Chronic obstructive pulmonary disease (COPD) is defined by airway obstruction and alveolar damage caused by exposure to noxious air particles. The physiologic results include varying degrees of gas-exchange abnormality and mechanical respiratory limitation, often in the form of dynamic hyperinflation. There's a third major contributor, though ─ dyspnea. That's right, skeletal muscle deconditioning. Only one of these abnormalities responds to inhalers.
When your patients with COPD report dyspnea or exercise intolerance, what do you do? Do you attempt to determine its character to pinpoint its origin? Do you quiz them about their baseline activity levels to quantify their conditioning? I bet you get right to the point and order a cardiopulmonary exercise test (CPET). That way you'll be able to tease out all the contributors. Nah. Most likely you add an inhaler before continuing to rush through your COPD quality metrics: Vaccines? Check. Lung cancer screening? Check. Smoking cessation? Check.
The physiology of dyspnea and exercise limitation in COPD has been extensively studied. Work-of-breathing, dynamic hyperinflation, and gas-exchange inefficiencies interact with each other in complex ways to produce symptoms. The presence of deconditioning simply magnifies the existing abnormalities within the respiratory system by creating more strain at lower work rates. Acute exacerbations (AECOPD) and oral corticosteroids further aggravate skeletal muscle dysfunction.
The Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease (GOLD) Report directs clinicians to use inhalers to manage dyspnea. If they're already on one inhaler, they get another. This continues until they're stabilized on a long-acting beta-agonist(LABA), long-acting muscarinic antagonist (LAMA), and an inhaled corticosteroid (ICS). The GOLD report also advises pulmonary rehabilitation for any patient with grade B through D disease. Unfortunately, the pulmonary rehabilitation recommendation is buried in the text and doesn't appear within the popularized pharmacologic algorithms in the report's figures.
The data for adding inhalers on top of each other to reduce AECOPD and improve overall quality of life (QOL) are good. However, although GOLD tells us to keep adding inhalers for the dyspneic patient with COPD, the authors acknowledge that this hasn't been systematically tested. It's important to remember that GOLD is a "statement" as opposed to a clinical practice guideline. The difference? A statement doesn't require the same formal, rigorous scientific analysis known as the GRADE approach. Using this kind of analysis, a recent clinical practice guideline by the American Thoracic Society found no benefit in dyspnea or respiratory QOL with step-up from inhaler monotherapy.
Inhalers won't do anything for gas-exchange inefficiencies and deconditioning, at least not directly. A recent CPET study from the CanCOLD network found ventilatory inefficiency in 23% of GOLD 1 and 26% of GOLD 2 to 4 COPD patients. The numbers were higher for those who reported dyspnea. Skeletal muscle dysfunction rates are equally high.
Thus, dyspnea and exercise intolerance are major determinants of QOL in COPD but inhalers will only get you so far. At a minimum, make sure you get an activity/exercise history from your patients with COPD. For those who are sedentary, provide an exercise prescription (really, it's not that hard to do). If dyspnea persists despite LABA or LAMA monotherapy, clarify the complaint before doubling down. Finally, try to get the patient into a good pulmonary rehabilitation program. They'll thank you afterwards.
Aaron B. Holley, MD, is an associate professor of medicine at Uniformed Services University and program director of pulmonary and critical care medicine at Walter Reed National Military Medical Center. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.