Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. The World Health Organization has projected that COPD will become the third leading cause of mortality and fifth highest cause of disability in 2020.1
With disease progression, COPD patients experience a progressive decrease in the ability to perform activities of daily living (ADL), which becomes more evident with the onset of dyspnea and fatigue during the performance of ADL that were previously performed without limitations.2 In addition, oxygen desaturation may occur during these activities because of imbalance between oxygen supply and demand, which can be attributed to ventilatory, hemodynamic, and peripheral muscle disorders, or a combination of these.3
Patients with COPD can achieve 55% oxygen uptake and 60% to 70% maximal voluntary ventilation (MVV) during ADL performance, with a consequent decrease in metabolic and ventilatory reserves.4 Patients with COPD may also present decreases in functional capacity and quality of life besides the limitations of ADL.
Therefore, assessing the limitations of ADL is important, since these can be used as a predictor of mortality5 and have an important role in the quality of life of COPD patients.6
The simplest methods to assess ADL performance are questionnaires and scales, which are accessible tools. Through reports from patients, it is possible to establish the difficulties in performing ADL. Among the scales, the London Chest Activity of Daily Living (LCADL)7 has been widely used to assess the impact of dyspnea when performing ADL in COPD patients, as it is disease-specific. Quality of life is commonly assessed by the St George's Respiratory Questionnaire (SGRQ), which is also disease-specific in assessing the overall impact on ADL and patient well-being.8
These assessment tools are self-reported and therefore rely on memory and cannot reflect the real limitations of COPD patients during ADL. Therefore, assessing ADL through simulations becomes important as it can represent the real limitations. Some studies have already been developed considering this topic.
Velloso et al4 showed that COPD patients presented high oxygen uptake (
O2) when performing 4 pre-selected ADL, which could explain the fatigue during the performance of ADL. Furthermore, the high ventilatory demand could be related to dyspnea. Jeng et al9 found greater dyspnea during the performance of ADL when comparing COPD patients with healthy individuals. Vaes et al10 found that COPD patients use a high proportion of aerobic capacity and ventilation (VE) with higher reported dyspnea during ADL than healthy elderly individuals.
Patients with few symptoms, assessed by the modified Medical Research Council (mMRC), showed significant dyspnea and oxygen desaturation during ADL. However, dyspnea and oxygen desaturation present independent and unrelated behaviors.11
Nevertheless, there are few studies in the literature that have evaluated how ADL and quality-of-life scales reflect the real limitations during ADL execution and simulation. Therefore, the objectives were to assess the peripheral oxygen saturation (SpO2), changes in SpO2 (ΔSpO2), dyspnea, and metabolic and ventilatory demand during ADL simulation to identify whether the LCADL Scale and SGRQ are able to reflect the patient's real limitations during ADL simulation.
PATIENTS AND METHODS
STUDY DESIGN AND PATIENTS
This was an observational, cross-sectional study conducted in the Laboratory of Spirometry and Respiratory Physiotherapy of the Federal University of São Carlos from October 2013 to January 2016. The study protocol was approved by the university's human research ethics committee (#0354.0.135.000-11).
Inclusion criteria included the following: patients with a confirmed diagnosis of moderate to severe COPD1; aged 60 y or older; both genders; and no change in medication and clinical stability for at least 2 mo. Exclusion criteria were as follows: severe heart disease; myocardial ischemia; musculoskeletal/orthopedic conditions that limited exercise; uncontrolled systemic hypertension; participation in a pulmonary rehabilitation program within the previous 6 mo; and exacerbation of clinical symptoms during the study. After the assessment, all patients were referred to a pulmonary rehabilitation program.
The assessments were conducted on 3 nonconsecutive days with a 48-hr interval between assessments. On the first day, data related to sample characteristics were collected including medical history, comorbidities (Charlson index), and disease impact on health status (COPD Assessment Test). In addition, the mMRC, LCADL Scale, and SGRQ were completed and the 6-Min Walk Test was performed. On the second day, a symptom-limited cardiopulmonary exercise test was performed. On the third day, the ADL assessment was performed with gas analysis. All scales and questionnaires were administered as an interview in a quiet environment and always by the same examiner.
The SGRQ assesses quality of life related to 3 domains that address aspects of respiratory symptoms, changes in physical activity, and the overall impact on ADL and patient well-being. Higher scores are related to poorer quality of life.8,12
The LCADL Scale assesses limitations to perform ADL because of dyspnea7 and a higher total score indicates greater limitation. It is composed of 4 domains: self-care, domestic activities, physical activities, and leisure. A total score7 and percentage of total (LCADL%total) were calculated. The LCADL%total calculation is described in our previously published study.11 Both SGRQ8,12 and LCADL Scale13 have been translated and validated for the Brazilian population.
The 6-Min Walk Test was performed according to the guidelines of the European Respiratory Society and the American Thoracic Society.14 Two tests were performed with a 30-min rest between tests and the greatest distance was used for the statistical analyses. In addition, a percentage of the predicted distance was calculated.15
To determine peak of oxygen uptake (
O2peak), a symptom-limited cardiopulmonary exercise test was performed to determine the metabolic demand during ADL. The test was performed on a cycle ergometer and the expired gas samples were collected on an average of every 3 breaths using a metabolic system (
O2000 system, MedGraphics). The test began with a 3-min rest, followed by a 1-min warm-up with subsequent load increases of 5 W each 2 min while maintaining a pedaling cadence between 50 to 60 revolutions/min. The criteria for stopping the test were according to the guideline of the American Thoracic Society/American College of Chest Physicians.16
The ADL simulations were performed as described in a previously published study11 and included (1) showering simulation (ADL1); (2) lifting and lowering containers from a shelf above the shoulder girdle (ADL2); and (3) raising and lowering pots on a shelf positioned below the pelvic girdle (ADL3). Ventilation,
O2, and metabolic equivalents were determined during ADL using the same metabolic system (Figure 1) as used for the cardiopulmonary exercise test. All 3 ADL involved trunk flexion and rotation and unsupported upper limb movements because these activities are capable of leading to greater increases in VE and oxygen uptake (
O2).2,10 The activities were all monitored by the same evaluator and patients were instructed to perform them in the same order, as a circuit, and as performed at home, with no time limit for their execution.
Maximal voluntary ventilation was calculated using the equation forced expiratory volume in the first second of expiration (FEV1) × 37.5.17 Ventilatory (VEADL/MVV) and metabolic (
O2peak) demands while performing the simulated ADL were subsequently calculated. Values >60% were considered as high metabolic and ventilatory demands.4 Furthermore, heart rate (HR), SpO2, dyspnea, and fatigue were determined at rest and immediately after each ADL.
The ΔSpO2 was calculated at the end of each ADL using the equation: ΔSpO2 = SpO2rest − SpO2ADL. Oxygen desaturation was defined as values below 88%18 and/or ΔSpO2 ≥4%.19
Data were analyzed using SPSS, v. 23.0 (Statistical Package of Social Sciences, IBM). The Shapiro-Wilk test was used to assess data normality and all variables were reported as mean ± standard deviation.
Repeated-measures analysis of variance was used to compare the metabolic and ventilatory variables at the end of each ADL and its nonparametric equivalent. Correlation coefficients were used to identify correlations between LCADL Scale and SGRQ and the outcomes ΔSpO2, dyspnea, fatigue, and metabolic and ventilatory demands. The correlation coefficients were classified by strength according to Bryman and Cramer: weak (r value: 0.2-0.39); moderate (r value: 0.4-0.69); and strong correlations (r value: 0.7-0.89).
Finally, a stepwise multiple linear regression was done using LCADL%total and SGRQ as the dependent variables and the variables with a moderate correlation as independent. The significance level for the statistical analysis was set at P < .05.
The sample size was calculated to achieve a correlation of at least 0.4 between the LCADL Scale and SGRQ and the outcomes: ΔSpO2, dyspnea, fatigue, and metabolic and ventilatory demands during ADL. With a bidirectional α of .05 and β = .20, the estimated sample size was 47 subjects.20
CLINICAL CHARACTERISTICS OF PATIENTS
There were 55 patients eligible for the study and, of those, 3 were excluded for exacerbations, 2 because of systemic hypertension, and 2 for incomplete assessments. As a result, 48 patients were included in the study and their clinical characteristics are described in Table 1. The GOLD system1 based on FEV1 was used to classify severity of COPD and those data are summarized in Figure 2.
COMPARISON OF VENTILATORY AND METABOLIC VARIABLES DURING ADL
The time required to perform all 3 ADL was 875 ± 190 sec. SpO2 and ΔSpO2 in ADL2 were statistically lower than in ADL3. The percentage of patients who presented oxygen desaturation in ADL1 (41.7%) was higher than in ADL2 (33.3%), and ADL3 (25%) (Table 2).
Heart rate, VE, and ventilatory demand were statistically higher in ADL2 and ADL3 than in ADL1 (Figure 3). Metabolic demand and other variables presented similar behavior during all 3 ADL (Table 2).
CORRELATION BETWEEN LCADL SCALE AND SGRQ WITH THE ADL LIMITATIONS
The LCADL%total showed a moderate correlation with dyspnea in ADL3 (r = 0.40, P = .008) and metabolic demand in ADL1 (r = 0.475, P = .006), besides weak correlation with dyspnea in ADL1 (r = 0.311, P = .032) and ADL2 (r = 0.334, P = .020) (Figure 4A).
The SGRQ score demonstrated a moderate correlation with dyspnea in ADL1 (r = 0.465, P = .001), ADL2 (r = 0.514; P < .001), and ADL3 (r = 0.642, P < .001), and with metabolic demand in ADL1 (r = 0.439, P = .012) and ADL3 (r = 0.413, P = .019). In addition, the SGRQ showed a weak correlation with fatigue in ADL2 (r = 0.304, P = .036) and ADL3 (r = 0.344, P = .017) and with ventilatory demand in ADL2 (r = 0.290, P = .046) and ADL3 (r = 0.351, P = .014) (Figure 4B).
The variability of dyspnea in ADL3 and metabolic demand in ADL1 (P = .026) explained 33% of the variability in LCADL%total. The variability of dyspnea and metabolic demand in ADL3 (P < .001) explained 67% of the variability in SGRQ (Table 3).
The main results of this study were that the 3 ADL involving trunk flexion and rotation and unsupported upper limb movements resulted in lower SpO2 values and higher VE and metabolic demand values. It was also noted that ADL1 presented the highest percentage of patients with oxygen desaturation and metabolic demand values were close to 90% of peak during the ADL. In addition, dyspnea and metabolic demand in ADL3 reflected 67% of the SGRQ score and dyspnea in ADL1 and metabolic demand in ADL3 reflected 34% of the LCADL Scale score (Figure 3).
The ADL of showering, lifting containers above the scapular girdle, and lowering pots below the pelvic girdle were chosen because some studies have shown that ADL are capable of leading to greater increases in VE and
Annegarn et al21 observed that among 820 patients classified as GOLD IV, self-care ADL, such as showering, personal hygiene, and basic home maintenance, were those classified as the most problematic. In addition, showering was classified as the fourth most problematic activity in this population. That study concluded that the clinical characteristics are weakly associated with problematic ADL, emphasizing that individual assessment of these activities is necessary to plan a personalized intervention.
Regarding disease severity, Castro et al2 showed that the greater the severity of COPD, the greater was the metabolic and ventilatory demand to perform ADL and, consequently, the lower was the ventilatory and aerobic reserve. Mild COPD patients achieved 20% of the metabolic demand while severe COPD patients achieved values close to 80% of peak values. In our study, 48% were classified as moderate and 52% were severe and very severe COPD patients. Contrasting with the literature, the patients in the present study achieved values near to 90% of peak metabolic values, demonstrating that the execution of ordinary activities leads to
O2 close to
O2peak. This suggests that when patients are performing certain ADL, they do so close to their peak limitation.
Higher metabolic demand during ADL has already been described.9,22 When patients performed more vigorous activities23 than those selected for the present study, they reached 75.4% to 85% of metabolic limits. Despite the fact that the activities selected for this study are not considered as intense, as in the other study, patients reached higher values of metabolic demand. This allows us to infer that despite the ADL classification of moderate or vigorous activities, it is necessary to consider the nature of ADL in a specific population. In our study, the ADL included a great range of upper limb motions combined with trunk flexion and rotation, so high metabolic demand was necessary to perform the ADL.
Associated with the high metabolic demand, the present study verified that a high metabolic equivalent level was required to perform the ADL. These values were twice those expected for healthy subjects23; thus, ADL that were previously classified as mild activities are classified as moderate for our patients. The systemic inflammation, oxidative stress, and muscle peripheral impairments have an adverse effect on respiratory and peripheral muscle function and thus affect exercise capacity24 and lead to high values of
O2 and a higher metabolic equivalent level to do mild activities.
Concerning ventilatory demand, Castro et al2 found values close to 54% for COPD patients with disease classified as severe. Some studies4,10 reported that severe and very severe COPD patients reached values close to 50% of ventilatory demand when sweeping the floor and placing containers on high shelves. Moreover, they showed a relationship between metabolic and ventilatory demand with disease severity. Those findings corroborate the results of the present study, in which moderate to very severe COPD patients reached 52% of ventilatory demand in activities encompassing upper and lower limb movements associated with trunk inclination and rotation. This reinforces the idea that this type of activity can lead to a reduced ventilatory reserve, causing limitations in execution the activities. It is known that dynamic hyperinflation occurs during ADL and may contribute to performance limitation25–27; however, we did not measure this component during our simulations.
Despite high metabolic and ventilatory demand, the onset of dyspnea and oxygen desaturation, the HR response was not higher than anticipated. Patients achieved values close to 65% of HRmax, with lower values in ADL1, and these values are similar to those found in the literature2,10 during ADL simulation. As a limitation, we just assessed the HR during ADL, which did not allow us to determine cardiac demand impairment.
In the present study, we found a correlation between metabolic limitations (increased metabolic demand) and ventilatory limitations (dyspnea and increased ventilatory demand during ADL) with the quality of life assessed by the SGRQ score. From this finding, it can be stated that, when we apply SGRQ, the total score is associated with the real limitation during the performance of ADL, being that SGRQ score reflected 67% of the real limitations during ADL such as increased metabolic demand and dyspnea. Although it is known that dyspnea is related to the real limitations in the ADL performance,28 this is the first study to show the relationship between SGRQ score and real limitations during ADL.
Regarding the assessment of ADL limitations, it is well known that direct assessments of ADL are not always possible and questionnaires and scales are commonly used. It has been previously described that dyspnea reported during the performance of ADL may not be related to dyspnea assessed by scales, such as the mMRC.11 This finding contrasts with the present study, wherein ADL limitation verified by LCADL Scale showed correlation with dyspnea and metabolic and ventilatory demands during ADL. This can be explained by the fact that the LCADL Scale involves 4 domains of 15 ADL, being much more comprehensive than the mMRC. Moreover, the ADL included in the LCADL Scale are similar to the ADL assessed in the present study, reflecting ADL commonly performed by the patients in “real life.” The present study found that the LCADL Scale score was able to explain 33% of the increase in metabolic demand and dyspnea for all 3 ADL.
Although ADL assessment through simulation requires a longer time and adequate environment, often making it unfeasible, the present study allows us to infer that, if there is no possibility of performing ADL simulation, the specific scales and questionnaires, such as LCADL Scale and SGRQ, can be performed, since these tools represent and reflect real limitations of the patients during ADL.
Dyspnea is related to the real limitations that patients experience during the performance of ADL, generally becoming a limiting factor.28 Accurate assessment of dyspnea during ADL will allow more adequate therapeutic management, avoiding the increase in dyspnea leading to a reduction in the quantity of ADL, decreasing functionality, and having a clear impact on quality of life.
A limitation of the study is that the attainment of
O2peak from a symptom-limited cardiopulmonary test performed on a cycle ergometer leads to lower values of
O2peak, in addition to recruiting a smaller muscle group; however, it is commonly used in COPD patients and described as a tool to evaluate and even compare with ADL.22 Another possible limitation was the fact that some ADL lasted less than 5 min, a time necessary to reach a steady-state level of metabolic and ventilatory effort. However, the idea of ADL simulation was conceived to represent, in the most realistic way, real-life execution of the activity.
A clinical implication of the results of this study is that the SGRQ can be used instead of assessment by ADL simulation, since it reflected the real limitations of high metabolic and ventilatory demands. Additional clinical implications are discussed in the Appendix (see Supplemental Digital Content 1, available at: http://links.lww.com/JCRP/A79).
In conclusion, ADL involving flexion and trunk rotation associated with unsupported upper limb movements were able to identify the patients who presented with oxygen desaturation and high ventilatory demand. In total, 20% to 40% of the patients presented with oxygen desaturation during these ADL. High metabolic demand was confirmed during performance of all 3 ADL. The LCADL Scale and the SGRQ were able to reflect functional limitations during ADL, such as dyspnea and high metabolic demand during ADL. These functional limitations reflected 67% in the SGRQ score, showing SGRQ to be better than LCADL Scale for reflecting ADL limitations. Thus, these 2 questionnaires represent important tools to use in clinical practice.
The Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) provided scholarships to fund this project.
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activities of daily living; chronic obstructive pulmonary disease; functional limitations; quality of life
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