KN Chan, MK Chakrabarti

We assessed the use of a valveless ventilator (SLE2000HFO), which uses an air jet to deliver the driving force for conventional ventilation and a spinning jet to provide pressure waves at high frequency. It differs from other jet ventilators in that its high-frequency pressure waves are truly sinusoidal. The latter can be superimposed on any phase of the breathing cycle (inspiratory, expiratory or both). We evaluated its use by combining high-frequency oscillation in the expiratory phase of the conventional intermittent positive pressure ventilation in 10 very low birthweight babies [median gestational age 25.5 (range 23-28) weeks and birth weight 828 (range 580-1102) g] with severe respiratory disease. All had had two doses of Exosurf (5 ml/kg/dose) at birth. All had progressively worsening respiratory failure (mean values of arterial PaCO₂ 7.87 kPa, pH 7.22, inspired oxygen concentration 84.4%, and oxygenation index of 188.9 at a mean airway pressure of 13.0 cm H₂O while on conventional mechanical ventilation. By superimposing high-frequency oscillation at a frequency of 10 Hz and an amplitude of 10 cmH₂O in the expiratory phase of the conventional positive pressure ventilation (ventilator settings unchanged), within 30 minutes there was a dramatic and highly significant improvement (mean values 5.88 kPa, 7.31, 71.5%, and 145.1, respectively, at the same mean airway pressure). The improvement was maintained. Four babies subsequently died [respiratory complications (2), sepsis (1) and necrotizing enterocolitis (1)]. This ventilation strategy may help to reduce barotrauma by providing for a better gas exchange for a given mean airway pressure, thus allowing lower ventilator settings to be used for a given situation in the management of babies with respiratory failure.