A nomogram for rapid calculation of metabolic requirements on intubated patients

Abstract

There is a need for estimating the calorific requirements of patients undergoing or about to undergo total parenteral nutrition (TPN) other than by complicated direct calorimetry or by guesswork. We describe a simple, cheap, indirect calorimetric method for determining energy requirements from the measurement of mixed expired carbon dioxide tension (P_ĒCO₂) in patients who are intubated, and in whom the breathing circuit characteristics allow collection of pure expired gas. This can be achieved by collection of expired gas from ventilators where an on-demand fresh gas flow rather than a continuous flow occurs during spontaneous or intermittent positive pressure ventilation, such as with the Siemens Servo 900C.