Exercise Limitations in COPD – More Inhalers?

Chronic obstructive pulmonary disease (COPD) is defined by airway obstruction and alveolar damage caused by exposure to harmful particles in the air. Physiological findings include varying degrees of gas exchange abnormality and mechanical respiratory limitation, often in the form of dynamic hyperinflation. There is, however, a third major contributor ─ dyspnea. It’s true, skeletal muscle deconditioning. Only one of these abnormalities responds to inhalers.

When your COPD patients report dyspnea or exercise intolerance, what do you do? Are you trying to determine its character to identify its origin? Do you ask them about their baseline activity levels to quantify their conditioning? I bet you cut to the chase and order a cardiopulmonary exercise test (CPET). This way you will be able to tease all contributors. No. Most likely you add a inhaler before you continue to rush your COPD quality metrics: Vaccines? Check. Screening for lung cancer? Check. Smoking cessation? Check.

physiology of dyspnea and exercise limitation in COPD has been widely 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 amplifies existing abnormalities in the respiratory system by creating more tension at lower work rates. Acute exacerbations (AECOPD) and oral corticosteroids worsen skeletal muscle dysfunction.

The Report on the Global Strategy for the Diagnosis, Management and Prevention of Chronic Obstructive Pulmonary Disease (GOLD) directs clinicians to use inhalers to manage dyspnea. If they are already on one inhaler, they are given another. This continues until they are stabilized on a long-acting beta-agonist (LABA), a long-acting muscarinic antagonist (LAMA), and a inhaled corticosteroid (ICS). The GOLD report also advises pulmonary rehabilitation for any patient with grade B to D disease. Unfortunately, the recommendation for pulmonary rehabilitation is buried in the text and does not appear in the pharmacological algorithms popularized in the numbers in the report.

There is good evidence on adding inhalers on top of each other to reduce AECOPD and improve overall quality of life (QOL). However, although GOLD tells us to continue adding inhalers for the dyspneic patient with COPD, the authors acknowledge that this has not been systematically tested. It is important to remember that GOLD is a “statement” as opposed to a clinical practice guideline. The difference? A statement does not require the same formal and rigorous scientific analysis known as the GRADE approach. Using this kind of analysis, a recent clinical practice guidelines from the American Thoracic Society found no benefit in dyspnea or respiratory quality of life with increasing inhaler monotherapy.

Inhalers won’t do anything for gas exchange inefficiencies and deconditioning, at least not directly. A recent CanCOLD network CPET study found ventilatory inefficiency in 23% of GOLD 1 patients and 26% of GOLD 2 to 4 COPD patients. The numbers were higher for those who reported dyspnea. Rates of skeletal muscle dysfunction are just as high.

Thus, dyspnea and exercise intolerance are major determinants of quality of life in COPD, but inhalers will only get you so far. At a minimum, make sure you get a activity/exercise history of your COPD patients. For those who are sedentary, provide a 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 will thank you afterwards.

Aaron B. Holley, MD, is associate professor of medicine at Uniformed Services University and director of the pulmonary and critical care medicine program at Walter Reed National Military Medical Center. It covers a wide range of topics in pulmonology, intensive care and sleep medicine.

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