Effects of Altitude on Single-Breath Diffusing Capacity for Carbon Monoxide

Effects of Altitude on Single-Breath Diffusing Capacity for Carbon Monoxide in Normal Subjects and Chronic Obstructive Pulmonary Disease

The purpose of this study is to further understand the effects of altitude on the physiology of gas exchange in the pulmonary microcirculation in normal subjects and in people with chronic obstructive pulmonary disease (COPD) measured as the single-breath diffusing capacity for carbon monoxide (DLCOsb). The study will determine a mathematical formula to allow for altitude corrections in both study populations to be used clinically in pulmonary labs.

The DLCOsb is one of the most common and widely tests clinically used across the world in pulmonary function laboratories to assess gas exchange from the lung to hemoglobin in the pulmonary circulation. This test is used in the differential diagnosis of respiratory related symptoms, to grade the degree of severity in lung disease, and to objectively monitor the progression of disease or the response to therapies. Therefore, it is important to have standard methods of performing and interpreting this test.This is a prospective study, collecting data from subjects at different simulated altitudes. The study hypothesis is that increasing altitude will increase the DLCOsb in a predictable manner that will allow for mathematical corrections to be applied for uniform interpretation in pulmonary labs at differing altitudes.

Inclusion Criteria:

• Ages 20- 80 years
• Subjects must be either healthy or have been diagnosed with COPD

Exclusion Criteria:

• Anemia (hemoglobin < 10.0 g/dL)
• Carboxyhemoglobin > 3%
• Active smoking
• Heart disease or heart failure
• Pulmonary hypertension
• COPD exacerbation
• Pneumothroax within 6 months
• Bullous emphysema on chest imaging (Chest X-ray or CT)
• Supplemental oxygen use
• Diabetes mellitus
• Alcohol dependence
• Non-English speaking