postinfectious obliterative bronchiolitis ( ob ) is an uncommon and severe form of 
 chronic obstructive lung disease that occurs in children after lower respiratory 
 tract injury .
( ) in terms of 
 diagnosis , there are no specific signs or symptoms of postinfectious ob .
clinical 
 and imaging findings are used in combination with laboratory test results in order 
 to identify the cause and rule out other forms of chronic lung disease .
the 
 diagnostic criteria for postinfectious ob are as follows : severe acute 
 bronchiolitis / viral pneumonia during the first 3 years of life in previously healthy 
 children ; evidence of persistent airway obstruction after the acute event , 
 identified by physical examination , pulmonary function testing , or both ; chest x - ray 
 findings of obstructive lung disease ; a mosaic pattern and air trapping ( at ) on 
 chest ct scans ; and exclusion of other chronic lung diseases progressing to 
 permanent respiratory symptoms .
( , ) histologically , ob is characterized by the presence of granulation tissue plugs in 
 the small airway lumen , complete small airway destruction , or both .
( ) showed that ob is histologically 
 characterized by a constrictive pattern with varying degrees of inflammation and 
 airway obliteration , ranging from minimal bronchiolar inflammation to complete 
 obliteration of the bronchioles and bronchi by fibrotic tissue .
indirect signs of 
 obstruction , such as macrophage accumulation , bronchiectasis , mucus accumulation , 
 and hyperinflation , are always present .
although there have been several reviews of studies examining long - term sequelae of 
 adenovirus pneumonia , ( , ) few studies have examined ct 
 findings in children with ob .
( , ) some 
 of these studies have reported that abnormal ct findings in such children can 
 predict abnormal lung function later in life .
( ) it has been reported that hrct is an important diagnostic tool for the evaluation of 
 pulmonary damage in patients with ob .
( ) the volume of an organ ( or the volume of abnormal parts of 
 an organ ) can be determined by the use of helical ct images and attenuation 
 coefficient values or densities on the hounsfield scale , expressed in hounsfield 
 units ( hu ) .
this method is known as volumetric ct densitometry or ct 
 densitovolumetry , ( , ) and it can be used in order to 
 measure the volume of areas of lung with low attenuation ( i.e. , at ) , as well as 
 total lung volume ( tlv ) , in children with ob . in addition , it can be used in order 
 to measure the percentage of at relative to tlv ( at% ) with the use of thresholds to 
 differentiate normal lung areas from ob areas .
it has been shown that at% is a major 
 contributing factor to chronic persistent airflow obstruction in asthma .
( , ) the clinical course following the onset of ob is 
 variable and depends on the volume of affected lung tissue .
( ) measures of clinical status and of the ability to 
 perform physically demanding activities - such as the number of hospital admissions or 
 missed school days , walk test distance , nutritional status , and oxygen saturation 
 ( so2 ) at rest or during exercise - facilitate the selection of 
 appropriate clinical interventions .
( , ) 
 because the prognosis of ob patients depends not only on patient behavior but also 
 on functional impairment and the extent of anatomical damage , clinicians should 
 gather information regarding the extent and type of anatomical abnormalities . 

bronchiectasis , atelectasis , lobar collapse , and areas of low density are known 
 consequences of postinfectious ob , and hrct is the best method of examining such 
 lesions , ( , , ) all of which can influence the clinical status of 
 patients and their pulmonary function test results .
( , , ) 
 previous studies have shown that low attenuation areas correlate well with pulmonary 
 function test results in patients with at of various causes.(- ) however , to our knowledge , no studies have shown a 
 correlation of ct densitovolumetry findings with pulmonary function in children with 
 ob .
( , , ) our objective was to describe the correlation between the volume of areas of at and 
 pulmonary function test results in children with ob .
in addition , we compared at% 
 values with so2 values , pulmonary function test results , and clinical 
 scores in those children in an attempt to obtain objective measurement criteria for 
 ob .
this was a prospective study including all of the children treated at our 
 postinfectious ob clinic for more than 5 years and having clinically stable ob and 
 symptom onset before the age of 2 years .
the study protocol was approved by the 
 local research ethics committee , and the parents or legal guardians of all 
 participants gave written informed consent .  
the diagnosis of ob was based on the identification of chronic obstructive 
 respiratory symptoms appearing after an episode of lower respiratory tract infection 
 before the age of 2 years in previously healthy children .
( , ) all clinical diagnoses were confirmed by characteristic 
 findings on contemporary hrct scans .
the inclusion criteria were as follows ( ) : acute bronchiolitis / viral pneumonia before the age of 2 
 years in previously healthy children ; evidence of persistent airway obstruction 
 after the acute event , identified by physical examination , pulmonary function 
 testing , or both , the obstruction being unresponsive to at least 2 weeks of 
 treatment with systemic corticosteroids and bronchodilators ; radiological findings 
 of obstructive lung disease , including hyperinflation , atelectasis , bronchial wall 
 thickening , and bronchiectasis , as well as a mosaic perfusion pattern and at on ct 
 scans ; and absence of other chronic lung diseases progressing to persistent 
 respiratory symptoms , including tuberculosis , cystic fibrosis , bronchopulmonary 
 dysplasia , immunodeficiency , asthma , and severe alpha-1 antitrypsin deficiency .
the 
 exclusion criteria were as follows : being unable to undergo pulmonary function 
 testing or ct without sedation ; being unable to hold breath for the duration of ct 
 scanning ; having disease exacerbation < 30 days before ct or pulmonary function 
 testing ; having other lung diseases ; and requiring continuous oxygen therapy .  
of those 25 patients , 6 
 were excluded ( because they were unable to perform the required respiratory 
 maneuvers ) . the final sample consisted of 19 children ( 14 males and 5 females ) in 
 the 7 - 15 year age bracket ( mean age , 10  2.5 years ) .  
all patients performed spirometry and six - minute walk tests ( 6mwts ) in accordance 
 with previous reports .
( , ) spirometry was performed with a 
 vitalograph alpha spirometer ( vitalograph , buckingham , uk ) before and 10 min after 
 the administration of an inhaled dose of albuterol ( 300 g ; aerolin ; 
 glaxosmithkline plc , ware , uk ) with a valve spacer ( fisonair ; 
 glaxosmithkline plc ) .
all children performed a 6mwt with so2 control . 
 because the 6mwt was performed after spirometry ( and on the same day as the latter ) , 
 all patients used albuterol before the 6mwt .  
clinical scores included the following : 1 ) nutritional status ( ) ( z score : 0 = good nutritional status ; 1 = mild 
 malnutrition ; 2 = moderate malnutrition ; and 3 = severe malnutrition ) ; 2 ) cough 
 during remission ( 0 = absent and 1 = present ) ; 3 ) cough within 2 weeks before the 
 examination ( 0 = absent and 1 = present ) ; 4 ) wheezing during remission ( 0 = absent 
 and 1 = present ) ; 5 ) wheezing on most days of the week ( 0 = absent and 1 = present ) ; 
 6 ) wheezing in the last 2 weeks ( 0 = absent and 1 = present ) ; 7 ) difficulty 
 breathing in the 2 weeks preceding the examination ( 0 = absent and 1 = present ) ; 8) 
 frequency of exacerbations in the last 6 months ( 0 = no exacerbations ; 1 = sporadic 
 exacerbations ; 2 = exacerbations every 2 months ; 3 = exacerbations every month ; and 
 4 = exacerbations every week ) ; 9 ) increased anteroposterior chest diameter ( 0 = 
 absent and 1 = present ) ; 10 ) so2 at rest (  95% = 0 ; 90 - 94% = 1 ; and 
 < 90% = 2 ) ; 11 ) minimum so2 during the 6mwt ( 6mwt_so2 ;  
 95% = 0 ; 90 - 94% = 1 ; and
< 90% = 2 ) , mean desaturation during exercise being 
 measured by calculating the difference between so2 at rest and 
 6mwt_so2 ; 12 ) desaturation > 4% during the 6mwt ( 0 = negative 
 and 1 = positive ) ; 13 ) the fev1/fvc ratio ; and 14 ) percent predicted 
 fev1 ( fev1% ; > 80% = 0 ; 61 - 80% = 1 ; 41 - 60% = 2 ; 
 < 41% = 3 ) .  
all ct images were acquired with the use of the lowest possible radiation dose and a 
 commercially available helical ct scanner ( xvision ex ; toshiba medical systems 
 corporation , otawara , japan ) , being post - processed on a workstation 
 ( o2 ; sgi , fremont , ca , usa ) running three - dimensional ( 3d ) 
 rendering software ( alatoview ; toshiba medical systems corporation ) .
an initial set of 
 nine axial hrct scans ( with 1-mm collimation at increments of 20 mm ) were acquired 
 with the use of a high - frequency algorithm .
those hrct images were evaluated by two 
 thoracic radiologists with more than 10 years of experience in chest ct .
two additional sets of images were acquired by the helical ct scanner during single 
 breath - hold maneuvers ( during inhalation and exhalation ) . to minimize respiratory 
 motion artifacts ,
on the 
 basis of previous studies,(- ) the 
 following parameters were used : collimation , 10 mm ; table speed , 14 mm / rotation 
 ( pitch , 1.4 ) ; and low radiation dose ( 120 kv and 50 mas ) . the mean total radiation 
 dose was 5  1.3 msv .
we used helical ct scans of 10 mm , low mas , and high pitch in 
 order to reduce radiation exposure .
a standard reconstruction algorithm was used in 
 order to avoid the effects of edge - enhancing filters on tissue density .
two 
 segmentation steps were applied to each set of helical ct images before the 
 calculation of tlv .
the lungs were isolated by eliminating from the image data any 
 structure with a density exceeding 250 hu .
subsequently , we eliminated the air 
 within the abdomen and outside the patient ( nonpulmonary air ) by selecting regions 
 of interest with the 3d rendering software .
the regions of interest were selected by 
 drawing a line between the lung and the nonpulmonary air on each slice .
different 3d 
 software , unavailable to us during the study period , might include different tools 
 for lung segmentation . in order to minimize operator - dependent variability , we 
 considered the air within the trachea or main bronchi to be pulmonary air rather 
 than excluding it .
the operator assessed segmentation accuracy by reviewing the 3d 
 lung image generated by volume rendering ( figure 
 1 ) .
figure 1 in a , coronal reformatted ct image ( minimum intensity projection ) 
 showing air trapping . in b ,
three - dimensional ct reconstruction showing 
 low attenuation volumes , which represent air trapping volumes . 
 
for measuring the volume of lung parenchyma with abnormally low attenuation values , 
 areas of extremely low attenuation or density were considered to be abnormal , 
 because of the disproportion between the volume of lung parenchyma ( including 
 interstitial tissue , vessels , blood , lymph , interstitial fluid , and airway walls ) 
 and the air in those regions . in order to simplify measurement
, we defined " at 
 volume " as the total volume of lung zones showing extremely low density values .  
we first calculated the lung volume 
 affected by at using a fixed threshold of 950 hu ( at%950 ) .
( ) 
 and has been used by many others in order to quantify emphysema .
( ) we considered any portion of the 
 lungs with a density below 950 hu to be affected by at .
we calculated at%950 by 
 dividing the at volume for that threshold by the tlv .
no 
 validated threshold is available for determining the volume of hyperinflation , at , 
 or emphysema in children . because the 950 hu threshold can underestimate the extent 
 of disease in this population , we also calculated at volume using a threshold 
 selected for each patient with the aid of a density mask .
the threshold level was 
 adjusted until the mask corresponded to our subjective visual impression of affected 
 lung portions ( figure 2 ) .
any portions of the lungs with densities below 
 the selected hu were considered abnormal .
figure 2 post - processing tools . after the use of a threshold , the air inside 
 and outside the lungs is isolated .
in a , axial ct scan showing air 
 inside and outside the lungs . in b , three - dimensional ( 3d ) volume 
 rendering of the same data .
in c , 3d volume rendering of total lung 
 volume after the exclusion of air outside the lungs . 
  the shrink ( deflation )
volume of the lungs was calculated by subtracting the tlv as 
 measured on images acquired during exhalation from the tlv as measured on images 
 acquired during inhalation .
the percentage of shrink volume was considered excellent 
 if it was > 50% , reasonable / good if it was 30 - 50% , and poor if it was < 
 30% .   for the statistical analysis ,
test results were entered into a microsoft excel 
 database and processed by means of excel tools , the analysis being performed with 
 the statistical package for the social sciences , version 11 ( spss inc . , chicago , il , 
 usa ) .
we assumed a power of 90% 
 for a sample size of 19 patients and statistical significance of p < 0.05 , on 
 the basis of a previous study .
( ) scatter plots ( figure 3 ) were used in order to 
 classify patients according to the severity of at% . for at%950 and at%dm ,
in addition , 
 at%950 values of 1 - 5% were considered to indicate moderate disease expression , and 
 at%950 values > 5% were considered to indicate severe disease expression . 

moreover , at%dm values of 1 - 10% were considered to indicate moderate disease 
 expression , and at%dm values > 10% were considered to indicate severe disease 
 expression .
the magnitude of variability in at%950 and at%dm guided the selection of 
 values to differentiate between moderate and severe disease expression ( figure 3 ) .  

figure 3 scatter plot illustrating the distribution of patients according to 
 the percentage of air trapping relative to total lung volume ( at% ) , 
 which was calculated for a fixed threshold of 950 hu ( at%950 ) and for 
 thresholds set by subjective analysis based on density masks ( at%dm ) . 
 note that at%dm allows better discrimination among the grades of disease 
 severity ( i.e. , grade 1 , normal / mild ; grade 2 , moderate ; and grade 3 , 
 severe ) , especially for moderate disease ( at% > 1% ) and severe 
 disease ( at% > 10% ) .
note also that the stratification of disease 
 severity changed from normal / mild to moderate in 1 patient ( case 10 ) and 
 from moderate to severe in 1 patient ( case 14 ) depending on the method 
 for selectin g the threshold . 
 
figure 4 distribution of the observations of the percentage of air trapping 
 relative to total lung volume ( at% ) , calculated for a fixed threshold of 
 950 hu - at%950-(red squares ) and for thresholds selected with the aid of 
 density masks - at%dm-(blue squares ) , including the corresponding linear 
 regression lines .
the distribution suggests that patients with fev1% 
 above 70% had only mild anatomical damage as measured by quantification 
 of areas of air trapping or hyperinflation .
some patients with fev1% in 
 the range of 50% or less had only mild disease as measured by at%950 , a 
 finding that highlights the limitations of a threshold of 950 hu for 
 the assessment of patients with obliterative bronchiolitis .
the 
 correlation between fev1% and at%dm was much better , as shown by the 
 regression line . 

of the 19 patients , 2 had normal clinical scores , 7 had clinical scores < 5 
 ( including the two patients with clinical scores = 0 ) , 6 had scores of 5 - 10 , and 6 
 had scores > 10 . in the evaluation of the nutritional status , 8 patients had z 
 scores < 0 .  
regarding 6mwt parameters , mean so2 at rest was 96  2% ( range , 92 - 99% ) , 
 and mean 6mwt_so2 was 92  4% ( range , 83 - 99% ) .
we found no correlation 
 between so2 at rest and so2 during exercise ( r = 0.00 ) .
mean 
 desaturation during exercise ( measured by calculating the difference between 
 so2 at rest and 6mwt_so2 ) was 4  4% ( range , 2% to 15% ) . 

the mean six - minute walk distance ( 6mwd ) was 552  131 m ( range , 90 - 705 m ) .
the 6mwd 
 correlated significantly with 6mwt_so2 ( r = 0.52 ; p < 0.05 ) and 
 desaturation during exercise ( r = 0.58 ; p < 0.05 ) but not with so2 
 at rest ( r = 0.26 ; p > 0.05 ) . regarding pulmonary function parameters ,
mean fvc 
 was 75  20% ( range , 43 - 106% ) , mean fev1% was 58  20% ( range , 36 - 100% ) , 
 and mean fev1/fvc was 72  16% ( range , 49 - 107% ) .
regarding ct densitovolumetry parameters , mean tlv was 3,009  1,184 ml ( range , 
 1,252 - 6,673 ml ) .
the 6mwd was longer in those with larger normal lung volumes ( r = 
 0.53 ) .
mean shrink volume was 1,174  789 ml ( range , 182 - 3,471 ml ) , and mean 
 percentage of shrink volume was 36  13% ( range , 9 - 63% ) .
mean at%dm was 7.28  9% 
 ( range , 0.03 - 24.67% ) , and mean at%950 was 2.4  3% ( range ,
in 9 , 5 , and 
 5 of the 19 patients , at%dm was classified as normal or mild , moderate , and severe , 
 respectively ( points above the gray line in figure 
 3 ) . in 10 , 5 , and 4 of the 19 patients , at%950 was classified as normal 
 or mild , moderate , and severe , respectively ( points above the blue line in figure 3 ) .
we found a correlation between at%dm 
 and at%950 , as evidenced by r = 0.83 ( or r = 0.93 after the exclusion of one 
 outlier ) .
no significant correlation was found between the percentage of shrink 
 volume and at%dm or between the percentage of shrink volume and at%950 .  
the correlations of ct densitovolumetry parameters with clinical scores , pulmonary 
 function test results , and 6mwt parameters are summarized in table 1 .
table 1 shows 
 the correlation values for each parameter before and after the exclusion of 
 outliers .
an uncommon and severe form of chronic obstructive lung disease in children and 
 adults , ob results from lower respiratory tract injury .
( ) the diagnosis of postinfectious ob in children is 
 based on a history of lower respiratory tract infection ( usually an acute viral 
 infection ) , followed by persistent chronic obstructive lung disease .
( , ) hrct is an excellent method for the identification of 
 anatomical damage following the onset of the disease , such damage including areas of 
 low attenuation , areas of consolidation / atelectasis , bronchial wall thickening , 
 bronchiectasis , and mosaic perfusion .
in addition , expiratory hrct scans can assist 
 in confirming the presence of at .
however , hrct allows only a subjective assessment 
 of the extent of the disease and is dependent on the experience and skill of 
 radiologists .
( , ) our study demonstrated that the 
 6mwd was longer in patients with larger normal lung ( r = 0.53 ) .
in addition , we 
 found that at%950 showed significant correlations ( before and after the exclusion of 
 outliers , respectively ) with the clinical score ( r = 0.72 ; 0.80 ) , fvc ( r = 0.24 ; 
 0.59 ) , fev1 ( r = 0.58 ; 0.67 ) , and fev1/fvc ( r = 0.53 ; r = 0.62 ) , as did at%dm 
 with the clinical score ( r = 0.58 ; r = 0.63 ) , so2 at rest ( r = 0.40 ; r = 0.61 ) , 
 6mwt_so2 ( r = 0.24 ; r = 0.55 ) , fvc ( r = 0.44 ; r = 0.80 ) , fev1 ( r = 0.65 ; r = 
 0.71 ) , and fev1/fvc ( r = 0.41 ; r = 0.52 ) .
these data suggest that objective ct 
 measurements adequately represent clinical scores and functional impairment in ob .  
ct densitovolumetry has been proven to overcome this limitation and is a standard 
 recommendation for the quantification of other lung diseases in which the proportion 
 between pulmonary air and the lung parenchyma is increased , therefore decreasing 
 lung density .
( , ) areas of decreased attenuation 
 can also result from decreased perfusion of hypoventilated alveoli distal to 
 obstructed bronchioles .
the main finding on expiratory ct scans is a geographic 
 heterogeneity of lung attenuation ( mosaic attenuation pattern ) , which is seen in 
 40 - 80% of patients .
( , ) the abnormalities can be subtle 
 on inspiratory ct scans , being usually easier to detect on expiratory ct 
 scans .
( ) in a previous study 
 of the correlation between pulmonary function abnormalities and the extent of hrct 
 features of ob , significant relationships were found only between fev1 
 and the number of bronchopulmonary segments affected by bronchiectasis .
( ) confirmed that the extent of 
 decreased attenuation was independently associated with a reduction in 
 fev1 . in contrast , bronchial wall thickening was independently 
 associated with the presence of at ( as measured by rv / tlc ) . in patients with 
 sauropus
androgynus - associated ob , pulmonary function test results were more closely 
 correlated with at than with any other ct parameter .
( ) to our knowledge , the present study is the first to 
 demonstrate significant correlations of at% with clinical scores and pulmonary 
 function test results .
the quantification of areas of abnormally low attenuation is 
 an important diagnostic tool for ob , and the technique has substantial advantages 
 over the traditional subjective assessment of hrct images.(- ) the quantification of anatomical damage is important in 
 patients with ob ; ct densitovolumetry can measure lung volumes directly and 
 therefore aid clinicians in making decisions regarding patient quarantining and the 
 aggressiveness of treatment .   in the present study ,
clinical scores were moderately correlated with fvc and 
 fev1/fvc ( r ~ 0.5 ) . although there was a stronger correlation between 
 clinical scores and fev1 ( r = 0.8 ) , these findings are possibly biased 
 because pulmonary function test results were included in the clinical score 
 parameters . additionally , both measures of at% were significantly correlated with 
 clinical scores ( r  0.6 ) ; the strength of those correlations increased when 
 outliers were eliminated ( censored at%950 , r = 0.8 ) , which suggests that it might 
 increase further in larger series .
we found that inspiratory ct scans were much more 
 informative than expiratory ct scans regarding the presence of at .
the extent of at 
 areas might have been underestimated on the expiratory ct scans because of the 
 higher expiratory lung density .
the 950 hu threshold was validated for emphysema 
 quantification in adult patients , and we used it in the present study despite our 
 conviction that segmentation at this level would result in an underestimation of 
 areas of low attenuation in children , especially in the absence of 
 hyperinflation / emphysema .
( ) 
 although histopathological findings were unavailable for our patients , previous 
 studies ( , ) have examined correlations 
 between imaging findings and histopathological findings in patients with ob . in 
 addition
, our clinical score has yet to be validated , its clinical application 
 requiring further investigation .   in conclusion , anatomical damage to the lungs as measured by ct ( i.e. , at% ) 
 correlated significantly with clinical scores and pulmonary function test results . 

after our censoring of extreme values , at%dm showed stronger correlations than did 
 at%950 .
  determinar as correlaes entre o volume de aprisionamento areo em relao 
 ao volume pulmonar total ( aa% ) e parmetros clnicos e funcionais em 
 crianas com bronquiolite obliterante ( bo ) .
  tcnicas de ps - processamento de imagem foram usadas em imagens de tc de 19 
 crianas com bo para quantificar aa% por meio de um limiar fixo de 950 uh 
 ( aa%950 ) e de limiares selecionados por meio de mscaras de densidade 
 ( aa%md ) .
os pacientes foram divididos em trs grupos , de acordo com a 
 gravidade de aa% .
foram examinadas as correlaes entre aa% e a saturao de 
 oxignio ( so2 ) em repouso , a distncia percorrida no teste de 
 caminhada de seis minutos ( dtc6 ) , a so2 mnima durante o teste de 
 caminhada de seis minutos ( so2_tc6 ) , a cvf , o vef1 , a 
 relao vef1/cvf e parmetros clnicos .
  a dtc6 foi maior nos pacientes com maiores volumes pulmonares normais ( r = 
 0,53 ) . na amostra como um todo , encontramos ( antes e depois da excluso de 
 valores extremos , respectivamente ) , correlaes estatisticamente 
 significativas entre aa%950 e o escore clnico ( r = 0,72 ; 0,80 ) , a cvf ( r = 
 0,24 ; 0,59 ) , o vef1 ( r = 0,58 ; 0,67 ) e a relao 
 vef1/cvf ( r = 0,53 ; r = 0,62 ) , bem como entre aa%md e o 
 escore clnico ( r = 0,58 ; r = 0,63 ) , a so2 em repouso ( r = 0,40 ; 
 r = 0,61 ) , a so2_tc6 ( r = 0,24 ; r = 0,55 ) , a cvf ( r = 0,44 ; r 
 = 0,80 ) , o vef1 ( r = 0,65
; r = 0,71 ) e a relao 
 vef1/cvf ( r = 0,41 ; r = 0,52 ) .
  os resultados deste estudo mostram que aa% correlaciona - se 
 significativamente com escores clnicos e testes de funo pulmonar em 
 crianas com bo .
a bronquiolite obliterante ( bo ) ps - infecciosa  uma forma incomum e grave de 
 doena pulmonar obstrutiva crnica que ocorre em crianas aps uma agresso ao 
 trato respiratrio inferior .
( ) no tocante ao diagnstico , no h sinais ou sintomas 
 especficos de bo ps - infecciosa .
achados clnicos e de imagem so usados em 
 conjunto com resultados de testes laboratoriais para identificar a causa e 
 descartar outras formas de doena pulmonar crnica .
os critrios diagnsticos 
 para bo ps - infecciosa so os seguintes : bronquiolite aguda grave / pneumonia 
 viral durante os 3 primeiros anos de vida em crianas previamente saudveis ; 
 evidncia de obstruo persistente das vias areas aps o evento agudo , 
 identificada por meio de exame fsico , teste de funo pulmonar ou ambos ; 
 achados de doena pulmonar obstrutiva na radiografia de trax ; padro em mosaico 
 e aprisionamento areo ( aa ) na tc de trax e excluso de outras doenas 
 pulmonares crnicas que progridem para sintomas respiratrios permanentes .
( , ) histologicamente , a bo  caracterizada pela presena de tampes de tecido de 
 granulao no lmen das pequenas vias areas , destruio completa das pequenas 
 vias areas ou ambas .
( ) 
 mauad et al . ( ) mostraram que 
 a bo  histologicamente caracterizada por um padro constritivo com diversos 
 graus de inflamao e obliterao das vias areas , desde inflamao bronquiolar 
 mnima at obliterao completa dos bronquolos e brnquios por tecido 
 fibrtico .
sinais indiretos de obstruo , tais como acmulo de macrfagos , 
 bronquiectasia , acmulo de muco e hiperinsuflao , esto sempre presentes .  
embora vrias revises tenham examinado as sequelas em longo prazo da pneumonia 
 por adenovrus , ( , ) poucos estudos examinaram os 
 achados tomogrficos em crianas com bo .
( , ) alguns desses estudos relataram que achados tomogrficos 
 anormais nessas crianas podem predizer a presena de funo pulmonar anormal 
 anos mais tarde .
( ) relatou - se que a tcar  uma importante ferramenta diagnstica para avaliar o dano 
 pulmonar em pacientes com bo .
( ) o volume de um rgo ( ou o volume de partes anormais 
 de um rgo ) pode ser determinado por meio de imagens de tc helicoidal e valores 
 do coeficiente de atenuao ou densidades na escala de hounsfield , em unidades 
 hounsfield ( uh ) .
esse mtodo  conhecido como densitometria e anlise 
 volumtrica pulmonar por tc ou densitovolumetria pulmonar por tc ( , ) e pode ser usado para medir o volume de reas 
 pulmonares com baixa atenuao ( ou seja , aa ) e o volume pulmonar total ( vpt ) em 
 crianas com bo .
alm disso , pode ser usado para medir a porcentagem de aa em 
 relao ao vpt ( aa% ) por meio de limiares para diferenciar reas pulmonares 
 normais de reas de bo .
demonstrou - se que aa% contribui sobremaneira para a 
 obstruo ao fluxo areo persistente e crnica na asma .
( ) a funo pulmonar permanece anormal durante longos perodos aps um episdio de 
 bo .
( , ) o curso clnico aps o 
 aparecimento de bo  varivel e depende do volume do tecido pulmonar afetado . 

( ) medidas do estado 
 clnico e da capacidade de realizar atividades fsicas intensas - medidas como o 
 nmero de internaes hospitalares ou de dias de aula perdidos , a distncia 
 percorrida em testes de caminhada , o estado nutricional e a saturao de 
 oxignio ( so2 ) em repouso ou durante o exerccio - facilitam a 
 seleo de intervenes clnicas apropriadas .
( , ) como o prognstico dos pacientes com bo depende no s de 
 seu comportamento , mas tambm do comprometimento funcional e da extenso do dano 
 anatmico , os clnicos devem reunir informaes sobre o tipo de anormalidade 
 anatmica e sua extenso .
bronquiectasia , atelectasia , colapso lobar e reas de 
 baixa densidade so conhecidas consequncias da bo ps - infecciosa , e a tcar  o 
 melhor mtodo para examinar tais leses , ( , , ) as 
 quais podem influenciar o estado clnico dos pacientes e seu desempenho nos 
 testes de funo pulmonar .
( , , ) 
 estudos anteriores demonstraram que reas de baixa atenuao correlacionam - se 
 bem com os resultados de testes de funo pulmonar em pacientes com aa de causas 
 variadas .
( - ) no entanto , at onde 
 sabemos , nenhum estudo mostrou uma correlao entre achados de densitovolumetria 
 pulmonar por tc e funo pulmonar em crianas com bo .
( , , ) nosso objetivo foi descrever a correlao entre o volume de reas de aa e os 
 resultados de testes de funo pulmonar em crianas com bo
. alm disso , 
 comparamos os valores de aa% aos valores de so2 , aos resultados dos 
 testes de funo pulmonar , e aos escores clnicos observados nessas crianas , na 
 tentativa de obter critrios objetivos de medio de bo .
trata - se de um estudo prospectivo incluindo todas as crianas que foram atendidas 
 em nossa clnica de bo ps - infecciosa durante mais de 5 anos e que apresentavam 
 bo clinicamente estvel e incio dos sintomas antes da idade de 2 anos
. o 
 protocolo do estudo foi aprovado pelo comit de tica em pesquisa da 
 instituio , e todos os pais ou responsveis assinaram um termo de consentimento 
 livre e esclarecido .  
o diagnstico de bo baseou - se na identificao de sintomas respiratrios 
 obstrutivos crnicos aps um episdio de infeco do trato respiratrio inferior 
 antes da idade de 2 anos em crianas anteriormente saudveis .
( , ) todos os diagnsticos clnicos foram 
 confirmados por achados caractersticos em tcar contempornea .
os critrios de incluso foram os seguintes ( ) : bronquiolite aguda / pneumonia viral antes dos 2 
 anos de idade em crianas previamente saudveis ; evidncia de obstruo 
 persistente das vias areas aps o evento agudo , identificada por meio de exame 
 fsico , teste de funo pulmonar ou ambos e sem resposta a pelo menos 2 semanas 
 de tratamento com corticosteroides sistmicos e broncodilatadores ; achados 
 radiolgicos de doena pulmonar obstrutiva , incluindo hiperinsuflao , 
 atelectasia , espessamento das paredes brnquicas e bronquiectasia , alm de 
 padro de perfuso em mosaico e aa na tc ; ausncia de outras doenas pulmonares 
 crnicas que progridem para sintomas respiratrios persistentes , incluindo 
 tuberculose , fibrose cstica , displasia broncopulmonar , imunodeficincias , asma 
 e deficincia grave de alfa-1 antitripsina .
os critrios de excluso foram os 
 seguintes : incapacidade de se submeter aos testes de funo pulmonar ou  tc sem 
 sedao ; incapacidade de segurar a respirao durante todo o exame de tc ; 
 exacerbao da doena < 30 dias antes da tc ou dos testes de funo 
 pulmonar ; presena de outras doenas pulmonares e necessidade de oxigenoterapia 
 contnua .   um total de 25 pacientes com bo preencheram os critrios de incluso .
desses 25 
 pacientes , 6 foram excludos ( porque no foram capazes de realizar as manobras 
 respiratrias necessrias ) . a amostra final foi composta por 19 crianas ( 14 do 
 sexo masculino e 5 do feminino ) de 7 - 15 anos de idade ( mdia : 10  2,5 anos )
.   todos os pacientes realizaram espirometria e teste de caminhada de seis minutos 
 ( tc6 ) em conformidade com relatos anteriores .
( , ) a espirometria foi realizada com um espirmetro 
 vitalograph alpha ( vitalograph , buckingham , reino unido ) antes e 10 min depois 
 da administrao de 300 g de salbutamol inalatrio ( aerolin ; 
 glaxosmithkline plc , ware , reino unido ) com um espaador valvulado 
 ( fisonair ; glaxosmithkline plc ) .
como o tc6 foi realizado aps a espirometria 
 ( e no mesmo dia que esta ) , todos os pacientes usaram salbutamol antes do tc6 .  
o escore clnico incluiu os seguintes itens : 1 ) estado nutricional ( ) ( escore z : 0 = bom estado 
 nutricional ; 1 = desnutrio leve ; 2 = desnutrio moderada e 3 = desnutrio 
 grave ) ; 2 ) tosse durante a remisso ( 0 = ausente e 1 = presente ) ; 3 ) tosse 2 
 semanas antes do exame ( 0 = ausente e 1 = presente ) ; 4 ) sibilncia durante a 
 remisso ( 0 = ausente e 1 = presente ) ; 5 ) sibilncia na maioria dos dias da 
 semana ( 0 = ausente e 1 = presente ) ; 6 ) sibilncia nas ltimas 2 semanas ( 0 = 
 ausente e 1 = presente ) ; 7 ) dificuldade para respirar nas 2 semanas anteriores 
 ao exame ( 0 = ausente e 1 = presente ) ; 8) frequncia de exacerbaes nos ltimos 
 6 meses ( 0 = sem exacerbaes ; 1 = exacerbaes espordicas ; 2 = exacerbaes a 
 cada 2 meses ; 3 = exacerbaes todos os meses e 4 = exacerbaes todas as 
 semanas ) ; 9 ) aumento do dimetro anteroposterior do trax ( 0 = ausente e 1 = 
 presente ) ; 10 ) so2 em repouso ( > 95% = 0 ; 90 - 94% = 1 e < 
 90% = 2 ) ; 11 ) so2 mnima durante o tc6 ( so2_tc6 ; > 
 95% = 0 ; 90 - 94% = 1 e < 90% = 2 ) , a dessaturao mdia durante o exerccio 
 sendo medida por meio do clculo da diferena entre so2 em repouso e 
 so2_tc6 ; 12 ) dessaturao > 4% durante o tc6 ( 0 = negativo e 
 1 = positivo ) ; 13 ) relao vef1/cvf e 14 ) vef1 em 
 porcentagem do previsto ( vef1% ; > 80% = 0 ; 61 - 80% = 1 ; 41 - 60% = 
 2 ; < 41% = 3 ) .  
todos as imagens de tc foram adquiridas com a dose de radiao mais baixa 
 possvel e um tomgrafo helicoidal disponvel comercialmente ( xvision ex ; 
 toshiba medical systems corporation , otawara , japo ) e foram ps - processadas em 
 uma estao de trabalho ( o2 ; sgi , fremont , ca , eua ) com software 
 para reconstruo tridimensional ( alatoview ; toshiba medical systems 
 corporation ) . o tomgrafo foi calibrado periodicamente , conforme recomendado 
 pelo fabricante .
um conjunto inicial de nove imagens de tcar axial ( com 1 mm de 
 colimao em incrementos de 20 mm ) foi adquirido por meio de um algoritmo de 
 alta frequncia .
essas imagens de tcar foram avaliadas por dois radiologistas 
 torcicos com mais de 10 anos de experincia em tc de trax . a deciso final foi 
 tomada por consenso .  
dois conjuntos adicionais de imagens foram adquiridos pelo tomgrafo helicoidal 
 durante manobras de pausa respiratria nica ( durante a inspirao e a 
 expirao ) .
para reduzir o nmero de artefatos causados pelo movimento 
 respiratrio , a tc helicoidal foi realizada no sentido caudocranial .
anteriores,(- ) foram usados os seguintes 
 parmetros : colimao = 10 mm ; velocidade da mesa = 14 mm / rotao 
 ( pitch = 1.4 ) e baixa dose de radiao ( 120 kv e 50 mas ) . a 
 mdia da dose total de radiao foi de 5  1,3 msv .
usamos cortes tomogrficos 
 helicoidais de 10 mm , mas baixa e pitch elevado para reduzir a 
 exposio  radiao .
um algoritmo de reconstruo convencional foi usado para 
 evitar os efeitos de filtros de realce de bordas sobre a densidade do 
 tecido .
o primeiro passo da densitovolumetria pulmonar por tc foi a segmentao pulmonar 
 para medir o vpt .
dois passos de segmentao foram aplicados a cada conjunto de 
 imagens tomogrficas helicoidais antes do clculo do vpt .
os pulmes foram 
 isolados por meio da eliminao de qualquer estrutura com densidade superior a 
 250 uh dos dados de imagem .
posteriormente , eliminamos o ar dentro do abdome e 
 fora do paciente ( ar no pulmonar ) selecionando regies de interesse com o 
 software de reconstruo tridimensional . as regies de interesse foram 
 selecionadas por meio de uma linha desenhada entre o pulmo e o ar no pulmonar 
 em cada corte .
diferentes programas de reconstruo tridimensional , 
 indisponveis para ns durante o perodo de estudo , podem incluir ferramentas 
 diferentes para a segmentao pulmonar . a fim de
reduzir a variabilidade 
 atribuda ao operador , o ar dentro da traqueia ou dos brnquios principais foi 
 considerado ar pulmonar em vez de ser excludo .
o operador avaliou a preciso da 
 segmentao por meio da reviso da imagem tridimensional do pulmo gerada pela 
 reconstruo volumtrica ( figura 1 ) . o 
 software ento calculou o vpt automaticamente .  

figura 1 em a , imagem tomogrfica coronal reformatada ( projeo de 
 intensidade mnima ) mostrando aprisionamento areo
. em b , tc com 
 reconstruo tridimensional mostrando volumes de baixa atenuao , 
 que representam volumes de aprisionamento areo . 
 
para medir o volume do parnquima pulmonar com valores de atenuao anormalmente 
 baixos , reas de atenuao ou densidade extremamente baixa foram consideradas 
 anormais , em virtude da desproporo entre o volume do parnquima pulmonar 
 ( incluindo o tecido intersticial , vasos , sangue , linfa , lquido intersticial e 
 paredes das vias areas ) e o ar nessas regies . a fim de simplificar a medio , 
 consideramos " volume de aa " o volume total de zonas pulmonares com valores de 
 densidade extremamente baixos .  
primeiro calculamos o volume pulmonar 
 afetado por aa usando um limiar fixo de 950 uh ( aa%950 ) .
( ) 
 qualquer poro dos pulmes com densidade inferior a 950 uh foi considerada 
 afetada por aa .
para calcular aa%950 , o volume de aa calculado com esse limiar 
 foi dividido pelo vpt .
o prximo passo foi calcular aa% com limiares selecionados por meio de mscaras 
 de densidade .
no h limiares validados para a determinao do volume de 
 hiperinsuflao , aa ou enfisema em crianas .
como o limiar de 950 uh pode 
 subestimar a extenso da doena nessa populao , tambm calculamos o volume de 
 aa com um limiar selecionado para cada paciente com o auxlio de uma mscara de 
 densidade . o limiar foi ajustado at que a mscara correspondesse a nossa 
 impresso visual subjetiva a respeito de pores pulmonares afetadas ( figura 2 )
aps o uso de um limiar , o ar 
 dentro e fora dos pulmes  isolado .
em a , imagem de tc axial 
 mostrando o ar dentro e fora dos pulmes .
em c , reconstruo tridimensional 
 do volume pulmonar total aps a excluso do ar fora dos 
 pulmes . 
 
para calcular o volume de encolhimento ( desinsuflao ) pulmonar , o vpt medido em 
 imagens adquiridas durante a expirao foi subtrado do vpt medido em imagens 
 adquiridas durante a inspirao . a porcentagem de volume de encolhimento era 
 considerada excelente se > 50% , razovel / boa se = 30 - 50% e ruim se < 
 30% .  
para a anlise estatstica , os resultados dos testes foram inseridos em um banco 
 de dados
a 
 anlise foi feita com o programa statistical package for the social 
 sciences , verso 11 ( spss inc . ,
assumiu - se um poder de 
 90% para uma amostra de 19 pacientes e significncia estatstica de p < 
 0,05 , com base em um estudo anterior .
( ) grficos de disperso ( figura 3 ) foram 
 usados para classificar os pacientes de acordo com a gravidade de aa% .
valores de aa%950 de 1 - 5% foram considerados 
 indicativos de moderada expresso da doena , e valores > 5% foram 
 considerados indicativos de grave expresso da doena .
alm disso , valores de 
 aa%md de 1 - 10 % foram considerados indicativos de moderada expresso da doena , 
 e valores > 10% foram considerados indicativos de grave expresso da 
 doena . a magnitude da
variabilidade de aa%950 e aa%md orientou a seleo de 
 valores para distinguir doena moderada de doena grave ( figura 3 ) .  

figura 3 grfico de disperso ilustrando a distribuio dos pacientes de 
 acordo com a porcentagem de aprisionamento areo em relao ao 
 volume pulmonar total ( aa% ) , calculada com um limiar fixo de 950 uh 
 ( aa%950 ) e com limiares estabelecidos por anlise subjetiva baseada 
 em mscaras de densidade ( aa%md ) . nota - se que aa%md permite melhor 
 discriminao dos graus de gravidade da doena ( ou seja , grau 1 , 
 normal / leve ; grau 2 , moderada e grau 3 , grave ) , especialmente doena 
 moderada ( aa% > 1% ) e grave ( aa% > 10% ) .
de normal / leve para 
 moderada em 1 paciente ( caso 10 ) e de moderada para grave em 1 
 paciente ( caso 14 ) dependendo do mtodo usado para selecionar o 
 limiar . 
 
todas as variveis foram analisadas por meio do coeficiente de correlao 
 produto - momento de pearson .
as correlaes foram determinadas antes e depois da 
 excluso de valores extremos ( figura 4 ) . 

os valores de r e p foram calculados separadamente para dados censurados e no 
 censurados .
foram tambm calculadas as correlaes com os resultados dos testes 
 de funo pulmonar e escores clnicos .  

figura 4 distribuio das observaes da porcentagem de aprisionamento 
 areo em relao ao volume pulmonar total ( aa% ) , calculada com um 
 limiar fixo de 950 uh - at%950 - ( quadrados vermelhos ) e com 
 limiares selecionados com o auxlio de mscaras de densidade - aa%md 
 - ( quadrados azuis ) , incluindo as linhas de regresso linear 
 correspondentes .
a distribuio sugere que os pacientes com vef1% 
 acima de 70% apresentavam dano anatmico leve conforme medido pela 
 quantificao das reas de aprisionamento areo ou hiperinsuflao . 

alguns pacientes com vef1% na faixa de 50% ou menos tinham doena 
 leve conforme medida por aa%950 , um achado que evidencia as 
 limitaes do limiar de 950 uh para avaliar pacientes com 
 bronquiolite obliterante . a correlao entre vef1% e aa%md foi muito 
 melhor , como mostra a linha de regresso . 

dos 19 pacientes , 2 apresentaram escores clnicos normais , 7 apresentaram escores 
 clnicos < 5 ( incluindo os dois pacientes com escore clnico = 0 ) , 6 
 apresentaram escores de 5 - 10 e 6 apresentaram escores > 10 .
na avaliao do 
 estado nutricional , 8 pacientes apresentaram escore z < 0 .   no tocante
aos parmetros do tc6 , a mdia da so2 em repouso foi de 96 
  2% ( variao : 92 - 99% ) , e a mdia da so2_tc6 foi de 92  4% 
 ( variao : 83 - 99% ) .
no encontramos nenhuma correlao entre so2 em 
 repouso e so2 durante o exerccio ( r = 0,00 ) . a dessaturao mdia 
 durante o exerccio ( medida por meio do clculo da diferena entre 
 so2 em repouso e so2_tc6 ) foi de 4  4% ( variao : 2% 
 a 15% ) . a mdia da distncia percorrida no tc6 ( dtc6 ) foi de 552  131 m 
 ( variao : 90 - 705 m ) . a dtc6 correlacionou - se significativamente com 
 so2_tc6 ( r = 0,52 ; p < 0,05 ) e dessaturao durante o 
 exerccio ( r = 0,58 ; p < 0,05 ) , mas no com so2 em repouso ( r = 
 0,26 ; p > 0,05 ) .
no tocante aos parmetros de funo pulmonar , a mdia da 
 cvf foi de 75  20% ( variao : 43 - 106% ) , a mdia do vef1% foi de 58  
 20% ( variao : 36 - 100% ) e a mdia da relao vef1/cvf foi de 72  16% 
 ( variao : 49 - 107% ) .  
no tocante aos parmetros da densitovolumetria pulmonar por tc , a mdia do vpt 
 foi de 3.009  1.184 ml ( variao : 1.252 - 6.673 ml ) . a dtc6 foi maior nos 
 pacientes com maiores volumes pulmonares normais ( r = 0,53 )
. a mdia do volume 
 de encolhimento foi de 1.174  789 ml ( variao : 182 - 3.471 ml ) , e a mdia da 
 porcentagem do volume de encolhimento foi de 36  13% ( variao : 9 - 63% ) . a mdia 
 de aa%md foi de 7,28  9% ( variao : 0,03 - 24,67% ) , e a mdia de aa%950 foi de 
 2,4  3% ( variao : 0,03 - 8,67% ) .
em 9 , 5 e 5 dos 19 pacientes , aa%md foi 
 classificada em normal ou leve , moderada e grave , respectivamente ( pontos acima 
 da linha cinza na figura 3 ) . em 10 , 5 e 4 
 dos 19 pacientes , aa%950 foi classificada em normal ou leve , moderada e grave , 
 respectivamente ( pontos acima da linha azul na figura 3 ) .
encontramos uma correlao entre aa%md e aa%950 , 
 evidenciada por r = 0,83 ( ou r = 0,93 , aps a excluso de um valor extremo ) .
no 
 encontramos correlao significativa entre a porcentagem do volume de 
 encolhimento e aa%md ou entre a porcentagem do volume de encolhimento e aa%950 .   as correlaes dos parmetros de densitovolumetria pulmonar por tc com os escores 
 clnicos , resultados dos testes de funo pulmonar e parmetros do tc6 esto 
 resumidas na tabela 1 .
a tabela 1 mostra os valores de correlao 
 para cada parmetro , antes e depois da excluso de valores extremos . a figura 4 ilustra as correlaes de aa%md e 
 aa%950 com os parmetros no densitomtricos .  

a bo  uma forma incomum e grave de doena pulmonar obstrutiva crnica em 
 crianas e adultos que resulta de uma agresso ao trato respiratrio 
 inferior .
( ) o diagnstico 
 de bo ps - infecciosa em crianas baseia - se em uma histria de infeco do trato 
 respiratrio inferior ( geralmente uma infeco viral aguda ) seguida de doena 
 pulmonar obstrutiva crnica persistente .
( , ) a tcar  um excelente mtodo para a identificao de dano 
 anatmico aps o incio da doena , incluindo reas de baixa atenuao , reas de 
 consolidao / atelectasia , espessamento das paredes brnquicas , bronquiectasia e 
 perfuso em mosaico .
alm disso , imagens de tcar expiratria podem ajudar a 
 confirmar a presena de aa .
no entanto , a tcar permite apenas uma avaliao 
 subjetiva da extenso da doena e depende da experincia e habilidade dos 
 radiologistas .
( , ) nosso estudo demonstrou que a 
 dtc6 foi maior em pacientes com maior pulmo normal ( r = 0,53 ) .
alm disso , 
 encontramos correlaes significativas ( antes e aps a excluso de valores 
 extremos , respectivamente ) entre aa%950 e o escore clnico ( r = 0,72 ; 0,80 ) , a 
 cvf ( r = 0,24 ; 0,59 ) , o vef1 ( r = 0.58 ; 0.67 ) e a relao 
 vef1/cvf ( r = 0,53 ; r = 0,62 ) , bem como entre aa%md e o escore 
 clnico ( r = 0,58 ; r = 0,63 ) , a so2 em repouso ( r = 0,40 ; r = 
 0,61 ) , a so2_tc6 ( r = 0,24 ; r = 0,55 ) , a cvf ( r = 0,44 ; r = 
 0,80 ) , o vef1 ( r = 0,65 ; r = 0,71 ) e a relao vef1/cvf 
 ( r = 0,41 ; r = 0,52 ) . esses dados sugerem que medidas tomogrficas objetivas 
 representam adequadamente escores clnicos e comprometimento funcional na bo .  
provou - se que a densitovolumetria pulmonar por tc supera essa limitao e  uma 
 recomendao - padro para a quantificao de outras doenas pulmonares nas quais 
 a proporo entre o ar pulmonar e o parnquima pulmonar  maior , diminuindo , 
 portanto , a densidade pulmonar .
( , ) 
 reas de atenuao reduzida tambm podem resultar da diminuio da perfuso de 
 alvolos hipoventilados distais aos bronquolos obstrudos . o principal achado 
 da tomografia expiratria  uma heterogeneidade geogrfica da atenuao pulmonar 
 ( padro de atenuao em mosaico ) , observado em 40 - 80% dos pacientes .
( , ) as alteraes podem ser sutis nas imagens de 
 tc inspiratria ; so geralmente mais fceis de detectar em imagens de tc 
 expiratria .
( ) em um 
 estudo anterior da correlao entre alteraes da funo pulmonar e a extenso 
 das caractersticas de bo na tcar , foram encontradas relaes significativas 
 somente entre vef1 e o nmero de segmentos broncopulmonares afetados 
 por bronquiectasia .
( ) confirmaram 
 que a extenso da diminuio da atenuao associou - se independentemente a uma 
 reduo do vef1 .
em contraste , o espessamento das paredes brnquicas 
 associou - se independentemente  presena de aa ( medida por vr / cpt ) .
em pacientes 
 com bo associada a sauropus androgynus , os resultados dos 
 testes de funo pulmonar correlacionaram - se mais com aa do que com qualquer 
 outro parmetro tomogrfico .
( ) at onde sabemos , o presente estudo  o primeiro a 
 demonstrar correlaes significativas entre aa% e escores clnicos e resultados 
 de testes de funo pulmonar .
a quantificao das reas de atenuao 
 anormalmente baixa  uma importante ferramenta para o diagnstico de bo , e a 
 tcnica tem vantagens substanciais sobre a tradicional avaliao subjetiva de 
 imagens de tcar.(- ) a quantificao do dano 
 anatmico  importante em pacientes com bo ; a densitovolumetria pulmonar por tc 
  capaz de medir volumes pulmonares diretamente e , portanto , ajudar os clnicos 
 a tomar decises sobre a quarentena de pacientes e a agressividade do 
 tratamento .  
no presente estudo , os escores clnicos correlacionaram - se moderadamente com a 
 cvf e a relao vef1/cvf ( r ~ 0,5 )
. embora a correlao entre os 
 escores clnicos e o vef1 tenha sido mais forte ( r = 0,8 ) , esses 
 resultados so possivelmente tendenciosos , pois os resultados dos testes de 
 funo pulmonar foram includos nos parmetros do escore clnico .
alm disso , 
 ambas as medidas de aa% correlacionaram - se significativamente com os escores 
 clnicos ( r  0,6 ) ; a fora dessas correlaes aumentou quando foram eliminados 
 os valores extremos ( aa%950 censurada : r = 0,8 ) , o que sugere que pode aumentar 
 ainda mais em sries maiores . as imagens de tc inspiratria foram muito mais 
 informativas que as de tc expiratria no tocante  presena de aa .
a extenso 
 das reas de aa pode ter sido subestimada nas imagens de tc expiratria por 
 causa da densidade pulmonar expiratria maior .
o limiar de 950 uh foi validado para a quantificao do 
 enfisema em pacientes adultos , e ns o usamos no presente estudo no obstante 
 nossa convico de que a segmentao nesse nvel resultaria em subestimao das 
 reas de baixa atenuao em crianas , especialmente na ausncia de 
 hiperinsuflao / enfisema .
( ) embora no tivssemos os achados histopatolgicos em 
 nossos pacientes , estudos anteriores ( , ) examinaram as correlaes entre achados de imagem e 
 achados histopatolgicos em pacientes com bo .
alm disso , nosso escore clnico 
 ainda no foi validado ; so necessrios mais estudos para sua aplicao clnica .  
em suma , o dano anatmico aos pulmes medido por meio de tc ( ou seja , aa% ) 
 correlacionou - se significativamente com escores clnicos e resultados de testes 
 de funo pulmonar .
aps a censura de valores extremos , aa%md apresentou 
 correlaes mais fortes do que aa%950 .
 objective : to determine whether air trapping ( expressed as the percentage of air 
 trapping relative to total lung volume [ at% ] ) correlates with clinical and 
 functional parameters in children with obliterative bronchiolitis ( ob ) . methods : ct scans of 19 children with ob were post - processed for at% quantification 
 with the use of a fixed threshold of 950 hu ( at%950 ) and of thresholds 
 selected with the aid of density masks ( at%dm ) . 
 patients were divided into 
 three groups by at% severity . 
 we examined at% correlations with oxygen 
 saturation ( so2 ) at rest , six - minute walk distance ( 6mwd ) , 
 minimum so2 during the six - minute walk test 
 ( 6mwt_so2 ) , fvc , fev1 , fev1/fvc , and 
 clinical parameters . 
 results : the 6mwd was longer in the patients with larger normal lung volumes ( r = 
 0.53 ) . 
 we found that at%950 showed significant correlations ( before and 
 after the exclusion of outliers , respectively ) with the clinical score ( r = 
 0.72 ; 0.80 ) , fvc ( r = 0.24 ; 0.59 ) , fev1 ( r = 0.58 ; 0.67 ) , and 
 fev1/fvc ( r = 0.53 ; r = 0.62 ) , as did at%dm with the 
 clinical score ( r = 0.58 ; r = 0.63 ) , so2 at rest ( r = 0.40 ; r = 
 0.61 ) , 6mwt_so2 ( r = 0.24 ; r = 0.55 ) , fvc ( r = 0.44 ; r = 
 0.80 ) , fev1 ( r = 0.65 ; r = 0.71 ) , and fev1/fvc ( r = 
 0.41 ; r = 0.52 ) . conclusions : our results show that at% correlates significantly with clinical scores and 
 pulmonary function test results in children with ob . 
Introduction
Methods
Results
Discussion
OBJETIVO:
MTODOS:
RESULTADOS:
CONCLUSES:
Introduo
Mtodos
Resultados
Discusso