This is the 3803rd most frequent Spanish word.
respiratorias
"Respiratorias" means "respiratory" in English, relating to breathing or the respiratory system.
In this sentence, 'respiratorias' functions as an adjective describing the type of diseases ('enfermedades') referred to — those related to respiration.
Las enfermedades respiratorias pueden ser graves si no se tratan.
Respiratory diseases can be severe if not treated.
Here, 'respiratorios' is used as an adjective to describe exercises ('ejercicios') focusing on respiration and breathing.
Los ejercicios respiratorios ayudan a mejorar la capacidad pulmonar.
Respiratory exercises help improve lung capacity.
In this case, 'respiratorios' describes the type of muscles ('músculos') that are involved in the process of respiration.