<P> The 1856 works of English physician and physiologist Marshall Hall recommended against using any type of bellows / positive pressure ventilation, views that held sway for several decades . A common method of external manual manipulation, introduced in 1858, was the "Silvester Method" invented by Dr. Henry Robert Silvester in which a patient is laid on their back and their arms are raised above their head to aid inhalation and then pressed against their chest to aid exhalation . </P> <P> The shortcomings of manual manipulation led doctors in the 1880s to come up with improved methods of mechanical ventilation, including Dr. George Edward Fell's "Fell method" or "Fell Motor", consisting of a bellows and a breathing valve to pass air through a tracheotomy, and his collaboration with Dr. Joseph O'Dwyer to invent the Fell - O'Dwyer apparatus, a bellows and instruments for the insertion and extraction of a tube down the patients trachea . Such methods were still looked upon as harmful and were not adopted for many years . </P>

Which of the following items is essential in order for artificial ventilation to be effective