Rationale: The Chartis® ( Pulmonx, CA, USA) measurement system is a tool to assess interlobar collateral ventilation during bronchoscopy. Assessing collateral ventilation is important when you intend to treat a patient with endobronchial valves. Chartis measurement of collateral ventilation can be performed under both conscious sedation as well as general anesthesia. There is no consensus on what is the preferred method of anesthesia for Chartis measurements in the literature.