Authors:
Neumann RP, Pillow JJ, Thamrin C, Larcombe AN, Hall GL, Schulzke SM.
Authors notes:
Neonatology. 2015;107(1):43-9.
Keywords:
Very-low birth weight infants, Premature infants, Tidal volume, Artificial respiration
Abstract:
BACKGROUND: Ventilated preterm infant lungs are vulnerable to overdistension and underinflation.
The optimal ventilator-delivered tidal volume (VT) in these infants is unknown and may depend on the extent of alveolarisation at birth.
OBJECTIVES: We aimed to calculate respiratory dead space (VD) from the molar mass (MM) signal of an ultrasonic flowmeter (VD,MM) in very preterm infants on volume-targeted ventilation (VT target, 4-5 ml/kg) and to study the association between gestational age (GA) and VD,MM-to-VT ratio (VD,MM/VT), alveolar tidal volume (VA) and alveolar minute volume (AMV).
METHODS: This was a single-centre, prospective, observational, cohort study in a neonatal intensive care unit.
Tidal breathing analysis was performed in ventilated very preterm infants (GA range 23-32 weeks) on day 1 of life.
RESULTS: Valid measurements were obtained in 87% infants.
Tidal breathing variables were analysed using multivariable linear regression.
VD,MM/VT was negatively associated with GA after adjusting for birth weight Z score.
This association was primarily influenced by the appliance dead space.
Despite similar VT/kg and VA/kg across all studied infants, respiratory rate and AMV/kg increased with GA.
CONCLUSIONS: VD,app rather than anatomical VD is the major factor influencing increased VD,MM/VTat a younger GA.
A volume guarantee setting of 4-5 ml/kg in the Drager Babylog(R) 8000 plus ventilator may be inappropriate as a universal target across the GA range of 23-32 weeks.
Differences between measured and set VT and the dependence of this difference on GA require further investigation.