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 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.

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: 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.

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;

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.

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.

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.

Objective: To develop and validate a protocol for the treadmill six-minute walk test (tread6MWT) to evaluate patients with pulmonary arterial hypertension (PAH). Methods: The study population comprised 73 patients with PAH, diagnosed by means of right heart catheterization, with or without NO inhalation. All patients performed a hallway 6MWT and three tread6MWTs based on a pre-determined incremental speed protocol and interposed by a rest period. The patients who had been submitted to hemodynamic testing using NO performed the third tread6MWT while inhaling the same dose of NO that had been used during the catheterization. Results: We found that the treadmill six-minute walk distance (tread6MWD) correlated with hemodynamic data, functional class and the hallway six-minute walk distance (6MWD). In addition, the tread6MWD correlated significantly with survival, thereby confirming the correlation with disease severity. Inhalation of NO during the tread6MWT led to variations that were consistent with the hemodynamic changes induced by the same dose of inhaled NO, suggesting that the protocol developed can reflect the effect of therapeutic interventions. Conclusions: We conclude that the tread6MWD is a useful prognostic and functional marker for the routine evaluation of PAH patients.

Keywords: Hypertension, pulmonary; Exercise test; Hemodynamics.

Objective: Asthma is the most common chronic pulmonary disease, characterized by bronchial inflammation. Some children with asthma have persistent pulmonary function impairment. The prevalence and etiology of this abnormality in children with asthma in developing countries remain unknown. The objective of this study was to estimate the proportion of patients with impaired pulmonary function who were unresponsive to treatment in a group of children and adolescents with asthma, and to describe the phenotypic characteristics of the sample. Methods: Using a standardized questionnaire, we selected outpatients (5-17 years of age) diagnosed with persistent asthma. These patients underwent spirometry and skin prick tests for sensitivity to common aeroallergens. Persistent pulmonary function impairment was defined as an FEV1/FVC ratio < 0.80, even after 10 days of treatment with bronchodilators and oral corticosteroids. We used the atopic index to differentiate between patients with little or no response to the skin prick test and those with a strong response (cut-off point: 4 allergens). Results: We included 96 patients with a mean age of 10.6 years. Of those, 52 (54.1%) were male, and 89 (92.7%) were atopic. Of the 96 patients, 8 (8.3%) had impaired pulmonary function even after the treatment. Among those patients, 8 (100%) were atopic, 7 (87.5%) had moderate or severe asthma, and 7 (87.5%) had a history of hospitalization for acute bronchiolitis. Conclusions: Children and adolescents with moderate or severe asthma can present with impaired pulmonary function and be unresponsive to treatment. This clinical situation has been little studied in developing countries, and its risk factors and etiology will be better understood only through birth cohort studies.

Keywords: Asthma; Respiratory function tests; Allergy and immunology.

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.

Objective: To evaluate the construct validity and reproducibility of the six-minute step test (6MST) in individuals with obstructive sleep apnea (OSA) treated with continuous positive airway pressure (CPAP). Methods: We evaluated 48 volunteers diagnosed with OSA and treated with CPAP for at least two months. The volunteers underwent the six-minute walk test (6MWT) and the 6MST, in random order and on different days, with an interval of, at most, seven days between the two tests. Results: A moderate positive correlation was found between the distance walked on the 6MWT and the number of steps climbed on the 6MST (r = 0.520; p < 0.001). There was no significant difference between the two 6MSTs in terms of the number of steps climbed (121.7 ± 27.1 vs. 123.6 ± 26.7). Reproducibility for performance on the 6MST and for cardiovascular variables was considered excellent (intraclass correlation coefficient > 0.8). Regarding cardiovascular responses, the 6MST produced higher values than did the 6MWT for HR at six minutes, percent predicted maximum HR, and leg fatigue at six minutes, as well as for systolic blood pressure at six minutes and at one minute of recovery. Conclusions: The 6MST is valid and reproducible, producing greater cardiovascular stress than does the 6MWT. However, the 6MST is also characterized as a submaximal test for the assessment of exercise tolerance in individuals with OSA treated with CPAP.

Keywords: Sleep apnea, obstructive; Reproducibility of results; Exercise test; Exercise tolerance.

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 assess COPD Assessment Test (CAT) scores in adults with and without COPD, as well as to compare the CAT scores for nonsmokers, former smokers, and smokers without COPD with those for patients with COPD. Methods: This was a cross-sectional population-based study (the Respira Floripa study). The study included adults ≥ 40 years of age residing in the city of Florianópolis, Brazil. A total of 846 households were surveyed. In addition to completing the Respira Floripa questionnaire and the CAT, participants underwent pulmonary function testing. Results: We analyzed data on 1,057 participants (88.1% of the predicted sample size). A functional diagnosis of COPD was made in 92 participants (8.7%). Of those, 72% were unaware that they had COPD. The mean CAT score was higher in the group of COPD patients than in that of individuals without COPD (10.6 [95% CI: 8.8-12.4] vs. 6.6 [95% CI: 6.1-7.0]; p < 0.01). Individual item scores were significantly higher in the patients with COPD than in the individuals without COPD (p < 0.001), the exception being the scores for the items related to sleep (p = 0.13) and energy (p = 0.08). The mean CAT score was higher in the group of COPD patients than in nonsmokers (5.8 [95% CI: 5.3-6.4]) and former smokers (6.4 [95% CI: 5.6-7.2]; p < 0.05). However, there were no significant differences in the mean CAT score between the group of COPD patients and smokers without COPD (9.5 [95% CI: 8.2-10.8]; p > 0.05), the exception being the mean scores for confidence leaving home (p = 0.02). Conclusions: CAT scores were higher in the group of patients with COPD than in nonsmokers and former smokers without COPD. However, there were no significant differences in CAT scores between COPD patients and smokers without COPD. Smokers with an FEV1/FVC ratio > 0.70 have impaired health status and respiratory symptoms similar to those observed in COPD patients.

Keywords: Respiratory function tests; Pulmonary disease, chronic obstructive; Smoking.

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.