPD).

METHODS

We undertook a multicenter observational study on COPD patients, collecting the daily walking time, COPD severity score (COPDSS), functional status [London Chest Activity of Daily Living (LCADL) questionnaire], health-related quality of life (QoL) rating [five-item EuroQL (EQ-5D) and Airways Questionnaire 20 (AQ20)], and anxiety and depression rating (Hospital Anxiety and Depression Scale). Multivariate logistic regression modeling was performed to identify the independent predictors of a low walking time (<30 min/day).

RESULTS

We included 4,574 patients with a mean (±standard deviation) age of 67.1 ± 10.0 years, with a mean FEV1 (%) of 54.0 ± 23.7. The mean daily walking time was 73.6 ± 67.1 min (58.9 % at ≥60 min and 13.7 % at <30 min). A strong direct relationship was observed between daily walking time and better QoL (EQ-5D and AQ20) and functional status (LCADL; p < 0.001 in all cases). The independent predictors of a low walking time were a worse score in EQ-5D [odds ratio (OR) (95 % confidence interval per one-point increase of 0.23 (0.15-0.35)], a higher COPDSS [OR per one-point increase of 1.04 (1.02-1.07)], and the presence of depression [OR 1.58 (1.25-2.01)].

CONCLUSIONS

After adjustment for age and severity of symptoms, poor health status, severity of COPD, and depression are the main factors associated with a low walking time in COPD patients.

Physical activity level and its clinical correlates in chronic obstructive pulmonary disease: a cross-sectional study

Background

Decreased physical activity is associated with higher mortality in subjects with COPD. The aim of this study was to assess clinical characteristics and physical activity levels (PALs) in subjects with COPD.

Methods

Seventy-three subjects with COPD (67 ± 7 yrs, 44 female) with one-second forced expiratory volume percentage (FEV₁%) predicted values of 43 ± 16 were included. The ratio of total energy expenditure (TEE) and resting metabolic rate (RMR) was used to define the physical activity level (PAL) (PAL = TEE/RMR). TEE was assessed with an activity monitor (ActiReg), and RMR was measured by indirect calorimetry. Walking speed (measured over 30-meters), maximal quadriceps muscle strength, fat-free mass and systemic inflammation were measured as clinical characteristics. Hierarchical linear regression was applied to investigate the explanatory values of the clinical correlates to PAL.

Results

The mean PAL was 1.47 ± 0.19, and 92% of subjects were classified as physically very inactive or sedentary. The walking speed was 1.02 ± 0.23 m/s, the quadriceps strength was 31.3 ± 11.2 kg, and the fat-free mass index (FFMI) was 15.7 ± 2.3 kg/m², identifying 42% of subjects as slow walkers, 21% as muscle-weak and 49% as FFM-depleted. The regression model explained 45.5% (p < 0.001) of the variance in PAL. The FEV₁% predicted explained the largest proportion (22.5%), with further improvements in the model from walking speed (10.1%), muscle strength (7.0%) and FFMI (3.0%). Neither age, gender nor systemic inflammation contributed to the model.

Conclusions

Apart from lung function, walking speed and muscle strength are important correlates of physical activity. Further explorations of the longitudinal effects of the factors characterizing the most inactive subjects are warranted.

Loss of quadriceps muscle oxidative phenotype and decreased endurance in patients with mild-to-moderate COPD

Being well-established in advanced chronic obstructive pulmonary disease (COPD), skeletal muscle dysfunction and its underlying pathology have been scarcely investigated in patients with mild-to-moderate airflow obstruction. We hypothesized that a loss of oxidative phenotype (oxphen) associated with decreased endurance is present in the skeletal muscle of patients with mild-to-moderate COPD. In quadriceps muscle biopsies from 29 patients with COPD (forced expiratory volume in 1 s [FEV1] 58 ± 16%pred, body mass index [BMI] 26 ± 4 kg/m2) and 15 controls (BMI 25 ± 3 kg/m2) we assessed fiber type distribution, fiber cross-sectional areas (CSA), oxidative and glycolytic gene expression, OXPHOS protein levels, metabolic enzyme activity, and levels of oxidative stress markers. Quadriceps function was assessed by isokinetic dynamometry, body composition by dual-energy X-ray absorptiometry, exercise capacity by an incremental load test, and physical activity level by accelerometry. Compared with controls, patients had comparable fat-free mass index, quadriceps strength, and fiber CSA, but quadriceps endurance was decreased by 29% ( P = 0.002). Patients with COPD had a clear loss of muscle oxphen: a fiber type I-to-II shift, decreased levels of OXPHOS complexes IV and V subunits (47% and 31%, respectively; P < 0.05), a decreased ratio of 3-hydroxyacyl-CoA dehydrogenase/phosphofructokinase (PFK) enzyme activities (38%, P < 0.05), and decreased peroxisome proliferator-activated receptor-γ coactivator-1α (40%; P < 0.001) vs. increased PFK (67%; P < 0.001) gene expression levels. Within the patient group, markers of oxphen were significantly positively correlated with quadriceps endurance and inversely with the increase in plasma lactate relative to work rate during the incremental test. Levels of protein carbonylation, tyrosine nitration, and malondialdehyde protein adducts were comparable between patients and controls. However, among patients, oxidative stress levels were significantly inversely correlated with markers of oxphen and quadriceps endurance. Reduced muscle endurance associated with underlying loss of muscle oxphen is already present in patients with mild-to-moderate COPD without muscle wasting.

Daily walking intensity as a predictor of quality of life in patients with chronic obstructive pulmonary disease

PURPOSE

This study aimed to assess independent predictors of quality of life (QOL) in patients with chronic obstructive pulmonary disease, in particular, to evaluate the relationship between QOL and functional exercise capacity measured with an activity monitor.

METHODS

Functional exercise capacity was measured with an accelerometer-based walking intensity. QOL was assessed by Short Form-36 and Saint Georges Respiratory Questionnaire. Stepwise multivariate regression analyses were used to identify significant independent predictors of health-related QOL.

RESULTS

Daily walking intensity (fast walk) was the only significant independent predictor of the Short Form-36 domains "physical function" (P = 0.002) and "role physical" (P = 0.034). Age and depression were significant independent predictors of the domain "social functioning" (P = 0.035 and P = 0.002, respectively). Age and fast walk were significant independent predictors of the domain "mental health" (P = 0.006 and P = 0.017, respectively). Percent predicted forced expiratory volume in 1 s and fast walk were both significant independent predictors of the domains "general health" (P = 0.04 and P = 0.02, respectively) and "physical component score" (P = 0.038 and P = 0.017, respectively). In terms of the Saint Georges Respiratory Questionnaire, fast walk was a significant independent predictor of "activity score" (P = 0.001), "impact score" (P = 0.022), and "total score" (P = 0.01).

CONCLUSIONS

QOL is an important aspect to be integrated into long-term disease management and the assessment of daily walking intensity using accelerometry can provide additional information about the patient's functional status and well-being during a certain period.

Relationship between oxygen consumption kinetics and BODE Index in COPD patients

BACKGROUND AND OBJECTIVE

Patients with chronic obstructive pulmonary disease (COPD) present with reduced exercise capacity due to impaired oxygen consumption (VO(2)), caused primarily by pulmonary dysfunction and deleterious peripheral adaptations. Assuming that COPD patients present with slower VO(2) and heart rate (HR) on-kinetics, we hypothesized that this finding is related to disease severity as measured by the BODE Index. In this context, the present study intends to evaluate the relationship between VO(2) uptake on-kinetics during high-intensity exercise and the BODE Index in patients with COPD.

METHODS

Twenty males with moderate-to-severe stable COPD and 13 healthy control subjects matched by age and sex were evaluated. COPD patients were screened by the BODE Index and then underwent an incremental cardiopulmonary exercise test and a constant speed treadmill session at 70% of maximal intensity for 6 minutes. The onset of the exercise (first 360 seconds) response for O(2) uptake and HR was modeled according to a monoexponential fit.

RESULTS

Oxygen consumption and HR on-kinetics were slower in the COPD group compared with controls. Additionally, VO(2) on-kinetic parameters revealed a strong positive correlation (r = 0.77, P < 0.05) with BODE scores and a moderate negative correlation with walking distance (r = -0.45, P < 0.05).

CONCLUSION

Our data show that moderate-to-severe COPD is related to impaired oxygen delivery and utilization during the onset of intense exercise.

Assessing patient report of function: content validity of the Functional Performance Inventory-Short Form (FPI-SF) in patients with chronic obstructive pulmonary disease (COPD)

Purpose

The performance of daily activities is a major challenge for people with chronic obstructive pulmonary disease (COPD). The Functional Performance Inventory (FPI) was developed based on an analytical framework of functional status and qualitative interviews with COPD patients describing these difficulties. The 65-item FPI was reduced to a 32-item short form (SF) through a systematic process of qualitative and quantitative item reduction and formatted for greater clarity and ease of use. This study examined the content validity of the reduced, reformatted form of the instrument, the FPI-SF.

Patients and methods

Qualitative cognitive interviews were conducted with COPD patients recruited from three geographically diverse pulmonary clinics in the United States. Interviews were designed to assess respondent interpretation of the instrument, evaluate clarity and ease of completion, and identify any new activities participants found important and difficult to perform that were not represented by the existing items.

Results

Twenty subjects comprised the sample; 12 (60%) were male, 14 (70%) were Caucasian, the mean age was 63.0 ± 11.3 years, 12 (60%) were retired, the mean forced expiratory volume in 1 second (FEV₁) was 1.5 ± 0.5 L, and the mean percent predicted FEV₁ was 48.4% ± 13.1%. Participants understood the FPI-SF as intended, including instructions, items, and response options. Two minor formatting changes were suggested to improve clarity of presentation. Participants found the content of the FPI-SF to be comprehensive, with items covering activities they felt were important and often difficult to perform.

Conclusion

These results, together with its development history and previously tested quantitative properties, suggest that the FPI-SF is content valid for use in clinical studies of COPD.

Daily step counts in a US cohort with COPD

BACKGROUND

Baseline values for daily step counts in US adults with COPD and knowledge of its accurate measurement, natural change over time, and independent relationships with measures of COPD severity are limited.

METHODS

127 persons with stable COPD wore the StepWatch Activity Monitor (SAM) for 14 days, and 102 of them wore it a median 3.9 months later. SAM counts were compared to manual counts in the clinic. We assessed change over time, the effect of season, and relationships with forced expiratory volume in 1 s (FEV(1)) % predicted, 6-min walk test (6MWT) distance, the modified Medical Research Council (MMRC) dyspnea score, and the St. George's Respiratory Questionnaire Total Score (SGRQ-TS).

RESULTS

98% of subjects were males, with mean age 71 ± 8 years and FEV(1) 1.48 ± 0.54 L (52 ± 19% predicted). All 4 GOLD stages were represented, with the most subjects in GOLD II (44%) and GOLD III (37%). The SAM had >90% accuracy in 99% of subjects. Average step count was 5680 steps/day, which decreased with increasing GOLD stage (p = 0.0046). Subjects walked 645 fewer steps/day at follow-up, which was partly explained by season of monitoring (p = 0.013). In a multivariate model, FEV(1) % predicted, 6MWT distance and MMRC score were weakly associated with daily step counts, while SGRQ-TS was not.

CONCLUSIONS

These findings will aid the design of future studies using daily step counts in COPD. Accurately measured, daily step counts decline over time partly due to season and capture unique information about COPD status.