2-year-old babies flat on their backs shortness of breath may be related to physiological factors such as excessive obesity, but also pathological factors such as viral myocarditis, upper respiratory tract infections and so on. 1. Physiological factors: due to obesity leads to more fat accumulation, limiting respiratory muscle movement, resulting in decreased thoracic adaptation, decreased lung function, may lead to the emergence of 2-year-old baby lying down shortness of breath. 2. Pathologic factors: (1) viral myocarditis: mainly due to viral infection, genetic, immune function, etc. can also induce the disease, often showing chest tightness, chest pain, weakness, fatigue, dyspnea, etc., which may lead to the emergence of a 2-year-old baby lying flat with shortness of breath. (2) Upper respiratory tract infections: mainly due to viral infections, cold, etc., often showing cough, runny nose, nasal congestion, dyspnea, etc., may lead to the emergence of 2-year-old baby lying down asthma. Therefore, if there is a 2-year-old baby lying down shortness of breath, if the symptoms do not get better or aggravation of the proposal should choose to seek medical advice, identify the causes, targeted treatment.