An adjusted and time-saving method to measure collateral ventilation with Chartis

Introduction Bronchoscopic lung volume reduction with endobronchial valves is an important treatment option in selected patients with severe emphysema and absence of collateral ventilation in the treatment target lobe. The Chartis system provides an important physiological assessment of the presence or absence of collateral ventilation. We aimed to evaluate a new feature and determine whether low flow during a Chartis measurement is predictive for the absence of collateral ventilation, and whether this allows for a procedure to be shortened by earlier terminating the Chartis measurement. This is measured with the "volume trend for the previous 20 s" (VT20). Methods We retrospectively evaluated 249 Chartis assessments of patients scheduled for bronchoscopic lung volume reduction procedures. The VT20 was calculated, and several thresholds were compared between patients with collateral ventilation (CV positive) and without collateral ventilation (CV negative). Results 100% of the CV negative patients reached a threshold of VT20 <= 6 mL, whereas all CV positive patients reached a VT20 >= 7 mL. The median "time saved" between VT20=6 mL and end of assessment was 60 s (range 5-354 s). Conclusion The threshold of VT20 <= 6 mL is a reliable method to exclude the presence of collateral ventilation when air flow rates are low and can therefore reduce bronchoscopic lung volume procedure times.