Abstract:
A device and method for treating bodily conduits involves the application of energy to the smooth muscle tissue of the conduit walls to reduce the bulk of smooth muscle tissue and mucus glands. The irradiation treatment of the smooth muscle tissue causes a reduction in the amount of smooth muscle tissue over time which increases the inner diameter of the body conduit for improved fluid flow and prevents smooth muscle spasms. The treatment is particularly useful in the lungs for treatment of asthma to prevent bronchospasms, increase the airway diameter for improved air exchange, and reduce mucus secretions in the lungs.

Description:
[0001]     This is a continuation of U.S. application Ser. No. 09/095,323 filed Jun. 10, 1998. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a method and apparatus for treating smooth muscle in the walls of body conduits, and more particularly, the invention relates to a method for treating medical conditions by reducing the bulk of smooth muscle surrounding a body conduit with radiant energy treatment of the smooth muscle.  
         [0003]     Asthma is a disease which involves heightened reactivity of the tracheobronchial tree to numerous stimuli causing contraction of smooth muscle surrounding the airways of the lungs. The hyperreactivity of the airways can result from abnormal tissue reactions in the airways, which may be immunologically induced, or from a biochemical or neurohumoral imbalance of other normally functioning responses. In a healthy patient, the smooth muscle surrounding the airways contracts, such as when the patient coughs, to increase the localized airflow through the airways and expel inhaled particles which enter the lungs. In a patient with asthma, the airways are hyperreactive. With these hyperreactive airways a very small amount of pollen, allergen, or other material in the air will stimulate a large amount of smooth muscle contraction or spasm. This repeated contraction of the smooth muscles exercises the muscle causing the muscle to hypertrophy and become larger. Because the tissue surrounding the smooth muscle is relatively rigid, the hypertrophied smooth muscle expands into the airways shrinking the inner diameter of the airways for passage of air. For example, a healthy person has smooth muscle thicknesses surrounding the airways of about 0.01 mm while the smooth muscle thickness in an asthma patient may enlarge to up to about 2 or 3 mm. Correspondingly, the inner diameter of the airways may be reduced from about 2 to 3 mm for a healthy person to about 0.5 mm or less for an asthma patient. This narrowing of the airways causes the whistling or wheezing sound associated with asthma.  
         [0004]     Asthma is also characterized by the excessive secretion of mucus by glands lining the airways. The disease is currently treated by inhalation of bronchodilating drugs to enlarge the airways and atropine and similar compounds to reduce mucus secretion. Bronchodilating drugs are typically beta agonists which react with beta receptors in the smooth muscle causing the smooth muscle to relax, opening the airways. However, if the smooth muscle is already hypertrophied and enlarged the bronchodilating drugs which cause the muscle to relax do little to increase the airway inner diameter.  
         [0005]     An additional disadvantage of the inhaled asthma drugs is that these drugs must be used repeatedly and regularly. Even with regular use of asthma drugs, patients frequently require hospitalization for more intensive therapy and sometimes die from severe bronchospasms and mucus plugging.  
         [0006]     Accordingly, it would be desirable to provide an asthma treatment which enlarges the airways and reduces mucus plugging without the need for repetitive drug treatments.  
         [0007]     In addition to the airways of the lungs, other body conduits such as the esophagus, ureter, urethra, and coronary arteries, are also subject to periodic spasms which cause hypertrophy of the smooth muscle around these body conduits reducing the inner diameter of the conduits.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to a device and method for treating bodily conduits by application of radiant energy to the smooth muscle tissue of the conduit walls to prevent the smooth muscle tissue from replicating. The treatment of the smooth muscle tissue causes a reduction in the amount of smooth muscle tissue over time which increases the inner diameter of the body conduit and prevents smooth muscle spasms.  
         [0009]     In accordance with one aspect of the present invention, an apparatus for the treatment of body conduits includes an elongated body configured to be inserted into a body conduit, the elongated body having a proximal end and a distal end, and a source of energy for emitting energy from the elongated body in an intensity which, when applied to walls of the body conduit causes a change in smooth muscle tissue which prevents the smooth muscle tissue from replicating.  
         [0010]     In accordance with another aspect of the present invention, an apparatus for the treatment of walls of airways in a patient&#39;s lungs includes an elongated body configured to be inserted into the airways of a patient&#39;s lungs, the device having a proximal end and a distal end, and a source of energy for emitting energy from the distal end of the elongated body in an intensity which, when applied to the walls of the airway causes a change in smooth muscle tissue which prevents the smooth muscle tissue from replicating.  
         [0011]     When the source of energy is a light source the apparatus further includes a light transmitting fiber extending from the proximal end to the distal end of the elongated body for transmitting light from the light source into the patient&#39;s lungs, a connector on the distal end of the elongated body for connecting the elongated body to the source of light, and a light directing member positioned at a distal end of the elongated device for diffusing or redirecting the light from the light transmitting fiber in a substantially radial pattern from the distal end of the elongated device.  
         [0012]     In accordance with an additional aspect of the present invention, a method of treating asthma to control bronchospasms includes irradiating the walls of an airway in a lung in a wavelength and intensity which causes a change in smooth muscle tissue cells and prevents the smooth muscle tissue cells from replicating, and controlling bronchospasms by reduction or elimination of smooth muscle tissue.  
         [0013]     In accordance with a further aspect of the invention, a method of treating respiratory conditions to control mucus plugging includes irradiating the walls of an airway in a lung in a wavelength and intensity which causes a change in mucus gland cells and prevents the mucus gland cells from replicating, and preventing mucus plugging by reduction or elimination of mucus glands.  
         [0014]     In accordance with another aspect of the present invention, a method of treating an esophagus, an ureter, or an urethra to control spasms includes irradiating the walls of a conduit to cause a change in smooth muscle cells and prevent the smooth muscle cells from replicating.  
         [0015]     The present invention provides advantages of a treatment for asthma or other enlargement or spasm of the smooth muscle by irradiation. The treatment enlarges airways, reduces or eliminates mucus plugging, and reduces or eliminates bronchospasm. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0016]     The invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which like elements bear like reference numerals, and wherein:  
         [0017]      FIG. 1  is a side cross sectional view of a body conduit and an apparatus for treating the body conduit;  
         [0018]      FIG. 2  is a schematic side view of lungs being treated with the treatment device;  
         [0019]      FIG. 3  is a side cross sectional view of a distal end of a first embodiment of a treatment device according to the present invention;  
         [0020]      FIG. 4  is a side cross sectional view of a distal end of a second embodiment of a treatment device according to the present invention;  
         [0021]      FIG. 5  is a side cross sectional view of a distal end of a third embodiment of a treatment device according to the present invention;  
         [0022]      FIG. 6  is a side cross sectional view of a fourth embodiment of a treatment device according to the present invention;  
         [0023]      FIG. 7  is a side cross sectional view of a fifth embodiment of a treatment device according to the present invention;  
         [0024]      FIG. 8  is a side cross sectional view of a sixth embodiment of a treatment device according to the present invention;  
         [0025]      FIG. 9  is a cross sectional view of an airway in a healthy patient; and  
         [0026]      FIG. 10  is a cross sectional view of an airway in an asthma patient. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]      FIG. 1  illustrates an energy delivery device  10  for the delivery of light energy to the walls  12  of a body conduit. The energy delivery device  10  includes an outer catheter or sheath  16  surrounding a light transmitting fiber  18 . A light directing member  20  is positioned at a distal end of the energy delivery device  10  for directing the light to the conduit walls. Although the present invention will be described in detail with respect to the treatment of airways in the lungs, it should be understood that the present invention may also be used for treatment of other body conduits.  
         [0028]     The energy delivery device  10  and method according to the present invention provide a more permanent treatment for asthma than the currently used bronchodilating drugs and drugs for reducing mucus secretion. In asthma patients, the cross sectional diameter of the airways are reduced due to bulking of the smooth muscle surrounding the airways.  FIG. 9  illustrates an airway  50  of a healthy individual. The airway is surrounded by smooth muscle tissue  52  which is capable of contracting to shrink the diameter of the airway. A plurality of mucus glands  54  are positioned around the airway  50  and secrete mucus into the airway.  FIG. 10  illustrates an airway  60  in an asthma patient in which the smooth muscle  62  has hypertrophied increasing the thickness of the smooth muscle and reducing the inner diameter of the airway. The energy delivery device  10  of the present invention is used to debulk or reduce the volume of smooth muscle  62  surrounding the airway  60  of an asthma patient and increase the airway diameter for improved air exchange.  
         [0029]     The energy delivery device  10  is used to irradiate the smooth muscle surrounding the airways causing the DNA of the smooth muscle cells to become cross linked. The treated smooth muscle cells with cross linked DNA are incapable of replicating. Accordingly, over time, as the smooth muscle cells die, the total thickness of smooth muscle decreases because of the inability of the cells to replicate. The programmed cell death causing a reduction in the volume of tissue is called apoptosis. This treatment does not cause an immediate effect but causes shrinking of the smooth muscle and opening of the airway over time and substantially prevents regrowth. The irradiation by the energy delivery device  10  of the walls of the airway also causes a cross linking of the DNA of the mucus gland cells preventing them from replicating and reducing mucus plugging over time.  
         [0030]     As shown in  FIG. 2 , the energy delivery device  10  is an elongated device such as a catheter containing a fiber optic. The energy delivery device  10  is connected by a conventional optical connection to a light source  22 . The treatment of an airway with the energy delivery device  10  involves placing a visualization system such as an endoscope or bronchoscope into the airways. The energy delivery device  10  is then inserted through or next to the bronchoscope or endoscope while visualizing the airways. The energy delivery device  10  which has been positioned with a distal end within an airway to be treated is energized so that radiant energy is emitted in a generally radially direction from a distal end of the energy delivery device. The distal end of the energy delivery device  10  is moved through the airway in a uniform painting like motion to expose the entire length of an airway to be treated to the energy. The energy delivery device  10  may be passed along the airway one or more times to achieve adequate treatment. The painting like motion used to exposed the entire length of an airway to the energy may be performed by moving the entire energy delivery device  10  from the proximal end either manually or by motor.  
         [0031]     The energy used may be coherent or incoherent light in the range of infrared, visible, or ultraviolet. The light source  22  may be any known source, such as a UV laser source. Preferably the light is ultraviolet light having a wavelength of about 240-280 nm or visible light in the red visible range. The intensity of the light may vary depending on the application. The light intensity should be bright enough to penetrate any mucus present in the airway and penetrate the smooth muscle cells and mucus gland cells to cause cross linking of the cell DNA. The light intensity may vary depending on the wavelength used, the application, the thickness of the smooth muscle, and other factors. Alternatively, a beta or gamma radiation source may be used instead of the light source as described in further detail below with respect to  FIGS. 7 and 8 .  
         [0032]      FIGS. 3-6  illustrate different exemplary embodiments of the distal tip of the energy delivery device  10  for irradiating the airway walls. In  FIG. 3 , the sheath  16  includes a plurality of windows  24  which allow the energy which has been redirected by the light directing member  20  to pass substantially radially out of the sheath. The light directing member  20  is fitted into the distal end of the sheath  16 . The light directing member  20  is a parabolic diffusing mirror having a reflective surface  26  which is substantially parabolic in cross section. The light passes from the light source along the light transmitting fiber  18  and is reflected by the reflective surface  26  of the light directing member  20  through the windows  24 . The windows  24  are preferably a plurality of energy transmitting sections spaced around the distal end of the sheath. The windows  24  may be open bores extending through the sheath  16 . Alternatively, the windows  24  may be formed of a material transparent to the energy being used which allows the energy to pass out of the sheath  16 .  
         [0033]      FIG. 4  illustrates an alternative embodiment of the energy delivery device  10  in which the light directing member  20  has a conical shaped reflective surface  32 . This conical shaped reflective surface may be formed at any desired angle which directs the light transmitted by the light transmitting fiber  18  radially out of the sheath  16 . The use of a conical reflective surface  32  creates a light delivery pattern in which the light rays are directed in a generally coherent radial pattern which is at a generally fixed angle with respect to a longitudinal axis of the light delivery device. In contrast, the light delivery device of  FIG. 3  with the parabolic reflective surface  26  directs light in a diverging radial pattern which will illuminate a larger area of the airway walls.  
         [0034]      FIG. 5  illustrates a further alternative embodiment of the invention in which the light directing member  20  is a substantially conical member including concave reflective surfaces  36 . These concave reflective surfaces  36  direct the light which passes in a generally parallel arrangement through the light transmitting fiber  18  out of the sheath  16  in a converging or crossing pattern. In addition, in the embodiment of  FIG. 5 , the windows have been replaced by a tip  38  of the sheath  16  formed of a material which is transparent to the energy being used.  
         [0035]     The light directing members  20  having a reflective surface as illustrated in  FIGS. 3-5  may be formed in any of the known manners, such as by coating a molded member with a reflective coating, such as aluminum or silver.  
         [0036]     As an alternative to the reflective light directing members of  FIGS. 3-5 , a diffusing lens  42 , such as a Teflon lens, may be positioned at the end of the light transmitting fiber  18  as illustrated schematically in  FIG. 6 . The diffusing lens  42  may direct the light from the light transmitting fiber  18  in a generally conical pattern as shown in  FIG. 6 . Alternatively, the diffusing lens  42  may direct the light in a more radially oriented pattern with the light rays being prevented from exiting the lens in a direction substantially parallel with the longitudinal axis of the light transmitting fiber  18  by a reflective or blocking member. In the embodiment of  FIG. 6 , the sheath  16  surrounding the light transmitting fiber  18  and the diffusing lens  42  may be eliminated entirely and the lens may be affixed directly to the end of the fiber.  
         [0037]     According to one alternative embodiment of the invention, the energy delivery device  10  can be used in conjunction with photo-activatable substances such as those known as psoralens. These light activatable compounds, when activated, enhance the ability of light to cross link the DNA in the smooth muscle tissue and mucus glands. The light activatable compound may by injected intravenously. The light delivered by the light delivery device  10  is matched to the absorption spectrum of the chosen light activatable compound such that the light exposure activates the compound. When such light activatable substances are employed, a lower light intensity may be used to achieve cross linking of the DNA than the light intensity required to achieve cross linking without the light activatable compounds.  
         [0038]      FIG. 7  illustrates an alternative embodiment of an energy delivery device  10  including an elongated body or shaft  66  having a radiation source  68  positioned at the distal end of the flexible shaft. The radiation source  68  may be any known source of radiation such as a radioactive pellet of iridium. The treatment of a bodily conduit of a patient with the energy delivery device  10  of  FIG. 7  is performed by moving the elongated shaft  66  back and forth in the body conduit in a painting like motion to cause a cross linking of the DNA in the smooth muscle surrounding the body conduit.  
         [0039]      FIG. 8  illustrates another alternative embodiment of an energy delivery device  10  having a source of radiation such as a radioactive pellet  72  positioned within a cannula  74 . According to this embodiment, in addition to moving the cannula itself to achieve a painting action within a body conduit, the pellet  72  may be moved within the cannula  74 . Movement of the radioactive pellet  72  may be performed by connecting a syringe to a proximal end of the cannula  74  and injecting or withdrawing fluid through the cannula to move the pellet in a piston like manner. A vent port  76  is provided at the distal end of the cannula  74  to allow fluid to pass into and out of the cannula. In use, the energy delivery device  10  of  FIGS. 7 and 8  are preferably delivered to a treatment site within the body through a shielded cannula which prevents radiation from being emitted into surrounding tissue as the device is inserted.  
         [0040]     In use, the embodiment of  FIG. 8  is inserted to a treatment site such as an airway of the lungs through a radiation shielding cannula. A syringe filled with air is then connected to the proximal end of the cannula  74  and air is injected and withdrawn to move the radioactive pellet within the cannula  74  to expose a desired section of the airway to radiation emitted from the radioactive pellet. Once the treatment has been completed, the cannula  74  and pellet  72  are retracted inside the shielding cannula and the device is withdrawn from the patient.  
         [0041]     The cross linking of the smooth muscle and mucus gland DNA according to the present invention will reduce or eliminate the smooth muscle and the secreting glands such as mucus glands from the area of the airway which is treated by preventing the treated cells from replicating. This light treatment provides improved long term relief from asthma symptoms for some asthma sufferers. However, over time, some amount of smooth muscle or mucus gland cells which were not affected by an initial light treatment may regenerate and treatment may have to be repeated after a period of time such as one or more months or years.  
         [0042]     Although the present treatment has been described for use in debulking enlarged smooth muscle tissue to open up the airways, it may also be used for eliminating smooth muscle altogether. The elimination of the smooth muscle tissue prevents the hyperreactive airways of an asthma patient from contracting or spasming, completely eliminating this asthma symptom.  
         [0043]     The light delivery device  10  may also be used for treatment of other conditions by reducing the volume of smooth muscle tissue surrounding other body conduits. For example, the treatment system may be used for reducing smooth muscle and spasms of the esophagus of patients with achalasia or esophageal spasm, in coronary arteries of patients with Printzmetal&#39;s angina variant, for ureteral spasm, for urethral spasm, and irritable bowel disorders.  
         [0044]     While the invention has been described in detail with reference to the preferred embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention.