Pressure-limited ventilation of infants with low-compliance lungs: The efficacy of an adult circle system versus two free-standing intensive care unit ventilator systems using an in vitro model

We compared the efficacy of a Drager Narkomed GS (North American Drager, Te lford, PA) equipped with an adult circle system with two free-standing infa nt ventilator systems (Servo 300; Siemens Medical Systems, Danvers, MA and Babylog 8000; North American Drager) to deliver minute ventilation (V-E) us ing pressure-limited ventilation to a test lung set to low compliance. To s imulate a wide variety of potential patterns of ventilation, VE was measure d at peak inspiratory pressures (PIP) of 20, 30, 40, and 50 cm H2O and at r espiratory rates (RR) of 20, 30, 40, and 50 breaths/min. Each measurement w as made three times; the average was used for data analysis using the multi ple regression technique. Delivered VE was positively correlated with both PIP (P = 0.001) and RR (P = 0.001). Only minimal differences in VE were obs erved between the circle and the two free-standing systems. At lower RR and PIP, the Babylog 8000 system delivered slightly higher VE than the circle system, whereas at higher RR and PIP, the Babylog 8000 delivered slightly l ower VE than the circle system; these differences in VE were not statistica lly significant (P = 0.45). The Servo 300 delivered slightly higher VE than the circle system in all test conditions, but these differences were not s tatistically significant (P = 0.09). None of the differences in delivered V -E between the Servo 300 and the circle system are of clinical importance. Implications: Our laboratory investigation suggests that pressure-limited v entilation delivered by a standard adult circle system compares favorably w ith that of freestanding infant ventilators used in pressure-limited mode. Changing from an adult circle system to a free-standing pressure-limited ve ntilator may not substantially improve ventilation of a low-compliance infa nt lung; the efficacy of such a practice should be investigated.