What are the symptoms of respiratory dysfunction?

Weakness of the respiratory muscles can manifest itself in the form of increased breathing effort (dyspnoea). It can initially occur during physical exertion (climbing stairs, running) (exertional dyspnoea). As respiratory dysfunction progresses, even minor physical exertion (e.g. getting dressed) can be associated with respiratory effort. Respiratory effort at rest is also possible (dyspnoea at rest). Lying down places particular demands on the respiratory function, as the respiratory mechanics are altered in the horizontal body position. The diaphragm receives less “support” from gravity. The contents of the abdominal cavity (especially the “stomach bubble”) can restrict the diaphragm’s mobility. As a result, breathing effort
can occur in the lying position, which is referred to as “orthopnoea”.

In the ALS Functional Rating Scale (ALSFRS-R), the respiratory effort during exertion and at rest (dyspnoea) as well as in the lying position (orthopnoea) is assessed separately. In addition to respiratory effort, the respiratory dysfunction can manifest itself in fatigue, exhaustion or depressive mood. These symptoms are due to the accumulation of carbon dioxide in the blood. In some patients, the accumulation of carbon dioxide in the blood is noticeable without breathing being experienced as physically strenuous. Therefore, in addition to the specific question of respiratory effort (dyspnoea and orthopnoea), the measurement of breathing capacity (vital capacity, VC) is of particular importance. If breathing capacity is reduced, a breathing aid should therefore be offered – even if there is no subjective experience of respiratory effort.