NETWORKS

Airways Disorders

The asthma COPD overlap syndrome: hype or reality?

In 2014, the Global Initiative for Asthma (GINA) and the Global Initiative for Chronic Obstructive Lung Disease (GOLD) published a joint document on the asthma COPD overlap syndrome (ACOS). While the concept of ACOS is not new, it remains highly debated since its introduction in 1961. ACOS is characterized by persistent airflow limitation with features that are shared with both asthma and COPD. For example, younger asthmatics may develop persistent expiratory airflow limitation from airway remodeling or smoking. Alternatively, patients with COPD may have concurrent features of atopy. Prevalence of ACOS is estimated at 20% in those with obstructive airway disease (Gibson. Thorax. 2015;70[7]:683). Data from the COPDGene cohort suggest that patients with ACOS have more frequent and severe respiratory exacerbations, less emphysema, and greater airway wall thickness (Hardin. Eur Respir J. 2014;44[2]:341).

The mechanisms behind ACOS remain poorly understood. Gelb and colleagues recently reported their observations of loss of lung elastic recoil and presence of centrilobular emphysema in a subset of nonsmokers with chronic asthma and persistent expiratory airflow limitation (Chest. 2015; 148[2]:313; J Allergy Clin Immunol. 2015;136[3]:553). In two COPD cohorts, Christenson and colleagues found that asthma-associated gene signatures were associated with increased disease severity, eosinophil counts, bronchodilator reversibility, and ICS response (Am J Respir Crit Care Med. 2015;191[7]:758). Data presented recently from Spiromics COPD and SARP severe asthma cohorts suggest that subjects with ACOS share a phenotype that falls between COPD and asthma. Allele frequency of candidate genes associated with smoking behavior and allergy in ACOS was intermediate between COPD and asthma (Li et al. Am J Respir Crit Care Med. 2016;A6237).

As with asthma and COPD, there exists significant heterogeneity within ACOS. Despite its high prevalence, evidence on how to consistently identify and best manage this group of patients is lacking. This is in part due to large clinical studies excluding patients with asthma COPD overlap. Additional research will help better understand the different phenotypes and endotypes of ACOS. Real life pragmatic studies evaluating differences in response to therapy are needed to make ACOS more relevant to the practicing clinician.

Dr. Sandhya Khurana, FCCP

Vice-Chair

Clinical Research Network

Airway clearance therapies

Many acute and chronic respiratory conditions such as pneumonia and bronchiectasis, are not only associated with an increase in the quantity and viscosity of respiratory secretions but also with impaired ciliary function and cough, with the latter being very common during mechanical ventilation and after strokes or thoracic surgical procedures. Retention of these secretions are associated with poor patient outcomes, and airway clearance therapies (ACT) are key to improving these outcomes and optimizing recovery after acute illnesses (Kim et. al. Chest. 2011;140[3]:626).

But despite this knowledge, the study of simple ACTs has been largely overlooked for decades. Many of the treatments we currently use, such as positive expiratory pressure devices (for example, the Acapella device), percussive vests, and intrapulmonary percussive ventilation have few studies to support their efficacy, with the ones that exist having very small sample sizes and show no superiority to simple manual techniques (Flume et al. Respir Care. 2009; 54[4]:522). As I walk by a patient’s room and see a respiratory therapist clapping on a patient’s back, I reflect on the fact that research on ACTs has essentially been at a standstill, and we continue to rely on therapies that are no better than the ones used in the 1800s. Our institution has established an Airway Clearance Research Group and has already conducted several bench studies evaluating some of these airway clearance therapies, with goals to develop novel techniques and to start clinical trials, with collaboration from this research steering committee. We hope that furthering the study of ACTs, and determining which therapies are most effective under different clinical settings will not only improve clinical outcomes in chronic conditions such as bronchiectasis but also improve outcomes after pneumonia, strokes, thoracic surgeries, and during mechanical ventilation, where airway clearance is key. Something so simple has the potential to impact a wide population of patients.

Dr. Bravein Amalakuhan

Fellow-in-Training Member

Critical Care

Early mobilization of the critically ill patient

Deconditioning is a well known complication of prolonged ICU stays. It is a factor in long-term mechanical ventilation and contributes to an increased length of stay and comorbidities. The severity of illness, presence of invasive catheters, and the need for sedation in order to provide adequate ventilation are risk factors for immobility. Critically ill patients who are not mobilized experience a decreased quality of life (Needham. JAMA. 2008;300:1685). The changes seen have been shown to persist up to a year after discharge, with a mean loss of 18% body weight, a 5% loss of muscle strength, and a decreased 6-minute walk distance (Herridge et al. N Engl J Med. 2003;348[8]:683; Herridge. Crit Care Med. 2009;37:S457).