Despite the controversies, there are no randomized controlled trials that have yet provided sound scientific and technical evidence by comparing conventional techniques such as modified postural drainage, clapping, vibration, and expiratory chest compression with new techniques such as prolonged slow expiration (PSE) which is a slow passive and progressive expiration from the Functional Residual Capacity (FRC) into the Expiratory Reserve Volume (ERV) and clearance rhinopharyngeal retrograde (CRR) which is a forced inspiratory maneuver that aims to clear the nasopharynx indicated for infants.