Abstract:
An embodiment of the present invention described and shown in the specification and drawings is a double lumen breathing tube for ventilating at least one lung of a subject. The distal ends of the tubes are predisposed to be spaced-apart and when in position in the airway of a human subject, each tube fits into a mainstem bronchus. A structure for temporarily positioning the distal ends of the tubes into a contacting or closely adjacent position is provided to facilitate introducing the breathing tube into the airway and for removing the breathing tube from the airway. Moreover, a method of ventilating at least one lung of a human subject is provided. This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to ascertain quickly the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 C.F.R. §1.72(b).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to endobronchial tubes for insertion through the mouth or nasal passages of a patient to facilitate artificial ventilation of the respiratory system. More particularly, this invention relates to endobronchial tubes with a double lumen and balloon cuffs for selective ventilation of one or both lungs of a patient. 
     2. Background Art 
     It is a common practice to provide human medical patients with artificial ventilation during surgery or in emergency situations. For example, accident victims will frequently require CPR or intubation by a paramedic in an emergency vehicle or by an anesthesiologist in an operating room. In such situations, intubation is accomplished by insertion of a breathing tube through the patient&#39;s mouth or nasal passages into the airway passage. Such devices have generally comprised a relatively pliable tube that is connectable to a respirator or other air supply mechanism for introduction of air into the lungs. An improvement to breathing tubes includes an inflatable-deflatable bag-like structure or balloon “cuff” around the exterior of the tube. The balloon cuff is conventionally located in a position along the breathing tube to engage the inner wall of the pharynx, larynx, or trachea, depending upon the specific breathing tube design. When the tube is in place, the cuff is inflated and forms an air tight seal between the tube and the surrounding body tissue to prevent the escape of air pumped from the respirator into the lungs. 
     Both single lumen and double lumen breathing tubes are known. Typically, a single lumen breathing tube is an elongated tube that extends into the trachea of a patient and includes one inflatable balloon cuff near its distal end. Commonly, the double lumen breathing tube is referred to as an endobronchial tube and, in addition to one lumen which extends to the trachea, has a second longer lumen which extends into the bronchus of a patient upon intubation. Typically, the double lumen breathing tube or endobronchial tube includes two inflatable balloon cuffs. The double lumen breathing tubes, such as the well known “Carlens” and “Robertshaw” tubes, allow for independent control of each lung through the separate lumens. One bronchus may be blocked by occluding one of the lumens at a position external to the patient, in order to isolate a particular lung. 
     The balloon cuffs are thin walled, high volume, and low pressure chambers or vessels that are designed to avoid compromising the blood flow in the tracheal or bronchial wall when inflated. Balloon cuffs are made of a soft expandable plastic and can be inflated by detachable syringes that are connected to smaller lumens or channels at the proximal end of the breathing tube. The seals formed by the inflated cuffs preclude the air that has been forced into the patient&#39;s lungs from escaping through the trachea or bronchus. Additionally, the seals formed by the inflated cuffs provide a barrier to the flow of blood and secretions. 
     The double lumen breathing tubes offer an anesthesiologist the ability to ventilate selectively either the right or left lung or both lungs as required. One potential problem with currently used double lumen breathing tubes, however, is the obstruction of the right upper lobe bronchus. Correct placement of the currently available double lumen tubes requires confirmation with fiberoptic bronchoscopy. Moreover, currently available double lumen tubes can be easily displaced after correct placement, especially when the patient is repositioned on the operating table. 
     The present invention provides an improvement over the prior art because its proper positioning is assured by its unique design; thus, the need for fiberoptic bronchoscopy is minimized. Moreover, the present invention is more securely placed with less risk for malposition after placement, compared to currently available double lumen tubes. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a double lumen breathing tube comprising two tubes disposed adjacent to each other. Each tube has a lumen, a proximal end, a distal end and a length extending between the proximal and distal ends. The two tubes are fixedly attached to each other along a portion of their respective lengths. A first branch section is a section of length of the first tube extending from the distal end of the first tube to a proximal location at which the first and second tubes are fixedly attached to each other. A second branch section is a section of length of the second tube extending from the distal end of the second tube to a proximal location at which the first and second tubes are fixedly attached to each other. The first branch section is preferably longer than the second branch section. The first branch section and the second branch section are also preferably predisposed to be spaced-apart from each other. Each proximal end can be individually attached to a ventilating machine, or respirator, so that either one or both tubes can be connected to a ventilation source at any given time. 
     As one skilled in the art will appreciate, the predisposition of the first branch section and the second branch section to be spaced-apart from each other hinders the insertion of the double lumen tube into the patient&#39;s airway. Accordingly, the present invention also provides a means for temporarily positioning the first branch section and the second branch section in contact with each other along at least a portion of their respective lengths. In one embodiment, the temporarily positioning means is a stylet having a central body portion connecting two spaced-apart arms that are disposed substantially parallel to each other so that the stylet is substantially U-shaped in plan view. When each arm of the stylet is positioned within a respective lumen of the double lumen tube, at least a portion of the first and second branch sections are in contact. 
     In another embodiment of the present invention, the temporarily positioning means comprises a sleeve. The sleeve has an interior surface of a size to complementarily receive the first and second tubes therein. When the sleeve is moved toward the distal ends of the first and second tubes so that the distal end of at least the second tube is disposed within the sleeve, at least a portion of the first and second branch sections contact each other. When the clinician moves the sleeve proximally after insertion into the patient&#39;s airway so that the distal end of the sleeve is proximal or adjacent to the point where the two tubes are fixedly attached, the first branch section and the second branch section move apart to their predisposed spaced-apart position. 
     The present invention further provides another temporarily positioning means comprising a primary spring and one or more wires interconnecting the primary spring and the distal ends of the two tubes. The wires extend along and are disposed adjacent to the first branch section and the second branch section respectively. The bottom ends of the wires are secured to the distal end of the tubes, and the wire also extends along the joined portion of the length of the first and second tubes that are fixedly attached to each other. The primary spring is movable between an extended position and a compressed position. When the primary spring is in the extended position, a portion of the first and second branch sections are in contact with each other. Alternatively, when the primary spring is compressed, the first branch section and the second branch section are spread apart from each other to their predisposed spaced-apart position. 
     Regardless of the temporarily positioning means used, once the double lumen breathing tube has passed through the vocal cords, the temporarily positioning means is discontinued or released, allowing the first branch section and the second branch section to move to their predisposed spaced-apart positions. Therefore, the first branch section is aligned to be positioned in the left mainstem bronchus and the second branch section is aligned to be positioned in the right mainstem bronchus. 
     Also, the present invention allows the clinician to place the double lumen breathing tube so that the first branch section is positioned in the left mainstem bronchus, and the second branch section is positioned in the right mainstem bronchus without obstructing the opening into either mainstem bronchus. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the double lumen tube of the present invention. 
     FIG. 2A is a top plan view of a stylet of the present invention. 
     FIG. 2B is a side elevational view of the stylet partially disposed within the lumens of the double lumen tube. 
     FIG. 2C is a view of FIG. 2B, in which the stylet is fully extended into the lumens, causing the portion of the individual tubes adjacent their distal ends to move together. 
     FIG. 3A is a side elevational view of a sleeve partially disposed over the exterior surface of the double lumen tube. 
     FIG. 3B is a view of FIG. 3A, in which the sleeve is disposed over the exterior surface of the double lumen tube distal to the point at which the two tubes are fixedly attached, causing the portion of the individual tubes adjacent their distal ends to move together. 
     FIG. 4A is a side elevational view of the double lumen tube with wires and a spring structure mechanism, in which the primary spring is in its extended position, causing the first branch section of the first tube and the second branch section of the second tube to be in a contacting or closely adjacent position. 
     FIG. 4B is a side elevational view of the double lumen tube with wires and a spring structure mechanism, in which the primary spring is in its compressed position, allowing the first branch section of the first tube and the second branch section of the second tube to be in their predisposed spaced-apart position. 
     FIG. 4C is a side view of the housing of the spring structure and slot. 
     FIG. 4D is a side view of FIG. 4C, showing the plate and protrusion inside the housing. 
     FIG.  4 D 1  is a side view of the plate and protrusion shown in FIG.  4 D. 
     FIG. 4E is a side elevational view of the spring structure with the primary spring in the compressed position and the secondary spring opposed to it, in which the double lumen tube is shown schematically. 
     FIG. 4F is a side elevational view of the spring structure with the primary spring in the extended position and the secondary spring opposed to it, in which the double lumen tube is shown schematically. 
     FIG. 4G shows the spring structure of FIG. 4F rotated 90 degrees. 
     FIG. 4H is a side elevation of the spring structure and the primary spring in the extended position. 
     FIG. 4I is a side elevation of the spring structure and the primary spring in the compressed position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. As used in the specification and in the claims, “a”, “an”, or “the” can mean one or more, depending upon the context in which it is used. The present invention is now described with reference to the figures, in which like numbers indicate like parts throughout the figures. 
     Referring first to FIG. 1, the present invention comprises a double lumen breathing tube  10  comprising two tubes  12 ,  14 , including a first tube  12  and a second tube  14 , that are disposed adjacent to each other. Each tube has a lumen  16 , an exterior surface  18 , a proximal end  20 , a distal end  22  and a length extending between the proximal and distal ends  20 ,  22 . The two tubes  12 ,  14  are attached to each other along a portion of their respective lengths. A first branch section  26  is a section of length of the first tube  12  extending from the distal end  22  of the first tube  12  to a location at which the first tube  12  and the second tube  14  are fixedly attached to each other. A second branch section  28  is a section of length of the second tube  14  extending from the distal end  22  of the second tube  14  to the same location at which the first tube  12  and the second tube  14  are fixedly attached to each other. The most distal, or lowermost, location  29  at which the first and second tubes  12 ,  14  are connected to each other is the point below which the first and second branch sections  26 ,  28  begin, i.e., the proximal ends of the first and second branch sections  26 ,  28 . 
     The first branch section  26  is preferably longer than the second branch section  28 . Also, the first branch section  26  and second branch section  28  are preferably predisposed to be spaced-apart from each other. Each proximal end  20  of the first and second tubes  12 ,  14  can be individually attached to a ventilating machine or respirator R (as shown schematically in FIG. 1) so that either one or both tubes  12 ,  14  can be connected to a ventilation source at any given time. The preferred materials used to form the tubes  12 ,  14  include polyvinyl chloride (PVC) and silicon, but one skilled in the art will appreciate that other surgical-grade materials can be used, such as plastics and polymers. 
     As noted above, two tubes  12 ,  14  are fixedly attached together along a portion of their lengths. By “fixedly attached,” it is contemplated that the first and second tubes  12 ,  14  do not become separated or spaced-apart from each other along the portion that is “fixedly attached” during the surgical procedure. In the embodiment using tubes  12 ,  14  formed of PVC, the preferred way to fixedly attach sections of the tubes  12 ,  14  together is by forming or molding the two tubes  12 ,  14  to be integrally formed together. Other designs connect the two tubes  12 ,  14 , such as by a chemical adhesive or by physical structures to stationarily position a portion of the two tubes  12 ,  14  relative to each other (for example, using a main inflation cuff  30  which is discussed below). 
     The preferred length of the first branch section  26  is 5 centimeters. A more preferred length is 3 centimeters, and the most preferred length of the first branch section  26  is 4 centimeters. The preferred length of the second branch section  28  is 2.5 centimeters. A more preferred length is 1.5 centimeters, and the most preferred length of the second branch section  28  is 2 centimeters. Thus, the first branch section  26  of the first tube  12  is preferably 1.5 centimeters to 3.5 centimeters longer than the second branch section  28  of the second tube  14 . 
     Further, the present invention provides that the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are predisposed to be spaced-apart from each other when in position in the airway of a patient. In one embodiment, when the second tube  14  is oriented substantially linearly along its length, the first branch section  26  is predisposed to form an angle of approximately 35 degrees to 50 degrees relative to the substantially linearly oriented second tube  14 . The preferred angle is 40 degrees. A more preferred angle is 50 degrees, and the most preferred angle is 45 degrees. This angle matches the angle that the left mainstem bronchus makes relative to the trachea when the left mainstem bronchus branches off the trachea. Thus, the first tube  12  of the present invention is designed to fit easily within the left mainstem bronchus to ventilate the left lung. 
     Alternatively, when the first tube  12  is oriented substantially linearly along its length, the second branch section  28  of the second tube  14  is predisposed to form an angle of approximately 15 degrees to 35 degrees to the substantially linearly oriented first tube  12 . The preferred angle is 20 degrees. A more preferred angle is 30 degrees, and the most preferred angle is 25 degrees. This angle matches the angle that the right mainstem bronchus makes relative to the trachea when the right mainstem bronchus branches off the trachea. Thus, the second tube  14  of the present invention is designed to fit easily within the right mainstem bronchus to ventilate the right lung. 
     In another design, both the first and second branch sections  26 ,  28  form an angle relative to the longitudinal axis of the tube  10  so that neither branch section  26 ,  28  is linear. In this design, the preferred angle between the two branch sections  26 ,  28  is 60 degrees. A more preferred angle is 80 degrees, and the most preferred angle is 70 degrees. 
     In designing and manufacturing the present invention, the double lumen tube  10  is formed by molding the two tubes  12 ,  14  in the desired position, which causes the first and second branch sections  26 ,  28  to be predisposed to be spaced-apart from each other. That is, when the two tubes  12 ,  14  are molded together in the desired positions relative to each other, the material will return to its originally molded position after being repositioned. 
     Because it would be difficult to introduce into the airway of the patient the breathing tube  10  with the first branch section  26  and the second branch section  28  in their predisposed spaced-apart position, the present invention includes either a structure or a means for temporarily positioning the first branch section  26  and the second branch section  28  in contact with (which is defined to include being closely adjacent to each other) at least along a portion of their respective lengths. In one embodiment shown in FIGS. 2A-2C, the temporarily positioning means is a stylet  80 . The stylet  80  has a central body  82  portion connecting two spaced-apart arms  84  that are disposed substantially parallel or at a near parallel orientation to each other so that the stylet is substantially U-shaped in plan view, as shown in FIG.  2 A. Each arm  84  is of a size to fit within the lumen  16  of one tube and extend substantially the length of the tube to be adjacent to its distal end  22 . As shown in FIG. 2B, each arm of the stylet  80  is partially inserted into the lumens  16  of the first and second tubes  12 ,  14 . Now referring to FIG. 2C, when each arm  84  of the stylet  80  is moved distally so that the arms  84  extend as far as possible within the lumens  16 , at least a portion of the first and second branch sections  26 ,  28  move from their predisposed spaced-apart positions to contact each other. As will be seen, although the term “contact” is used, the first and second branch sections  26 ,  28  do not contact each other but are closely adjacent to each other. The stylet  80  can be made of a material that is reusable and able to be sterilized for more than one use. Examples of materials from which the stylet  80  can be formed include, but are not limited to, stainless steel, chromium and alloys, as well as polymers such as polyethylene and other plastics. 
     In another embodiment shown in FIGS. 3A and 3B, the temporary positioning means comprises a sleeve  48 . The sleeve  48  has an interior surface  49  of a size to complementarily receive the first tube  12  and the second tube  14  therein. FIG. 3A shows the sleeve  48  extending along a portion of the length of the tubes  12 ,  14 . As shown in FIG. 3B, when the sleeve  48  is moved toward the distal ends  22  of the first tube  12  and the second tube  14  so that the distal ends  22  of each tube  12 ,  14  are disposed within the sleeve  48  or the sleeve is adjacent to the distal ends  22 , at least a portion of the first and second branch sections  26 ,  28  are in contact with each other. When the clinician moves the sleeve  48  proximally so that the distal end  56  of the sleeve  48  is proximal to or at the lower most or distal most point where the two tubes  12 ,  14  are fixedly attached, the first branch section  26  and the second branch section  28  move apart to their predisposed spaced-apart position. The sleeve  48  can be made of stainless steel, chromium and alloys, as well as polymers such as polyethylene and other plastics. A plastic sleeve  48  is preferred, however. 
     In still another embodiment of the present invention, the temporary positioning means comprises at least one wire and a spring operatively connected to the wires. Referring now to FIG. 4A, this embodiment is shown comprising three wires  42 ,  44 ,  46  including a first wire  42 , a second wire  44 , and a third wire  46 , each wire respectively having a top end  52 ′,  52 ″,  52 ′″ and a bottom end  54 ′,  54 ″,  54 ′″. The first and second wires  42 ,  44  extend along and are disposed adjacent to the first branch section  26  and the second branch section  28 , respectively. The bottom end  54 ′ of the first wire  42  is secured adjacent the distal end  22  of the first tube  12  and the bottom end  54 ″ of the second wire  44  is secured adjacent the distal end  22  of the second tube  14 . The third wire  46  extends along the joined portion of the length of the first tube  12  and the second tube  14  that are fixedly attached to each other. The bottom end  54 ′″ of the third wire  46  is attached to the top ends  52 ′,  52 ″ of the first and second wires  42 ,  44  respectively. Each wire  42 ,  44 ,  46  extends along the length of its respective tube in a channel which is of a size to complementarily receive the wires  42 ,  44 ,  46 . Each wire  42 ,  44 ,  46  preferably has a diameter of approximately 0.1 millimeters to 0.5 millimeters. In FIG. 4A, the primary spring  76  is in the extended position, and the first branch section  26  and the second branch section  28  are in a contacting or closely adjacent position. Further, referring to FIG. 4B, the primary spring  76  is in the compressed position, and the first branch section  26  and the second branch section  28  are in their predisposed spaced-apart position. 
     Further, referring to FIG. 4C, the device preferably includes a spring structure  75  comprising a housing  60  having an outer surface  62 , an upper end  64 , and a lower end  66  and defining a bore  70  extending substantially between the upper and lower ends  64 ,  66 . The housing  60  defines a slot  68  interconnecting the bore  70  and the outer surface  62  that extends between a portion of the upper and lower ends  64 ,  66 . Referring to FIGS.  4 D and  4 D 1 , a plate  72  is disposed within the bore  70  and slidably movable within the bore  70 . The top end  52 ′″ of the third wire  46  is connected to a portion of the plate  72 , as shown schematically in FIGS. 4E-4G. The plate  72  also includes a protrusion  74  having an end  78  extending from the plate  72  so that the end  78  of the protrusion  74  extends through the slot  68  of the housing  60 . Referring to FIG.  4 D 1 , the protrusion  74  can be a bolt or any other similar device for manually depressing the plate  72  within the bore  70 . 
     As shown in FIG. 4H, a primary spring  76  is disposed within the housing  60  between its lower end  66  and the plate  72 . The primary spring  76  is movable between an extended position, in which the plate  72  is disposed adjacent the upper end  64  of the housing  60 , and a compressed position, as shown in FIG. 4I, in which the plate  72  is slid toward the lower end  66  of the housing  60  from the extended position. Referring to FIGS. 4A and 4F, when the primary spring  76  is in the extended position, the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are in a contacting or closely adjacent position with each other. Alternatively, when the primary spring  76  is in the compressed position, the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are spread apart from each other, as shown in FIGS. 4B and 4E. To keep the primary spring  76  in the compressed position, the clinician rotates the protrusion  74  into a portion of the slot  68  that extends perpendicularly to the length of the two tubes  12 ,  14 , as shown in FIG.  4 D. Once the protrusion is in this portion of the slot  68 , the primary spring  76  is held in the compressed position. 
     Referring back to FIG. 4E, an alternative embodiment of the spring structure  75  comprises a secondary spring  77  which is disposed within the bore  70  of the housing intermediate the upper end  64  thereof and the plate  72 , the secondary spring  77  being opposed to the primary spring  76 . In this embodiment, the secondary spring  77  stabilizes the plate  72  within the bore  70  so that the plate  72  resists being tilted as the clinician depresses the protrusion  74 , thereby compressing the primary spring  76 . Further, the secondary spring  77  allows the plate  72  to move more smoothly within the bore  70  by dampening the excursion of the plate  72  within the bore  70 . FIG. 4F shows the primary spring  76  in the extended position with the protrusion  74  locked into the slot  68  at the upper end  64  of the housing  60 . FIG. 4G is the spring structure  75  rotated 90 degrees. The secondary spring  77  is not required in the present invention, however, because the spring structure functions properly with only the primary spring  76 . 
     Although the embodiment shown in FIGS. 4A-4B is described as using three wires for convenience, one skilled in the art will appreciate that other designs can be used. For example, a single wire can be used, in which the strands are separated to form the first and second wires  42 ,  44 . Likewise, two wires can be used, in which one wire forms the first and second wires  42 ,  44  and the other wire forms the third wire  46 , or one wire forms the first and third wires  42 ,  46  and the other wire forms the second and third wires  44 ,  46 . However, regardless of the embodiment, the contemplated materials to form the wires  42 ,  44 ,  46  are polyvinyl chloride, silicone, stainless steel, titanium and other surgical instrument grade metals. 
     Referring back to FIG. 1, the breathing tube of the present invention  10  also preferably includes a main inflation cuff  30  circumscribing the exterior surface  18  of both the first tube  12  and the second tube  14 . The main inflation cuff  30  has an inflation port  32  and an inflation catheter  34  which extends through the wall  40  of the first tube  12  and connects the cuff to the inflation port  32 . By selectively injecting fluid into the main inflation cuff  30 , a seal can be made to block air and secretions from escaping from the lungs around the tube  10 . When fluid is removed from the main inflation cuff  30 , the seal is removed, and air and secretions are able to escape from the lungs around the tube  10 . As a person of skill in the art will appreciate, the fluid may be any suitable liquid or gas, the preferred fluid being air. 
     Still referring to FIG. 1, the present invention preferably also includes a first inflation cuff  36  circumscribing the exterior surface  18  of the first tube  12 . Like the main inflation cuff  30 , the first inflation cuff  36  has an inflation port  32 ′ and an inflation catheter  34 ′ which extends through the wall  40  of the first tube  12  and connects the cuff to the port. As for the main cuff  30 , by selectively injecting fluid into or removing fluid from the first inflation cuff  36 , a seal blocks and unblocks, respectively, air and secretions from escaping from the left lung around the first tube  12 . Again, the fluid may be any suitable liquid or gas, in which the preferred fluid is air. 
     Referring to FIG. 2B, another embodiment of the present invention includes a second inflation cuff  38  circumscribing the exterior surface  18  of the second tube  14 . The second inflation cuff  38  has an inflation port  32 ″ and an inflation catheter  34 ″ which extends through the wall  40  of the second tube  14  and connects the cuff  38  to the inflation port  32 ″. As for the main cuff  30 , by selectively injecting fluid into or removing fluid from the second inflation cuff  38 , a seal blocks and unblocks air and secretions from escaping from the right lung around the second tube  14 . Again, the fluid may be any suitable liquid or gas, in which the preferred fluid is air. 
     The present invention also provides a method for ventilating at least one lung of a subject, comprising passing into a trachea of a human subject a breathing tube  10  of the present invention. To safely pass the tube  10  through the vocal cords and into the trachea and bronchi, a clinician must temporarily dispose the first branch section  26  and the second branch section  28  into a contacting or closely adjacent relationship. Of the ways of positioning the first and second branch sections  26 ,  28  adjacent to each other, one method uses a stylet  80  as described above. The stylet  80  is introduced into the tube  10  prior to intubation of the subject. The first branch section  26  and the second branch section  28  are held in contact by the action exerted by each arm  84  of the stylet  80  on the medial wall  40  of the tube in which it is located. In this contacting position, the two tubes  12 ,  14  are in the safest configuration for the passage of the breathing tube  10  into the airway of a subject, past the vocal cords into the trachea and bronchi. After the breathing tube  10  has been properly positioned, the stylet  80  is removed by the clinician. Once the stylet  80  is out of the breathing tube  10 , the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  resume their predisposed position, in which they are spaced-apart from each other, forming an angle of approximately 50 degrees to 85 degrees. The angle thus formed is the same as the angle formed by the divergence of the left and right mainstem bronchi as they branch from the trachea. After the removal of the stylet  80 , the clinician can connect either one or both proximal ends  20  of the double lumen tube  10  to a respirator R, depending on whether one-lung or two-lung ventilation is necessary. 
     In another method of the present invention, a sleeve  48  temporarily disposes the first branch section  26  and the second branch section  28  in a contacting position with each other. When the clinician slides the sleeve  48  distally so that it circumscribes at least a portion of each tube  12 ,  14  distal to the point  29  where the two tubes  12 ,  14  are fixedly attached to each other, the first branch section  26  and the second branch section  28  are in a contacting or closely adjacent position with each other. With the sleeve  48  in this position, the double lumen breathing tube  10  can safely be passed into the airway of a human subject, past the vocal cords into the trachea and mainstem bronchi. Once the tube  10  has been properly positioned, the clinician can slide the sleeve  48  proximally so that the distal end  56  of the sleeve  48  is proximal to the point  29  where the first tube  12  and the second tube  14  are fixedly attached. With the sleeve  48  in this position, the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are free to return to their predisposed, spaced-apart position. The angle formed between the distal ends  22  of the first tube  12  and the second tube  14  is approximately 50 degrees to 85 degrees, the same angle formed between the left and right mainstem bronchi as they bifurcate from the trachea. After the sleeve  48  has been moved proximally and the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  have entered their respective bronchi, the clinician can connect either one or both proximal ends  16  of the double lumen breathing tube  10  to a respirator R, depending on whether one-lung or two-lung ventilation is necessary. 
     In another method of temporarily disposing the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  in a contacting or closely adjacent position with each other, a spring structure  75  is used. With the primary spring  76  in its extended position, a plate  72  to which a wire  46  is attached is at the upper end  64  of the housing  60 , thereby exerting tension on the wire  46  which is attached to the distal ends  22  of the two tubes  12 ,  14 . When the wire  46  is under tension, the distal ends  22  of the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are temporarily disposed in a contacting position with each other, thereby permitting a clinician to safely pass the tube  10  through the vocal cords into the trachea and bronchi. Once the tube  10  has been properly positioned, a clinician can depress a protrusion  74  extending from the plate  72  and lock the plate  72  in place by rotating the protrusion  74  into a portion of the slot  68  that extends perpendicularly to the length of the two tubes  12 ,  14 . By compressing the primary spring  76  and reducing the tension on the wire  46 , the first branch section  26  of the first tube  12  and the second branch section  28  of the second tube  14  are free to return to their predisposed, spaced-apart position. The angle formed between the distal ends  22  of the first tube  12  and the second tube  14  is approximately 50 degrees to 85 degrees, the same angle formed as they bifurcate from the trachea. After the two tubes  12 ,  14  have entered their respective bronchi, the clinician can connect either one or both proximal ends of the double lumen  16  breathing tube  10  to a respirator R, depending on whether one-lung or two-lung ventilation is necessary. 
     The present invention also provides a method for ventilating at least one lung of a subject. In the preferred method, a respirator R is connected to the double lumen breathing tube  10  to provide ventilation to one or both lungs of a subject. In particular, the proximal end  20  of either the first tube  12  or the proximal end  20  of the second tube  14  can be attached to a respirator R which moves a mixture of oxygen and other gases, particularly anesthetics, into and out of the airway of a subject. When a clinician needs to ventilate only the left lung, the proximal end  20  of the first tube  12  is connected to the respirator R and only the left lung will receive the mixture of gases. The proximal end  20  of the second tube  14  can be occluded to prevent ventilation of the right lung. To ensure that no gas is introduced into the right lung, the clinician can inflate the first inflation cuff  36  circumscribing the first tube  12  and the main inflation cuff  30  circumscribing the exterior surface  18  of the first tube  12  and the second tube  14 . When both the main inflation cuff  30  and the first inflation cuff  36  are inflated and the respirator R is connected to only the proximal end  20  of the first tube  12 , the right lung will not be ventilated. 
     Alternatively, when a clinician needs to ventilate only the right lung, the proximal end  20  of the second tube  14  is connected to the respirator R and only the right lung will receive the mixture of oxygen and other gases from the respirator R. The proximal end  20  of the first tube  12  can be occluded to prevent ventilation of the left lung. To ensure that no gas is introduced into the left lung, the clinician can inflate the second inflation cuff  38  circumscribing the second tube  14  and the main inflation cuff  30  circumscribing the exterior surface  18  of the first tube  12  and the second tube  14 . When both the main inflation cuff  30  and the second inflation cuff  38  are inflated and the respirator R is connected only to the proximal end  20  of the second tube  14 , the left lung will not be ventilated. 
     Although the present invention has been described with reference to specific details of certain embodiments thereof, it is not intended that such details should be regarded as limitations upon the scope of the invention except as and to the extent that they are included in the accompanying claims.