MECHANICAL VENTILATORS OPTIMIZED FOR PEDIATRIC USE DECREASE WORK OF BREATHING AND OXYGEN-CONSUMPTION DURING PRESSURE-SUPPORT VENTILATION

Objectives: a) To investigate whether the patient work of breathing ne eded to trigger inspiration is affected by the type of ventilator deli vering pressure-support ventilation for mechanically ventilated pediat ric patients. b) To determine whether changes in oxygen consumption (V o(2)) trend with changes in work of breathing and would thus be helpfu l in tracking work of breathing. Design: Prospective study. Setting: P ediatric intensive care unit at a university hospital. Patients: Nine mechanically ventilated patients (2 to 75 months of age). Intervention s: While maintaining a constant pressure-support ventilation level, pa tients were alternately supported with the Siemens Servo 900C, the Bir d VIP, and the Newport Wave E200 ventilators in random order. Measurem ents and Main Results: Work of breathing, defined as the integral of t he pressure-volume curve corresponding to negative pressure, was calcu lated with a pulmonary monitoring system. ($) over circle Vo(2) was me asured with a metabolic cart. Patient distress levels were assessed us ing the COMFORT scale, a behavioral scoring system. Mean values (20 br eaths/patient) for measured variables with each ventilator were compar ed using analysis of variance and Scheffe tests, with p < .05 indicati ng statistical significance. The lowest ($) over circle Vo(2) (103 +/- 35 ml/min/m(2)) and work of breathing (24 +/- 15 g.cm/m(2)) were achi eved with the Bird VIP ventilator and were significantly (p < .05) low er than those values obtained with either the Siemens Servo 900C ($) o ver circle Vo(2) 147 +/- 33 mL/min/m(2); work of breathing 49 +/- 18 g .cm/m(2)) or the Newport Wave E200 (($) over circle Vo(2) 122 +/- 33 m l/min/m(2); work of breathing 35 +/- 15 g.cm/ m(2)). Also, the values of work of breathing and ($) over circle Vo(2) obtained using the Newp ort Wave E200 were significantly (p < .05) lower than those values obt ained using the Servo 900C. No change in behavioral distress occurred when the ventilators were changed. In all patients, there was a clear similarity in the trends of ($) over circle V0(2) and work of breathin g. Conclusions: We conclude that ($) over circle Vo(2) and work of bre athing may be reduced significantly using the latest generation of mec hanical ventilators optimized for infant and pediatric use. Because wo rk of breathing is less with the Bird VIP than the other two ventilato rs tested, leading to a corresponding decrease in ($) over circle Vo(2 ), we suggest that the Bird VIP better adapts the patient to the venti lator and may facilitate weaning from ventilatory support. We also sug gest that changes in ($) over circle Vo(2) might be helpful in trackin g changes in work of breathing.