Help Me, I Need Air: Patient Satisfaction after Endobronchial Valve Placement for Emphysema

Abstract

Chronic obstructive pulmonary disease (COPD) is defined as a disease state characterized by airflow limitation that is not fully reversible. As we are aware, the main symptom of COPD is dyspnea or breathlessness. We are all too familiar with the patient with severe COPD whose quality of life is significantly degraded by their breathlessness and their frustration with their abilities to do important activities in their lives because of dyspnea and decreased exercise tolerance despite medical therapy. The causes of dyspnea and decreased exercise capacity in COPD are multiple and complex and include airway obstruction with expiratory flow limitation, static and dynamic hyperinflation, intrinsic positive end-expiratory pressure (PEEPi), increased respiratory muscle load, decreased respiratory muscle capacity, changes in neural respiratory drive with efferent– afferent receptor mismatch, pulmonary vascular changes, and peripheral muscle changes (1). Of these causes, hyperinflation, particularly dynamic hyperinflation, plays a central role in patients with severe emphysema with a poor quality of life because of breathlessness and inability to do activities. Lung hyperinflation is defined as an abnormal increase in the amount of air at the tidal expiration, that is, end-expiratory lung volume (EELV) or functional residual capacity (FRC) (2). With destruction of lung parenchyma in emphysema, there is damage to the elastic fibers of the lung, leading to decreased lung elastic recoil pressure with unchanged chest wall compliance. Thus, EELV or FRC will occur at a higher lung volume (3). In addition, in the dependent lung regions, there is small airway closure and extreme expiratory flow limitation at low lung volumes, resulting in air-trapping and an increase in the residual volume (RV) (4). Both mechanisms increase total lung capacity and produce static hyperinflation. Dynamic hyperinflation, as the name implies, is a variable increase in lung volume above EELV or FRC owing to dynamic forces. In general, dynamic hyperinflation results from a mismatch of the expiratory time constant of the lung and time between consecutive breaths (4). The expiratory time constant for lung emptying for patients with severe emphysema is increased because of decreased lung elastic recoil pressure and increased airway resistance (3, 5). During activity, the expiratory time needed for exhalation becomes insufficient as the respiratory rate increases, and thus EELV increases, resulting in dynamic hyperinflation. A number of negative consequences results from lung hyperinflation. There is an increase in the work of breathing. In addition to the lung elastic recoil, an increase in the inspiratory elastic load results from EELV moving above the relaxation volume of the chest wall with significant hyperinflation such that at EELV the chest wall will recoil inward (1). When dynamic hyperinflation occurs, the expiratory alveolar pressure remains positive throughout expiration until the next breath, PEEPi. The inspiratory muscles must overcome PEEPi before negative pressure can be generated to produce inspiratory flow (4). Lastly, there is decreased capacity of the inspiratory muscles to generate negative intrathoracic pressure in the presence of hyperinflation owing to muscle sarcomere shortening, flattening of the diaphragm, and reduced zone of apposition of the diaphragm (1, 4). Treatments that decrease hyperinflation should improve breathlessness and exercise capacity in patients with severe emphysema. Lung volume reduction surgery (LVRS) has been shown to decrease total lung capacity and RV with improvements in forced expiratory volume in 1 second (FEV1), forced vital capacity, and inspiratory capacity (6). Global inspiratory muscle strength has been observed to increase after LVRS, as has maximal exercise capacity (6). In NETT (National Emphysema Treatment Trial), patients undergoing LVRS compared with medical therapy had greater improvements in exercise capacity, 6-minute walk distance, severity of dyspnea, and disease-specific quality of life (7). To obviate the morbidity and mortality issues with LVRS, various bronchoscopic modalities to produce bronchoscopic lung volume reduction (BLVR) have been studied. Of these, bronchoscopically implanted one-way valves have been the most successful and have been able to obtain U.S. Food and Drug Administration approval. One of these valves, the Zephyr valve (Pulmonx Corporation) has been shown to improve FEV1, RV, 6-minute walk distance, and quality of life as measured by the St. George’s Respiratory Questionnaire (8). Although studies evaluating BLVR have reported on patient-centered outcomes such as dyspnea, walking distance, and disease-specific quality of life, patientreported outcomes such as treatment satisfaction and improvements in patient pretreatment individual goals have not been evaluated. In this issue of AnnalsATS, Hartman and colleagues (pp. 68–74) provide information about these important questions (9). Their aims were to investigate patient satisfaction level 1 year after treatment and patient-specific goals before and 1 year after endobronchial valve (EBV) placement. Patients with severe emphysema 4 C /F P O