lung volume reduction is performed by collapsing a target lung tissue segment , usually within sub - lobular regions of the lung which receive air through a single air passage , i . e ., segment of the branching bronchus which deliver to and receive air from the alveolar regions of the lung . such isolated lung tissue segments are first isolated and then collapsed by aspiration of the air ( or other gases or liquids which may have been introduced , as discussed below ) from the target lung tissue segment . lung tissue has a very high percentage of void volume , so removal of internal gases can reduce the lung tissue to a small percentage of the volume which it has when fully inflated , i . e . inflated at normal inspiratory pressures . the exemplary and preferred percentages for the volume reduction are set forth above . in particular , the present invention provides methods and apparatus for enhancing the aspiration and collapse of the target lung tissue segment . such methods and apparatus may involve one or more of the following improvements . first , various approaches may be taken to remove or lessen obstructions to gas flow within the target tissue region . second , methods and apparatus may be employed to apply external pressure over the lung to enhance the collapse achieved by internal aspiration . third , aspiration of the gases within the target tissue segment may be enhanced by inducing absorption atelectasis prior to aspiration . absorption atelectasis may be induced , for example , by introducing an oxygen - rich gas to the lung tissue segment , usually at least 50 % oxygen by volume , more usually at least 75 % oxygen by volume , and preferably substantially pure oxygen . absorption atelectasis is a phenomena which occurs when an enriched oxygen mixture is inspired . the high oxygen concentration causes an increase in the partial oxygen pressure which in turn causes the rate of oxygen transfer into the capillary blood within the alveolar regions to increase greatly . the increased oxygen flux may increase so much that the net flow of gas into the blood exceeds the inspired flow of gas , causing the lung unit to become progressively smaller . fourth , the access methods and apparatus may be used for performing in situ diagnosis , usually as part of the collapse procedure . any one of a number of lung performance characteristics may be measured , typically by sampling using the isolation / access catheter . the methods of the present invention will generally rely on accessing the target lung tissue segment using an isolation / access catheter adapted to be introduced endotracheally into the bronchus of the lung . an exemplary isolation / access catheter 10 is illustrated in fig1 and 2 and comprises a catheter body 12 having a distal end 14 , a proximal end 16 , an inflatable occlusion balloon 18 near its distal end , and at least one lumen therethrough . usually , the catheter will have at least two lumens , and catheter 10 includes both a central lumen 20 and an annular lumen 22 defined by inner body member 24 and outer body member 26 which is coaxially disposed about the inner body member . the annular lumen 22 opens to port 30 on a proximal hub 32 and provides for inflation of balloon 18 . the central lumen 20 opens to port 36 on hub 32 and provides for multiple functions , including optional introduction over a guidewire , aspiration , introduction of secondary catheters , such as sealing catheters described below , and the like . the dimensions and materials of isolation / access catheter 10 are selected to permit endotracheal introduction and intraluminal advancement through the lung bronchus , optionally over a guidewire and / or through a primary tracheal tube structure ( as illustrated in fig4 b below ). suitable materials include low and high density polyethylenes , polyamides , nylons , ptfe , peek , and the like , particularly for the inner tubular member 24 . the outer member , including the occlusion balloon , can be made from elastomeric materials , such as polyurethane , low density polyethylene , polyvinylchloride , silicone rubber , latex , and the like . optionally , portions of the outer tubular member 26 proximal to the inflatable balloon can be made thicker and / or reinforced so that they do not dilate upon pressurization of the balloon . exemplary dimensions for the isolation / access catheter 10 are set forth in the table below . the isolation / access catheter 10 may be modified in a number of ways , some of which are illustrated in fig3 a - 3f . for example , instead of an inner and outer coaxial tube construction , the catheter can be a single extrusion having a catheter body 30 with a circular main lumen 32 and a crescent - shaped inflation lumen 34 , as illustrated in fig3 a . alternatively , catheter body 40 may be formed as a single extrusion having three lumens , i . e ., a primary lumen 42 for receiving a guidewire , applying aspiration , and / or delivering secondary catheters . a second lumen 44 can be provided for inflating the occlusion balloon , and a third lumen 46 can be provided as an alternative guidewire or aspiration lumen . catheter body 50 comprising a main tubular body 52 having an outer layer 54 fused thereover to define a lumen 56 suitable for balloon inflation as shown in fig3 c . a primary lumen 58 is formed within the main tubular member 52 . as a slight alternative , catheter body 60 can be formed from a primary tubular member 62 , and a secondary tubular member 64 , where the tubular members are held together by an outer member 66 , such as a layer which is applied by heat shrinking . the primary tubular member 62 provides the main lumen 68 while secondary tube 64 provides a secondary lumen 70 . the secondary lumen 70 will typically be used for balloon inflation , while the primary lumen 68 can be used for all other functions of the isolation / access catheter . optionally , the isolation / access catheter in the present invention can be provided with optical imaging capability . as shown in fig3 e , catheter body 80 can be formed to include four lumens , typically by conventional extrusion processes . lumen 82 is suitable for passage over a guidewire . lumens 84 and 86 both contain light fibers 88 for illumination . lumen 90 carries an optical wave guide or image fiber 92 . lumen 82 can be used for irrigation and aspiration , typically after the guidewire is withdrawn . balloon inflation can be effected through the space remaining and lumens 84 and 86 surrounding the light fibers 88 . a second catheter body 100 is formed as a coaxial arrangement of a number separate tubes . outer tube 102 contains a separate guidewire tube 104 defining lumen 106 which permits introduction over a guidewire as well as perfusion and aspiration after the guidewire is removed . second inner tubular member 110 will carry an optical image fiber 112 and a plurality of light fibers 112 are passed within the remaining space 114 within the outer tubular member . in both catheter constructions 80 and 100 , forward imaging can be effected by illuminating through the light fibers and detecting an image through a lens at the distal end of the catheter . the image can be displayed on conventional cathode - ray or other types of imaging screens . in particular , as described below , forward imaging permits a user to selectively place the guidewire for advancing the catheters through a desired route through the branching bronchus . referring now to fig4 a , a catheter 10 can be advanced to a diseased region dr within a lung l through a patient &# 39 ; s trachea t . advancement through the trachea t is relatively simple and will optionally employ a guidewire to select the advancement route through the branching bronchus . as described above , steering can be effected under real time imaging using the imaging isolation / access catheters illustrated in fig3 e and 3f . optionally , the isolation / access catheter 10 may be introduced through a visualizing tracheal tube , such as that described in u . s . pat . no . 5 , 285 , 778 , licensed to the assignee of the present application . the visualizing endotracheal tube 120 includes an occlusion cuff 122 which may be inflated within the trachea just above the branch of the left bronchus and right bronchus lb and rb , respectively . the visualizing endotracheal tube 120 includes a forward - viewing optical system , typically including both illumination fibers and an image fiber to permit direct viewing of the main branch between the left bronchus lb and right bronchus rb . thus , initial placement of isolation / access catheter can be made under visualization of the visualizing endotracheal tube 120 and optionally the isolation / access catheter 10 itself . referring again in particular to fig4 a , the isolation / access catheter 10 is advanced until its distal end 14 reaches a region in the bronchus which leads directly into the diseased region dr . once in place , the balloon 18 can be inflated and the lung tissue segment which includes the diseased region isolated from the remainder of the lung . by isolated , it is meant that air or other gases will not pass between the isolated region and the remaining portions of the lung to any significant extent . as shown in fig4 c , it is the object of the present invention to apply a vacuum to a lumen within the isolation / access catheter 10 to aspirate the internal regions within the isolated lung tissue segment in order to collapse the tissue . this results in a collapsed lung tissue region clt , as shown as a shaded region in fig4 c . according to the present invention , a variety of steps and protocols may be performed prior to aspirating the isolated lung tissue region in order to enhance gas removal from the region . the region may be over inflated , subjected to vibrations , subjected to a dilating or mucolytic agent , or otherwise treated in order to remove gas flow obstructions within the region . each of these methods has been well described above and will generally rely on performance of at least one aspect of the procedure using a lumen of the isolation / access catheter 10 . for example , over inflation can be effected simply by introducing an inflation gas through the isolation / access catheter to a desired pressure . pressure may be measured using a transducer at the distal tip of the catheter 10 , but will usually be measured statically at a location proximal of the catheter . alternatively or additionally , an oxygen - rich gas can be introduced through the isolation / access catheter in order to induce absorption atelectasis . for vibratory stimulation incompressible fluid may be introduced through the isolation / access catheter . stimulation may be imparted using an external probe and / or a vibratory catheter which is introduced through an access lumen of the isolation / access catheter . as shown in fig4 d , in some instances it will be desirable to reduce or selectively control the inflation of the lung tissue adjacent to the target lung tissue segment in order to enhance aspiration of the target segment . for example , an entire one - half lung can be selectively controlled by an isolation or shunting catheter having a balloon 132 near its distal end . the balloon is inflated to occlude a portion of the selected bronchus , typically about 60 % of the area . thus , pressure within the lung can be reduced and the lung partly collapsed other than in the isolated region . in this way , inflation of the target lung tissue segment can be enhanced which can assist in breaking up occlusions within the lung which would otherwise interfere with subsequent aspiration of the segment . in addition to such in situ techniques for enhancing lung aspiration and collapse , the present invention can rely on application of an external force to assist in collapse . as illustrated in fig5 , a needle or other cannula 200 can be percutaneously introduced into a peritoneal space ps between the parietal pleural pp and visceral pleural vp . insufflation gas , such as carbon dioxide , can be introduced through the needle 200 , either using a syringe or other pressure source . the gas will typically be introduced to a pressure in the range from 30 cm h 2 o to 200 cm h 2 o in spontaneously breathing patients and 70 cm h 2 o to 250 cm h 2 o in positive pressure ventilated patients . use of an unconstrained insufflation gas , however , is disadvantageous since it is not directed at a particular target location . in order to more specifically direct an external pressure against the lung , a balloon 210 can be introduced to the pleural space , typically through a thoracic trocar 212 . the balloon can be placed based on fluoroscopic observation . depending on the particular area which is to be collapsed , a variety of specific balloon configurations can be employed , as illustrated in fig7 a - 7d . a generally spherical balloon 220 is shown attached to shaft 220 in fig7 a . other configurations include a winged profile ( fig7 b ), a cylindrical or spatula profile ( fig7 c ), and a convex profile ( fig7 d ). each of these will be attached to a shaft which permits inflation after introduction into the pleural space . as a further alternative to needle insufflation and balloon expansion , a target lung tissue segment can be externally collapsed using a simple probe 250 , usually introduced through a thoracic trocar 252 , as shown in fig8 . a variety of probes for mechanically engaging and compressing the outer lung surface are illustrated in fig9 a - 9c . optionally , a needle can be used to puncture at a desired point in the target tissue lung segment in order to release and / or aspirate air , usually as a supplement to a primary catheter - based aspiration . the puncture can then be sealed with fibrin glue or other suitable sealant . the methods of the present invention will optionally comprise sealing or occluding the air passage leading to the collapsed tissue region clt . such sealing can be performed in a variety of ways , including suturing , gluing , energy - mediated tissue adhesion , and the like . in a preferred aspect of the present invention , a sealing catheter 280 can be used to deliver a plug 282 , typically a partially hydrated collagen hydrogel , as illustrated in fig1 a - 10c . usually , the catheter will have dimensions which permit it to be introduced through the main access lumen of isolation / access catheter 10 . the plug 282 will be contained in the distal tip of a lumen in the catheter , and a push rod 284 extends the length of the catheter to permit the treating physician to deploy the plug 282 after the tip of the catheter is properly located , as illustrated in fig1 , usually while the balloon on the isolation / access catheter remains inflated and the target lung tissue remains sealed and in an aspirated , collapsed configuration . once deployed within the moist environment of the lung bronchus , the plug 282 will absorb water and will swell substantially , typically from 100 % to 1000 % in order to fully occupy and plug the air passage into the collapsed lung tissue region clt . positioning of the isolation / access catheter 10 within the lung can be performed using on - board optical imaging capability , as discussed above . usually , positioning of a guidewire through the branching bronchus will be manipulated while viewing through the imaging components of the isolation / access catheter . in this way , the isolation / access catheter can be “ inched ” along by alternately advancing the guidewire and the isolation / access catheter . as an alternative to providing the isolation / access catheter with imaging , positioning could be done solely by fluoroscopy . as a further alternative , a steerable , imaging guidewire 300 ( fig1 a - 12c ) could be used . the guidewire 300 includes a deflectable tip 302 which can be deflected in a single plane using push / pull ribbon 304 . usually , the tip will comprise a spring 306 to facilitate deflection . in addition to steerability , the guidewire 300 will include an optical imaging wave guide 310 and illuminating optical fibers 312 , as best seen in cross - sectional view of fig1 c . thus , the guidewire 300 can be steered through the branching bronchus to reach the target tissue segment using its own in situ imaging capability . once the guidewire 300 is in place , an isolation / access catheter can be introduced to the target lung tissue segment as well . since the guidewire has imaging capability , the isolation / access catheter need not incorporate such imaging . this can be an advantage since it permits the access lumen to be made larger since the catheter need not carry any optical wave guides . in addition to the methods and devices described previously , the lung sealing protocols of the present invention can be performed with a variety of two component systems comprising generally an expandable plug or barrier and an adhesive which is introduced against the expandable plug or barrier . while in many instances a single expandable plug or barrier , as described previously , may be sufficient , in other instances it may be desirable to combine such a plug / barrier with an adhesive , sealant , glue , or other similar substance which can facilitate sealing around the periphery of the plug as well as enhanced sealing across the surface of the plug itself . referring now to fig1 a - 14c , a catheter system 500 comprising an outer sheath 502 , and inner tube 504 is used to deliver an expansible barrier 506 . as shown in fig1 a , the barrier 506 is initially contained over a distal end of the inner tube 504 and within a lumen 508 of the outer sheath 502 . barrier 506 can have a variety of forms , but will generally be formed from a resilient metal , optionally a shape memory alloy , which is configured to be released from the catheter assembly 500 and to expand across the lung passage lp , as shown in fig1 b . the barrier may be in the form of a mesh , grid , membrane , or other specific structures , and will have a peripheral edge 510 which is configured to engage against the wall of the lung passage lp . optionally , the barrier 506 will have an impermeable fabric or other layer attached across its surface for inhibiting passage of air and / or contain a sealant . while the barrier 506 could be delivered in a variety of ways , it is shown to be delivered by retracting the outer sheath 502 from over the inner tube 504 so that the barrier 506 expands radially outwardly after the sheath 502 is withdrawn . while in certain embodiments the expansible barrier 506 could be sufficient to occlude the lung passage lp , i . e ., prevent the flow of gasses thereacross , it will generally be preferred to enhance occlusion by delivering an adhesive material 520 , as shown in fig1 c . conveniently , the adhesive 520 will be a liquid or other flowable material which can be introduced through a lumen of the inner tube 504 . suitable materials include albumin , collagen or fibrin based , synthetic or non - synthetic adhesives , preferably mixed with radiopaque tracers , such as silver nitrate , barium sulfate or any other traceable biocompatible material . the adhesive will generally be curable so that it forms a solid mass adjacent to the barrier 520 , which in particular seals the peripheral portion 510 against the wall . referring now to fig1 a - 15c , catheter system 600 includes catheter body 602 having a balloon - expansible barrier 604 at its distal end . a balloon 608 at the distal end of catheter 602 may best be used to expand the barrier 604 , as shown in fig1 b . the barrier 604 may be composed of a wide variety of malleable materials , such as stainless steel , and will typically be in the form of a mesh , braid , or other similar structure . optionally , the barrier 604 may include a fabric or membrane barrier laminated thereto to enhance impermeability . adhesive 610 is typically introduced through either the balloon catheter 602 or optionally a separate adhesive delivery catheter 612 , as shown in fig1 c . referring now to fig1 a - 16e , a third approach for delivering a two - component sealing system according to the present invention will be described . a system 700 comprises a catheter 702 having an optical fiber viewing component 704 at its distal end . the catheter 702 is initially positioned in the lung passage lp at the region to be occluded . a swellable collagen or other plug is then released from the catheter 702 , as shown in fig1 b . preferably , the plug 706 will be advanced by a positioning wire 708 which remains attached to the plug 706 to allow positioning of the plug 706 while it is expanding . after the plug 706 is fully expanded and properly positioned , the wire 708 may be withdrawn , as shown in fig1 c . it will be appreciated that all of the foregoing steps are optionally accomplished while viewing with the use of the fiberoptic viewing component 704 . a separate adhesive delivery tube 710 may then be introduced through the catheter 702 , as shown in fig1 d . adhesive 712 may then be delivered through the tube 710 , again while the procedure is preferably being viewed via the optical viewing component 704 . after the adhesive 712 is introduced , the catheter 702 and all associated components may be withdrawn , as shown in fig1 f , leaving the barrier comprising the swellable plug 702 and adhesive substance 712 in place . referring now to fig1 , kits 400 according to the present invention comprise at least an isolation / access catheter 10 and instructions for use ifu . optionally , the kits may further include any of the other system components described above , such as a balloon probe 210 , a sealing catheter 280 , a reagent container 420 ( optionally including any of the dilating or mucolytic agents described above ), or other components . the instructions for use ifu will set forth any of the methods as described above , and all kit components will usually be packaged together in a pouch 450 or other conventional medical device packaging . usually , those kit components , such as isolation / access catheter 10 , which will be used in performing the procedure on the patient will be sterilized and maintained sterilely within the kit . optionally , separate pouches , bags , trays , or other packaging may be provided within a larger package , where the smaller packs may be opened separately and separately maintain the components in a sterile fashion . while the above is a complete description of the preferred embodiments of the invention , various alternatives , modifications , and equivalents may be used . therefore , the above description should not be taken as limiting the scope of the invention which is defined by the appended claims .
lung volume reduction is performed in a minimally invasive manner by isolating a lung tissue segment , optionally reducing gas flow obstructions within the segment , and aspirating the segment to cause the segment to at least partially collapse . further optionally , external pressure may be applied on the segment to assist in complete collapse . reduction of gas flow obstructions may be achieved in a variety of ways , including over inflation of the lung , introduction of mucolytic or dilation agents , application of vibrational energy , induction of absorption atelectasis , or the like . optionally , diagnostic procedures on the isolated lung segment may be performed , typically using the same isolation / access catheter .