Being more positive about negative ventilation?

Mechanical ventilation is undoubtedly a lifesaving procedure for patients with acute respiratory failure [1]. Unfortunately the procedure is also associated with a number of unwanted side-effects. Firstly, until recently, mechanical ventilation required endotracheal intubation either through a tracheostomy or with a translaryngeal tube, procedures which can carry some risks [2, 3]. Secondly, by disrupting the physiological upper airway barrier, endotracheal intubation increases the risk of acquiring bronchopneumonia [4]. Thirdly, discontinuing mechanical ventilation in intubated patients is difficult and may un-neccessarily increase the duration of mechanical ventilation [5]. Finally, positive pressure is used to unload the respiratory system resulting in excessive elevation of intrathoracic pressures which can jeopardize the patient's haemodynamic status because of interactions between the heart and the lung. Such high positive intrathoracic pressures may also induce barotrauma and act to worsen pre-existing pulmonary lesions [6]. Since positive-pressure ventilation is far from physiological, a great deal of effort has been expended to reduce the consequent side-effects [7–9]. Delivering positive-pressure ventilation through a non-invasive interface (noninvasive positive-pressure ventilation (NIPPV)) avoids intubation-related complications, reduces the length of stay in intensive care, and lowers the mortality rate in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) [10]. NIPPV is also able to reduce the time required to withdraw the patient from the ventilator and has recently been proposed as a powerful method of weaning in COPD patients intubated for an acute exacerbation of their illness [5]. A further advance in reduction of mechanical ventilation related side-effects might be to avoid supraphysiolo-gical positive intrathoracic pressures by using perithoracic negative pressure as proposed by CORRADO et al. [11] in this issue. Noninvasive negative ventilation (NINV) increases trans-pulmonary pressure and assists ventilation by applying a negative pressure around the thorax and the abdomen. This is made possible by ventilators which intermittently generate a negative pressure in a space enclosing the tho-rax and the abdomen. An extensive description of the method and of devices used to provide NINV can be found in a recently published review [12]. Tank ventilators consist of either a tank or cylinder, e.g. the iron lung, which envelope the body up to the neck. NINV using the iron lung was the first body ventilator to receive widespread use and was the main device employed for both acute and long-term ventilatory support from 1931 until the late 1950s [12]. Compared to other devices for NINV such as chest shells or body …