Natural language learning in context is provided by generating combined text of a user’s native tongue and language to be learned. The first guide plates make an opening angle \u03b81 in between greater than an opening \u03b82 the second guide plates make in between. A corresponding computation of arterial minus venous oxygen saturation is particularly advantageous for oxygen therapy management. The retention structure projecting laterally from and configured non-concentrically along the longitudinal axis of the shaft retains the incontinence prevention device within the patient.