Background:
Lung isolation is frequently used in thoracic surgery. The quality of the isolation is crucial, especially for video-assisted thoracoscopic surgery (VATS). Two techniques are principally used to obtain lung isolation: the double lumen tube (DLT) and the bronchial blocker (BB).
The left-sided DLT (L-DLT) is used by the majority of anesthesiologists, as much for left as for right thoracic surgeries. The standard right-sided DLT (Rs-DLT) is rarely used since positioning its lateral orifice with the origin of the right upper lobe (RUL) can be difficult.(1-4) In 2007, the investigators have published their results suggesting an enlargement of the lateral orifice of the Rs-DLT.(5) They have demonstrated that the modified right-sided double lumen tube (Rm-DLT) remained more frequently in optimal position than the Rs-DLT (77% vs. 37%, p=0.0121) and that it was also easier to reposition the tube after turning the patient in lateral decubitus (97% vs. 74%, p=0.0109).
More recently, investigators have demonstrated, with three dimensional reconstruction of computed tomography of 106 patients, that angulation between the RUL and the horizontal posterior plane varies from -26 to +58°, justifying the modification of the Rs-DLT proposed in 2007. (Unpublished data)
The use of BB for lung isolation is believed to provide a slower and a poorer quality of lung collapse (LC) than DLT. Over the years, the investigators have demonstrated an equivalent quality of lung collapse between the L-DLT and BB when two apnea periods are used at the beginning of one-lung ventilation (OLV). (Unpublished data) Further to complementary analysis, investigators have noted a significant difference in time to get complete lung collapse between left and right thoracic surgery when using the L-DLT. Time to obtain complete lung collapse (CLC) was not different when comparing BB and L-DLT in left thoracic surgery.
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.
In past studies comparing L-DLT to BB, time to get CLC was measured from the beginning of OLV. Nevertheless, the interval between this time point and the pleural opening (PO) is sometime difficult to control. Technical incidents can prolong this period and induce a bias. Furthermore, in the last investigator's protocol, the second period of apnea is done at pleural opening. For these reasons, the authors consider that the time to get CLC should be measured from the pleural opening since it is the crucial moment for the surgical team. Investigators are proposing to evaluate the PO-CLC interval as a primary objective.(6)
Hypothesis:
The hypothesis of the proposed study is that the use of the L-DLT will allow for a slower and a poorer quality of CLC compared to the ones obtained with the Rm-DLT in left VATS.
