BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical methods and apparatus. More particularly, the present invention relates to methods and apparatus for endobronchial residual lung volume reduction by passive deflation of hyperinflated segments with functional lung volume expansion as a result.

Chronic obstructive pulmonary disease is a significant medical problem affecting 16 million people or about 6% of the U.S. population. Specific diseases in this group include chronic bronchitis, asthmatic bronchitis, and emphysema. While a number of therapeutic interventions are used and have been proposed, none are completely effective, and chronic obstructive pulmonary disease remains the fourth most common cause of death in the United States. Thus, improved and alternative treatments and therapies would be of significant benefit.

Of particular interest to the present invention, lung function in patients suffering from some forms of chronic obstructive pulmonary disease can be improved by reducing the effective lung volume, typically by resecting diseased portions of the lung. Resection of diseased portions of the lungs both promotes expansion of the non-diseased regions of the lung and decreases the portion of inhaled air which goes into the lungs but is unable to transfer oxygen to the blood. Lung volume reduction is conventionally performed in open chest or thoracoscopic procedures where the lung is resected, typically using stapling devices having integral cutting blades.

While effective in many cases, conventional lung volume reduction surgery is significantly traumatic to the patient, even when thoracoscopic procedures are employed. Such procedures often result in the unintentional removal of healthy lung tissue, and frequently leave perforations or other discontinuities in the lung which result in air leakage from the remaining lung. Even technically successful procedures can cause respiratory failure, pneumonia, and death. In addition, many older or compromised patients are not able to be candidates for these procedures.

As an improvement over open surgical and minimally invasive lung volume reduction procedures, endobronchial lung volume reduction procedures have been proposed. For example, U.S. Pat. Nos. 6,258,100 and 6,679,264 describe placement of one-way valve structures in the airways leading to diseased lung regions. It is expected that the valve structures will allow air to be expelled from the diseased region of the lung while blocking reinflation of the diseased region. Thus, over time, the volume of the diseased region will be reduced and the patient condition will improve.

While promising, the use of implantable, one-way valve structures is problematic in at least several respects. The valves must be implanted prior to assessing whether they are functioning properly. Thus, if the valve fails to either allow expiratory flow from or inhibit inspiratory flow into the diseased region, that failure will only be determined after the valve structure has been implanted, requiring surgical removal. Additionally, even if the valve structure functions properly, many patients have diseased lung segments with collateral flow from adjacent, healthy lung segments. In those patients, the lung volume reduction of the diseased region will be significantly impaired, even after successfully occluding inspiration through the main airway leading to the diseased region, since air will enter collaterally from the adjacent healthy lung region. When implanting one-way valve structures, the existence of such collateral flow will only be evident after the lung region fails to deflate over time, requiring further treatment.

For these reasons, it would be desirable to provide improved and alternative methods and apparatus for effecting residual lung volume reduction in hyperinflated and other diseased lung regions. The methods and apparatus will preferably allow for passive deflation of an isolated lung region without the need to implant a one-way valve structure in the lung. The methods and apparatus will preferably be compatible with known protocols for occluding diseased lung segments and regions after deflation, such as placement of plugs and occluding members within the airways leading to such diseased segments and regions. Additionally, such methods and devices should be compatible with protocols for identifying and treating patients having diseased lung segments and regions which suffer from collateral flow with adjacent healthy lung regions. At least some of these objectives will be met by the inventions described hereinbelow.

2. Description of the Related Art

Methods for performing minimally invasive and endobronchial lung volume reduction are described in the following U.S. Pat. Nos. 5,972,026; 6,083,255; 6,258,100; 6,287,290; 6,398,775; 6,527,761; 6,585,639; 6,679,264; 6,709,401; 6,878,141; 6,997,918; 2001/0051899; and 2004/0016435. Balloon catheter devices for use in body passageways have previously been described in U.S. Pat. Nos. 4,976,710; 4,470,407; 4,681,093 and 6,174,307, and. U.S. Pat. No. 4,976,710 describes an angioscope with a transparent occlusion balloon at its distal end. Similarly, U.S. Pat. No. 6,174,307 describes an endovascular catheter with a transparent portion near the distal tip that can be used to view the body passageway. Similarly, issued U.S. Pat. Nos. 4,470,407 and 4,681,093 also describe endovascular devices with a transparent expandable balloon covering the lens. Though these catheters utilize the balloons to view the passageways, their use for viewing pulmonary passageways is limited in several aspects. Practically, the use of these devices in pulmonary passageways would be limited to those passageways large enough to accommodate a similarly constructed bronchoscope. These devices are also limited by the fact that treatment is limited to the exact site of visualization, rather than at a point distal to the visualization point. Further, the flexibility of these devices would be limited by the inherent properties of a visualization catheter. Hence, it would be beneficial to have a catheter that is flexible and to use it to visualize points that are distal to the location of the distal tip of the catheter.

SUMMARY OF THE INVENTION

The present invention provides methods and apparatus for passively reducing the residual volume (the volume of air remaining after maximal exhalation) of hyperinflated or otherwise diseased lung compartments or segments. By “passively reducing,” it is meant that air can be removed from the diseased lung region without the use of a vacuum aspiration to draw the air from the region. Typically, such passive reduction will rely on a non-implanted one-way flow element, structure, or assembly which permits air to be exhaled or exhausted from the lung region while preventing or inhibiting the inspiration of air back into the lung region. By non-implanted, it is meant that some portion of the element, structure, or assembly will be temporarily placed in an airway or bronchus leading to the lung region in a manner that allows that portion to be removed later, typically within days or hours, without the need for surgical intervention Thus, the methods of the present invention will not require the permanent implantation of valves or other structures prior to actually achieving the desired residual lung volume reduction, as with the one-way implantable valve structures of the prior art.

The methods and apparatus of the present invention can be terminated and all apparatus removed should it appear for any reason that the desired residual lung volume reduction is not being achieved. Commonly, such failure can be the result of collateral flow into the diseased lung region from adjacent healthy lung region(s). In such cases, steps can be taken to limit or stop the collateral flow and allow resumption of the passive lung volume reduction protocols. In other cases, it might be desirable or necessary to employ open surgical, thoracoscopic, or other surgical procedures for lung resection.

Patients who successfully achieve residual volume reduction of hyperinflated or other diseased lung regions in accordance with the principles of the present invention will typically have those regions sealed permanently to prevent reinflation. Such sealing can be achieved by a variety of known techniques, including the application of radiofrequency or other energy for shrinking or sealing the walls of the airways feeding the lung region. Alternatively, synthetic or biological glues could be used for achieving sealing of the airway walls. Most commonly, however, expandable plugs will be implanted in the airways leading to the deflated lung region to achieve the sealing.

In a first aspect of the present invention, methods for reducing the residual volume of a hyperinflated lung compartment comprise sealingly engaging a distal end of a catheter in an airway feeding the lung compartment. Air is allowed to be expelled from the lung compartment through a passage in the catheter while the patient is exhaling, and air is blocked from re-entering the lung compartment through the catheter passage while the patient is inhaling. As the residual volume diminishes, the hyperinflated lung compartment reduces in size freeing up the previously occupied space in the thoracic cavity. Consequently, a greater fraction of the Total Lung Capacity (TLC), which is the volumetric space contained in the thoracic cavity that is occupied by lung tissue after a full inhalation becomes available for the healthier lung compartments to expand and the volume of the lung available for gas exchange commonly referred to in clinical practice as the lung's Functional Vital Capacity (FVC) or Vital Capacity (VC) increases, the result of which is effectively a functional lung volume expansion.

The hyperinflated lung compartment will usually be substantially free of collateral flow from adjacent lung compartments, and optionally the patient can be tested for the presence of such collateral flow, for example using techniques taught in copending, commonly assigned application Ser. No. 11/296,951, filed on Dec. 7, 2005; Ser. No. 11/550,660, filed on Oct. 18, 2006; and application Ser. No. 11/428,762, filed on Jul. 5, 2006, the full disclosures of which are incorporated herein by reference.

Alternatively, the methods of the present invention for reducing residual lung volume can be performed in patients having collateral flow channels leading into the hyperinflated or other diseased lung compartment. In such cases, the collateral flow channels may first be blocked, for example, by introducing glues, occlusive particles, hydrogels or other blocking substances, as taught for example in copending application Ser. No. 11/684,950, filed on Mar. 12, 2008, the full disclosure of which is incorporated herein by reference. In other cases, where the flow channels are relatively small, those channels will partially or fully collapse as the residual lung volume is reduced. In such cases, the patient may be treated as if the collateral flow channels did not exist. The effectiveness of reduction in hyperinflation however will depend on the collateral resistance between the hyperinflated compartment and the neighboring compartments, as illustrated inFIG. 9, where residual volume reduction is negligible when the resistance to collateral flow Rcoll is very small (significant collateral flow channels) and maximally effective when Rcoll is very high (no collateral flow channels).

In all of the above methods, it may be desirable to introduce an oxygen-rich gas into the lung compartment while or after the lung volume is reduced in order to induce or promote absorption atelectasis. Absorption atelectasis promotes absorption of the remaining or residual gas in the compartment into the blood to further reduce the volume, either before or after permanent sealing of the lung volume compartment or segment.

In a second aspect, the present invention provides catheters for isolating and deflating hyperinflated and other diseased lung compartments. The catheter comprises a catheter body, an expandable occluding member on the catheter body, and a one-way flow element associated with the catheter body. The catheter body usually has a distal end, a proximal end, and at least one lumen extending from a location at or near the distal end to a location at or near the proximal end. At least a distal portion of the catheter body is adapted to be advanced into and through the airways of a lung so that the distal end can reach an airway which feeds a target lung compartment or segment to be treated. The expandable occluding member is disposed at or near the distal end of the catheter body and is adapted to be expanded in the airway which feeds the target lung compartment or segment so that said compartment or segment can be isolated with access provided only through the lumen or catheter body when the occluding member is expanded.

The catheter of the present invention can be used in conjunction with, or independent of, a viewing scope such as a bronchoscope. Since it is generally configured to be narrower than a visualization tube such as a bronchoscope, the catheter may be introduced into narrower passageways and is used to isolate a portion of lung tissue.

In one embodiment of the catheter, the expandable occluding element is disposed near the distal end of the catheter body. In this embodiment, the expandable occluding element is configured such that both the proximal and distal ends of the expandable occluding element are attached to the outer surface of the catheter body.

In another embodiment of the catheter, the expandable occluding element is disposed at the distal end of the catheter body, and is configured to form a cover over the rim of the lumen. This embodiment prevents or inhibits entry of mucus into the lumen, and prevents the catheter tip from contacting the airway wall. A method of manufacturing this embodiment of the catheter is also disclosed. One end of the occluding element is attached to the internal surface of the central passageway at the tip of the catheter. The occluding element is then inverted over the catheter body and a second end of the occluding element is attached to the outer surface of the catheter body. The expandable occluding element is optionally transparent to enable viewing the body passageway (for example during diagnostic or treatment procedures).

The one-way flow element is adapted to be disposed within or in-line with the lumen of the catheter body in order to allow flow in a distal-to-proximal direction so that air will be expelled from the isolated lung compartment or segment as the patient exhales. The one-way flow element, however, inhibits or prevents flow through the lumen in a proximal-to-distal direction so that air cannot enter the isolated lung compartment or segment while the patient is inhaling.

For the intended endobronchial deployment, the catheter body will typically have a length in the range from 20 cm to 200 cm, preferably from 80 cm to 120 cm, and a diameter near the distal end in the range from 0.1 mm to 10 mm, preferably from 1 mm to 5 mm. The expandable occluding member will typically be an inflatable balloon or cuff, where the balloon or cuff has a width in the range from 1 mm to 30 mm, preferably from 5 mm to 20 mm, when inflated. The one-way flow element is typically a conventional one-way flow valve, such as a duck-bill valve, a flap valve, or the like, which is disposed in the lumen of the catheter body, either near the distal end or at any other point within the lumen. Alternatively, the one-way flow element could be provided as a separate component, for example, in a hub which is detachably mounted at the proximal end of the catheter body. In other instances, it might be desirable to provide two or more one-way flow elements in series within the lumen or otherwise provided in-line with the lumen in order to enhance sealing in the inspiratory direction through the lumen. In a particular illustrated embodiment, a one-way flow control assembly is provided as part of an external console attached in-line with the catheter lumen. The flow-control assembly comprises a valve that is controlled electrically or through other means, sensors for sensing flow and pressure in the lumen, and a valve controller for controlling the valve based on input from the sensors. The sensors monitor flow to detect the beginning of an inhalation cycle and pressure to detect the beginning of an exhalation cycle. Based on the input from the sensors, the valve controller opens the valve at the beginning of the exhalation cycle to deflate the lung region and closes the valve at the beginning of the inhalation cycle to prevent reinflation of the lung region.

