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traditionally , post bronchodilator forced expiratory volume in 1 second ( pb fev1 ) is used to assess the severity of chronic obstructive pulmonary disease ( copd ) .
however , it has now been shown that functional exercise capacity is a strong predictor of survival following pulmonary rehabilitation and so assessment of functional status is very important for proper prescription of medical therapy and rehabilitation programs .
van stel et al . suggested that 6 min walk test ( 6mwt ) was an easy to perform procedure and was able to predict functional status in all patients with chronic respiratory disease ; however , pinto - plata et al . argued that walking by itself might not reflect the true functional status in these patients as a person has to do several other activities in addition to walking .
a sit - to - stand test ( stst ) was proposed as a better alternative to 6mwt , but it lacks universal application , more specifically in countries like india where people resort to squat ( sit on the floor ) rather than sitting on chair . a more practical approach for them will be to assess the functional ability to stand from the squatting position , i.e. , squat - to - stand test ( sqtst ) .
therefore , a study was undertaken to compare sqtst with pb fev1 , 6mwt , and stst and to assess whether it is a feasible and effective tool in evaluating the functional status of the copd patients .
all patients attending the outpatient department of respiratory medicine , national institute of medical sciences , jaipur , with clinical history , consistent with copd , were recruited .
twenty age- and sex - matched , healthy and nonsmoking attendants / hospital staff were also recruited to serve as controls .
was also taken from all the patients and controls after duly explaining the study protocol .
all the recruited patients were evaluated in detail , including present and past clinical history , physical examination , complete blood counts , random blood sugar , renal and liver function tests , two sputum smears for acid - fast bacillus using ziehl  neelsen staining , skiagram chest posteroanterior view , and a standard electrocardiogram .
patients showing obvious pulmonary or other system abnormalities such as active pulmonary tuberculosis , malignancy , diabetes mellitus , coronary artery disease , stroke , and renal or hepatic disease were excluded .
the remaining patients were subjected to spirometry including the reversibility test as per the american thoracic society guidelines using an rms helios spirometer .
three attempts were made , and the best was selected and recorded to obtain the cases of forced vital capacity ( fvc ) , fev1 , and fev1/fvc ratio .
a repeat spirometry was performed 20 min after inhaling 200 g of salbutamol to obtain pb fvc , fev1 , and fev1/fvc ratio .
all patients with fev1/fvc ratio < 70% and fixed airway obstruction on spirometry ( pb improvement in fev1 of < 200 ml or in fev1/fvc of < 12% ) were included in the study , but patients with history of wheeze , chest tightness , eye allergy , nasal allergy , or skin allergy , suggesting bronchial asthma , those suffering from osteoarthritis and oxygen saturation < 90% , were also excluded from the study . the body mass index ( bmi ) of the study patients was calculated as body weight in kg / height in meters square and was classified as follows : underweight  < 18.5 kg / m , normal 
18.525.0 kg / m or overweight  > 25 kg / m as per the world health organization criteria .
pack years of smoking was calculated as : number of bidi packs smoked / day  number of years smoked ( where a bidi pack was calculated as number of bidies/20 ) .
the study patients were further subjected to combined risk assessment , which included the modified british medical research council questionnaire , history of exacerbations in the past 2 years , and history of exacerbations needing hospitalization in the past 2 years and categorized as risk category a , b , c , or d as per gold guidelines .
all the patients and controls were then subjected to 6mwt , stst , and sqtst ( a modified form of stst , used for the first time for rural patients ) as follows : the participants were instructed by the command  start  for them to stand from their squatting position and they then asked to go to their squatting position without any delay , repeating these steps as many times as possible in 1 min at a self - selected speed which was felt safe and comfortable by them or until asked to stop . in case
a patient was unable to stand unaided , support of a wide block of one feet height was allowed .
the patient 's functional status was recorded as ( a ) unable to stand even with support , ( b ) able to stand with support only , and ( c ) number of times he was able to stand in 1 min without support . since normal ranges of 6mwt in meters ( m ) , stst , and sqtst are not available for universal use , the mean of the respective parameters minus twice the standard deviation in normal controls was used as cutoff for normal values for these parameters .
data so obtained were tabulated and assessed for statistical significance using student 's t - test , anova test / test , and fisher 's exact test , as and when applicable .
ninety stable copd patients and twenty controls could be studied , between july 2014 and january 2016 .
the basic parameters of the study patients and the controls are shown in table 1 .
the mean age of the patients in the four categories was similar to that of the controls ( p = 0.0059 ) .
the mean age was higher in category b patients , but the differences from other categories were statistically insignificant ( p = 0.058 ) .
males outnumbered the females in all the risk categories but the sex - wise distribution was also fair ( p = 1.000 ) .
the duration of illness was higher in category a patients as compared to the rest , but the differences from other categories were statistically insignificant ( p = 0.823 ) .
sixty - eight patients were current smokers and the rest 22 were reformed or ex - smokers .
there were no differences in the copd categories with regard to the smoking status ( p = 0.913 ) , but the mean pack years of smoking was lower in category a patients as compared to the rest ( p = 0.914 ) .
the mean bmi and pb fev1% were significantly lower in category d patients as compared to the rest ( p = 0.000 ) .
basic parameters of the patients and controls the mean of 6mwt , stst , and sqtst in controls were 244 + 30.15 m , 27.05 + 7.89 , and 17.8 + 5.38 , respectively , so the respective cutoff values were derived as 184 m , 11 , and 07 .
the mean distance walked by category d patients was lower as compared to the rest ( f = 1.47 , p = 0.109 ) , but the difference was statistically insignificant . on the contrary ,
the stst and sqtst values were significantly lower in category d patients as compared to the rest ( p = 0.000 ) .
eight patients desaturated ( sao2 < 90% ) at the end of sqtst in group d as compared to 3 and 2 in group c and b , respectively , but all recovered of their own in due course . none of the patients in group a or the controls desaturated .
the study of functional status is very vital in assessment of severity of copd as it has been shown to be a strong predictor of survival following pulmonary rehabilitation . 6mwt and
more recently stst have been used in functional assessment of copd , but for rural population , squatting is also an important routine activity .
this study was , therefore , undertaken to assess the feasibility and efficacy of sqtst in evaluation of the functional status of the copd patients residing in rural areas .
data of this study were found to be valid for statistical comparisons as the controls in the study were age and sex matched , and the distribution of the patients in various risk categories of copd was fair .
the mean age of the patients , sex , duration of illness , smoking status , and pack years of smoking did not correlate to severity of copd in this study ( p > 0.5 ) .
have reported more dyspnea , lower exercise tolerance , and higher incidence of severe exacerbations in the elderly ( p < 0.05 ) .
movahed and milne could observe a direct correlation between amount of expectoration / cough and the duration or amount of smoking .
some of these observations , made at variance from the current study , can be explained on the basis of differences in the disease progression in copd in individual patients of different studies .
it has been observed that smoking patterns of the cases , such as depth of smoking and the holding time , may play a more crucial role in pathogenesis of copd than the duration or pack years of smoking .
further , it was significantly lower in category d patients as compared to the rest of the risk categories in this study ( p = 0.000 ) .
harik - khan et al . reasoned that the nutritional abnormality and weight loss in copd are caused due to decreased caloric intake and increased basal metabolic rate .
stated that copd produced malnutrition due to loss of fat as well as fat - free components .
the mean distance covered in 6 min ( 6mwt ) was significantly lower in copd patients as compared to controls ( p = 0.003 ) .
further , it progressively declined with progression of the severity of the disease , but at the cutoff distance of 184 meters , there was a significant overlap in different categories and the correlation was rather poor ( p = 0.109 ) .
suggested stst as a superior alternative to 6mwt , the former being less stressful , easier to apply , and more sensitive for the patient 's clinical status , compared to the latter . in the present study ,
further , at a cutoff of 11 , all patients in category a were classed as normal and all patients in category d as abnormal .
thus , stst was found to be superior to 6mwt in the present study also . in this study ,
cutoff , none of the category a patients had abnormal sqtst and none in category d was classed as normal .
further , the mean sqtst value was highest in category a and lowest in category d as compared to rest ( p  0.000 ) .
thus , a strong correlation was observed between sqtst and disease severity ( p = 0.000 ) .
further , a strong correlation was also observed between sqtst and stst ( p = 0.000 ) , but its correlation with 6mwt was moderate ( p = 0.004 ) and to that with fev1% , was poor ( p = 0.091 ) .
the major limitations of the study are the small number of patients and exclusion of patients with evident hypoxia due to fear of further drop in oxygen saturation . in spite of these limitations ,
sqtst was found to be an easy , feasible , and effective tool to study the functional status in stable , rural copd patients , as the test is very close to their routine daily activities . whether the findings of this study are applicable to other population groups who routinely resort to squat or not needs to be studied further .
sqtst is an easy , feasible , and effective tool to study the functional status in stable copd patients of rural india as it is physiologically more close to their routine daily activities .
further , bmi of the patients was observed to be an important surrogate marker of the functional status in these patients .
background : assessment of functional status is vital for proper therapy and rehabilitation programs in chronic obstructive pulmonary disease ( copd ) patients . traditionally , 6 min walk test ( 6mwt ) has been used but it by itself may not reflect the total functional status in these patients as it poorly correlates to the disease severity . a sit - to - stand test ( stst ) has been proposed as a better alternative to 6mwt but to test their ability to stand from the squatting position , i.e. , a squat - to - stand test ( sqtst ) will be more appropriate in rural patients.material and methods : all patients , diagnosed to have stable copd , after exclusion of asthma and other respiratory or nonrespiratory diseases were evaluated by applying 6mwt , stst , and sqtst in them . 
 data so obtained were statistically analyzed.results:ninety patients and twenty healthy controls were studied . 
 sixteen , 24 , 23 , and 27 of the patients were classed as copd risk category a , b , c , and d , respectively . 
 the mean post bronchodilator forced expiratory volume in 1st second ( pb fev1 ) and body mass index ( bmi ) were significantly lower in category d as compared to the rest . 
 the cutoff values for 6mwt , stst , and sqtst were derived as 184 m , 11 , and 07 , respectively . 
 6mwt correlates poorly to disease severity ( p = 0.109 ) but there was a strong correlation between disease severity and sqtst and stst ( p = 0.000).conclusion : sqtst is a feasible and effective tool to assess functional status of copd patients residing in rural areas . 
 bmi is an important surrogate marker of the functional status in these patients .