[Indirect calorimetry in mechanically ventilated children. 3. Clinical use of a new measurement procedure].

After the new device for measurement of oxygen uptake (VO2) and carbon dioxide elimination (VCO2) was tested in a pneumatic lung model, we investigated its clinical practicability. First the level of VO2 and VCO2 in the early postoperative phase was determined. Secondly we examined alterations in gasexchange caused by various intensive care activities. Whereby main concern was the change from mechanical ventilation to spontaneous CPAP-breathing. Ten children undergoing cardiac surgery (age: 10 days to 10 years) were included in the study. Three children were primarily investigated on the CPAP-system. Data from another six were collected under controlled ventilation as well as under spontaneous CPAP-breathing. One child had to be ventilated for a longer time (greater than 24 h). The change from mechanical ventilation to spontaneous breathing was accompanied with a temporary increase of VO2 and VCO2. As expected, all stressful factors like tracheal suction, pain or anxiety increased these two variables. Also some drugs showed remarkable changes. While marked increases under Normastigmine, Naloxone, and Dopamine could be observed, gas exchange was decreased under Morphine. However, heart rate showed no good correlation with VO2. We conclude that the developed prototype is a reliable device for measuring VO2 and VCO2. Our results suggest that spontaneous CPAP-breathing is not always accompanied with increased gas exchange. If there is an increased gas exchange, it may refer to transient changes during the adaption phase. Therefore, a continuous monitoring of VO2 and VCO2 over a longer period of time is necessary. Consequently the first phase after changing ventilatory support has to be viewed carefully. The heart rate in children, undergone cardiac surgery, is not a good predictor for determination of VO2 and thus for energy expenditure. This device allows to quantify accurately oxygen consumption and carbon dioxide elimination in ventilated children. Furthermore, alterations in metabolism and cardiopulmonary variables caused by intensive care and therapeutic interventions can be examined continuously. It seems to be a valuable tool for metabolic and cardiopulmonary monitoring in critically ill children.