Respiration is known to influence cardiac signals through the modulation of both cardiac activity and thoracic motion. The respiratory contribution on the modulation of the electrocardiogram (ECG) both in amplitude and frequency is well established. On the other side, similar respiratory-related variations may also affect heart sounds, visible in the phonocardiogram (PCG). In this study, both ECG and PCG signals were analyzed to evaluate the influence of respiration on these signals and, in particular, its impact on the timing of heart valve closures. The latter have a clinical application in noninvasively assessing the hemodynamics of the heart. In this context, the aim of this thesis is to assess whether accounting for respiratory information could improve the accuracy of Cardiac Time Intervals (CTIs) estimation.