[Evaluation of the Engstrom metabolic computer].
The Engstrom Metabolic Computer (EMC), in association with the Erica Ventilator, uses indirect calorimetry to carry out continuous on-line gas exchange measurements. A laboratory assessment of the different parts of this equipment is described. The variability of FIO2 was less than 0.05. The accuracy and stability of the inspiratory flowmeter were only slightly modified by changes in the I/E ratio and gas flow rates. The overestimation of flow on increasing FIO2 was taken into account by the computer. The hygrometry of inspiratory and expiratory air samples reached that of room air, with an absence of saturation during prolonged measurements. The CO2 analyser also showed a good stability. The accuracy of the oxygen cell needed to be checked periodically. A global evaluation was carried out using Damask's method: a lung model was used into which CO2 and N2 were insufflated at precise rates to simulate CO2 production and O2 consumption. The measured respiratory quotient was also compared with the known RQ of burning methanol. The difference between measured and real values was less than 5%. Therefore, it was concluded that the EMC was reliable for indirect calorimetry measurements.