Methods of treating a lung

#This invention relates to a method for treating a lung, and more particularly, to a method for treating a lung by applying energy to an airway wall to increase the diameter of the airway during an asthma attack.

#Asthma is a serious chronic condition affecting an estimated 10 million Americans. Asthma is characterized by (i) bronchoconstriction, (ii) excessive mucus production, and (iii) inflammation and swelling of airways. These conditions cause widespread and variable airflow obstruction thereby making it difficult for the asthma sufferer to breathe. Asthma further includes acute episodes or attacks of additional airway narrowing via contraction of hyper-responsive airway smooth muscle. Other obstructive diseases such as COPD may also have a reversible component caused by one or more of the above mentioned three elements.

#Asthma generally includes excessive mucus production in the bronchial tree. Usually, there is a general increase in bulk (hypertrophy) of the large bronchi and chronic inflammatory changes in the small airways. Excessive amounts of mucus are found in the airways and semisolid plugs of mucus may occlude some small bronchi. Also, the small airways are narrowed and show inflammatory changes. The reversible aspects of COPD include partial airway occlusion by excess secretions, and airway narrowing secondary to smooth muscle contraction, bronchial wall edema and inflammation of the airways.

#The invention will now be described in greater detail with reference to the various embodiments illustrated in the accompanying drawings wherein:

#FIG. 1. is a cross sectional view of an airway in a healthy lung;

#FIG. 2. shows a section through a bronchiole having an airway diameter smaller than that shown in FIG. 1;

#This invention relates to methods for improving airflow through the airways of a lung having reversible obstructive pulmonary disease. In accordance with the invention an airway may be treated during an acute episode of reversible obstructive pulmonary disease such as an asthma attack. The invention comprises applying or transferring energy to an airway wall to increase the diameter of the airway or otherwise reduce resistance to airflow through the airway. The energy may be transferred in an amount sufficient to temporarily or permanently increase the diameter of the airway. Notably, the method may be performed while the airway is open, closed or partially closed. The inventive method thus can “rescue” an asthma sufferer during an acute asthma episode by increasing the diameter of a constricted airway.

#Various airways are shown in FIGS. 1-3. FIGS. 1 and 2 show a cross section of two different airways in a healthy patient. The airway of FIG. 1 is a medium sized bronchus having an airway diameter D1 of about 3 mm. FIG. 2 shows a section through a bronchiole having an airway diameter D2 of about 1.5 mm. Each airway includes a folded inner surface or epithelium 10 surrounded by stroma 12 and smooth muscle tissue 14. The airway is thus quite different from other tissues such as blood vessel tissue which does not include such folds. The larger airways including the bronchus shown in FIG. 1 also have mucous glands 16 and cartilage 18 surrounding the smooth muscle tissue 14. Nerve fibers 20 and blood vessels 24 surround the airway.

#FIG. 3 illustrates the bronchus of FIG. 1 in which the smooth muscle 14 has hypertrophied and increased in thickness causing the airway diameter to be reduced from the diameter D1 to a diameter D3. Accordingly, the airways to be treated with the device of the present invention may be 1 mm in diameter or greater. The airways to be treated are often second to eighth generation, and more preferably airways of the second to sixth generation.