Metabolic gas exchange in critically ill surgical patients : physical, methodological, therapeutic and prognostic aspects

The aims of these studies are: - To design and to validate an automatic instrument for the measurement of oxygen consumption (Vo,), carbon dioxide production (Vco,) and respiratory quotient (R.Q.) (Appendix I). - - To assess the influence of artifacts in metabolic gas-exchange recordings due to patient-ventilator disconnections and to validate a new method for automatic detection and suppression of these artifacts (Appendix II). - To survey the disturbing influences of several clinical circumstances (especially of acetate hemodialysis) on metabolic gas-exchange measurements (Appendix III). - To quantify the stochastic and systematic errors, which are introduced when diurnal values of Vo,, Vco, and R.Q. are extrapolated from short recording periods (Chapter 5). - To analyze the systematic influence of a possible diurnal rhythm in gasexchange on such extrapolations (Chapter 5). - To determine the discrepancy between (Chapter 6): a. Basal Energy Expenditure (= BEE; i.e. the energy expenditure under basal conditions) calculated by means of the anthropometric uncorrected Harris-Benedict formula and Total Energy Expenditure (= TEE) measured by means of continuous indirect calorimetry; b. TEE calculated by means of the corrected Harris-Benedict formula and continuously measured TEE; c. intermittently measured TEE and continuously measured TEE. - To analyze to what extent a standard nutritional regimen leads to hypoor hyperalimentation and to determine whether a tailored caloric supply based on anthropometric data gives a better match to energy expenditure than a standard supply (Chapter 7). - To determine whether Vo, -indices of survivors are different from those of nonsurvivors and to analyze whether the potency of a frequently used system to predict the patient's ultimate outcome (SAPS) can be improved by addition of Vo2-index as a supplemental physiological variable (Chapter 8). - To survey the present nutritional, mechanical and pharmacological methods to reduce metabolic rate (Chapter 9).

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