Therapeutic application of collateral ventilation with pulmonary drainage in the treatment of diffuse emphysema: report of the first three cases

The Clinical Significance of Collateral Ventilation

Oxygen delivery and carbon dioxide removal being critical to cell survival, mammals have developed collateral vascular and ventilation systems to ensure tissue viability. Collateral ventilation, defined as ventilation of alveoli via pathways that bypass normal airways, is present in humans and many other species. The presence of collateral ventilation can be beneficial in certain disease states, whereas its relative absence can predispose to other diseases. These well defined anatomical pathways contribute little to ventilation in normal humans, but modulate ventilation perfusion imbalance in a variety of diseases, including obstructive diseases, such as asthma and emphysema. These pathways can be affected by pharmaceuticals and inhaled gas compositions. The middle lobe and lingula, constrained by their isolated, segmental anatomy, have reduced collateral ventilation, which predisposes them to disease. Recently, attempts to improve the quality of life of patients with emphysema, by performing nonsurgical lung volume reduction via use of endobronchial valves, have led to mixed results, because the role of collateral ventilation in the success or failure of the procedure was not initially appreciated. This review describes the anatomical pathways of collateral ventilation, their physiology and relationship to disease states, their modulatory effects on gas exchange, treatment considerations, and their effect on diagnostic procedures.

The fissure: interlobar collateral ventilation and implications for endoscopic therapy in emphysema

In patients with severe emphysema, bronchoscopic lung volume reduction using one-way valves is a promising therapeutic option to improve lung function and quality of life. The goal of this treatment is to achieve a complete lobar atelectasis. In a significant proportion of patients, this atelectasis cannot be achieved due to interlobar collateral ventilation. This collateral ventilation is generated through incomplete lobar fissures. Therefore, only patients with complete fissures and no collateral ventilation can be selected for endobronchial therapy with one-way valves.

Incomplete fissures are very common and exhibit a great variation in anatomy. The reported prevalence is 17%–85% for the right major fissure, 19%–74% for the left major fissure, and 20%–90% for the minor fissure. There are several methods of measuring or predicting the presence of collateral ventilation, with computed tomography (CT)-fissure analysis and the Chartis measurement being the most important. CT-fissure analysis is an indirect method to measure the completeness of fissures as a surrogate for collateral ventilation. The Chartis system is an endobronchial method to directly measure the presence of collateral ventilation. Both methods have unique value, and the combination of both can accurately predict the treatment response to the bronchoscopic placement of endobronchial valves. This review provides an in-depth view of lung fissure and collateral ventilation to help understand its importance in selecting the appropriate patients for new emphysema treatments and thus avoid useless treatment in unsuitable patients.

Advanced therapies for COPD-What's on the horizon? Progress in lung volume reduction and lung transplantation

Advanced chronic obstructive pulmonary disease (COPD) is a significant cause of morbidity. Treatment options beyond conventional medical therapies are limited to a minority of patients. Lung volume reduction surgery (LVRS) although effective in selected subgroups of patients is not commonly undertaken. Morbidity associated with the procedure has contributed to this low utilisation. In response to this, less invasive bronchoscopic lung volume techniques are being developed to attempt to mitigate some of the risks and costs associated with surgery. Of these, endobronchial valve therapy is the most comprehensively studied although the presence of collateral ventilation in a significant proportion of patients has compromised its widespread utility. Bronchial thermal vapour ablation and lung volume reduction (LVR) coils are not dependent on collateral ventilation. These techniques have shown promise in early clinical trials; ongoing work will establish whether they have a role in the management of advanced COPD. Lung transplantation, although effective in selected patients for palliation of symptoms and improving survival, is limited by donor organ availability and economic constraint. Reconditioning marginal organs previously declined for transplantation with ex vivo lung perfusion (EVLP) is one potential strategy in improving the utilisation of donor organs. By increasing the donor pool, it is hoped lung transplantation might be more accessible for patients with advanced COPD into the future.

Bronchoscopic interventions for chronic obstructive pulmonary disease

Over the past decade, several non-surgical and minimally invasive bronchoscopic lung volume reduction (BLVR) techniques have been developed to treat patients with severe chronic obstructive pulmonary disease (COPD). BLVR can be significantly efficacious, suitable for a broad cohort of patients, and associated with a solid safety profile at a reasonable expense. The introduction of BLVR is also expected to accelerate the further development of interventional pulmonology worldwide. Recently, results from clinical studies on BLVR techniques have been published, providing valuable information about the procedure's indications, contraindications, patient-selection criterion and outcomes. BLVR utilizing one-way endobronchial valves is gaining momentum as an accepted treatment in regular medical practice because of the identification of best responders. Patients with a heterogeneous emphysema distribution and without inter-lobar collateral ventilation show encouraging results. Furthermore, for patients with collateral ventilation, who are not considered candidates for valve treatment, and for patients with homogeneous emphysema, the introduction of lung volume reduction coil treatment is a promising solution. Moreover, with the development of newer treatment modalities, that is, biochemical sealant and thermal water vapor, the potential to treat emphysema irrespective of collateral flow, may be further increased. Nevertheless, patient selection for BLVR treatment will be crucial for the procedure's success and should be performed using a multidisciplinary team approach. Consequently, BLVR needs to be concentrated in high-volume centres that will offer better quality and experience with treatment challenges and adverse events. This review gives a general overview of BLVR from an expert and scientific perspective.

Technical validation of pulmonary drainage for the treatment of severe pulmonary emphysema: a cadaver-based study

OBJECTIVE:

A cadaver-based study was carried out in order to describe the pulmonary drainage surgical technique, to determine whether the site for the insertion of the chest tube is appropriate and safe, and to determine the anatomical relationship of the chest tube with the chest wall, lungs, large blood vessels, and mediastinum.

METHODS:

Between May and November of 2011, 30 cadavers of both genders were dissected. The cadavers were provided by the Santa Casa de São Paulo Central Hospital Mortuary, located in the city of São Paulo, Brazil. A 7.5-cm, 24 F steel chest tube was inserted into the second intercostal space along the midclavicular line bilaterally, and we measured the distances from the tube to the main bronchi, upper lobe bronchi, subclavian vessels, pulmonary arteries, pulmonary arteries in the upper lobe, superior pulmonary vein, azygos vein, and aorta. Weight, height, and chest wall thickness, as well as laterolateral and posteroanterior diameters of the chest, were measured for each cadaver.

RESULTS:

Of the 30 cadavers dissected, 20 and 10 were male and female, respectively. The mean distance between the distal end of the tube and the main bronchi (right and left) was 7.2 cm (for both).

CONCLUSIONS:

The placement of a fixed-size chest tube in the specified position is feasible and safe, regardless of the anthropometric characteristics of the patients.

The National Emphysema Treatment Trial (NETT) Part II: Lessons learned about lung volume reduction surgery

Substantial information regarding the role of lung volume reduction surgery (LVRS) in severe emphysema emanates from the National Emphysema Treatment Trial (NETT). The NETT was not a crossover trial and therefore was able to examine the effects of optimal medical management and LVRS on short- and long-term survival,as well as lung function, exercise performance, and quality of life.The NETT generated multiple insights into the preoperative, perioperative,and postoperative management of patients undergoing thoracotomy; described pain control techniques that were safe and effective; and emphasized the need to address nonpulmonary issues to optimize surgical outcomes. After the NETT, newer investigation has focused on bronchoscopic endobronchial interventions and other techniques less invasive than LVRS to achieve lung reduction.In this review, we summarize what we currently know about the role of LVRS in the treatment of severe emphysema as a result of insights gained from the NETT and provide a brief review of the newer techniques of lung volume reduction.

Alternatives to lung transplantation: lung volume reduction for COPD

Emphysema is disabling and progressive and hallmarked by decreased exercise tolerance and impaired quality of life. Surgical interventions that reduce lung volume have been the focus of multiple interventions for decades; however, until recently, limited evidence has documented their effectiveness. Lung volume reduction surgery (LVRS) underwent rigorous study in the National Emphysema Treatment Trial (NETT), which demonstrated its short-term and long-term effectiveness, associated morbidity and mortality, and the essential factors that predict LVRS success or failure. This article summarizes the major results of the NETT and briefly reviews newer bronchoscopic lung volume reduction techniques that show promise as alternative treatments for select patients with COPD undergoing consideration for lung transplantation.

Unilateral extrapulmonary airway bypass in advanced emphysema

BACKGROUND

Gas trapping in emphysema results in resting and dynamic hyperinflation. We tested the hypothesis that a direct connection between the lung parenchyma and the atmosphere could increase expiratory flow and thereby potentially improve dyspnea through the relief of gas trapping.

METHODS

Ex vivo we studied 7 emphysematous lungs and 3 fibrotic lungs (as controls) and measured expiratory flow before and after airway bypass insertion during a forced maneuver in an artificial thorax. Pilot studies were conducted in vivo in 6 patients with advanced emphysema using a size 9 endotracheal tube as a bypass surgically placed through the chest wall into the upper lobe.

RESULTS

In the ex vivo emphysematous lungs the volume expelled during a forced expiratory maneuver increased from 169 to 235 mL (p < 0.05). In the in vivo group 4 patients retained the bypass tube for 3 months or more; total lung capacity was reduced, and the forced expiratory volume in 1 second increased by 23% (mean percent predicted at baseline versus 3 months, 24.4% versus 29.5%).

CONCLUSIONS

An extrapulmonary airway bypass increases expiratory flow in emphysema. This may be a useful approach in hyperinflated patients with homogeneous emphysema.