In partnership with Maureen Young, a specialist in perinatal physiology, Donald conducted a study of respiratory disorders in infants. Donald's study included an examination of available medical respirators, and he was not satisfied with the design and efficiency of the current models. As Donald had an interest in mechanical and technological devices from his childhood, he decided to build a new respirator. By 1952, Donald and Young had built a new medical negative-pressure respirator that they demonstrated at a Physiological Society meeting in the Royal Free Hospital. Trip spirometer Later in 1952, Donald resigned his role at St Thomas's Hospital Medical School to take up a position as a reader at the Institute of Obstetrics and Gynecology at Royal Postgraduate Medical School located in Hammersmith Hospital. At the medical school, Donald continued his research into neonatal breathing disorders. He worked to improve the device that he and Young had built: the servo patient-cycled respirator . Later, he worked with Josephine Lord, a registrar, to build the Trip spirometer, later called the spirometer, whose purpose was to measure the respiratory efficiency of a newborn. As well as being a diagnostic device, Donald used it to make a quantitative determination of normal respiration with the goal of determining the physiology and pathology of neonatal pulmonary disease. Puffer In 1953, Donald published a review of best practices in neonatal resuscitation. While at the school, Donald worked on a third device: a positive-pressure respirator. Donald found that the negative-pressure device he had built with Young was not ideal, as it was complicated to set up, difficult to use, and required more than one person to operate; the servo respirator seemed to be ideally suited to the long-term treatment of babies with breathing difficulties. His rationale for creating a new device was based on the idea that a respirator that could be used with a mask applied to a child in a cot or incubator was needed. He built a positive-pressure respirator that was later known in Hammersmith Hospital as the Puffer. It sent a stream of oxygen mixture onto the baby's face and the device could be applied to an ailing infant in under a minute. After treating several infants, colleagues asked him to convert the device to treat adults, which he did with successful outcomes. The device was noticed by the British Oxygen Company, who wanted to commercially develop the positive-pressure respirator. In