The manual summarizes the history, components, use, and importance of the manual respiratory bypass (MRB) or Ambu bag. It traces the development of the Ambu bag by German engineer Dr. Holger Hesse and Danish anaesthetist Henning Ruben in the 1950s. The manual describes the key parts of the Ambu bag including the flexible mask, filter and valve, and compressible bag. It outlines how the Ambu bag is used to provide positive pressure ventilation through a tight-sealing face mask when a patient is not breathing adequately. Regular training is emphasized to properly operate the important emergency device.