DOI:10.2214/AJR.05.0732
AJR 2007; 189:W92-W93
© American Roentgen Ray Society
Endobronchial Valves: Radiographic Appearance of a New Device for Lung Volume Reduction
Stephen C. Wei1,
Darel E. Heitkamp,
Shawn D. Teague and
Mark S. Frank
1 All authors: Department of Radiology, Indiana University School of Medicine,
University Hospital, 550 N University Blvd., Room 0279, Indianapolis, IN
46202-5253.
Received April 29, 2005;
accepted after revision July 25, 2005.
Address correspondence to D. E. Heitkamp
(deheitka{at}iupui.edu).
WEB This is a Web exclusive article.
Keywords: airway • endobronchial valves • lung • radiography
Introduction
Lung volume reduction surgery (LVRS) has been shown to improve
exercise capacity and to decrease symptoms in patients with severe emphysema.
The procedure is associated with a decrease in mortality in a sub-group of
patients with upper-lobe-predominant emphysema and poor exercise capacity
[1] and has been approved for
treatment of this group only. A substantial number of patients are not
candidates for LVRS, in part because of the mortality, morbidity, and cost of
the procedure. A search is underway for a less invasive and less expensive
means of allowing patients with emphysema and comorbid conditions to benefit
from lung volume reduction [2].
We discuss the radiologic findings and general use of endobronchial valves, an
innovative nonsurgical approach to lung volume reduction in patients with
emphysema.
Case Report
A 67-year-old man underwent portable anteroposterior chest radiography
while in the post-anesthesia care unit. He was found to have dyspnea but was
functioning near his baseline value. Electronic review of the patient's
records showed poor pulmonary function test values, as follows: forced
expiratory volume in the first second of respiration, 0.64 L (22%); diffusing
capacity of the lung for carbon monoxide, 28%; total lung capacity, 141% of
predicted. Recent blood gas measurement on room air revealed a
PO2 of 61 mm Hg, PCO2 of 44 mm Hg,
pH of 7.43, and oxygen saturation of 90%. The portable chest radiograph showed
hyperexpanded lungs with severe emphysematous changes, primarily in the upper
lobes. Further inspection revealed several small metallic objects in the
perihilar regions of both lungs (Figs.
1A and
1B). The number and precise
orientation of these objects suggested that they had been intentionally
placed. Im mediate consultation with the referring physician revealed that the
patient had recently undergone bronchoscopic placement of endobronchial
valves, an investigational procedure for the management of
upper-lobe-predominant emphysema.
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Fig. 1A —67-year-old man with dyspnea in postanesthesia care unit.
Anteroposterior portable chest radiograph shows radiolucent hyperexpanded
lungs and severe upper lobe emphysema. Several metallic objects are present in
perihilar regions of both lungs.
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Fig. 1B —67-year-old man with dyspnea in postanesthesia care unit. Magnified
portion of A shows precisely placed metallic objects in right perihilar
region. Larger umbrella-shaped portion of each valve has central
orientation.
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Discussion
LVRS has been shown to benefit patients with severe emphysema when medical
therapy has failed. Resection of nonfunctional end-stage portions of lung
increases aeration to the remaining tissue and improves respiratory mechanics,
thus improving overall respiratory efficiency. The improvement typically
manifests as increased exercise tolerance, fewer symptoms, and increased
oxygenation. Although it has been shown to improve survival among patients
with upper-lobe-predominant emphysema and poor baseline exercise capacity,
LVRS carries a 90-day postoperative mortality as high as 29% among patients at
high risk [1,
3]. Patients with 20% or less
of predicted forced expiratory volume in the first second of respiration and
either homogeneous emphysema on CT or 20% or less of predicted diffusing
capacity of the lung for carbon monoxide are categorized as being at high risk
and are not candidates for LVRS. The endobronchial valve was developed as a
minimally invasive alternative for the treatment of these patients.
The intrabronchial valve (IBV, Spiration) is one of two endobronchial valve
designs undergoing clinical trial. It is an umbrella-shaped one-way valve
consisting of a nitinol frame covered with a polyurethane membrane
(Fig. 2). A preloaded delivery
catheter is passed through the working channel of a bron-choscope to deploy
the intrabronchial valve into the targeted bronchus, excluding the distal
diseased portion of the lung from the proximal airway. The one-way valve
configuration prevents air from entering the excluded portion of the lung but
allows normal clearance of mucus and debris, preventing postobstructive
complications. Over time, the excluded lung is expected to undergo volume loss
and become atelectatic, allowing the more functional portion of the lung to
expand and perform improved gas exchange. Intrabronchial valves have been
shown to result in lung volume reduction in canine models (Mink SN et al.,
presented at the 2003 annual meeting of the American College of Chest
Physicians), and multicenter clinical trials with human subjects are underway.
Use of a similar endobronchial valve (Zephyr, Emphasys Medical) has been
associated with improvement in functional status, quality of life, and relief
of dyspnea in selected patients with emphysema
[4].
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Fig. 1C —67-year-old man with dyspnea in postanesthesia care unit. Coronal CT
volume-intensity-projection image shows position of two intrabronchial valves
within segmental bronchi of right upper lobe of lung. Severe emphysematous
changes in lungs are evident.
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The nitinol skeleton of the intrabronchial valve is visible
radiographically as a grouping of linear metallic densities with a
characteristic umbrella-like configuration on one end. The polyurethane
membrane is radiolucent. Intrabronchial valves are produced in several
deployment diameters (4, 5, 6, and 7 mm) for excluding airways ranging from
segmental to subsegmental bronchi. Deployed valves can be repositioned or
removed bronchoscopically by grasping the central metallic stem on the
proximal end of the valve (Fig.
2). Endo-bronchial valves should always be superimposed on the
expected distribution of the bronchi and should not migrate once deployed.
When an intrabronchial valve is properly positioned, the wide, umbrella-shaped
end faces the proximal aspect of the bronchus and the shorter end faces the
distal aspect.
Possible complications of endobronchial valve placement include
pneumothorax, postobstructive pneumonia, valve migration, and valve
dislodgment. Pneumothorax was the most frequently encountered problem in early
studies [4]. Frequent serial
chest radiographic or CT examinations are performed in the months after valve
placement to monitor upper lobe atelectasis. Coronal CT volume intensity
projection reformatted images depict valve position within the bronchi with
great detail (Fig. 1C).
Intrabronchial valves are a promising new treatment for emphysema. Knowledge
of their characteristic radiographic appearance and anatomic distribution is
essential for proper evaluation.
Acknowledgments
We acknowledge the following additional contributors to this article:
Francis D. Sheski and Praveen N. Mathur, both with the Pulmonary Division of
the Indiana University Department of Medicine, and Dewey J. Conces, Jr., of
the Indiana University Department of Radiology.
References
- National Emphysema Treatment Trial Research Group. A randomized
trial comparing lung-volume-reduction surgery with medical therapy for severe
emphysema. N Engl J Med 2003;348
: 2059-2073[Abstract/Free Full Text]
- Brenner M, Hanna NM, Mina-Araghi R, et al. Innovative approaches to
lung volume reduction for emphysema. Chest2004; 126:238
-248[CrossRef][Medline]
- National Emphysema Treatment Trial Research Group. Patients at high
risk of death after lung-volume-reduction surgery. N Engl J
Med 2001; 345:1075
-1083[Abstract/Free Full Text]
- Yim AP, Hwong TM, Lee TW, et al. Early results of endoscopic lung
volume reduction for emphysema. J Thorac Cardiovasc
Surg 2004; 127:1564
-1573[Abstract/Free Full Text]
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Introduction
Case Report
