Optimizing care of ventilated infants by improving weighing accuracy on incubator scales

OBJECTIVES: To determine the accuracy of weighing ventilated infants on incubator scales and whether the accuracy can be improved by the addition of a ventilator tube compensator (VTC) device to counterbalance the force exerted by the ventilator tubing.
STUDY DESIGN: Body weights on integral incubator scales were compared in ventilated infants (with and without a VTC), with body weights on standalone electronic scales (true weight). Individual and series of trend weights were obtained on the infants. The method of Bland and Altman was used to assess the introduced bias.
RESULTS: The study included 60 ventilated infants; 66% of them weighed <1000 g. A total of 102 paired-weight datasets for 30 infants undergoing conventional ventilation and 30 undergoing high frequency oscillator ventilation (HFOV) supported by a SensorMedics oscillator, (with and without a VTC) were obtained. The mean differences and (95% CI for the bias) between the integral and true scale weighing methods was 60.8 g (49.1 g to 72.5 g) without and –2.8 g (–8.9 g to 3.3 g) with a VTC in HFOV infants; 41.0 g (32.1 g to 50.0 g) without and –5.1 g (–9.3 g to –0.8 g) with a VTC for conventionally ventilated infants. Differences of greater than 2% were considered clinically relevant and occurred in 93.8% without and 20.8% with a VTC in HFOV infants and 81.5% without and 27.8% with VTC in conventionally ventilated infants.
CONCLUSIONS: The use of the VTC device represents a substantial improvement on the current practice for weighing ventilated infants, particularly in the extreme preterm infants where an over- or underestimated weight can have important clinical implications for treatment. A large-scale clinical trial to validate these findings is needed.

*Corresponding Author: 

Ula El-Kafrawy, MD, Department of Neonatology, Royal Bolton Hospital, Minerva Road, Bolton, BL4 0JR, UK. Tel.: +44 204 390335/07815197407; Fax: +44 204 390211; E-mail: Ula.el-kafrawy@boltonft.nhs.uk.