The hypothesis to explain these observations is that when the bronchial extremity of the L-DLT is inserted into the left main stem bronchus (LMSB), the LMSB and its relative superior position, associated to a progressive collapse of the left lung, could induce a dynamic obstruction of the distal extremity of the L-DLT lumen, and consequently slowing the lung collapse. Investigators have also regularly observed this type of obstruction during bronchoscopic examination when positioning the L-DLT.