Objective: To determine the probability of oxygen desaturation in healthy individuals undergoing the incremental shuttle walk test (ISWT). Methods: We enrolled 83 healthy subjects: 55 males (including 1 smoker) and 28 females. We determined pre-ISWT FEV1, FEV6, HR and SpO2, as well as post-ISWT HR and SpO2. Results: Mean values overall were as follows: age, 35.05 ± 12.53 years; body mass index, 24.30 ± 3.47 kg/m2; resting HR, 75.12 ± 12.48 bpm; resting SpO2, 97.96 ± 1.02%; FEV1, 3.75 ± 0.81 L; FEV6, 4.45 ± 0.87 L; FEV1/FEV6 ratio, 0.83 ± 0.08 (no restriction or obstruction); incremental shuttle walk distance, 958.30 ± 146.32 m; post-ISWT HR, 162.41 ± 18.24 bpm; and post-ISWT SpO2, 96.27 ± 2.21%. In 11 subjects, post-ISWT SpO2 was higher than was pre-ISWT SpO2. In 17 subjects, there was a 4% decrease in SpO2 after the ISWT. There were no statistically significant differences between the groups with and without post-ISWT oxygen desaturation in terms of age, gender, FEV1, FEV6, FEV1/FEV6, pre-ISWT SpO2, incremental shuttle walk distance, HR, or percentage of maximal HR. In the individuals with post-ISWT oxygen desaturation, the body mass index was higher (p = 0.01) and post-ISWT SpO2 was lower (p = 0.0001). Conclusions: Healthy individuals can present oxygen desaturation after the ISWT. Using the ISWT to predict subtle respiratory abnormalities can be misleading. In healthy subjects, oxygen desaturation is common after the ISWT, as it is during any intense physical activity.

Keywords: Heart function tests; Respiratory function tests; Body mass index; Oximetry

Objective: One of the common limitations after COVID-19 pneumonia is the decrease in exercise capacity. The identification of the factors affecting exercise capacity and the assessment of patients at risk are important for determining treatment strategy. This study was conducted to determine the predictors of decreased exercise capacity in long post-COVID-19 patients. Methods: We investigated the association of exercise capacity as measured by the incremental shuttle walk test (ISWT) with age, sex, spirometric variables, respiratory and peripheral muscle strength, quality of life, fatigue, hospital anxiety depression scale, chest X-ray involvement, and hospitalization. The patients were divided into three groups: outpatients, inpatients, and ICU patients. Regression analysis was used to determine which parameters were significant predictors of exercise capacity. Results: Of the 181 patients included in the study, 56 (31%) were female. The mean ISWT in percentage of predicted values (ISWT%pred) was 43.20% in the whole sample, whereas that was 52.89%, 43.71%, and 32.21% in the outpatient, inpatient, and ICU patient groups, respectively. Linear regression analysis showed that predictors of decreased ISWT%pred were sex (ß = 8.089; p = 0.002), mMRC scale score (ß = -7.004; p = 0.001), FVC%pred (ß = 0.151; p = 0.003), and handgrip strength (ß = 0.261; p = 0.030). Conclusions: In long post-COVID-19 patients, sex, perception of dyspnea, restrictive pattern in respiratory function, and decrease in peripheral muscle strength are predictors of reduced exercise capacity that persists three months after COVID-19. In this context, we suggest that pulmonary rehabilitation might be an important therapy for patients after COVID-19.

Keywords: COVID-19; Exercise; Muscle strength; Rehabilitation; Walk test.

Objective: To determine reference values for incremental shuttle walk distance (ISWD) and peak physiological responses during the incremental shuttle walk test (ISWT), as well as to develop a series of predictive equations for those variables in healthy adults. Methods: We evaluated 103 healthy participants ≥ 40 years of age (54 women and 49 men). We fitted each participant with a gas analysis system for use during the ISWT. Oxygen consumption (VO2), carbon dioxide production, minute ventilation, heart rate (HR), ISWD, and maximal walking velocity (MWV) were obtained as primary outcomes. We also assessed hand grip strength (HGS) and lean body mass (LBM). Results: The regression analysis models, including physiological variables, ISWD, and MWV (adjusted for age, body mass, height, and sex), produced R2 values ranging from 0.40 to 0.65 (for HR and peak VO2, respectively). Using the models including LBM or HGS, we obtained no significant increase in the R2 values for predicting peak VO2, although the use of those models did result in slight increases in the R2 values for ISWD and MWV (of 8% and 12%, respectively). The variables ISWD, MWV, and ISWD Î body mass, respectively, explained 76.7%, 73.3%, and 81.2% of peak VO2 variability. Conclusions:áOur results provide reference values for ISWD and physiological responses to the ISWT, which can be properly estimated by determining simple demographic and anthropometric characteristics in healthy adults ≥ 40 years of age. The ISWT could be used in assessing physical fitness in the general adult population and in designing individualized walking programs.

Keywords: Reference values; Pulmonary gas exchange; Walking; Exercise test.

Objective: To evaluate the applicability of the incremental (shuttle) walk test in patients with chronic obstructive pulmonary disease and compare the performance of those patients on the shuttle walk test to that of the same patients on the encouraged 6-minute walk test. Methods: A cross-sectional study was conducted, in which 24 patients with chronic obstructive pulmonary disease were selected. In random order, patients were, after an initial practice period, submitted to a shuttle walk test and an encouraged 6-minute walk test. Results: The patients obtained a higher heart rate (expressed as a percentage of that predicted based on gender and age) on the encouraged 6-minute walk test (84.1 ± 11.4%) than on the shuttle walk test (76.4 ± 9.7%) (p = 0.003). The post-test sensation of dyspnea (Borg scale) was also higher on the encouraged 6-minute walk test. On average, the patients walked 307.0 ± 89.3 meters on the shuttle walk test and 515.5 ± 102.3 meters on the encouraged 6-minute walk test (p < 0.001). There was a good correlation between the two tests in terms of the distance walked (r = 0.80, p < 0.001). Conclusion: The shuttle walk test is simple and easy to implement in patients with chronic obstructive pulmonary disease. The encouraged 6-minute walk test produced higher post-test heart rate and greater post-test sensation of dyspnea than did the shuttle walk test.

Keywords: Pulmonary disease, chronic obstructive/rehabilitation; Exercise test; Motor activity; Reproducibility of results;

Objective: To analyze the shuttle walk test, and its respective retest, comparing children with cystic fibrosis (CF) to normal children. Methods: The children were divided into two groups: the CF group, composed of children in whom the diagnosis had been confirmed through sweat testing; and the control group, composed of normal children with no history of pulmonary diseases and no alterations in respiratory function. The children were submitted to at least two consecutive tests, 30 min apart. We evaluated distance walked, cardiac overload, peripheral oxygen saturation (SpO2) and subjective perception of exertion (dyspnea at rest scale and Borg dyspnea scale). Results: A total of 28 children were evaluated. Ages ranged from 7 to 15 years (11.57 ± 2.50 and 11.28 ± 1.85 years for the CF and control groups, respectively). The Borg scale scores were significantly higher in the controls (p = 0.007). No differences were found regarding cardiac overload and SpO2. In relation to the intergroup retest, the controls presented significant improvements on the second test, both in the distance walked and in dyspnea at rest (p = 0.014 and p = 0.036, respectively). The CF group presented a significant improvement only in the dyspnea at rest score (p = 0.168 and p = 0.042, respectively). Conclusion: The cardiac overload imposed by the test did not differ between the groups. The greater fatigue at the beginning of the second test suggests that the 30 min rest between the tests was insufficient.

Keywords: Cystic fibrosis; Exercise test; Heart rate.

Objectives: This study primarily aimed to investigate the clinical determinants of the Modified Incremental Step Test (MIST) in adults with non-cystic fibrosis bronchiectasis (NCFB). A secondary objective was to compare the cardiopulmonary responses after the MIST and Incremental Shuttle Walk Test (ISWT), two commonly adopted symptom-limited maximum field tests in chronic respiratory diseases. Methods: Forty-six patients with clinically stable bronchiectasis participated in this cross-sectional study. MIST and ISWT were performed to determine exercise capacity, while disease severity, fatigue, and quality of life were assessed using the Bronchiectasis Severity Index (BSI), the Fatigue Severity Scale (FSS), and St. George's Respiratory Questionnaire (SGRQ), respectively. Quadriceps muscle strength was evaluated using a hand-held dynamometer, walking speed with a wireless inertial sensing device, and the level of physical activity (steps/day) with a pedometer. Results: The BSI score, quadriceps muscle strength, daily step count, and the SGRQ total score explained 61.9% of the variance in the MIST (p < 0.001, R2 = 0.67, AR2 = 0.619). The BSI score (r = -0.412, p = 0.004), quadriceps muscle strength (r = 0.574, p = 0.001), daily step count (r = 0.523, p < 0.001), walking speed (r = 0.402, p = 0.006), FSS score (r = -0.551, p < 0.001), and SGRQ total score (r = -0.570, p < 0.001) correlated with the MIST. The patients achieved higher heart rates (HR), HR%, desaturation, dyspnea, and leg fatigue in the MIST compared to the ISWT (p < 0.05). Conclusions: Disease severity, quadriceps muscle strength, physical activity level, and quality of life were determinants of MIST. The advantages of the MIST, including higher cardiopulmonary response than ISWT and greater portability, which facilitates its use in various settings, make MIST the preferred choice for investigating symptom-limited exercise capacity in patients with NCFB.

Keywords: bronchiectasis, exercise capacity, step test, physical activity, walking speed, quality of life.

Objective: To develop regression equations for six-minute walk distance (6MWD) in healthy adults (20-80 years of age) in Brazil. Methods: We included 132 volunteers (66 males) without respiratory disease, cardiac disease, or comorbidities that affect ambulation. The volunteers completed three six-minute walk tests. Prior to and at the end of each test, we obtained SpO2 and maximal HR, as well as the Borg scale scores for sensation of dyspnea and lower limb fatigue. The data included in the final analysis were derived from the test with the greatest 6MWD. Results: The mean 6MWD values were 566 ± 87 m and 538 ± 95 m in males and females, respectively (p = 0.08). The 6MWD was greater in taller individuals and decreased in parallel with increases in age or body index mass (BMI). The best adjusted model was the quadratic model. We derived the following equation (valid for both genders): 6MWD = 511 + stature2 (cm) × 0.0066 − age2 × 0.030 − BMI2 × 0.068. This equation explained 55% of the variance in 6MWD. Conclusions: Reference values explaining a high proportion of the variance were derived by a quadratic regression model in healthy adults (of a wide range of ages) in Brazil. Keywords: Reference values; Exercise test; Walking.

Keywords: Reference values; Exercise test; Walking.

Over the last few years, the use of exercise tests has come to be recognized as a convenient method of evaluating respiratory function, because the reserves of the various systems in the human body should be known in order to provide a more complete portrayal of the functional capacities of the patient. Because walking is one of the main activities of daily living, walk tests have been proposed in order to measure the state or the functional capacity of patients. The six-minute walk test has proven to be reproducible and is well tolerated by patients. It evaluates the distance a person can walk on a flat, rigid surface in six minutes. Its main objective is to determine exercise tolerance and oxygen saturation during submaximal exercise. In this review, we present various clinical areas in which the test can provide useful data.

Keywords: Hypertension, pulmonary; Pulmonary circulation; Pulmonary heart disease; Exercise.

Objective: To evaluate the behavior of oxygen saturation curves throughout the six-minute walk test (6MWT) in patients with COPD. Methods: We included 85 patients, all of whom underwent spirometry and were classified as having moderate COPD (modCOPD, n = 30) or severe COPD (sevCOPD, n = 55). All of the patients performed a 6MWT, in a 27-m corridor with continuous SpO2 and HR monitoring by telemetry. We studied the SpO2 curves in order to determine the time to a 4% decrease in SpO2, the time to the minimum SpO2 (Tmin), and the post-6MWT time to return to the initial SpO2, the last designated recovery time (RT). For each of those curves, we calculated the slope. Results: The mean age in the modCOPD and sevCOPD groups was 66  10 years and 62  11 years, respectively. At baseline, SpO2 was > 94% in all of the patients; none received supplemental oxygen during the 6MWT; and none of the tests were interrupted. The six-minute walk distance did not differ significantly between the groups. The SpO2 values were lowest in the sevCOPD group. There was no difference between the groups regarding RT. In 71% and 63% of the sevCOPD and modCOPD group patients, respectively, a ≥ 4% decrease in SpO2 occurred within the first minute. We found that FEV1% correlated significantly with the SpO2 (r = −0.398; p < 0.001), Tmin (r = −0.449; p < 0.001), and minimum SpO2 (r = 0.356; p < 0.005). Conclusions: In the sevCOPD group, in comparison with the modCOPD group, SpO2 was lower and the Tmin was greater, suggesting a worse prognosis in the former.

Keywords: Pulmonary disease, chronic obstructive; Exercise test; Blood gas monitoring, transcutaneous.

Objectives: To report the results obtained in six-minute walk tests (6 MWT) performed in a group of patients under a pulmonary rehabilitation program (PRP) as a contribution to a better interpretation and the proper use of this test. Some factors that interfere with physical training during pulmonary rehabilitation were also studied. Methods: Retrospective data on 18 males and 5 females under a PRP were evaluated. During 3 months, the patients had 3 weekly training sessions to exercise the muscles of the lower extremities. The following parameters were analyzed before and after training: the distance walked during the 6 MWT and its relationship with the reference values calculated by the equations of Enright and Sherril; forced expiratory volume in one second, training load, heart rate (HR), respiratory rate (RR), oxygen saturation by pulse oxymeter (SpO2) and body mass index (BMI). Results: The values obtained during pre-training 6 MWT did not differ from the reference values calculated by Enright and Sherril equations (P = 0.777). After training, these values differed significantly (P = 0.001). The mean 6 MWT distance increase was 76 m. However, 3 patients did not reach the minimally significant increase of 54 m. Post-training 6 MWT correlated positively with pre-training FEV1 (P = 0.012), but not with load increase during training (P = 0.693). No significant difference in RR and SpO2 was observed before and after training. HR increased significantly at the end of post-training 6 MWT (P = 0.035). In 9 patients BMI was lower than the inferior limit. Six of them (66%) presented post-training distance increased in 54 m or more. Conclusions: The use of standardized methods for 6 MWT performance is recommended, even when reference values are targeted. The equations of Enright and Sherril for healthy subjects tended to yield underestimated values, with no statistical differences in training values in COPD patients. Differences in the encouragement technique employed could explain these conflicting results. Physical gain after rehabilitation was confirmed regardless of the patient's initial functional status, justifying the indication of rehabilitation even to those with severe respiratory limitations. The heterogeneous responses to load increase suggest the analysis of the predictive factors of the best response to training is necessary to customize load increase and thus obtain the best performance possible.

Keywords: Exercise test. Obstructive lung diseases. Rehabilitation. Respiratory function tests. Exercise.

Abstract Objective: To evaluate the influence of pleural drainage on the distance covered on the six-minute walk test, pain intensity and vital capacity in patients submitted to pulmonary resection. Methods: Thirteen consecutive patients from the Thoracic Surgery Infirmary of Hospital São Paulo, Brazil, submitted to closed pleural drainage (0.5-in multiperforated chest tube) in the postoperative period following pulmonary resection (lobectomy, segmentectomy and pulmonary nodule resection) were evaluated. The decision for chest tube removal followed clinical criteria defined by the surgical team, who did not participate in the study. Vital capacity, pain intensity (using a visual analog pain scale) and the distance covered on the six-minute walk test were determined 30 min prior to and 30 min after the removal of the chest tube. The statistical analysis was performed using paired t-tests, and the level of significance was set at 0.05. Results: After the removal of the chest tube, the visual analog scale pain scores were significantly lower (3.46 cm vs. 1.77 cm; p = 0.001) and the distance covered on the six-minute walk test was significantly higher (374.34 m vs. 444.62 m; p= 0.03). Vital capacity prior to and after chest tube removal was not significantly affected (2.15 L and 2.25 L, respectively; p = 0.540). Conclusions: The results of the present study suggest that the presence of a chest tube is a factor significantly associated with postoperative pain and functional limitation in patients submitted to pulmonary resection.

Keywords: Thoracic surgery; Exercise test; Respiratory function tests; Pain, postoperative.

Objective: To compare patients with cystic fibrosis and healthy individuals in terms of their functional performance on the six-minute walk test (6MWT). Methods: A prospective, cross-sectional study involving healthy individuals and patients with cystic fibrosis treated at a referral university hospital in the city of Campinas, Brazil. The 6MWT was administered in accordance with the American Thoracic Society guidelines, and it was repeated after a 30-min rest period. For all of the participants, RR, HR, SpO2, and Borg scale scores were obtained. For the cystic fibrosis patients, nutritional status and spirometric values were determined. Patients with pulmonary exacerbation were excluded. Spearman's correlation coefficient and repeated measures ANOVA were used. Results: The cystic fibrosis group comprised 55 patients, and the control group comprised 185 healthy individuals. The mean ages were 12.2 ± 4.3 and 11.3 ± 4.3 years, respectively. The six-minute walk distance (6MWD) was significantly shorter in the cystic fibrosis group than in the control group for both tests (547.2 ± 80.6 m vs. 610.3 ± 53.4 m for the first and 552.2 ± 82.1 m vs. 616.2 ± 58.0 m for the second; p < 0.0001 for both). The 6MWD correlated with age, weight, and height only in the cystic fibrosis group. During the tests, SpO2 remained stable, whereas HR and RR increased. Conclusions: In our sample, functional performance on the 6MWT was poorer among the cystic fibrosis patients than among the healthy controls in the same age bracket, and we found immediate repetition of the test to be unadvisable.

Keywords: Cystic fibrosis; Exercise tolerance; Dyspnea.

Objective: To identify the predictive factors of oxygen desaturation during the six-minute walk test (6MWT) in patients with cystic fibrosis (CF). Methods: Prospective cross-sectional study involving clinically stable patients with CF aged ≥ 10 years. The patients were submitted to nutritional evaluations, oral glucose tolerance tests, pulmonary function tests, chest X-rays and 6MWTs. Results: The study included 88 patients (43 females and 45 males; mean age, 19.9 ± 7.2 years; mean FEV1, 65.4 ± 28.4%). We observed oxygen desaturation in 13 patients (OD+ group) and no oxygen desaturation in 75 (OD− group). In comparison with OD− group patients, OD+ group patients presented higher mean age (p = 0.004), worse clinical score (p < 0.001), worse radiological score (p < 0.001), higher incidence of glucose intolerance (p = 0.004), lower incidence of methicillin-sensitive Staphylococcus aureus infection (p < 0.001), higher incidence of methicillin-resistant S. aureus infection (p = 0.016), higher incidence of Pseudomonas aeruginosa infection (p = 0.008), lower mean resting SpO2 (p < 0.001) and lower mean FEV1 (p < 0.001). In the logistic regression analysis, oxygen desaturation during the 6MWT correlated with resting SpO2 (OR = 0.305, p < 0.001) and FEV1 (OR = 0.882, p = 0.025). The parameters maximizing the predictive value for oxygen desaturation were resting SpO2 < 96% and FEV1 < 40%. In this sample, 15% of the patients with CF aged ≥ 10 years presented oxygen desaturation during the 6MWT. Conclusions: Resting SpO2 < 96% and FEV1 < 40% can predict oxygen desaturation during the 6MWT.

Keywords: Cystic fibrosis; Respiratory function tests; Exercise tolerance.

Background: The six minutes walk test has been increasingly utilized to assess the effectiveness of different clinical and surgical treatment options in pulmonary diseases. However lack of standardization for their performance may influence measurements and jeopardize assessment of the functional capacity of patients with cardiopulmonary disease. Objective: To determine the possible effects of learning on the distance covered during the six minute walk test for bearers of chronic obstructive pulmonary disease. Method: A retrospective analysis of 35 medical records of COPD patients referred to the Pulmonary Rehabilitation Program of the University Hospital of Brasília was carried out. On alternate days these patients had performed two six minutes walk tests, spirometry and arterial blood gas analysis. Clinical and functional diagnosis was based upon the history of exposure to risk factors, mucus production, dyspnea and spirometric dysfunction after use of bronchodilators. The Student test was used for the comparison of results that were different. Results: The distances covered in the second six-minute walk test (515 ± 82 meters) were greater than those covered in the first six-minute walk test (480 ± 85 metros), with statistically significant differences (p<0.05). However measurements of the muscular effort and perception of dyspnea (Borg scale), peripheral blood oxygen saturation (SpO2), respiratory and heart rates did not disclose any statistically significant differences between the two tests (p<0.05). Conclusion: The present study suggests that in order to standardize the six minutes walk test, the procedure should be performed at least twice to better assess the functional capacity of patients, bearers of chronic obstructive pulmonary disease.

Keywords: Walking. Effectiveness. Lung diseases, obstrutive.

Objective: To evaluate respiratory muscle strength and six-minute walk test (6MWT) variables in patients with uncontrolled severe asthma (UCSA). Methods: This was a cross-sectional study involving UCSA patients followed at a university hospital. The patients underwent 6MWT, spirometry, and measurements of respiratory muscle strength, as well as completing the Asthma Control Test (ACT). The Mann-Whitney test was used in order to analyze 6MWT variables, whereas the Kruskal-Wallis test was used to determine whether there was an association between the use of oral corticosteroids and respiratory muscle strength. Results: We included 25 patients. Mean FEV1 was 58.8  21.8% of predicted, and mean ACT score was 14.0  3.9 points. No significant difference was found between the median six-minute walk distance recorded for the UCSA patients and that predicted for healthy Brazilians (512 m and 534 m, respectively; p = 0.14). During the 6MWT, there was no significant drop in SpO2. Mean MIP and MEP were normal (72.9  15.2% and 67.6  22.2%, respectively). Comparing the patients treated with at least four courses of oral corticosteroids per year and those treated with three or fewer, we found no significant differences in MIP (p = 0.15) or MEP (p = 0.45). Conclusions: Our findings suggest that UCSA patients are similar to normal subjects in terms of 6MWT variables and respiratory muscle strength. The use of oral corticosteroids has no apparent impact on respiratory muscle strength.

Introduction: Spirometry and analysis of blood gases data have been extensively used to assess ventilatory limitation and prognosis of COPD patients. However, functional physical tests, such as the six-minute walk test (6wt) have been used for the dynamic assessment of COPD patients. Objective: To determine correlations between respiratory function test data and the six-minute walk test in COPD patients. Patients and methods: 45 patients were submitted to clinical history survey and complete physical examination performed by the medical staff of the Pneumology Department of the Brasilia University Hospital, followed by spirometry, analysis of arterial blood gases, maximal respiratory pressures data, and the six-minute walk test. Results: Concerning the spirometric, analysis of blood gases and maximal respiratory pressures data, statistically significant positive correlations (p < 0.05) between FEV1, PaO2, SpO2, MEP and the six-minute walk test were obtained. Conclusions: For the studied group, the six minute walk test has significant correlation with FEV1, PaO2, SpO2 and MEP, and can be used as an alternative functional assessment of COPD patients.