 Therefore, evaluation of ANS is of great interest for diagnosis, prognosis and monitoring of this respiratory disorder. Direct evaluation of the PNS is infeasible or impractical in these situations. However, non-invasive evaluation of the PNS is proposed through the HRV according to the standards of measurement, physiological interpretation and clinical use of guides working group of the European Society and American Cardiology and Electrophysiology that are made through the electrocardiogram ECG. 