The Jackson-Rees breathing system, also known as the Jackson-Rees modification of Ayre's T-piece, is a medical device used in anesthesia to provide mechanical ventilation and deliver inhalational anesthetics to patients during surgery or other medical procedures. It is named after the two anesthesiologists who developed it: Dr. Ivan Jackson and Dr. David Rees. The Jackson-Rees breathing system is particularly useful for providing positive pressure ventilation to pediatric and adult patients.