FEEDING-INDUCED CHANGES IN ENERGY-EXPENDITURE IN CHILDREN WITH CYSTIC-FIBROSIS

Seven children with cystic fibrosis (aged 7 to 12 years) were studied in the fasted and fed states. Using a primed, constant, intravenous infusion of NaH13CO3, the rate of appearance of co(2) (Raco(2)) was estimated. Net co(2) excretion (Vco(2)) was also measured. Energy expenditure was calculating using the food quotient. Raco(2) (mean +/- SD) (mu mol.kg(-1).min(-1)) in the fasted and fed states (297 +/- 59 and 359 +/- 67) was 117% and 105% of Vco(2) (259 +/- 48 and 352 +/- 72). Feeding induced a 23% and a 37% increase in Raco(2) and Vco(2), respectively, and respective 19% and 33% increases in energy expenditure (p <.05). Measurement of co(2) production by isotopic dilution is a useful index of group changes in energy expenditure, including those induced by feeding.