biological fuels that produce heat are called biomass . it is predicted that half of the world population and more than 90% of the rural population in developing countries uses biomass fuels . in turkey , the most commonly utilized biomass fuel is called turd , a fuel type produced by dehumidifying animal waste . turd is used for cooking bread and meal in a closed oven called a tandir . biomass smoke is a mixture of complex particles , gases such as carbon monoxide , sulfur oxides , nitrous oxides , aldehydes , and poly - organic matter , including polycyclic aromatic hydrocarbons . the correlation between the effects of biomass smoke in respiratory functions , the structure of the lungs , and numerous pulmonary pathologies like chronic obstructive pulmonary disease , interstitial pulmonary disease , cancer , asthma , and lower respiratory tract infections has already been established [ 48 ] . the relation of biomass with pulmonary hypertension and cor pulmonale has been reported in several studies [ 2,913 ] . in van province in eastern turkey , we reported a higher level of pulmonary hypertension in pulmonary diseases of women exposed to biomass than in pulmonary diseases related to cigarette smoking . previously , we reported that pulmonary hypertension could develop even without the presence of a pulmonary disease . however , it is an invasive procedure with risks of complications . for this reason , the aim of this study was to investigate the feasibility of main pulmonary artery diameter quantification by intravenous ( iv ) contrast agent administered thoracic computerized tomography ( ct ) in the diagnosis of pulmonary hypertension secondary to biomass smoke exposure . in this study , 104 female subjects with biomass smoke exposure and 20 healthy female subjects were enrolled . age , biomass smoke exposure duration and density , echocardiographic estimation of spap , mpad measured by thoracic ct , and diagnoses were recorded . biomass smoke exposure was recorded as the number of exposure - years , the number of days per week , and hours per day . for example , if a person is exposed to biomass smoke for 1 hour per day for a year , her biomass smoke exposure density is 1 hour / year . patients with the following criteria were included in the study as the biomass smoke - exposed group : ( 1 ) clinical or radiological evidence of pulmonary hypertension and cor pulmonale , ( 2 ) long - term biomass smoke exposure ( at least 10 years ) , and ( 3 ) the presence of measurable spap in echocardiographic evaluation . twenty female patients who were evaluated for suspected pulmonary embolism , but who had normal findings by echocardiography and thorax ct , served as the control group . patients were excluded from either the biomass smoke - exposed or control groups if they had primary left ventricular dysfunction or acute cardiac illness , obesity , a history of significant organic and/or inorganic dust exposure , a history of cigarette smoking , passive cigarette smoke exposure , or a clear history of a known chronic lung disease before exposure to biomass smoke ( e.g. , tuberculosis , childhood respiratory diseases , thoracic structural anomalies ) . the study protocol was carried out in accordance with the helsinki declaration as revised in 2000 . the study protocol was approved by the local ethics committee , and informed consent was obtained from each subject . the patients in the biomass smoke - exposed group were further divided into 4 subgroups for the purpose of determining the correlation of the mpad measurements with the clinical features in each group . chronic obstructive pulmonary disease was diagnosed by the signs and symptoms of chronic bronchitis and/or pulmonary emphysema , and the presence of chronic and irreversible airflow obstruction ( forced expiratory volume in 1 second ( fev1)/forced vital capacity below 70% , fev1 below 80% predicted ) . asthma was excluded , as assessed by clinical history and response to bronchodilators ( 12% increase in fev1 following 400 mg of inhaled salbutamol ) . the criterion used for diagnosis of pulmonary embolism on iv contrast medium - administered thoracic ct was an intraluminal filling defect . a ct scan was interpreted as revealing positive findings for an embolus only if a definite filling defect was seen on more than 1 contiguous axial image . group 3 patients had pulmonary hypertension associated complaints and findings such as dyspnea and/or peripheral edema and/or cor pulmonale , while group 4 patients did not have these same findings . we previously reported on a group of women exposed to biomass smoke ; they did not have airway obstruction , but had pulmonary hypertension and cor pulmonale . therefore ; group 3 was termed the idiopathic pulmonary arterial hypertension - like group and group 4 was termed the asymptomatic idiopathic pulmonary arterial hypertension - like group . the last 2 groups might have prominent pulmonary artery involvement that could be related to biomass smoke exposure . echocardiography was performed by the same cardiologist ( with 7 years of experience ) using a vivid 3 instrument ( general electric , usa ) and by utilizing a 2-mhz probe . the gradient between the right ventricular peak systolic pressure and right atrium pressure was measured by doppler echocardiography at rest in cases with tricuspid insufficiency . the modified bernoulli equation was used to calculate pap pressure : pap=4  ( tricuspid systolic jet ) . right atrial pressure is estimated to be 5 mmhg when the diameter of the inferior vena cava ( ivc ) is < 1.7 cm and a 50% decrease in the diameter with inspiration , 10 mmhg when ivc is > 1.7 cm and with normal inspiratory collapse ( 50% ) , and 15 mmhg when ivc is > 1.7 cm and inspiratory collapse is less than 50% . when spap is > 35 mmhg , the presence of pulmonary hypertension is established according to the new recommendations of the working group on diagnosis and assessment of pulmonary arterial hypertension in the 4 world symposium on pulmonary hypertension . a thoracic ct scan was performed using a 4-detector multislice ct scanner ( somatom sensation 4 , siemens , erlangen , germany ) by injecting contrast agents intravenously while the patient held her breath . the non - ionic contrast material ( ultravist 300 , schering , berlin , germany ) at an average volume of 100 ml and concentration of 300 mg i/100 ml ) was administered by a power injector at a rate of 3 ml / second via an 18-gauge plastic angiocatheter inserted into the cubital vein . imaging parameters were 120 kv and 152 ma , with 0.5 second rotation time , 42 mm collimation , and 5 mm slice thickness . data were transferred to a network computer workstation ( leonardo ; siemens medical systems , germany ) and diameters were measured using a window level of 400 hu , with the center at 60 hu . the widest diameter perpendicular to the long axis of the main pulmonary artery was measured with computer calipers at the level of the pulmonary artery bifurcation by mediastinal window ( figure 1 ) . a pearson correlation analysis was conducted to examine liner relationships among variables ( age , years of exposure , density of exposure ) with spap and mpad , and between spap and mpad in the exposed group and in each subgroup . receiver operating characteristic ( roc ) curve analysis was performed to find a cut - off value of mpad for diagnostic ability to predict spap > 35 mmhg as pulmonary hypertension . the test measurement sensitivity , specificity , positive predictive rate , negative predictive rate , and truth value were all estimated by standard formulas . chronic obstructive pulmonary disease was diagnosed by the signs and symptoms of chronic bronchitis and/or pulmonary emphysema , and the presence of chronic and irreversible airflow obstruction ( forced expiratory volume in 1 second ( fev1)/forced vital capacity below 70% , fev1 below 80% predicted ) . asthma was excluded , as assessed by clinical history and response to bronchodilators ( 12% increase in fev1 following 400 mg of inhaled salbutamol ) . the criterion used for diagnosis of pulmonary embolism on iv contrast medium - administered thoracic ct was an intraluminal filling defect . a ct scan was interpreted as revealing positive findings for an embolus only if a definite filling defect was seen on more than 1 contiguous axial image . group 3 patients had pulmonary hypertension associated complaints and findings such as dyspnea and/or peripheral edema and/or cor pulmonale , while group 4 patients did not have these same findings . we previously reported on a group of women exposed to biomass smoke ; they did not have airway obstruction , but had pulmonary hypertension and cor pulmonale . therefore ; group 3 was termed the idiopathic pulmonary arterial hypertension - like group and group 4 was termed the asymptomatic idiopathic pulmonary arterial hypertension - like group . the last 2 groups might have prominent pulmonary artery involvement that could be related to biomass smoke exposure . echocardiography was performed by the same cardiologist ( with 7 years of experience ) using a vivid 3 instrument ( general electric , usa ) and by utilizing a 2-mhz probe . the gradient between the right ventricular peak systolic pressure and right atrium pressure was measured by doppler echocardiography at rest in cases with tricuspid insufficiency . the modified bernoulli equation was used to calculate pap pressure : pap=4  ( tricuspid systolic jet ) . right atrial pressure is estimated to be 5 mmhg when the diameter of the inferior vena cava ( ivc ) is < 1.7 cm and a 50% decrease in the diameter with inspiration , 10 mmhg when ivc is > 1.7 cm and with normal inspiratory collapse ( 50% ) , and 15 mmhg when ivc is > 1.7 cm and inspiratory collapse is less than 50% . when spap is > 35 mmhg , the presence of pulmonary hypertension is established according to the new recommendations of the working group on diagnosis and assessment of pulmonary arterial hypertension in the 4 world symposium on pulmonary hypertension . a thoracic ct scan was performed using a 4-detector multislice ct scanner ( somatom sensation 4 , siemens , erlangen , germany ) by injecting contrast agents intravenously while the patient held her breath . the non - ionic contrast material ( ultravist 300 , schering , berlin , germany ) at an average volume of 100 ml and concentration of 300 mg i/100 ml ) was administered by a power injector at a rate of 3 ml / second via an 18-gauge plastic angiocatheter inserted into the cubital vein . imaging parameters were 120 kv and 152 ma , with 0.5 second rotation time , 42 mm collimation , and 5 mm slice thickness . data were transferred to a network computer workstation ( leonardo ; siemens medical systems , germany ) and diameters were measured using a window level of 400 hu , with the center at 60 hu . the widest diameter perpendicular to the long axis of the main pulmonary artery was measured with computer calipers at the level of the pulmonary artery bifurcation by mediastinal window ( figure 1 ) . a pearson correlation analysis was conducted to examine liner relationships among variables ( age , years of exposure , density of exposure ) with spap and mpad , and between spap and mpad in the exposed group and in each subgroup . receiver operating characteristic ( roc ) curve analysis was performed to find a cut - off value of mpad for diagnostic ability to predict spap > 35 mmhg as pulmonary hypertension . the test measurement sensitivity , specificity , positive predictive rate , negative predictive rate , and truth value were all estimated by standard formulas . there were no statistically significant differences between subjects with biomass smoke exposure and healthy subjects with respect to age ( p>0.05 ) . the mean mpad and the mean spap were significantly higher in subjects with biomass smoke exposure than in healthy subjects ( p<0.001 for both ) . the biomass smoke exposure characteristics of the patients in the study subgroups are shown in table 2 . there were no statistically significant differences between the mean ages of the participants in the subgroups ( p>0.05 ) . likewise , no significant difference was observed between the biomass smoke exposure durations or the biomass smoke exposure densities in the subgroups ( p>0.05 ) . the mean mpad and the spap value were significantly lower in the asymptomatic idiopathic pulmonary arterial hypertension - like group compared to the other subgroups ( p<0.001 ) ( table 2 ) . spap was significantly correlated with the mpad in the total biomass smoke - exposed group and in each subgroup ( r=0.614 , p<0.01 ) ( table 3 , figure 2 ) . in the roc analysis , the threshold value for predicting pulmonary hypertension at which the highest diagnostic sensitivity and specificity intersected was found when mpad was 29 mm ( area under the curve ( auc)=0.86 ) . its sensitivity , specificity , positive predictive value , negative predictive value , and accuracy were 91% , 80% , 97% , 50% , and 84% , respectively ( figure 3 ) . biomass smoke is composed of a relatively equal mixture of coarse ( 2.53.5 m ) and ultrafine / fine ( 0.022.5 m ) particles and can penetrate deeply into the lung , producing a variety of morphologic and biochemical changes . a recent meta - analysis , which reviewed risk of chronic obstructive pulmonary disease from exposure to biomass smoke , concluded that biomass smoke exposure is a clear risk factor for chronic obstructive pulmonary disease   and reported that clinical characteristics , quality of life , and mortality rates of biomass smoke - related chronic obstructive pulmonary disease cases were similar in degree to that of tobacco smokers [ 1922 ] . the relationship between biomass smoke exposure and pulmonary hypertension and cor pulmonale has long been established [ 911 ] . because the prevalence of cor pulmonale is high in female patients with ages ranging from 20 to 60 years , padmavati et al . conducted an autopsy study in delhi , india . they reported that none of the cases had a history of cigarette smoking ; however , the common anamnesis was the exposure to biomass smoke in ill - ventilated environments . they concluded that pulmonary hypertension and cor pulmonale development might have a correlation with biomass smoke exposure . furthermore , sandoval et al . reported a clinical picture with chronic pulmonary disease and significantly high pulmonary hypertension that they have frequently observed among women exposed to wood smoke . another autopsy study , which compared the chronic obstructive pulmonary disease cases caused by biomass smoke exposure and cigarette smoking , reported that vascular changes were prominent in both groups , but were more severe in the biomass smoke group , which could explain common pulmonary hypertension and cor pulmonale in women exposed to biomass smoke . in our region , we frequently see female patients with symptoms suggestive of biomass smoke exposure . we investigated and compared the pulmonary hypertension prevalence between biomass smoke - exposed and non - exposed women who had no apparent diseases . we found a higher prevalence of pulmonary hypertension in the biomass smoke - exposed subjects ( 48% and 12% , respectively ) . several studies have been conducted on the utility of the diameter of the main pulmonary artery and its main branches scanned by ct in the diagnosis of pulmonary hypertension [ 2325 ] . these studies found an upper limit of normal mpad of 33.2 mm , 28.6 mm , and 29 mm . they established that mpad > 29 mm and > 33.2 mm have a sensitivity of 58% and 84% , and a specificity of 95% and 75% , respectively , for a pulmonary hypertension diagnosis . we found that biomass smoke - exposed subjects had increased mpad compared with healthy subjects ( p<0.001 ) . we also found that mpad  29 mm has a sensitivity of 91% and a specificity of 80% for a pulmonary hypertension diagnosis in the biomass smoke - exposed group . some studies have reported that ct can be used to differentiate the causes of pulmonary hypertension . in our study , we evaluated pulmonary embolism , the presence of interstitial involvement , and aeration increase with ct , all of which can contribute to pulmonary hypertension . numerous studies have examined the correlation between mpad measured by ct and mean pap measured by right - sided heart catheterization with the purpose of assessing ct for pulmonary hypertension diagnosis in different diseases . a positive correlation was found between the 2 methods in studies of heart and lung diseases ( r=0.83 , p<0.001 ; r=0.74 , p<0.0005 ; r=0.67 , p<0.001 ) , but no correlation was found in another study [ 24,3032 ] . in thromboembolic pulmonary hypertension and primary pulmonary hypertension , 2 studies found a correlation between mpad and mean pap ( r=0.43 , p<0.01 ; r=0.42 , p<0.001 ) , but no correlation was found in a third study [ 3234 ] . in contrast , we found a significant correlation between spap and mpad in patients with chronic lung diseases , as well as in idiopathic pulmonary arterial hypertension - like group patients and asymptomatic idiopathic pulmonary arterial hypertension - like group patients , who may share similar pathogenesis with primary pulmonary hypertension and chronic thromboembolic pulmonary hypertension . burakowska et al . studied the correlation between pulmonary artery diameters measured by ct and echocardiographic spap in cases with acute pulmonary hypertension associated with pulmonary embolism and chronic pulmonary hypertension . they reported that while the spap and mpad correlation was significant in pulmonary hypertension cases developed in association with acute pulmonary embolism ( r=0.487 , p<0.003 ) , this correlation was not observed in chronic pulmonary hypertension ( r=0.223 ) . we observed a significant correlation between spap and mpad in the biomass smoke - exposed group ( r=0.634 p<0.01 ) and in the chronic obstructive pulmonary disease , pulmonary embolism , idiopathic pulmonary arterial hypertension - like , and asymptomatic idiopathic pulmonary arterial hypertension - like subgroups . the results of most of these studies are in agreement with our findings and suggest that ct measurements may be used in a pre - diagnosis of pulmonary hypertension . roc curve analysis showed that mpad > 29 mm provides the best sensitivity and specificity for detecting pulmonary hypertension by ct scan as reported in previous studies . a linear correlation was established between ct mpad and echocardiographic spap in the diseases related to biomass smoke exposure . therefore , ct mpad should be used to evaluate the presence of pulmonary hypertension , which is common in biomass smoke - exposed women , and mpad 29 mm should be a warning for the presence of pulmonary hypertension . our results indicate that main pulmonary artery diameter measurements by thoracic ct may suggest presence of pulmonary hypertension in biomass smoke - exposed women .