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Long-term variation in oxygen consumption rate in preterm infants
Insights
Short-term oxygen consumption rate (VO2) measurements in preterm infants are less reliable than previously thought. Daily VO2 measurements showed significant variation, impacting energy expenditure calculations.
Area of Science:
- Neonatal physiology
- Indirect calorimetry
- Energy metabolism
Background:
- Accurate assessment of energy expenditure is crucial for preterm infant growth.
- Previous studies often relied on short-term measurements of oxygen consumption rate (VO2).
- Understanding long-term VO2 variation is essential for precise nutritional management.
Purpose of the Study:
- To investigate the long-term variation in oxygen consumption rate (VO2) in preterm infants.
- To determine the reliability of short-term (e.g., 24-hour) VO2 measurements in this population.
- To assess the impact of measurement duration on the precision of VO2 estimation.
Main Methods:
- Open-circuit, indirect calorimetry was used to measure VO2.
- Four preterm infants (gestational age 27-34 weeks) were studied over 5 days each.
- Between-subject and between-measurement coefficients of variation were calculated for different time intervals.
Main Results:
- Mean VO2 values were within the reported range for preterm infants.
- Between-measurement variation in daily VO2 (3.8%) exceeded between-subject variation (2.1%).
- VO2 measurement variation increased significantly with shorter intervals, reaching 8.3% for 1-hour periods.
Conclusions:
- Even 24-hour VO2 measurements in preterm infants may not accurately represent individual energy expenditure over 3-5 days.
- Short-term VO2 measurements can lead to substantial errors in calculated energy deposition, affecting nutritional studies.
- Longer measurement durations or refined methodologies are needed for reliable energy expenditure assessment in preterm infants.
Abstract:
An investigation was made of long-term variation in oxygen consumption rate (VO2) in preterm infants. Four subjects (gestational age 27-34 weeks, postnatal age 17-38 days, weight at study 1.1-2.6 kg) were studied for 5 days each using open-circuit, indirect calorimetry. The mean VO2 for each subject (11.0-11.5 litres/kg/day) was within the reported range. However, the between-subject coefficient of variation during the study (2.1%) was smaller than the mean between-measurement coefficient of variation for daily VO2 (3.8%, range 1.7-6.3%). In addition, the between-measurement coefficient of variation was increased further for measurement intervals of less than 24 h (reaching a mean of 8.3% for 1-hour periods), and a relationship between measurement duration and the precision of estimating VO2 over 3 or 5 days is described. Thus, even 24-hour measurements of VO2 in these preterm infants were less representative of the individual's VO2 over 3 days than the group mean estimate. This finding is of relevance to future studies in this area, particularly those in which short-term measurements of energy expenditure are combined with a nutrient balance study to determine the composition of weight gain, because even small errors in the estimate of total energy expenditure can lead to unacceptably large errors in calculated energy deposition.