To the Editor: I commend the authors of the Perspective article “Evidence Underlying Breathing Retraining in People With Stable Chronic Obstructive Pulmonary Disease” (December 2004) on their observations, interpretations, and recommendations regarding pursed-lips breathing (PLB). As a person who has emphysema and as a clinical psychologist who has presented with physical therapists on yoga and chronic obstructive pulmonary disease (COPD),1 and as someone who serves on the Board of Directors of the National Emphysema/COPD Association and is a member of COPD-ALERT, I was particularly interested in this article. However, I believe the conclusions regarding diaphragmatic breathing (DB) training warrant further scientific investigation. The following questions and suggestions can be used for testable hypotheses: 1. Pursed-lips breathing is a conscious and deliberate action and can be tiring after a short period. I believe, therefore, that diaphragmatic breathing stands a better chance of becoming an automatic habit or behavior. Should PLB or DB be the method of choice for cultivating slow breathing as a habitual pattern of breathing? 2. Should people with COPD, who are not likely to benefit from PLB, be taught DB instead in order to slow down their breathing? 3. Should PLB or DB be the method of choice for reaching a very slow rate of breathing, such as 6 breaths per minute? Recent studies showed that 6 breaths per minute improved the efficiency of gas exchange in people without known pathology or impairments2 and improved 6-minute walk distance in people with COPD.3 4. Which of the 2 techniques has greater overall health benefit for people with COPD? Diaphragmatic breathing, according to the teachings of some yoga schools, gently stimulates and massages the heart and abdominal organ areas, aids peristaltic movement, increases cerebral blood flow, and promotes spinal flexibility and improvement in posture. 5. Many patients use secondary breathing muscles. Would …