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ORIGINAL ARTICLE
Year : 2023 | Volume
: 22
| Issue : 4 | Page : 526-531
Study the association between spirometry based functional grading and six minute walk distance in chronic respiratory disease patients at a rural tertiary care centre of India
Prashant Yadav1, Ajay Kumar Mishra1, Adesh Kumar1, Ashish Kumar Gupta1, Aditya Kumar Gautam1, Naresh Pal Singh2
1 Department of Respiratory Medicine, UP University of Medical Sciences, Etawah, Uttar Pradesh, India
2 Community Medicine, UP University of Medical Sciences, Etawah, Uttar Pradesh, India
Correspondence Address:
Prashant Yadav
Department of Respiratory Medicine, UP University of Medical Sciences, Saifai, Etawah, Uttar Pradesh
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/aam.aam_19_23
Abstract
Introduction: Six-min walk test (6MWT) is easy to use, the least expensive, and a quick measure of physical function and it reflects the capacity to perform our day-to-day activities hence quality of life can be assessed with 6MWT. This study was planned to assess the role of 6MWT in chronic respiratory disease patients and its association with spirometry-based functional grading at a rural tertiary care center of northern India. Materials and Methods: This was a hospital-based cross-sectional study done between December 2019 and July 2021. In this study, 110 patients were included as per inclusion and exclusion criteria. 6MWT and spirometry were conducted as per the American Thoracic Society/European Research Society recommendation using Spiropalm 6MWT and the association between 6MWT and spirometry was assessed. Results: A total of 110 chronic respiratory disease patients were included in the study. There were 69 (63%) males while 41 (37%) were females. Among study participants, chronic obstructive pulmonary disease patients were the most common 48 (43.6%) patients, followed by asthma 28 (25.5%), posttuberculosis sequelae patients 22 (20%), interstitial lung disease 9 (8.2%), and bronchiectasis 3 (2.7%) patients were found. There was a significant positive correlation of 6-min walk distance (6MWD) and % predicted 6MWD with spirometric parameters, forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and there was a significant positive correlation of 6MWD with FEV1% (predicted) also. 6MWD and % predicted 6MWD negatively correlated with FEV1/FVC and association between 6MWD and FEV1/FVC was not statistically significant and between % predicted 6MWD and FEV1/FVC, it was found statistically significant. Conclusion: The 6MWD traveled by chronic respiratory disease patients was significantly lower than the predicted 6MWD and 6MWD correlated with spirometric variables well. Therefore, it can conclude that 6MWT is a useful alternative of spirometry in the management of chronic respiratory disease patients in resource-limited settings.
Abstract in French Résumé
Introduction: Le test de marche de six minutes (6MWT) est facile à utiliser, le moins coûteux et constitue une mesure rapide de la fonction physique. Il reflète la capacité à effectuer nos activités quotidiennes et la qualité de vie peut donc être évaluée à l'aide du test de marche de six minutes. Cette étude avait pour but d'évaluer le rôle du6MWT chez les patients atteints de maladies respiratoires chroniques et son association avec le classement fonctionnel basé sur la spirométrie dans un centre de soins tertiaires rural du nord de l'Inde. Matériels et méthodes: Il s'agit d'une étude transversale en milieu hospitalier réalisée entre décembre 2019 et juillet 2021. Dans cette étude, 110 patients ont été inclus selon les critères d'inclusion et d'exclusion. Le 6MWT et la spirométrie ont été effectués conformément aux recommandations de l'American Thoracic Society et de l'European Research Society. Thoracic Society/European Research Society en utilisant le Spiropalm 6MWT et l'association entre le 6MWT et la spirométrie a été évaluée. Résultats: Au total, 110 patients atteints de maladies respiratoires chroniques ont été inclus dans l'étude. Il y avait 69 hommes (63 %) et 41 femmes (37 %).41 (37 %) étaient des femmes. Parmi les participants à l'étude, les patients atteints de bronchopneumopathie chronique obstructive étaient les plus nombreux (48 (43,6 %)), suivis de l'asthme (28 (25,5 %)) suivis par l'asthme 28 (25,5%), les séquelles de la tuberculose 22 (20%), la pneumopathie interstitielle 9 (8,2%) et la bronchectasie 3 (2,7%).3 (2,7 %). Il existe une corrélation positive significative entre la distance de marche de 6 minutes (6MWD) et le % prédit de la 6MWD avec les paramètres spirométriques, l'expiration forcée et le taux de mortalité.avec les paramètres spirométriques, le volume expiratoire forcé en 1 s (VEMS), la capacité vitale forcée (CVF) et le volume de l'air expiré.) et la capacité vitale forcée (CVF), et il existe une corrélation positive significative entre le 6MWD et le VEMS.entre le 6MWD et le VEMS(prédit). Le 6MWD et le % prédit du 6MWD étaient négativement corrélés avec le VEMS / CVF et l'association entre le 6MWD et le % prédit du VEMS./CVF et l'association entre le6MWD et le VEMS/n'était pas statistiquement significative et entre le % prédit du 6MWD et le VEMS/CVF, elle s'est avérée statistiquement significative. Conclusion: Le 6MWD parcouru par les patients atteints de maladies respiratoires chroniques était significativement plus bas que le 6MWD prédit et le 6MWDétait bien corrélé avec les variables spirométriques. On peut donc conclure que le 6MWT est une alternative utile à la spirométrie dans la prise en charge des patients atteints de maladies respiratoires chroniques dans les pays à ressources limitées.des patients souffrant de maladies respiratoires chroniques dans des contextes où les ressources sont limitées.
Mots-clés: distance de marche de 6 minutes, test de marche de 6 minutes, maladies respiratoires chroniques, spirométrie
Keywords: 6-min walk distance, 6-min walk test, chronic respiratory diseases, spirometry
Introduction 
Six-min walk test (6MWT) is used for the assessment of combined responses of the respiratory system, cardiovascular system, blood, and neuromusculoskeletal system. The 6MWT represents activities of daily living more efficiently and well tolerated by most of the chronic respiratory disease patients and does not require any expertise to perform. 6MWT is practically simple and requires 100-feet straight hallway without any specific instrument or advance training for technician. This test measures the distance that a patient can walk quickly on a flat, hard surface during the period of 6 min. This test does not provide any specific information about the function of each of the different organs and systems involved in exercise or mechanisms of exercise limitation. The self-paced 6MWT assesses the submaximal level of exercise capacity. Most patients do not achieve the maximal level of exercise capacity during 6MWT; instead, they choose their own intensity of exercise and are allowed to stop and rest during the test. The 6-min walk distance (6MWD) may better reflect the functional exercise level of daily physical activities because most of the routine work requires a submaximal level of exertion. Several studies have been reported where 6MWT was used and 6MWD estimated in either healthy subjects or among subjects with individual respiratory or cardiac diseases.[1] Decreased forced expiratory volume in 1 s (FEV1) was reportedly associated with reduced walk distance.[2] When performing 6MWT, not only distance walked, but also oxygen saturation and dyspnea rating are usually recorded. In patients with idiopathic pulmonary fibrosis, for example, both walk distance and desaturation at 6MWT are significant prognostic markers.[3],[4],[5],[6],[7] As in the literature, there is little information available about bronchiectasis and posttuberculosis (TB) sequelae patients regarding to predict the prognosis spirometric by 6MWT, on the other hand, large population of chronic respiratory disease patients is used to live in the rural area of our country where spirometric parameters are neither available easily or if available nor properly interpreted there, consequently to improve the quality of life of such patients an easy, inexpensive method such as 6MWT should be used in the overall management of patients, therefore, this study was planned to assess the role of 6MWT in chronic respiratory disease patients, and its association with spirometry-based functional grading at a tertiary care center of northern India.
Materials and Methods It was a hospital-based cross-sectional study, carried out between January 2020 and June 2021 on patients who attended the Outpatient Department and Indoor Patient Department of Respiratory Medicine, UPUMS, Saifai, Etawah. Ethical clearance was taken from Institutional Ethical Committee (IEC) and the IEC number was 112/2019-20. All the patients with chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis, bronchial asthma, posttubercular sequelae, and interstitial lung diseases (ILD) were included in the study as per the inclusion and exclusion criteria of the study. Pulmonary function tests were conducted as per the American Thoracic Society (ATS)/European Research Society (ERS) recommendation using COSMED Spiropalm 6MWT (Spirometer and 6MWT) device with, the patient was given proper instruction during the test and the test was performed. Exhalation time was at least 6 s and the end of the test was indicated by a 2 s volume plateau. Spirometric indices including forced expiratory volume in 1st s (FEV1), forced vital capacity (FVC), and FEV1/FVC were tested. At least three forced expiratory maneuvers that satisfied ATS/ERS criteria were done for each patient of which the test with the highest values was accepted. The 6MWT is a simple and practical test which needs a 100-ft (30 m) straight hallway without any exercise equipment or training for technicians. This test measures the distance that patients walked with their own pace on a hard and flat surface during a period of 6 min (the 6MWD).
It assesses the combined responses of all the systems involved during exercise, i.e., pulmonary and cardiovascular systems, circulatory systems, blood, neuromuscular system, and metabolism.
The self-paced 6MWT evaluates the submaximal level of functional status because most of the day-to-day activities are performed at submaximal exertion, thus 6MWD better reflects the functional exercise status for daily physical activities. All the patients underwent the 6MWT within 1 h of spirometry. Each patient rested for at least 10 min before the 6MWT. At the start of the test and completion of the test, the patients' heart rate, blood pressure (BP), and oxygen saturation were measured.
Inclusion criteria
Patients with chronic respiratory diseases of age 15 years and abovePatients who were hemodynamically stable and cooperativePatients who provided consent to participate in the study.Exclusion criteria
Patients with recent myocardial infarctionPatients with unstable anginaPatients with heart rate of more than 120 beats/minPatients with systolic BP of more than 180 mmHgPatients with diastolic BP of more than 100 mmHgJoint diseases or any neuromuscular disorder.As our exclusion criteria, those patients who have a history of ischemic heart disease, hypertension, and heart failure were excluded from the study. All the patients were subjected for cardiac evaluation clinically and by electrocardiography (ECG) and two-dimensional echocardiography and those who had abnormal ECG and echocardiography were also excluded from the study.
Tools
6MWT machinePulmonary function test (Spirometry).The data thus collected were encoded in Microsoft Excel Worksheet and analyzed using SPSS is a statistical software suite developed by IBM for data management advanced analytics, multivariate analysis (IBM (International Business Machine Corporation), Chicago, United states of America). Proportions, mean, standard deviation (SD), Chi-square test, student paired t-test, and the association between various parameters were assessed by analysis of variance.
Results A total of 110 chronic respiratory disease patients were included in the study. There were 69 (63%) males while 41 (37%) were females. Among study participants, COPD patients were the most common 48 (43.6%) patients, followed by asthma 28 (25.5%), post-TB sequelae patients 22 (20%), ILD 9 (8.2%), and bronchiectasis 3 (2.7%) patients were found.
The most common symptom was dyspnea in 110 (100%), followed by cough in 104 (94.5%) and expectoration in 87 (79.1%) patients. Out of 110 study participants, 53 (48%) patients were smokers while 11 (10%) were alcoholics.
The baseline systolic BP of study participants was 133.3 ± 16.6 mmHg, while at the end of 6MWT, the BP was 137.3 ± 16.5 mmHg (P < 0.001). The baseline diastolic BP of the study participants was 81.6 ± 6.9 mmHg, while at the end of 6MWT, diastolic BP was 83.9 ± 5.9 mmHg (P < 0.001). The baseline pulse rate was 85.6 ± 10.9 beats/min and the pulse rate after 6MWT was 119.8 ± 12.7 beats/min (P < 0.001), baseline SpO2 of the study participants was 95.4 ± 1.7% at room air and after completion of 6MWT, SpO2 was 87.9 ± 3.8 at room air (P < 0.001) and baseline respiratory rate was 18.2 ± 2.2/min and after 6MWT was 23.5 ± 3.3/min (P < 0.001) and 7 (6%) patients were required oxygen supplementation during the test.
COPD patients had 6MWD, 394.6 ± 76.7 m which was 73.9% ± 9.2% of the predicted distance (P < 0.001), and bronchial asthma had a maximum 6MWD of 467.0 ± 105.6 m which was 73.6% ± 8.2% of the predicted distance (P < 0.001). Patients with bronchiectasis had distance covered in 6 min was 433.0 ± 100.1 m and it was 72.3% ± 3.2% of predicted distance (P < 0.001) and of post-TB sequelae patients 6MWD was 406.9 ± 86.4 m which was 66.0% ± 5.8% of the predicted distance (P < 0.001), and 6MWD was minimum in ILD patients (306.7 ± 41.8 m) which was 56.1% ± 5.0% of the predicted distance (P < 0.001) [Table 1].
Table 1: Predicted 6-min walk distance and recorded 6-min walk distance in study participantsSpirometric parameters of chronic respiratory disease patients are depicted in [Table 2].
Table 2: Comparison of mean spirometry parameters among patients with different chronic respiratory diseasesForced expiratory volume 1st s (in FEV1 in liter) was maximum in asthma (1.9 ± 0.6), followed by in COPD group (1.8 ± 0.4), it was found minimum in ILD (1.6 ± 0.3) (P < 0.001). FVC (in liter) was maximum in asthma at 3.2 ± 0.7, followed by in COPD = 3.0 ± 0.7 and it was found minimum in ILD – 2.1 ± 0.5, (P < 0.001).
FEV1/FVC was found maximum in ILD (77.8% ± 12.1%) (P < 0.001), followed by in bronchiectasis (68.6% ± 9.0%) and it was found minimum in asthma (58.6% ± 7.0%).
The correlation between 6MWD and % predicted 6MWD with spirometric parameters was assessed and it was found that there was a significant positive correlation of 6MWD and % predicted 6MWD with spirometric parameters FEV1 and FVC and there was a significant positive correlation of 6MWD with FEV1% (predicted) also. 6MWD and % predicted 6MWD negatively correlated with FEV1/FVC and the association between 6MWD and FEV1/FVC was not statistically significant and between % predicted 6MWD and FEV1/FVC, it was found statistically significant [Table 3].
Table 3: Correlation of 6-min walk distance and percentage predicted 6-min walk distance with spirometric parametersCorrelation of obstructive , restrictive disorders with 6 mintue walk distance and spirometry were also assessed [Table 4] and found that FEV1 was maximum for obstructive group (1.9 ± 0.5 lit, pred, 2.0 ±0.6), followed by mixed disorder group (1.7 ± 0.4 lit, pred 1.7 ± 0.4lit) and least for restrictive group (1.4 ± 0.3lit, pred 1.5 ± 0.3lit). FVC was maximum for obstructive group (3.1 ± 0.8lit, pred 3.1 ± 0.8lit), followed by mixed group (2.2 ± 0.5lit, pred 2.2 ± 0.5lit) and least for restrictive group (2.1 ± 0.5lit, pred 2.2 ± 0.5lit). FEV1/FVC was (60.5 ± 6.8%) for obstructive group, (68.2 ± 7.1%) for mixed rgroup and (77.9 ± 12.1%) for restrictive group . Six-minute walk distance (6MWD) was 421.2 ± 94.6 meters and pred 6MWD was 566.8 ± 90.3 meters for obstructive group, 410.1 ± 86.3 meters and pred 6MWD was 609.8 ± 104.1 meters for mixed group, 306.8 ± 41.8 meters and pred 6MWD was 546.7 ± 48.7 meters for restrictive group. ANOVA (analysis of variance test)applied to compare mean values of various parameters of obstructive ,restrictive and mixed pattern of diseases [Table 4].
Table 4: Comparison of mean spirometry parameters and 6MWD among patients with obstructive, restrictive, and mixed pattern respiratory diseasesComorbidities were found in 66.3% of chronic respiratory disease patients and hypertension was the most common comorbidity in 33 (30%), followed by Type 2 diabetes mellitus (T2DM) in 23 (20.9%) and 16 (14.5%) patients were having T2DM along with hypertension. There was one patient of each chronic liver disease (CLD) and chronic kidney disease (CKD) (0.9%). Patients with CKD had a maximum 6MWD, 438.0 m, followed by in diabetes mellitus patients (414.0 ± 64.1 m). Patients with CLD had a minimum 6MWD, 324.0 m, while the predicted 6MWD for them was 564.0 m. There was a significant correlation between comorbidities and 6MWD [Table 5].
Discussion In this study, the mean age of chronic respiratory disease patients was 53.6 ± 3.76. There were 62.7% males and 37.3% were females, indicating a higher prevalence of chronic pulmonary diseases among adult males, similar results reported by previous studies as well.[8]
Among chronic respiratory patients, COPD patients had 6MWD, 394.6 ± 76.7 m which was 73.9% ± 9.2% of the predicted distance (P < 0.001) and bronchial asthma had maximum 6MWD of 467.0 ± 105.6 m which was 73.6% ± 8.2% of the predicted distance (P < 0.001). 6MWD was minimum in ILD patients (306.7 ± 41.8 m) which was 56.1% ± 5.0% of the predicted distance (P < 0.001).
Forced expiratory volume in 1st s (FEV1 in liter) was maximum in asthma (1.9 ± 0.6), followed by in COPD group (1.8 ± 0.4), it was found minimum in ILD (1.6 ± 0.3) (P < 0.001). FVC (in liter) was maximum in asthma at 3.2 ± 0.7, followed by in COPD = 3.0 ± 0.7 and it was found minimum in ILD – 2.1 ± 0.5 (P < 0.001).
It was demonstrated in a previous study as well that there was a direct correlation between pulmonary function tests and 6MWT in chronic respiratory disease patients and also suggested that patients who were having lower measurements were unable to walk for longer distances. However, the correlation between FVC and the 6MWD was found significant (P = 0.038), while the correlation between forced expiratory volume in 1st s -and 6MWD was not significant (P = 0.074).[9]
It was also reported in the previous study that forced expiratory volume in 1st s was significantly correlated with %predicted 6MWD in chronic respiratory disease patients and FVC was also correlated with %predicted 6MWD. FEV1/FVC correlated only with postexercise pCO2 while maximal voluntary ventilation correlated with %predicted 6MWD and only basal pCO2 and exercise desaturation correlated only with FVC.[10]
In our study, there was a significant positive correlation of 6MWD and % predicted 6MWD with spirometric parameters-forced expiratory volume in 1st s (FEV1) and FVC and there was a significant positive correlation of 6MWD with FEV1% (predicted) also. 6MWD and %predicted 6MWD negatively correlated with FEV1/FVC and the association between 6MWD and FEV1/FVC was not statistically significant, and however, between % predicted 6MWD and FEV1/FVC, it was found statistically significant similar observation was noted previous study too.[8]
In previous study, it was also seen that % predicted FVC was a good predictor of 6MWD and also found that 6MWD correlated positively with FVC (r = 0.52, P < 0.01).[11],[12]
Kundu et al. showed a positive linear correlation of 6MWT with absolute values of FEV1, FVC.[13] In another study done by Sivaranjini et al. found that the distance walked by normal individuals was (mean ± SD), 445 ± 56.64 m, and for post-TB sequelae patients 6MWD (mean ± SD), 265.06 ± 78.13 m (P < 0.001).[14]
Most of the previous studies in past done in COPD patients and they found a significant positive linear correlation between disease severity and 6MWD. A strong positive correlation was also reported between 6MWD and % predicted FEV (r = 0.57)[15] and in another study, the mean 6MWD of COPD patients was 334.46 ± 69.69 m (range: 180–470 m) and it was correlated positively to all spirometry parameters FEV1% predicted, FVC % predicted, peak expiratory flow rate % predicted, FEV1/FVC.[16] 6MWD was also found significantly associated with forced expiratory volume in 1st s (FEV1.0), FEV1.0 (% predicted).[17]
Conclusion In the past, most of the research regarding 6MWT was limited to COPD only, our was study done in chronic respiratory diseases (COPD/asthma/bronchiectasis/post-TB sequelae/ILD) as chronic respiratory diseases contributed a huge burden in health impairment and found the 6MWD traveled by chronic respiratory disease patients was significantly lower than predicted 6MWD and 6MWD correlated with spirometric variables as well. Therefore, it is concluded that 6MWT is a useful, easy-to-use alternative of spirometry to assess treatment response, prognosis, and overall management of chronic respiratory disease patients in resource-limited settings.
Financial support and sponsorship
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Conflicts of interest
There are no conflicts of interest.
References 
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