Sleep apnea, between other sleep disorders, is still a major cause of fatality, because it increases the risk of acute myocardial infarction, cerebrovascular accident and sudden death. The previous diagnosis is based on the use of sensors of Airflow Breathing or sensors for breathing movements of thorax. Considering this need, this paper analyzes two sensors proposed to analyze the thoracic movement. Based on the operating principles of inductive and capacitive change, both sensores are monitoring displacement relative due to respiration. The sensors are characterized and compared for this purpose and the conditional circuits are discussed. Finally, it points to the inductive sensor with best results among the presented prototypes due linearity, repeatability and constructive facility.