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In the lungs of patients with severe emphysema (COPD), relatively large spaces previously containing lung tissue (obliterated by smoking) become filled with stagnant air that doesn't circulate with breathing. This ominously-named "dead-space ventilation" reduces the overall mechanical efficiency of breathing, often causing disabling dyspnea.
Lung volume reduction surgery (cutting out the dead space, usually at the tops of the lungs) can be remarkably effective at improving breathing -- but only a tiny number of patients undergo the major, somewhat risky surgery. Lung transplantation can effectively cure COPD, but trades it for a ticking clock of organ rejection. With hundreds of thousands of potential patient-customers affected, device makers have long sought a less invasive method of improving the efficiency of airflow in people with severe emphysema.
Endobronchial valves (EBV) are one-way valves inserted via bronchoscopy, which divert inspired air to healthy lung away from non-functioning dead spaces. Such valves have been prototyped, tweaked and tested over the past decade, but their uncertain benefits and sometimes concerning rates of complications kept EBVs in the development stages.
In 2018 an EBV device finally gained FDA approval: called Zephyr, it has been shown to significantly improve lung function, exercise capacity and quality of life for patients living with emphysema. The manufacturer has stated 12,000 patients were studied worldwide, although their website shows n ~ 450 were enrolled in five randomized trials.
One reason why previous device-based solutions failed was likely the presence of so-called collateral ventilation, which allowed air to slip back into patients' dead spaces, defeating any benefit from the devices. The Zephyr manufacturer touts its proprietary system (using a catheter deployed during endoscopy) to confirm low collateral ventilation, increasing the chances of EBV utility.
The UK health system's advisory board (NICE) supported routine use of the Zephyr device, which is available in Europe. The company plans to begin marketing Zephyr in the U.S. soon.
What's not to like? In a word, pneumothorax. More than a quarter of patients receiving EBV developed pneumothorax in the latest published study (LIBERATE), with four deaths within 45 days after device placement (3% mortality vs. none in the control group). The pneumothorax rate was as high or higher (26% and 29%) in the IMPACT and TRANSFORM trials, but with only 1 death in those receiving EBV.
Removable endobronchial valves should soon come to centers in the U.S., where interventional pulmonologists will likely celebrate and promote their use. Given the observed complication rates, the device seems perfect for risk-tolerant patients with emphysema so disabling they are willing to ride out a pneumothorax (with a chest tube and average two-week hospitalization) to finally get some relief in their breathing.