BENEFITS OF THE LOW-PRESSURE MULTICHANNEL ENDOTRACHEAL VENTILATION

Mechanical ventilation using a modified endotracheal tube, allowing by pass and washout of the endotracheal dead space (McETV), was compared with conventional controlled mechanical ventilation (CMV) in healthy a nd in surfactant-depleted rabbits. In healthy animals, shifting from C MV to McETV led to an increase in Pa-O2 (89 +/- 16 versus 104 +/- 13 m m Hg; p < 0.05) and a decrease in Pa-CO2 (41.5 +/- 3 versus 30 +/- 3 m m Hg; p < 0.05). As a result of reducing the peak inspiratory pressure (PIP) from 21 +/- 2 to 12 +/- 2 cm H2O (p < 0.05), it was possible in McETV mode to maintain comparable ventilation to that achieved by CMV . In surfactant-depleted animals, compared with CMV, McETV produced a rise in Pa-O2 without change in thoracic volume (from 100 +/- 40 to 15 0 +/- 60 mm Hg, p < 0.05) and a fall in Pa-CO2 (from 46 +/- 5 to 37 +/ - 4 mm Hg, p < 0.05). After 4 h of ventilation, the surfactant-deplete d animals from the CMV group developed thoracic overdistension quicker (at hour 1, p < 0.05) and, consequently, more animals died from pneum othorax compared with the McETV group (five versus two). We concluded that McETV ensured adequate gas exchanges with lower insufflation pres sures and could diminish positive pressure ventilation-induced injury.