The Double-Lumen Bronchoscope (DLB) procedure uses a Double-Lumen Tube (DLT) to achieve One-Lung Ventilation (OLV). This technique mechanically separates the two lungs, allowing clinicians to ventilate one lung while the other remains deflated. The DLB procedure is primarily utilized during complex thoracic surgery or in critical care scenarios where isolating a diseased lung is necessary. This isolation is required for surgical access to the chest cavity or to prevent contamination between the lungs.
Defining the Double-Lumen Bronchoscope
The Double-Lumen Tube (DLT) is an advanced endotracheal tube designed to separate the left and right mainstem bronchi. It has two distinct, parallel tubes of unequal length fused together, each forming a separate channel, or lumen, for gas passage. The shorter channel is the tracheal lumen, which terminates in the trachea above the carina, where the trachea divides into the main bronchi.
The longer channel is the bronchial lumen, selectively placed deep into either the left or right main bronchus to provide ventilation to only that side’s lung. To ensure complete isolation, the DLT incorporates two inflatable cuffs: a clear, high-volume cuff around the tracheal lumen and a blue, low-volume cuff situated at the tip of the bronchial lumen. When both cuffs are inflated, they prevent air from crossing between the two lungs, achieving the required separation.
A left-sided DLT is the most frequently used device because the anatomy of the left main bronchus offers a longer, straighter path, providing a greater margin of safety for tube placement. However, a right-sided DLT is also available and includes a specialized side slot, sometimes called a Murphy eye, which aligns with the opening of the right upper lobe bronchus to ensure its continued ventilation. The external diameter of the tubes is measured in French gauge, with sizes ranging from 26 to 41, with larger sizes used for adult males.
Mechanism of One-Lung Ventilation
The process of One-Lung Ventilation (OLV) begins once the patient is under general anesthesia and the DLT is advanced past the vocal cords. Clinicians use a laryngoscope during initial insertion and then employ a flexible fiberoptic bronchoscope to confirm the tube’s final position. This visualization is performed by passing the bronchoscope through the tracheal lumen to see the carina, and then through the bronchial lumen to confirm correct placement within the designated main bronchus.
After the selective placement is confirmed, the cuffs are inflated to create a hermetic seal against the tracheal and bronchial walls, effectively dividing the airway into two independent systems. Once the separation is complete, the lung on the side of the surgical field is isolated by clamping the corresponding lumen of the DLT. The open port on the clamped side allows the trapped air to escape, causing the lung to passively deflate or collapse, which is the goal of OLV.
The remaining, non-operative lung is then actively ventilated through the second, open lumen, ensuring the patient continues to receive oxygen and expel carbon dioxide. The tube position must be re-checked with the fiberoptic bronchoscope after the patient is moved into the lateral position, as changes in body position can cause the tube to shift. This ensures that the intended lung remains isolated and deflated, providing the surgeon with a clear, motionless field of view.
Clinical Applications and Necessity
The double-lumen bronchoscope procedure is implemented anytime independent control over each lung is required, falling into two categories: surgical and non-surgical indications. In the surgical context, the goal is to achieve lung collapse to improve visualization and access for procedures within the chest cavity. This is common for operations including lobectomy (removal of a lung lobe), pneumonectomy (removal of an entire lung), and surgeries on the esophagus, thoracic aorta, or spine.
The non-surgical, or medical, indications center on preventing the spread of harmful materials from one lung to the other. For instance, a DLT isolates a lung experiencing massive hemorrhage, stopping blood from entering and contaminating the healthy lung. Similarly, it is employed when a patient has a severe infection or abscess to prevent secretions from spilling into the unaffected side. Maintaining independent ventilation allows for selective treatment or suctioning of the diseased lung without interrupting oxygen delivery to the healthy lung.