Chronic obstructive pulmonary disease (COPD), characterized by persistent and progressive airflow obstruction, is a chronic, preventable, and treatable disease. There are pulmonary and extrapulmonary components of impairments in COPD.1 Dyspnea and fatigue are the primary symptoms in patients with COPD arising due to the deteriorative effects of these components.1,2 Acute-on-chronic lung hyperinflation during exercise increases the mechanical loading of weak inspiratory muscles and inspiratory neural drive.3,4 Limitation of tidal volume increase as a result of decreased inspiratory capacity is primary reason for exertional dyspnea perception and exercise limitation.1,3,4

The activities of daily living (ADLs) are the involvement in activities on a daily basis. Whereas simple tasks such as mobility, drinking, eating, dressing, washing hands, and bathing can be described as basic ADLs, more complex tasks such as repairing a device, cutting fabric, ironing, managing finance, and home can be described as instrumental ADLs. The extrapulmonary effects of COPD may restrict the patients with COPD in maintaining their ADLs and their independence at home and/or outdoors.5 Lower extremity muscle strength was shown to be independent predictor of ADL performance in patients with COPD.6 Otherwise, aerobic exercise capacity must be sufficient to meet the increased oxygen demand to perform the simple ADLs.7 The patients with COPD experience higher metabolic load and symptom perceptions than healthy subjects during performing ADLs,8 and have limitations during ADLs. The most problematic ADLs were reported to be walking, household activities and stair climbing in moderate-very severe COPD.9

Although several studies investigated the relationship between submaximal exercise capacity and ADLs,10,11 there was any study investigating the relationship between maximal exercise capacity and ADL in patients with COPD. Accordingly, we aimed to investigate the relationship between maximal exercise capacity and ADLs with a performance based test in patients with GOLD stage II–III COPD. Our hypothesis was there was a more strong association between submaximal exercise capacity and ADL performance compared to maximal exercise capacity.

The characteristics of 27 patients with COPD were shown in Table 1. Thirteen of COPD patients (48.1%) had moderate severity COPD (GOLD stage II), 14 of them (51.9%) had severe COPD (GOLD stage III). Twenty-one of the patients (77.8%) were ex-smokers, six of them (22.2%) were never smoked. Median MMRC score of COPD patients was 2.

Data on the patients’ outcomes of Glittre ADL test, ISWT, and 6MWT are demonstrated in Table 2. The reasons for termination of the ISWT were as mainly because the patients were not as fast as to reach the signals’ speed. Twelve of the patients (44.4%) missed two cones. The mean distance of ISWT was 382.59±152.83m, and the mean percentage of the predicted ISWT distance was 50.31±16.80%. The mean distance of 6MWT was 488.26±96.80m. The mean percentage of predicted 6MWT distance was 98.40±20.50%.

There was a negative correlation between 6MWT distance and Glittre-ADL test time (r=−0.506, p=0.007, Fig. 2). The ISWT distance was significantly correlated with Glittre-ADL test time (r=−0.517, p=0.006, Fig. 3). In addition, the MMRC dyspnea score was significantly correlated with 6MWT distance (r=−0.535, p=0.004) and the ISWT distance (r=−0.417, p=0.031). Although there was any correlation between MMRC dyspnea score and Glittre-ADL test time (p>0.05), MMRC dyspnea score was weakly associated with the increase in dyspnea perception during ADL (r=0.423, p=0.028).

Fig. 2.

The relationship between submaximal exercise capacity and Glittre ADL test (r=−0.506, p=0.007).

(0.05MB).

Fig. 3.

The relationship between maximal exercise capacity and Glittre ADL test (r=−0.517, p=0.006).

(0.05MB).

When we look at the correlations between symptom perceptions during exercise tests and ADL performance, increase in dyspnea perception during 6MWT was moderately associated with the increase in dyspnea perception during ADL (r=0.667, p<0.001). The leg fatigue perception increase in 6MWT was moderately correlated with the increase in leg fatigue perception during ADL (r=0.498, p=0.008). The change in SpO2 during 6MWT was moderately associated with the change in SpO2 during ADL (r=0.608, p=0.001). The increase in HR during 6MWT was correlated with the increase in HR during ADL (r=0.568, p=0.002). Otherwise, the change in SpO2 during ISWT was moderately associated with the change in SpO2 during ADL (r=0.620, p=0.001). The leg fatigue perception increase in ISWT was moderately correlated with the increase in leg fatigue perception during ADL (r=0.592, p=0.002) and also arm fatigue increase during ADL (r=0.524, p=0.005).

This study revealed that as the maximal or submaximal exercise capacity decrease, level of ADL performance is adversely affected in similar magnitude in moderate–severe patients with COPD. In addition, dyspnea perception level in daily life is related with increased dyspnea perception in ADL performance and decreased exercise capacity. Otherwise, only dyspnea perception increase during submaximal exercise is related with increase in dyspnea during ADL performance.

Shouza et al. showed that although there was any difference between Glittre-ADL test times between GOLD 1–3 COPD patients, as the disease severity progresses, the ratio of Glittre-ADL oxygen consumption (VO2)/peak VO2 during cardiopulmonary exercise testing (CPET) increased significantly. In addition, the severe COPD patients presented lower ventilator and cardiac reserve, higher dyspnea perception and SpO2 decline at the end of the Glittre-ADL test.22 Vaes et al. reported that patients with COPD used a significantly higher proportion of their peak exercise capacity and ventilation than healthy controls during five specific ADLs, which are putting on socks, shoes, and vest; folding eight towels; putting away groceries; washing four dishes, cups, and saucers; and sweeping the floor for four minutes.8 Different studies are supporting the evidence that VO2 and ventilatory demand were higher in patients with COPD than in healthy controls during daily activities.23,24 Our patients had reduced maximal exercise capacity (50.31±16.80%) and this reduction was correlated with the poor ADL performance. Although we were unable to assess the oxygen uptake during activities of the patients in our study, ISWT distance and peak oxygen uptake have similar accuracy for the estimation of peak exercise capacity in patients with COPD.25 These result supports the findings that reduced ventilator and metabolic reserve during exercise are reflected in daily life that contains movements of upper and lower extremities.8,22 Otherwise, the deoxygenation and increased leg fatigue perceptions during ISWT was associated with deoxygenation and increased leg and arm fatigue perceptions during ADL performance. These findings demonstrates us that ADL performance is negatively affected and level of deoxygenation and fatigue perceptions increases during daily activities as a result of diminished ventilator reserve during exercise in COPD patients.4 In line with these results, dyspnea perception during life that was evaluated by MMRC score was correlated with ISWT distance. A recently published study in 2018 suggested that phases of desaturation (especially <88%) during laboratory based ADL test is correlated with desaturation phases during daily life.26 In accordance with these results, change in oxygenation level was correlated between ISWT and Glittre-ADL test. Therefore, the ISWT as a field test, may be a practical alternative to estimate the ADL performance in patients with COPD when oxygen uptake cannot be measured in the clinical settings.

In a study investigating the relationship between functional performance and Glittre-ADL test, Glittre-ADL test time of GOLD II and GOLD III COPD patients was reported to be 4.02 and 4.87min, respectively.27 Gulart et al. reported that the mean Glittre-ADL test time was 4.63±1.95min, the 6MWT distance was 424±1.60m in their study of approximately 62% GOLD II–III COPD patients of the participants.28 In the present study, Glittre-ADL test time was lower, and 6MWT distance was longer compared to the previous studies.27,28 This difference may be a result of different patient characteristics such as lower mean age, lower body mass index, higher FEV1 values, and mostly male gender in the present study.

Ozsoy et al. showed that London Chest ADL score (LCADL) that is a paper-based ADL questionnaire is correlated with 6MWT distance (r=−0.48, p=0.001) and functional exercise capacity, symptom perceptions increase and expiratory muscle strength are predictors of ADL in COPD.11 Another study demonstrated that the Glittre-ADL test performance is related with the walking and sitting time during daily life.27 The Glittre-ADL test performance was also associated with the daily physical activities (r=0.67, p<0.05) and with 6MWT distance (r=−0.64, p<0.05) in a trial by Correa et al. in 2011.10 Our study was in agreement with previous findings that submaximal exercise capacity is more closely associated with ADLs and more reflects the influence on ADLs.10,11,27 The COPD Assessment Test that evaluates impact of disease on functional status and symptom perceptions (cough, phlegm, chest tightness, dyspnea, activities, confidence, sleep, and energy) was shown to be related with 6MWT distance, performance based Glittre-ADL test time and LCADL score.28 We also demonstrated that dyspnea and leg fatigue perceptions, oxygenation level and HR increase during 6MWT and Glittre-ADL test was similar. Also the MMRC score was correlated with dyspnea increase in ADL. This supports that 6MWT and Glittre-ADL test are two important functional tests that can reflect daily living activities. The other reason for the symptom perceptions and changes in HR and SpO2 at same amount during both tests are that they are submaximal tests.

Some limitations of this study have to be made clear. First of all, we did not include a control group. Secondly, we were unable to measure the oxygen consumption during Glittre-ADL test, ISWT, and 6MWT due to the laboratory facilities. Measuring oxygen consumption during ADL and field tests may provide the determination of the ventilatory limitation and metabolic cost of these activities and enable the comparison of these outcomes among different tests such as Glittre-ADL test, 6MWT, and ISWT. Additionally, we did not include mild and very severe patient group. Therefore, this can limit the generalizability of the outcome of the study.

In conclusion, the reduction in exercise capacity has adverse effects on ADLs in patients with GOLD stage II–III COPD. In addition, increase dyspnea perception cause decline in maximal and submaximal exercise capacity and symptom perception increase during exercise is related with symptom perception increase during ADLs. These results strengthen the necessity of exercise interventions in order to reverse the unfavorable outcomes in the ADLs resulting from reduced exercise capacity. To our knowledge, there is limited data about the relationship between maximal exercise capacity and daily living activities in literature and present study is the important for investigating this topic. Further randomized controlled studies with larger sample size and COPD patients from all stages are needed that evaluates maximal exercise capacity and activities of daily living relation. There is also need for researches that investigate the effects of exercise training on ADLs.

The authors declare no conflict of interests.