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Journal of Cardiovascular Disease Research
ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
873
A Prospective Study On The Correlation Between Six
Minute Walk Test And Forced Expiratory Volume At
One Second In Chronic Obstructive Pulmonary
Disease Patients
Dr. Sanjeev Shivashankaran1*, Dr. Jesin Kumar Chakkamadathil2 ,Dr. C. P. Rauf3
1*MBBS, DNB, EDRM, FAPSR, MNAMS, Assistant Professor, Department Pulmonary Medicine,
DMWIMS Medical college, Wayanad, Kerala
2 MBBS, MD, Assistant Professor, Department Pulmonary Medicine, Karuna Medical College,
KUHS, Palakkad, Kerala
3MBBS, MD, Consultant Physician, Department of Pulmonology, Delhi University
*Correspondent Author: drsanjeev1210@gmail.com
ABSTRACT
COPD is a major cause of morbidity and mortality around the world. At present COPD is diagnosed
and severity is assessed by spirometry base on FEV1 / FEC ratio and FEV1 percentage. In order to
substitute spirometry a prospective cross sectional study is conducted to find the correlation between
6MWD and FEV1 for grading of COPD severity as per GOLD criteria. Materials and methods used
are, a spirometer, pulse oximeter, bp apparatus, timer and 30meter hall was used to conduct the study
from 70 patients diagnosed as COPD according to GOLD criteria. Study was conducted at chest
hospital, Calicut, India from 2012 to 2014. Correlation between 6MWD and FEV1 was calculated
using Spearmans Rank correlation coefficient. The results obtained are that, there was no correlation
between six minute walk distance and FEV1 in COPD patients. There was significant statistical
association between FEV1 and SpO2, i.e. as severity of airflow obstruction based on FEV1 values
increases, chances of de-saturation also increases. And it is concluded that, there was no correlation
between six minute walk distance and FEV1 in COPD patients.
KEYWORDS: Six minute walk test, Chronic obstructive pulmonary disease (COPD), forced
expiratory volume in 1second (FEV1), 6-min walk distance (6MWD), Spirometry, pulse oximeter,
GOLD guidelines, Burden of Obstructive Lung Disease (BOLD)
INTRODUCTION:
Chronic obstructive pulmonary disease (COPD) is a major cause of disability and death all over the
world. Its prevalence is increasing worldwide and is now the fourth leading cause of death world over.
Factors, including forced expiratory volume in 1second (FEV1), gas exchange disturbances, lung
hyperinflation airway hyper-responsiveness, severity of dyspnea, pulmonary hypertension,
malnutrition-impaired exercise capacity and health-related quality of life, anemia and other co
morbidities have been identified as individual predictors of mortality in COPD. Spirometry is the
present gold standard diagnostic tool for diagnosing COPD. FEV1/FVC ratio is generally used to
define the presence or absence of airflow limitation, but FEV1 is used to define the severity of the
disease. To assess the functional status of patients with COPD a 6-min walk distance (6MWD) test a
sub maximal exercise test can be used. 6 MWD test had proved to be reliable, inexpensive, safe and
easy to apply. The global and integrated response of all systems involved during exercise like
cardiovascular, pulmonary, musculoskeletal and neuromuscular is evaluated by 6 MWD. As spirometry
depends on effort, all patients may not be comfortable in doing the test. Very severe COPD patients,
based on FEV1 have variable exercise ability. On the other hand 6MWD test is easy to perform as it is
representing daily activity. If there is correlation between 6MWD and FEV1, 6MWD test can be used
for assessing the severity of COPD where spirometry cannot be done. In this study, t he relation
between 6MWD test and spirometric parameter FEV1 in patients with COPD is investigated. Aim and
objective of this study is to test the validity of 6 minute walk test (6MWT) in assessing the severity of
COPD which is measured by means of FEV1 as per the GOLD criteria (Table 1).
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
874
Table-1: Gold Criteria
GOLD 1
MILD
FEV1/FVC < 0.70
FEV1 ≥ 80 % Predicted
GOLD 2
MODERATE
FEV1/FVC < 0.70
50% ≤ FEV1 < 80 % Predicted
GOLD 3
SEVERE
FEV1/FVC < 0.70
30 % ≤ FEV1 < 50 % Predicted
GOLD 4
VERY SEVERE
FEV1/FVC < 0.70
FEV1 < 30 % Predicted
MATERIALS AND METHODS:
MATERIALS:
1. Spirometer (vitalograph)
2. Pneumotrac spirotrac 6800: flow head, tubing.
MATERIALS FOR SIX MINUTE WALK DISTANCE:
1. Countdown timer (stopwatch)
2. Mechanical lap counter
3. Two small cones to mark the turnaround points
4. A chair that can be easily moved along the walking course
5. Worksheets on a clipboard
6. A source of oxygen
7. Sphygmomanometer
8. Telephone
9. Automated electronic defibrillator
METHODS:
Spirometry is performed in a room with the patient sitting comfortably. The procedure is performed
according to ATS guidelines. COPD is diagnosed according to GOLD guidelines (Table-1). The
6MWT should be performed indoors, along a long, flat, straight, enclosed corridor with a hard surface
that is seldom traveled. The walking course must be 30 m in length. A 100 -ft hallway is, therefore,
required. The length of the corridor is marked every 3 m. The turnaround points should be marked with
a cone (traffic cone). A bright colored tap eon the floor which marks the beginning and end of each 60-
m lap, should be marked properly.
PATIENT PREPARATION:
1. Comfortable clothing should be worn.
2. Appropriate shoes for walking should be worn.
3. Patients should use their usual walking aids during the test (cane, walker, medical regimen
should be continued).
4. A light meal is acceptable.
5. The patient’s usual before early morning or early afternoon tests.
6. Patients should not have exercised vigorously within 2 hours of beginning of test.
Patients who are diagnosed to have COPD by histor y, physical examination and spirometry are made
to do six minute walk test on the same day. Patients are selected according to the inclusion and
exclusion criteria. The 6MWT is conducted in ICU of our hospital.
Calculating BMI:
The distinction between overweight and obesity is made on the basis of the body mass index (BMI):
BMI = body weight (in kg) ÷ height (in meters) 2
The BMI can also be obtained from a nomogram, a table, or a calculator Classification of BMI - The
recommended classifications for BMI adopted by the National Institute of Health (NIH) and World
Health Organization (WHO). The definition of overweight and obesity varies by race. The WHO and
NIH guidelines are currently applied to blacks, hispanics and whites. For Asians, overweight is a BMI
between 23 and 29.9 kg/m2 and obesity a BMI >30 kg/m2.. We have considered obesity as BMI
>30kg/m2 and below it as non-obese.
METHOD OF DATA COLLECTION:
Medical records, spirometric data and six minute walk distance of 70 COPD patients were collected for
analysis from the period October 2012 to May 2014. All eligible patients had been monitored in the
Dept of Respiratory Medicine of Chest Hospital, Calicut. Data regarding age gender and BMI were
Journal of Cardiovascular Disease Research
ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
875
analysed.6MWD AND FEV1 is correlated using Spearmanꞌs rank correlation coefficient. All the
associations were calculated with Chi square test. Statistical analysis were done using SPSS version
18. This prospective cross sectional study conducted in Dept of respiratory medicine, chest hospital
Calicut consisted of 73 patients sample size. This study has obtained clearance from internal ethical
committee of the institution. The duration of this study was From OCTOBER 2012 to MAY 2014.
Inclusion criteria: Patient diagnosed with COPD as per gold criteria between age 40 to 85 years.
Exclusion criteria: COPD patients with acute exacerbations within last 6 weeks, Post bronchodilator
reversibility > 12% and >200 ml, Patients receiving domiciliary oxygen therapy, Patients who could
not perform spirometry or walk test, Patients with other diseases affecting respiratory and
cardiovascular systems, Recent thoracic or abdominal surgery/eye surgery or retinal detachment,
Patients who were musculoskeletal pain limiting, claudication pain and syncope, Recent history of
myocardial infarction, and Unstable angina.
Sample size is calculated by using the formula:
n = [Z1-α/2 [√ 2 π0(1- π0)] + Z1- β [√[π1 (1- π1)+ π2 (1- π2)]]²
(π2- π1)²
n = sample size.
Z1- α/2 π is a constant, if alpha error is 5% its value = 1.96β
Z1- β is a constant, if beta error is 20% its value =0.84
π1 is sensitivity/specificity of a gold standard test =100%
π2 is the expected sensitivity/specificity of this test= 90%
π0 is the average of π1 & π2
n = {(1.96×0.308) + (0.84×0.3)}2
(0 .01)
= 73
By applying this equation calculated sample size is 73.
RESULTS:
1. Majority of the patients were males, contributing more than three fourth in this study. Among
70 patients selected for study, 77.1% were males and 22.9% were females. Of the 70 patients,
47.1% were from age group 60-69Yrs (Table-2 and Fig-1).
Table-2: Distribution of age
Age
Frequency
Percent
40-49
4
5.7
50-59
16
22.9
60-69
33
47.1
70-79
15
21.4
≥ 80
2
2.9
Total
70
100.0
Fig-1: Distribution of patients according to age group
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
876
2. Majority of the patients were normal by BMI. 20% were underweight and 17.1 % were of
overweight or obese (Table-3 and Fig-2).
Table-3: Distribution of BMI
BMI Category
Frequency
Percent
Under Weight
14
20.0
Normal Weight
44
62.9
Over Weight
9
12.9
Class I Obese
2
2.8
Class II Obese
1
1.4
Total
70
100.0
Fig-2: Distribution of COPD patients according to BMI
3. 44% of patients were having moderate airflow obstruction, 37% severe, 14.3% very severe
and 4.3% mild airflow obstruction according to GOLD staging of COPD based on FEV1(
Table-4 and Fig-3).
Table-4. Distribution of severity based on FEV1.
Severity
Frequency
Percent
Very severe
10
14.3
Severe
26
37.1
Moderate
31
44.3
Mild
3
4.3
Total
70
100.0
Fig-3. Distribution of severity OF COPD based on FEV1
4. 34.3% patients had six minute walk distance of range 201-300 meters. 32.9% patients walked
less than 200 meters, 20% had 6MWD of 301-400 meters, while 12.9% walked more than 400
meters (Table-5).
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
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Table-5: Distribution of 6-Minute Walk distance
6 Minute Walk Distance
Frequency
Percent
<200
23
32.9
201-300
24
34.3
301-400
14
20.0
>400
9
12.9
Total
70
100.0
5. Most of the patients had 21-30 pack years of smoking (Table-6). p-value obtained is 0.780
using Chi square test. Indicating severity is independent of gender.
Table-6: Pack years of smoking
Pack years
Frequency
Percent
<10
11
15.7
10-20
12
17.1
21-30
28
40.0
31-40
19
27.1
Total
70
100.0
6. Examination of cell frequency shows that majority of patients fall in moderate and severe
group, irrespective of the Gender (Table-7, Fig-4).
Table- 7: Association between FEV1 and Sex
Severity Based on FEV1
Sex
Total
Male
Female
Very severe
8 (14.8%)
2 (12.5%)
10
Severe
20 (37%)
6 (37.5%)
26
Moderate
23 (42.6%)
8 (50%)
31
Mild
3 (5.6%)
0
3
Total
54 (100%)
16 (100%)
70
Fig-4. Association between FEV1 and Sex
7. p value obtained is 0.994 which is not significant indicating that there is no association
between FEV1 and age in our study ( Table-8, Fig-5).
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
878
Table-8: Association between FEV1 and Age
Severity based on FEV1
Age
Total
< 60
≥ 60
Very severe
3(15%)
7(14%)
10
Severe
7(35%)
19(38%)
26
Mild
9(45%)
22(44%)
31
Moderate
1(5.0%)
2(4%)
3
Total
20(100%)
50(100%)
70
Fig-5: Association between age and severity of copd
8. As p-value 0.191 there was no association between FEV1 and BMI (Table-9, Fig-6). P-value
of 0.047 was found to be indicating association between 6 minute walk distance and sex.
Table- 9: Association between FEV1 and BMI
Severity Based on FEV1
BMI
Under Weight
Normal Weight
Over Weight/ Obese
Very severe
2(14.3%)
7(15.9%)
1(8.3%)
Severe
7(50.0%)
16(36.4%)
3(25.0%)
Moderate
3(21.4%)
20(45.5%)
8(66.7%)
Mild
2(14.3%)
1(2.2%)
0
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
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Fig-6: Association between severity of COPD and weight distribution
9. In this study female (56%) patients walked less than 200 meters, while 38.9% of male patients
walked more than 300 meters (Table-10, Fig-7). In patients above t he age of 60 years, 36%
(i.e. 18 out of 50) walked less than 200 meters, similarly 36% patients less than 60 years of
age walked 201-300 meters.
Table-10: Association between 6 minute walk distance and Sex
MWD
Sex
Total
Male
Female
<200
14 (25.9%)
9 (56.3%)
23 (32.9%)
201-300
19 (35.2%)
5 (31.3%)
24 (34.3%)
>300
21 (38.9%)
2 (12.5%)
23 (32.9%)
Total
54 (100%)
16 (100%)
70 (100%)
*p- Value 0.047, significant
Fig-7: Association between 6 minute walk distance and Sex
10. In patients less than 60 years, majority 45% (9 out of 20) walked more than 300 meters in 6
minutes but p value was found to 0.380 which is not significant suggesting no correlation
between 6MWD and age(Table-11, Fig-8) .
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ISSN: 0975-3583, 0976-2833 VOL 12, ISSUE 03, 2021
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Table-11: Association between 6 minute walk in distance and Age
6MWD
Age
Total
<60
≥60
<200
5 (25%)
18 (36%)
23 (32.9%)
201-300
6 (30%)
18 (36%)
24 (34.3%)
>300
9 (45%)
14 (28%)
23 (32.9%)
Total
20 (100%)
50 (100%)
70(100%)
*p-value 0.380, not significant
Fig-8: Association between 6 minute walk in distance and Age
11. The correlation obtained between the variable is a low positive one having correlation
coefficient r= 0.089, not statistically significant (p value 0.461). There is no correlation
between six minute walk distance and FEV1 in COPD patients (Fig-9).
Fig-9: Scatter plot of FEV1 and 6 Minute walk distances
DISCUSSION:
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881
Chronic obstructive pulmonary disease (COPD), a common preventable and treatable disease is
characterized by persistent airflow limitation that is usually progressive and associated with enhanced
chronic inflammatory response in the lung to noxious particles and gases. Exacerbations and
comorbidities contribute to overall severity in individual patients1. According to the Burden of
Obstructive Lung Disease (BOLD) study, the average prevalence of COPD is 10.1%, with wide
variation2. The prevalence of COPD in India was 3.67% (4.46 and 2.86% among males and females,
respectively). The estimated burden of COPD in India is about 15 million cases (males and females
contributing to 9.02 and 5.75 million, respectively)3,4. Chronic obstructive pulmonary disease (COPD)
is the fourth leading cause of death in the world1. In India, COPD causes about 500,000 deaths per
year5. According to the preliminary report of the “Million Death Study”, CRDs were the second and
the third common cause of death among adults in rural and urban population6. Globally, COPD is the
ninth leading cause of loss of disability adjusted life years (DALYs) according to the Global Burden of
Disease Study (GBDS)7. In India, chronic respiratory diseases (CRDs) account for 3% of DALYs, and
COPD is the major cause among CRDs8. COPD also accounts for more than 3 million deaths per year
globally making it the third leading cause of death worldwide9. It accounts for 2.3-8.4% of all deaths.
This proportion is more among men than women, and more among the elderly as compared to the
young10,11 .
Risk factors of COPD mainly includes of smoking. Tobacco is abused in two forms, mainly smoking
and smokeless tobacco, Pipe, cigar and water pipe are various forms of tobacco smoking.
Environmental Tobacco Smoke is the passive exposure to cigarette smoke. The rise in COPD incidence
has paralleled the rise in tobacco smoking throughout the world12,13. There is a strong dose-response
relationship (for amount and duration) between tobacco smoking and COPD14,15. The risk of COPD
increases with increase in the number of cigarettes/ bidis as well as with the duration of smoking. Any
amount of smoking is harmful, although the risks are lower at low dose16. Prevalence of COPD in
smokers with less than 20 pack years was 9.6%, and 18% in smokers with more than 20 pack years17.
In India more than 70% people use biomass fuel for cooking purposes compared to 25% who smoke.
Burning of biomass fuel such as dried dung, etc is associated with various health hazards, including
respiratory problems like COPD which is the biggest risk factor for COPD in India18. About 15% of
COPD cases might be related to exposure at workplace like rubber, plastics, and leather manufacturing,
textile mill product manufacturing; and food product manufacturing 19. AAT deficiency and mutations
in glutathione s-transferase-1 are associated with COPD20. Other risk factors for COPD may include air
pollution, socioeconomic factors, asthma/bronchial hyperactivity, chronic bronchitis, and infections
like Tuberculosis.
Inhaled cigarette smoke and noxious particles causes inflammation of lung which may induce
parenchymal tissue destruction resulting in emphysema, disrupt the normal repair and defence
mechanisms. These pathological change leads to air trapping and progressive airflow limitation.
Oxidative stress and excess of proteinases in the lung modify lung function and is an important
mechanism in COPD. Oxidants such as hydrogen peroxide, 8 -isoprostane are biomarkers of oxidative
stress. Protease – antiproteinase imbalance causes destruction of elastin leading to emphysema.
Inflammatory cells: Increased number of CD8+ (cytotoxic) TC1 lymphocytes along with neutrophils
macrophages interact with structural cells in airways, lung parenchyma, vasculature and cause
disease21. Inflammatory mediators like chemotactic factors, cytokines, growth factors are increased in
COPD. Systemic manifestation of COPD include unintentional weight loss, skeletal muscle
dysfunction, increased risk of cardiovascular disease, osteoporosis, and depression. COPD patients
have raised levels of CRP, fibrinogen, leucocytes, and TNF-a, indicating that persistent systemic
inflammation is present in COPD22.
Inflammation, fibrosis, luminal exudates in the small airways causes reduction in FEV1 and FEV1/
FVC ratio. Peripheral airway obstruction along with destruction of alveolar attachments to airways
causes air trapping during expiration, resulting in hyperinflation. Hyperinflation reduces inspiratory
capacity, increases functional residual capacity, causing dynamic hyperinflation during exercise
resulting in exhertional dyspnea. Gas transfer for O2 and CO2 decreases as the disease progresses.
Reduced ventilation may also be due to reduced ventilator drive which leads to carbon dioxide
retention. These abnormalities in the alveolar ventilation and reduced pulmonary vascular bed worsen
the VA/Q abnormalities23. Hypoxic vasoconstriction causes remodeling of pulmonary vasculature such
as hypertrophy / hyperplasia of pulmonary vascular smooth muscles, intimal thickening and causes
pulmonary hypertension. Endothelia Cell Dysfunction and loss of pulmonary capillary bed in
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emphysema contribute to increased pressure in the pulmonary circulation. Pulmonary hypertension
leads to RVH and finally leads to right sided heart failure.
Characteristic symptoms of COPD are chronic progressive dysnea, cough and sputum production that
can be variable from day to day. Cough is often the first symptom to develop. Chronic cough and
sputum production may precede the development of airflow limitation by many years, nevertheless
may be unproductive sometimes. Purulent sputum reflects an increase in inflammatory mediators and
onset of bacterial exacerbation. Dyspnea is the cardinal symptom. Patients describe as sense of
increased effort to breathe, heaviness, air hunger, or gasping which is progressive, persistent and worse
with exercise. Wheezing and chest tightness may vary between days, and over the course of single
day. A diagnosis of COPD cannot be excluded by absence of wheezing or chest tightness. Additional
features include fatigue, weight loss, anorexia. Symptoms of depression or anxiety may also coexist 24.
A clinical diagnosis of COPD should be considered in any patient who has dysnea, chronic cough or
sputum production, and a history of exposure to risk factors for the disease. Spirometry is required to
make diagnosis. Post bronchodilator FEV1/FVC < 0.70 confirms the presence of limitation and thus of
COPD. Classification of severity of airflow limitation in COPD (based on post bronchodilator
FEV1)(Table-11) .
Once COPD has been diagnosed, effective management should be based on an individual assessment
of disease in order to reduce current symptoms and future risk.
Goals for treatment of stable COPD by reducing the symptoms, Improve exercise tolerance and
improve health status. Reduce the risk by Prevent disease progression, Prevent and treat exacerbations
and Reduce mortality. Non pharmacological Treatment includes smoking cessation, physical activity,
pulmonary rehabilitation, vaccination and surgical intervention like lung volume reduction surgery,
bullectomy and lung transplantation. Pharmacological includes inhaled bronchodilators, inhaled
corticosteroids, methyl xanthenes, phosphodiesterase inhibitors, systemic corticosteroids, oxygen
therapy and non invasive ventilation.
Six minute walk test: Stair climbing, a 6MWT, a shuttle-walk test, detection of exercise-induced
asthma, a cardiac stress test, and a cardiopulmonary exercise test25,26 are the most popular clinical
exercise tests in order of increasing complexity. Among this 6 MWT is easy to perform. It is better
tolerated, and reflects the activities of daily living than the other similar walk tests. It requires only a
100-ft hallway and practically a easier test. There is no need of exercise equipment or advanced trained
technicians. Walking is an activity performed daily by all but the most severely impaired patients. This
test measures the distance that a patient can walk as fast as possible on a flat, hard surface in a period
of 6 minutes (the 6MWD). It evaluates the global and integrated responses of all the systems involved
during exercise, including the pulmonary and cardiovascular systems, systemic circulation, peripheral
circulation, blood, neuromuscular units, and muscle metabolism. It does not provide on the function of
each of the different organs and systems involved in exercise or the mechanism of exercise limitation,
as is possible with maximal cardiopulmonary exercise testing. The submaximal level of functional
capacity can be assessed by self-paced 6MWT. Patients can choose their own intensity of exercise and
they also can stop and take rest during the test as patients do not achieve maximal exercise capacity
during the 6MWT. The 6MWD may better reflect the functional exercise level for daily physical
activities. The strongest indication for the 6MWT is for measuring the response to medical
interventions in patients with moderate to severe heart or lung disease.
The 6MWT does not determine peak oxygen uptake, diagnose the cause of dyspnea on exertion, or
evaluate the causes or mechanisms of exercise limitation25,26. The data collected from a 6MWT should
be regarded as complementary to cardiopulmonary exercise testing, but not a replacement. Even though
there is difference between these two functional tests, some good correlations have been reported. For
example patients with end-stage lung diseases reported a significant correlation (r-0.73) between
6MWD and peak oxygen uptake.. The reproducibility of the 6MWD (with a coefficient of variation of
approximately 8%) appears to be better than the reproducibility of 1-second forced expiratory volume
in patients with chronic obstructive pulmonary disease (COPD)27.
Indications for the six-minute walk test includes- Pre-treatment and post-treatment comparisons, Lung
transplantation, Lung resection, Lung volume reduction surgery, Pulmonary rehabilitation, COPD,
Pulmonary hypertension Heart failure, Functional status (single measurement)COPD, Cystic fibrosis,
Heart failure, Peripheral vascular disease, Fibromyalgia, Older patients, Predictor of morbidity and
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mortality, Heart failure. Primary pulmonary hypertension. Absolute contraindications for the 6MWT
include unstable angina during the previous month and myocardial Infarction during the previous
month.
If the Patients are having any of these findings he/she should be referred to the physician ordering the
test for individual clinical assessment. The readings from a resting electrocardiogram done during the
previous 6 months should also be reviewed before testing. Stable exertional angina is not an absolute
contraindication for a 6 MWT, but patients with these symptoms should perform the test after using
their antiangina medication, and rescue nitrate medication should be readily available. The 6MWT is a
useful measure of functional capacity targeted at people with at least moderately severe impairment.
The test has been widely used for preoperative and postoperative evaluation and for measuring the
response to therapeutic interventions for pulmonary and cardiac disease.
SPIROMETRY: Spirometry is a physiological test that measures how an individual inhales or exhales
volumes of air as a function of time. The primary signal measured may be volume or flow. Indications
of spirometry can be categorized as diagnostic, monitoring, disability/impairment evaluation and public
health. Under diagnosis evaluate symptoms, signs or abnormal laboratory tests , measure the effect of
disease on pulmonary function, screen individuals at risk of having pulmonary disease, assess pre-
operative risk , assess prognosis and to assess health status before beginning strenuous physical activity
programmes28. Spirometry uses include monitoring of therapeutic intervention, describe the course of
diseases that affect lung function, people exposed to injurious agents and to monitor for adverse
reactions to drugs with known pulmonary toxicity. In public health for Epidemiological surveys,
derivation of reference equations and for clinical research. Contraindications of spirometry includes
Haemoptysis of unknown origin, Pneumothorax, Unstable cardiovascular status or ‘recent’ myocardial
infarction or pulmonary embolus, Thoracic, abdominal or cerebral aneurysms , ‘Recent’ eye surgery
(eg, cataract), Presence of an acute illness or symptom that might interfere with test performance (eg,
nausea, vomiting) and Recent thoracic or abdominal surgery.
FEV1 AND FVC MANOEUVRE: FVC is defined the maximal volume of air exhaled with
maximally forced effort from a maximal inspiration, i.e. vital capacity performed with a maximally
forced expiratory effort, expressed in litres at body temperature and ambient pressure saturated with
water vapour (BTPS). FEV1 is the maximal volume of air exhaled in the first second of a forced
expiration from a position of full inspiration, expressed in litres at BTPS. There are three distinct
phases to the FVC manoeuvre, are maximal inspiration, a ‘‘blast’’ of exhalation; and continued
complete exhalation to the end of test (EOT). Many studies have suggested a relationship between the
six minute walk test and pulmonary function test PFT parameters in patients with COPD. In a study by
Hatem FS Al Ameri et al29, in 2006, they found correlation of 6 minute walk distance with DLCO,
FVC and FEV1 published in Iranian Heart Journal 2005. In another study conducted in India by Manoj
Khandelwal et al30 6MWD negatively correlated to breathlessness (MMRC grade), there was
statistically significant association between 6MWD to all spirometry parameters like FEV1 %
predicted, FVC% predicted. The different GOLD stages were found to have positively correlated to
6MWD. A study conducted by Anil Kumar Kodavala31 showed no statistical correlation between
6MWD AND FEV1. Since many studies all over the world showed significant correlation between
6MWD and FEV1 in COPD, this study emphasizes the significance of correlation between 6MWD and
FEV1 in COPD patients.
CONCLUSION:
COPD is one of the most common chronic disorder encountered in day today practice of both
respiratory physician and general practitioner. To confirm a diagnosis of COPD and grade its severity
spirometry is the current gold standard. But since spirometry is a specialized device which requires
certain technical knowledge to operate and perform optimal testing, it cant be made available in
peripheral health systems. To device a simple test which doesn’t require any qualified technician and
specialized equipment 6MWT was performed to find the correlation between the distance travelled and
FEV1. This study was conducted whether there is correlation between 6MWD and FEV1 and other
factors. From this study it was found that
1. There was no correlation between six minute walk distance and FEV1 in COPD patients.
2. Female COPD patients have less six minute walk distance as compared to male COPD patients.
3. No significant association was found between 6MWD and BMI.
4. 6 MINUTE WALK DISTANCE in COPD patients was not associated with BMI in our study.
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5. No association was found between 6MWD and saturation (SpO2).
6. There was significant statistical association between FEV1 and SpO2, i.e. as severity of airflow
obstruction based on FEV1 values increases, chances of desaturation also increases.
Hence it is safe to conclude that measuring 6 MINUTE WALK D ISTANCE is not sufficient for
assessment of severity of COPD.
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