ABSTRACT
The notion of ventilation as the result of the action of a muscular negative pressure pump led to attempts to devise negative pressure breathing apparatuses during the first half of the nineteenth century (1). But more than 50 years earlier, positive pressure had been proposed as the means to force air into the lungs during resuscitation maneuvres (2). Animal experiments led to a still common complication of positive pressure ventilation: a fatal pneumothorax, which prompted the Acadernie Fran'raise and the Royal Humane Society to condemn this technique. Positive pressure ventilation resurfaced in 1952, when Lassen demonstrated that positive pressure manual (i.e., bag) ventilation through a tracheostomy tube was by far superior to negative pressure mechanical ventilation, the standard form of assisted ventilation at that time (3). The results were so extraordinary that negative pressure ventilation was almost completely abandoned worldwide, and the new concept of specialized units for the care of patients with transient life-threatening organ failure came to life (4). Manual bag ventilation was rapidly replaced by mechanical pumps, and the modern mechanical ventilator emerged (4).
