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Effects of Gas Leak Around Endotracheal Tubes on Indirect Calorimetry Measurement
Author(s) -
Dietrich Kenneth A.,
Romero Michael D.,
Conrad Steven A.
Publication year - 1990
Publication title -
journal of parenteral and enteral nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.935
H-Index - 98
eISSN - 1941-2444
pISSN - 0148-6071
DOI - 10.1177/0148607190014004408
Subject(s) - leak , tidal volume , calorimetry , anesthesia , ventilation (architecture) , volume (thermodynamics) , medicine , cuff , mechanical ventilation , respiratory system , surgery , thermodynamics , physics
The use of uncuffed endotracheal tubes (ETT) in pediatric patients raises concern over the accuracy of indirect calorimetry measurement in the presence of a gas leak around an ETT. We examined the effects of ETT gas leak on respiratory gas measurements in a dog model. Mongrel dogs (n=12) were sedated, paralyzed, intubated, and placed on mechanical ventilation. Leak was achieved by adjusting cuff volume. Oxygen consumption (VO 2 ), CO 2 production (VCO 2 ), respiratory exchange ratio (RER), and resting energy expenditure (REE) were measured at each leak pressure (Pleak). Peak inspiratory pressure (PIP), Pleak, inspiratory and expiratory tidal volume (VTinsp, VTexp), VE, end tidal CO 2 (ETCO 2 ), and blood gases were recorded at each leak pressure. VO 2 , VCO 2 , and REE decreased significantly with increasing gas leak. There was a linear relationship between VO 2 , VCO 2 , and REE with both TVratio (VTexp/VTinsp) and Pdiff (PIP‐Pleak). Multiple regression equations based on TVratio and Pdiff were obtained which allowed correction of the measurement error in VO 2 , VCO 2 , and REE, with correlation coefficients ( R 2 ) of 0.71, 0.75, and 0.73, respectively. ETT gas leak affects measurements of VO 2 , VCO 2 , and REE, but not RER. Measurements made with TVratio > 0.80 required no correction. Measurements made with TVratio > 0.45 could be corrected to actual values in our model with regression equations based on TVratio and Pdiff. We conclude that indirect calorimetry measurements can be useful in the presence of tracheal gas leak around an ETT. ( Journal of Parenteral and Enteral Nutrition 14:408–413, 1990)