[Indirect calorimetry by means of displacement spirometry of the respiratory minute volume (author's transl)].
One factor limiting the accuracy of indirect calorimetry is the measurement of the respiratory minute volume. The precision of available gasometers can scarcely ever be reduced beyond plus or minus 1% of the volume which is to be measured. A new method is presented which enables the metabolic rate to be determined with far greater accuracy by increasing the precision of respiratory volume measurements. Expired air is collected in a metal cylinder and its volume is determined by forcing it under water and measuring the weight necessary to accomplish this. This force is equivalent to the buoyancy force of the measured volume. The lower limit of accuracy in measurement of compensatory weights is 1 g, which is equivalent to an accuracy of 1 ml gas volume, independent of the size of the spirometer. Losses caused by mechanical friction reduce the factual accuracy to plus or minus 0.1%. After volume determination, the O2 and CO2 content of the collected air is determined in analysers connected to the displacement spirometer.
D002245:Carbon Dioxide / Q000097:blood; D006801:Humans; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D013147:Spirometry / Q000379:methods*
D002245:Carbon Dioxide; D010100:Oxygen
Indirekte Kalorimetrie mit Auftriebsmessung des Atemminutenvolumens