Importance of Negative Pressure Phase in Mechanical Respirators

The management of medical emergencies involving respiratory failure remains an important challenge in clinical medicine. Despite many years of vigorous controversy, the question of which is the best mechanical method of artificial respiration is still unsettled. The problem concerns in part the respective merits of respirators producing intermittent positive pressure and those producing alternating positive-negative pressure. Thompson,1and Birnbaum and Thompson2have stood almost alone in claiming for positive-negative pressure a desirable effect on the circulation. These workers found that alternating positive-negative pressure stimulates the return of normal respiration and produces some degree of passive circulation in the dead animal. Other investigators believe that a negative pressure phase during expiration serves no useful purpose.3The opinions of those opposed to the use of any type of mechanical breathing machine, especially those employing a negative pressure phase, have been clearly stated by Henderson.4As Schwerma and Ivy