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Use of a Ventilated Canopy for Assessment of [13C]Leucine Oxidation in Patients Receiving Total Parenteral Nutrition
Author(s) -
Just Bernard,
Darmaun Dominique,
Koziet Joseph,
Rongier Monique,
Messing Bernard
Publication year - 1991
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 - 10.1177/014860719101500165
Subject(s) - parenteral nutrition , mouthpiece , canopy , dilution , enteral administration , kerma , zoology , medicine , chemistry , surgery , nuclear medicine , biology , botany , dosimetry , physics , dentistry , thermodynamics
Rates of oxidation of infused 13 C‐labeled substrates are calculated from CO 2 production and 13 C enrichment in breath CO 2 . Breath sampling through a mouthpiece is not appropriate in severely ill patients; the authors therefore validated the use of direct air sampling from the ventilated canopy of an indirect calorimeter for measuring the oxidation of 13 C‐labeled substrates. Infusions of H 13 CO 3 Na or L‐[1‐ 13 C]leucine were performed in four healthy postabsorptive adults and six malnourished patients receiving total parenteral nutrition (TPN). At each sampling point, air was collected from the canopy to compare with breath air sampled through a mouthpiece and 13 CO 2 enrichment determined by isotope ratio mass spectrometry. Despite five‐fold dilution of expired air by room air within the canopy (a dilution required to maintain safe CO 2 levels in inspired air): (1) Breath 13 CO 2 enrichment was accurately predicted using samples from the canopy, with a correction taking into account the measured CO 2 fractions in canopy and room air; (2) the precision in isotopic determination was similar with both methods (SD/mean of 12 determinations = 2.5 ± 1.0% us 3.0 ± 1.0%). These data demonstrate that the use of a ventilated canopy allows for combined assessment of energy expenditure and rates of oxidation of 13 C‐labeled substrates even in sick, debilitated patients receiving total parenteral nutrition. (Journal of Parenteral and Enteral Nutrition 15: 65–70, 1991)