Abstract:
Lung volume reduction is performed by the placement of a device ( 2 ) into a branch of the airway ( 34 ) to prevent air from entering that portion of lung. This will result in adsorption atelectasis of the distal portion of lung. The physiological response in this portion of lung is hypoxic vaso-constriction. The net effect is for a portion of lung to be functionally removed, i.e. a selected portion of lung is removed from both the circulation and ventilation. The build up of secretions is accommodated by using a valve ( 5, 15, 29 ) in the obstructive device, the valve opening upon coughing etc.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to devices for bronchiopulmonary occlusion, inter alia for inducing lung volume reduction, and surgical procedures using such devices, including methods of lung volume reduction.  
         BACKGROUND ART  
         [0002]    Emphysematous lungs are characterised by abnormally large air spaces. Lung compliance characteristics are such that the lung is ‘too large’ for its pleural cavity.  
           [0003]    Lung volume reduction surgery (LVRS) was developed as an intervention procedure to alleviate respiratory distress in a patient with a minimal reserve. In this procedure, a portion of less efficient lung is removed under general anaesthetic, allowing the remaining lung to expand. The net effect is, paradoxically to improve respiratory function by excising a section of lung. LVRS is associated with moderate mortality, approximately 5% and frequently high morbidity such as prolonged air leakage. To optimiise patient outcome, selection criteria are strict and an extensive pre- and postoperative physiotherapy programme is undertaken. The length of hospitalisation for the surgery and initial postoperative care can be in the order of threemonths. The intervention, as a whole, is a very expensive procedure and generally is 7  not covered by insurance schemes. In the USA, this high cost has resulted in the procedure being substantially funded within FDA approved trials.  
           [0004]    Other indications for which the devices and methods of the present invention may be applied include bronchial occlusion for the treatment of spontaneous pneumothorax, persistent pneumothoraces and as an adjuvant to the chemotherapeutic treatment of tuberculosis.  
         DISCLOSURE OF INVENTION  
         [0005]    It is an object of the present invention to provide a relatively non-invasive and comparatively inexpensive lung volume reduction procedure by forming a temporary or permanent obstruction in a bronchus. It is a further object of the present invention to provide an efficient and relatively inexpensive occluding device which can be deployed by an endoscope. Endoscopic insertion of an obstructive device is likely to reduce mortality and morbidity compared with traditional surgery in patients having limited reserve and thus permit more liberal case selection.  
           [0006]    The target site may be a portion of a trachobronchial tree. More preferably, the target site is a third or fourth generation bronchus. Preferably the occluding device is removable by endoscopic probe deployment and retrieval. If necessary, the occluding device can be compressed or deformed by the probe to facilitate removal. Optionally the device is biodegradable being composed of biocompatible material having a predetermined life span to provide temporary occlusion.  
           [0007]    The blocking mechanism may be a transverse partitioning member such as an end wall, or resilient diaphragm. Alternatively, the blocking mechanism is an occlusive plug such as an inflatable balloon or pivotable stopper biased to a sealing position. Preferably, however, the blocking means is in the form of a one-way valve, which functions to allow the egress of gases or fluids from the targeted volume.  
           [0008]    Lung volume reduction is thus performed by the placement of a device into a branch of the airway to prevent air from entering that portion of lung. This will result in adsorption atelectasis of the distal portion of lung. The physiological response in this portion of lung is hypoxic vasoconstriction. The net effect is for a portion of lung to be functionally removed, i.e. a selected portion of lung is removed from both the circulation and ventilation. The build up of secretions is accommodated by the valve in the obstructive device, the valve opening upon coughing etc.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    By way of example only, preferred embodiments of the present invention are described in detail with reference to the accompanying drawings in which:  
         [0010]    [0010]FIG. 1 is an end view of an occluding device in accordance with present invention;  
         [0011]    [0011]FIG. 2 is a cross-sectional view of the occluding device taken on the line  2 - 2  in FIG. 1;  
         [0012]    [0012]FIG. 3 shows in side elevation an occluding device according to a second embodiment of the invention;  
         [0013]    [0013]FIG. 4 shows an end view of the device of FIG. 3;  
         [0014]    [0014]FIG. 5 shows a delivery system for the device of FIG. 3;  
         [0015]    [0015]FIG. 6 shows an inflation device;  
         [0016]    [0016]FIG. 7 shows the device of FIG. 3 mounted on the inflation device;  
         [0017]    [0017]FIG. 8 shows a further alternative embodiment of the occluding device;  
         [0018]    [0018]FIG. 9 is an end view of a frame for an occluding device;  
         [0019]    [0019]FIG. 10 is a side elevation of the frame of FIG. 9;  
         [0020]    [0020]FIG. 11 is an end view of an occluding device incorporating the frame of FIGS. 9 and 10;  
         [0021]    [0021]FIG. 12 is a cross-sectional elevation of the occluding device of FIG. 11, and  
         [0022]    FIGS.  13  to  16  schematically illustrate methods of insertion and removal of the device of FIGS. 11 and 12.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]    The occluding device shown in FIGS. 1 and 2 includes an elongate member in the form of a tapered tubular sleeve  3 , a transverse partition  4  incorporating a flutter valve  5 , and a frame  6 . In this embodiment the periphery of the occluding device  2  is longitudinally tapered to aid insertion in a bronchus as described below, but this is not essential, as the tissue is normally sufficiently elastic to allow insertion.  
         [0024]    The partition  4  subdivides the internal cavity of the occluding device  2  into a proximal rear section  11  and a distal head section  12 . The flutter valve  5  is pivotally secured at one end to a wall portion of the partition  4  and moveable between an open and a closed position in the direction of Arrow A, FIG. 2. The flutter valve  5  is biased to the closed position, sealing the central aperture defined by the walls of the transverse partition  4  as shown in FIG. 2.  
         [0025]    The head end of the sleeve  3  is provided with a series of equidistantly spaced peripheral projections  7 . In use, each inclined projection  7  acts as a lateral anchor to prevent axial migration of the occluding device  2 . Preferably the projections  7  are composed of a resilient material.  
         [0026]    The frame  6  is coupled to the partition  4  and supports the rear sleeve section  11 . The frame  6  essentially comprises an arcuate member  8  and an inwardly tapered skirt  9 . A portion of the arcuate member  8  protrudes from mouth of the rear section  11  to act as a handle to assist in the insertion and/or removal of the occluding device  2 .  
         [0027]    The occluding device  2  can be utilised in a bronchoscopic procedure to selectively ‘sculpture’ the collapse of an emphysematous lung. The occluding device  2  is inserted and retained in the mouth of an endoscopic probe such that a portion of the distal section  12  protrudes from the mouth. Alternatively, the occluding device  2  can be grasped by the handle-like arcuate member  8 . The probe is then introduced into the trachobronchial system by deployment through the nasal cavity, mouth/tracheal conduits of a patient. The probe is fed down the trachea into the bronchial tree of the target lung and positioned adjacent a pre-selected target site. For example, a third or fourth generation bronchus located in the apex of that lung.  
         [0028]    The operator using visual and/or tactile feedback cues manipulates the occluding device  2  so that the occluding device becomes radially lodged in the bronchial cavity. If necessary, the arcuate member  8  is used as a handle for the probe to toggle the occluding device into position. The projections  7  engage or abut the bronchial wall of the target site and the rear section  11  is wedged like a cork, the elastic bronchial walls effecting an interference fit.  
         [0029]    The probe is withdrawn from the patients body. Any tracheal or abdominal incision for insertion of bronchoscopic equipment is sutured appropriately,  
         [0030]    The biased flutter valve  5  prevents the ingress of respiratory gas past the partition  4 . The body will gradually absorb the gaseous content upstream of the occluding device  2 . The blood flow to this lung section is minimised by the physiological hypoxic vasoconstriction. Occlusion of the bronchus by the occluding device  2  induces collapse of the downstream portion of the bronchial tree, functionally removing a section of the lung.  
         [0031]    Fluid build-up is often associated with bronchial occlusion. In this case, the pressure of gas and mucous secretions adjacent the distal section  12  will override the bias of the flutter valve  5  allowing egress through the partition  4  and proximal section of the occluding device  2 .  
         [0032]    The occluding device  2  is removable by endoscopic probe retrieval. The frame  6  being coupled to the partition  4  enables radial collapse of the occluding device  2 . The protruding portion of the arcuate member  8  is crushed and pulled downstream within the jaws of a probe to deform the skirt  9  and partition  4 , compressing and dislodging the occluding device  2 . The probe is withdrawn from the patients body.  
         [0033]    It will be understood that the optimum location of the occluding device within the lung will be determined by the purpose of the intervention. As mentioned above, in the treatment of emphysema, a fourth generation bronchus may be preferred. In the treatment of pneumothorax, the location of the occluding device will be determined by the location of the breach in lung tissue. Where the device and method of the invention is used to isolate a diseased region of the lung, as in the treatment of tuberculosis, the clinician will determine the optimum location as part of the treatment strategy.  
         [0034]    The occluding device shown in FIGS. 3 and 4 includes an expandable cylindrical stent  13 , which may be of metal or plastics, carrying on its proximal end portion a valve member  14  which has a tapered end portion  15  forming a one-way valve having lips  16  and a slit  17 . The valve member may be formed from a biologically compatible resilient plastics material such as silicone or polyurethane, or suitable biological materials. The device of FIGS. 3 and 4 is intended to be delivered by means of a system as illustrated in FIG. 5, consisting of a lumen  18  provided at its proximal end with a Luer connector  19  for attachment to an inflation device, and at its distal end with an inflatable and deflatable balloon  20 , the lumen terminating in a rounded solid tip  21 .  
         [0035]    As shown in FIG. 6, the balloon  20  is sealed to the shaft of the lumen  18 , and within the walls of the balloon  20  the shaft is provided with ports  22  for inflation and deflation of the balloon.  
         [0036]    As shown in FIG. 7, the occluding device comprising the stent portion  13  and the valve  14  is mounted on the balloon  20  by passing the end of the lumen through the lips of the valve. Upon correct location of the device in the bronchus, the balloon  20  is inflated, expanding the stent portion and fixing the device in place against the bronchial wall. The stent portion  13  will normally be expanded to a diameter which is greater than the normal internal diameter of the bronchus at the site, so that upon relaxation after inflation the device remains in engagement with the bronchial wall. Sealing against the bronchial wall is provided by the material of the valve member  14 .  
         [0037]    In an alternative construction of such an occluding device, the valve member  14  may be fixed within, rather than outside, the stent body  13 . Such an arrangement is shown in cross-section in FIG. 8. Where this arrangement is used, it may be preferred to attach the valve material to the stent device by suturing or glueing to achieve a gas-proof seal.  
         [0038]    Another approach to the design of an occluding device for the purposes of the invention is shown in FIGS.  9  to  12 . Here a frame  25  consisting of an expandable ring  26  and an arcuate “handle”  27  is also provided with barbs  28  around its periphery. A valve member of flexible material with a proximally directed valve aperture  30  is fixed within the frame  25  by having its outer edge  24  engaged over the barbs  28 . Such a valve is capable of expanding into the position shown in FIGS. 11 and 12 with the frame  25 , upon ejection from a delivery tube in which the device has been inserted, as described below.  
         [0039]    As shown in FIGS. 13 and 14, such a device may be located and fixed within the target bronchus  34  by means of a delivery tube  31  containing an ejector  32 , mounted within the biopsy channel of a bronchoscope  33 . The device is compressed within the delivery tube, and expands upon ejection, with the barbs  28  engaging the bronchial wall to resist migration of dislodgement of the device.  
         [0040]    The frame  25  is preferably elastic so that it expands automatically into contact with the bronchial wall upon ejection, but alternatively it may be expanded by means of a balloon or other expanding device.  
         [0041]    An advantage of the device of FIGS.  9 - 12  is that it is capable of removal by a simple endoscopic procedure. This is illustrated in FIGS. 15 and 16. A removal catheter consisting of an inner member  35  provided with a hook or grasping device  36  and an outer sheath  37  is deployed to the site by means of a bronchoscope  33 . The hook  36  is engaged with the “handle”  27 , and the sheath  37  advanced to compress the device, releasing the barbs  28  from the bronchial wall. The compressed device is then removed by withdrawing the members  35  and  37 .  
         [0042]    The devices and methods described above may be used in the treatment tuberculosis, particularly where multi-resistant strains are involved. In such a case the collapse of the target region of the lung following the introduction of an occluding device at the target site, and the subsequent hypoxic vasoconstriction, will rob bacilli in the target region of blood supply and effectively increase the potency of the antibiotics employed.  
         [0043]    As mentioned above, the device may be manufactured from biodegradable material to remove the need for physical removal where persistence of the device is not required.