SOB, but 'normal' oxygen levels

Read the full article here. Although the article is about COPD, it applies to PH as well.

Skeletal Muscle Abnormalities

Rising from bed – getting dressed – taking a shower – going to work – we rely upon our skeletal muscles to perform all our daily activities. Skeletal muscles are found throughout the body. Their primary role is that of supporting the skeleton and voluntarily moving the bones. When our muscles are fit and well-conditioned, daily activities are a breeze; when our muscles fatigue easily from prolonged disuse, daily activities are far more challenging.

Although COPD primarily affects the lungs, skeletal muscle abnormalities are a secondary consequence of the disease. Shortness of breath and fatigue, common symptoms of COPD, often cause patients to limit their physical activity for fear of worsening breathlessness. The vicious cycle of prolonged inactivity, fatigue, and increased breathlessness with exertion leads to decreased muscle fitness and weakness. Remaining immobile for long periods of time causes the skeletal muscles to slowly decrease in size and eventually atrophy, or waste away.2

How Do Skeletal Muscle Abnormalities affect Oxygen Saturation?

When your muscles are called upon to perform any type of physical task, they have to work harder, which increases their demand for oxygen; this is why exerting yourself increases your heart rate and breathing.  In contrast, calling upon weak muscles to perform physical activity requires much more effort, leading to greater fatigue and breathlessness, more so than if your muscles were fit. Take, for example, climbing 3 flights of stairs; even if you’re moderately active, you’re likely to experience some degree of breathlessness by the time you reach the top. Now imagine your muscles are extremely weak from inactivity; simply rising from a chair or walking across a room can lead to breathlessness.

Unlike shortness of breath directly related to lung impairment however, breathlessness caused by skeletal muscle abnormalities may not always correlate with oxygen saturation. This means it’s entirely possible to experience breathlessness, without seeing a drop in your oxygen saturation level.3

Exercise: The Key to Breathlessness

The answer to breathlessness from COPD, heart failure, and/or skeletal muscle dysfunction is exercise. In fact, the American College of Cardiology reports that people who have COPD and heart failure together are prime candidates for exercise training. What’s more, skeletal muscle abnormalities can be completely reversed by participating in an exercise training program or a cardiopulmonary rehabilitation program.3