bronchoscopic lung volume reduction ( blvr ) using endobronchial valves ( ebvs ) has been utilized in the treatment of copd with emphysema . this technique relieves the hyperinflation status and improves lung function , exercise capacity , and quality of life.1,2 the elements of successful blvr using ebvs include successful lobe occlusion and complete fissures.1,36 in addition to evaluating fissure integrity with computed tomography ( ct ) , the chartis system ( pulmonx inc . , redwood city , ca , usa ) can help physicians to detect collateral ventilation ( cv ) with high positive ( 71% ) and negative ( 83% ) predictive values . therefore , this system provides satisfactory evaluation of patients requiring lung volume reduction,7,8 with the exception of some situations , such as a low - flow chartis phenotype in the target lobe . few studies have focused on the low - flow chartis phenotype,911 and this condition has been attributed to a so - called  dynamic collapse  phenomenon . although the occurrence of  low flow  in chartis assessment has been documented , the effects of this phenomenon on the clinical outcomes of ebv - based blvr remain unclear . here , we report a case of blvr failure caused by latent cv between the right upper lobe ( rul ) and right middle lobe ( rml ) , which was masked by a low - flow chartis phenotype in the rul . this patient experienced significant clinical benefit after the elimination of the latent cv via the implantation of an ebv in the rml . the patient provided written informed consent to have the case report and any accompanying images published . a 63-year - old chinese male with copd was admitted to our hospital in october 2013 . the patient was an ex - smoker ( 40 pack - years ) , had suffered from secondary tuberculosis before 30 years , and had been taking salmeterol / fluticasone propionate ( 50/500 g ) twice daily for 2 years . pulmonary function tests administered on admission revealed severe irreversible airflow obstruction after bronchodilator inhalation ( forced expiratory volume in one second [ fev1]/forced vital capacity [ fvc ] = 46.9% ; fev1 = 0.89 l , 28.9% of predicted value ) and severe hyperinflation ( residual volume [ rv ] = 5.03 l , 222% of predicted value , total lung capacity [ tlc ] = 7.92 l , 131% of predicted value ) . additional tests revealed the following : 6-min walking distance ( 6mwd ) , 144 m ; st george respiratory questionnaire ( sgrq ) score , 64 ; and modified medical research council ( mmrc ) dyspnea score , 4 . analysis of the blood gases at ph 7.40 revealed the following : pao2 , 65.7 mmhg and paco2 , 42.1 mmhg . high - resolution chest ct ( hrct ) indicated heterogeneous emphysema with a marked predominance in the bilateral upper lobes and middle lobe ( figure 1a and b ) . the right oblique fissure was complete , and a peripheral minor defect was found on the horizontal fissure in the coronary and sagittal views ; however , we calculated the integrity of horizontal fissure to be 91.6% and 91% , respectively ( figure 1c and d ) . we performed a purified protein derivative test , erythrocyte sedimentation rate analysis , contrast ct , sputum smears , and cytopathology . no evidence of lung cancer or active secondary tuberculosis was present . with the patient s informed consent for blvr , we administered 0.5 mg atropine to minimize bronchial secretion and 50 mg pethidine to reduce the cough . we performed bronchoscopy using 20 ml lidocaine as a local anesthetic and measured the cv using the chartis system . we blocked the right upper bronchus using a balloon catheter and measured the expiratory airflow . this assessment revealed sudden stops in expiratory flow during the three breathing maneuvers that were accompanied by sharp increases in resistance , which is a common characteristic of the low - flow phenotype ( figure 1e ) . it was difficult to confirm whether cv was present ; therefore , we measured cv in the ipsilateral lobes . assessment of the middle lobe revealed that cv was negative or cv was positive with on / offs in expiratory flow that occurred during deeper and lower breathing maneuvers , which were signs of mini - collaterals that were open only during deeper inspirations ( figure 1f ) . assessment of the right lower lobe ( rll ) revealed a good signal with a gradual downward trend without cv ( figure 1 g ) . we implanted three ebvs ( zephyr ebv 4.0 ; pulmonx ) in the right upper bronchus for economic reasons . one month later , the patient exhibited limited improvements in lung function , 6mwd , and volume reduction of the rul on hrct ( figure 1h ) . we speculated that this lack of improvement might have been associated with latent cv between the rul and rml that caused a minor leak in the horizontal fissure . therefore , we decided to block the right middle bronchus using another ebv ( zephyr ebv 5.5 ) . two weeks later , quantitative analysis of the hrct images ( lung cad1.2 ; neusoft , shenyang , people s republic of china ) revealed that the volume of the right lung had decreased from 3,838 to 2,935 ml , the rul and rml had begun to shrink , the right diaphragm had become elevated , and the mediastinum had shifted to the right side ( figure 1i and j ) . the fev1 increased to 1.52 l ( + 0.63 l ) and the 6mwd increased to 216 m ( + 72 m ) ; in addition , the rv decreased to 4.21 l ( 16.3% ) , the tlc decreased to 7.10 l ( 10.4% ) , the sgrq score decreased to 41 , and the mmrc dyspnea score decreased to 2 . the patient reported slight chest pain after the second ebv implantation , and hrct revealed some pleural effusion , which was localized to the minor fissure and absorbed spontaneously . a 63-year - old chinese male with copd was admitted to our hospital in october 2013 . the patient was an ex - smoker ( 40 pack - years ) , had suffered from secondary tuberculosis before 30 years , and had been taking salmeterol / fluticasone propionate ( 50/500 g ) twice daily for 2 years . pulmonary function tests administered on admission revealed severe irreversible airflow obstruction after bronchodilator inhalation ( forced expiratory volume in one second [ fev1]/forced vital capacity [ fvc ] = 46.9% ; fev1 = 0.89 l , 28.9% of predicted value ) and severe hyperinflation ( residual volume [ rv ] = 5.03 l , 222% of predicted value , total lung capacity [ tlc ] = 7.92 l , 131% of predicted value ) . additional tests revealed the following : 6-min walking distance ( 6mwd ) , 144 m ; st george respiratory questionnaire ( sgrq ) score , 64 ; and modified medical research council ( mmrc ) dyspnea score , 4 . analysis of the blood gases at ph 7.40 revealed the following : pao2 , 65.7 mmhg and paco2 , 42.1 mmhg . high - resolution chest ct ( hrct ) indicated heterogeneous emphysema with a marked predominance in the bilateral upper lobes and middle lobe ( figure 1a and b ) . the right oblique fissure was complete , and a peripheral minor defect was found on the horizontal fissure in the coronary and sagittal views ; however , we calculated the integrity of horizontal fissure to be 91.6% and 91% , respectively ( figure 1c and d ) . we performed a purified protein derivative test , erythrocyte sedimentation rate analysis , contrast ct , sputum smears , and cytopathology . no evidence of lung cancer or active secondary tuberculosis was present . with the patient s informed consent for blvr , we administered 0.5 mg atropine to minimize bronchial secretion and 50 mg pethidine to reduce the cough . we performed bronchoscopy using 20 ml lidocaine as a local anesthetic and measured the cv using the chartis system . we blocked the right upper bronchus using a balloon catheter and measured the expiratory airflow . this assessment revealed sudden stops in expiratory flow during the three breathing maneuvers that were accompanied by sharp increases in resistance , which is a common characteristic of the low - flow phenotype ( figure 1e ) . it was difficult to confirm whether cv was present ; therefore , we measured cv in the ipsilateral lobes . assessment of the middle lobe revealed that cv was negative or cv was positive with on / offs in expiratory flow that occurred during deeper and lower breathing maneuvers , which were signs of mini - collaterals that were open only during deeper inspirations ( figure 1f ) . assessment of the right lower lobe ( rll ) revealed a good signal with a gradual downward trend without cv ( figure 1 g ) . we implanted three ebvs ( zephyr ebv 4.0 ; pulmonx ) in the right upper bronchus for economic reasons . one month later , the patient exhibited limited improvements in lung function , 6mwd , and volume reduction of the rul on hrct ( figure 1h ) . we speculated that this lack of improvement might have been associated with latent cv between the rul and rml that caused a minor leak in the horizontal fissure . therefore , we decided to block the right middle bronchus using another ebv ( zephyr ebv 5.5 ) . two weeks later , quantitative analysis of the hrct images ( lung cad1.2 ; neusoft , shenyang , people s republic of china ) revealed that the volume of the right lung had decreased from 3,838 to 2,935 ml , the rul and rml had begun to shrink , the right diaphragm had become elevated , and the mediastinum had shifted to the right side ( figure 1i and j ) . the fev1 increased to 1.52 l ( + 0.63 l ) and the 6mwd increased to 216 m ( + 72 m ) ; in addition , the rv decreased to 4.21 l ( 16.3% ) , the tlc decreased to 7.10 l ( 10.4% ) , the sgrq score decreased to 41 , and the mmrc dyspnea score decreased to 2 . the patient reported slight chest pain after the second ebv implantation , and hrct revealed some pleural effusion , which was localized to the minor fissure and absorbed spontaneously . the absence of cv is a strong predictor of successful blvr.13 the chartis system has been proven to be useful for detecting cv and predicting the success of blvr , but how to analyze and judge the chartis reading should be paid more attention . it is difficult in some conditions because different breathing efforts and/or variable levels of conscious sedation may lead to the variable amplitude of the chartis reading.3,4,8,9,12 however , some patients exhibit poor clinical responses even when the chartis analysis has detected no cv , and the ebv has completely blocked the target bronchus . treatment failure in these patients is ultimately determined to have resulted from latent cv that was undetected by the chartis system . such false negative readings result from several causes , including catheter blockage and low flow in the target lobe.8,13 low flow is a unique chartis phenotype and can be classified as either cv positive or cv negative . low flow is likely a sign of dynamic collapse of the airways distal to the balloon of chartis catheter . other possible causes of low flow include extra - wide collateral channels between the lobes that induce a reverse flow in the catheter that can not be displayed on the monitor . the chartis catheter itself may also be responsible for the inherent resistance in these particular assessments . when low flow exists in chartis reading of target lobe , ipsilateral lobes should be carefully assessed . previous study revealed that low - flow patients with ipsilateral cv - negative lobe also showed an improvement in pulmonary function and target lobe volume reduction ( tlvr ) after valve insertion.11 but the relationship should be focused between the varying levels of volume reduction and the clinical outcomes . patients in whom tlvr was obtained had greater improvements in clinical outcomes , even in the patients with incomplete fissures who had a tlvr > 50%.14 in our case , the low - flow chartis phenotype led us to fail to recognize latent cv between the rul and rml . these findings may be attributable to the existence of mini - collaterals that open only during deeper inspirations . in addition , the minor defect in the fissure should be considered as one of the risk factors of treatment failure , even when its integrity was more than 90% on hrct . although the accuracy of chartis assessment or hrct fissure analysis for the prediction of tlvr < 80% , evaluations of figure integrity using hrct and the chartis system are complementary.15 moreover , our case revealed that chartis assessment in combination with hrct fissure analysis also has difficulties in assessing cv when the low - flow chartis phenotype exists . pu et al found that defects in the right horizontal fissure make the rul a poor target for valves.16 our case showed that patients with low - flow chartis phenotype in the rul that masks cv positivity can still benefit from blvr if an ebv is used to block the middle bronchus and eliminate the cv . if cv is found between the rul and rll , blvr with a thermal vapor or coil may be an effective alternative.17,18 last but not the least , caution should be in place not only in patient selection but also in the follow - up of treatment , when the potentially malignant lesions in the target lobe . just like the lesions located in the rul of our case , lung cancer should be excluded carefully because lung cancer is one of the common comorbidities of copd . in conclusion , low flow in the target lobe can lead to incorrect evaluations of cv in patients who are scheduled for ebv - based blvr , especially when the cv of ipsilateral lobes is difficult to judge . our experience suggests that at least some low - flow patients with micro - cv between the rul and rml can benefit from implantation of ebvs into the upper and middle bronchi .
satisfactory functional outcomes following bronchoscopic lung volume reduction ( blvr ) using endobronchial valves ( ebvs ) depend on the absence of collateral ventilation ( cv ) between the target and adjunct lobes . 
 the chartis system has proven to be useful for determining whether cv is present or absent , but this system can also erroneously indicate the absence of cv , which can lead to blvr failure . here , we describe low - flow chartis phenotype in the target lobe resulted in difficult judgment of existence of cv . consequently , blvr with ebvs implanted into the right upper bronchus failed to reduce lung volume or induce atelectasis . inserting another ebv into the right middle 
 bronchus blocked the latent cv , which led to significant lung volume reduction in the right upper lobe ( rul ) and right middle lobe ( rml ) and to improve the pulmonary function , 6-min walking distance , and st george respiratory questionnaire scores over a 2-week follow - up period . 
 low flow in the target lobe is a unique chartis phenotype and represents the uncertainty of cv , which is a risk factor for the failure of blvr using ebvs . 
 clinicians should be aware of this possibility and might be able to resolve the problem by blocking the rul and rml between which the cv occurs .