The indirect calorimetry in very low birth weight preterm infants: An easier and reliable procedure.

Background and aim Preterm infants are at increased risk to develop extrauterine growth restriction, which is associated with worse health outcomes. The energy needs are not well known as the measurement of resting energy expenditure(REE) using indirect calorimetry has critical issues when applied to infants. One of the main issues is the time required to obtain reliable data due to the difficulty to keep infants quiet during the entire duration of the exam. Thus, aim of this study was to define the minimum duration of calorimetry in order to obtain reliable data. Methods Oxygen consumption(VO2) and carbon dioxide production (VCO2) were recorded for a mean duration of 90 consecutive minutes. REE was calculated using neonatal prototype calculator. We extracted data regarding VO2, VCO2 and REE at 10(T1), 20(T2), 30(T3), 40(T4), 50(T5) minutes of steady state and compared them to those of entire steady state period. Results Twenty-six very low birth weight preterm infants were evaluated at 36.58±0.99 weeks corrected age. Infants were appropriate for gestational age, clinically stable without comorbities.. There were no significant differences between mean VO2 and REE at T1(8.26±1.45ml/kg-57.80±10.51kcal/kg), T2(8.15±1.41ml/kg-56.87±10.05kcal/kg), T3(8.04±1.41ml/kg-56.32±9.73kcal/kg), T4(8.05±1.41ml/kg-56.07±10.28kcal/kg) and T5(8.06±1.55ml/kg-57.17±11.62kcal/kg) respectively, compared to steady state(8.13±1.33ml/kg-56.77±9.34kcal/kg). The median values of VCO2 were significantly different only when T1 data were compared with other time slots(7.02±1.02ml/kg at SS; 7.26±1.23ml/kg at T1; 7.13±1.20ml/kg at T2; 7.02±1.19ml/kg at T3; 6.85±1.16ml/kg at T4; 6.91±1.24ml/kg at T5). Conclusion Twenty consecutive minutes in steady state condition are sufficient to obtain reliable data on REE instable VLBWI.