The reduced respiratory capacity can be determined using the vital capacity (VC) respiratory test. In addition to determining the cough and body weight, measuring vital capacity is a key parameter that is regularly determined in ALS outpatient clinics and used as a basis for deciding on possible treatment measures. The measurement of vital capacity can be carried out in different ways: by breathing in and out quickly (FVC, forced vital capacity) or by breathing in and out slowly (SVC slow vital capacity).