Comparison of different methods for dead space measurements in ventilated newborns using CO2-volume plot

Area of Science:

• Neonatal Medicine
• Respiratory Physiology
• Critical Care

Background:

• Accurate measurement of respiratory dead space (VD) is crucial for managing ventilated neonates.
• Existing methods for VD measurement may have limitations in this population.

Purpose of the Study:

• To evaluate the applicability of the Ventrak 1550/Capnogard 1265 (V-C) system for respiratory dead space measurement in ventilated neonates.
• To determine anatomic (VDana), physiologic (VDphys), and alveolar dead spaces (VDalv) in this patient group.

Main Methods:

• A prospective study was conducted in a neonatal intensive care unit.
• 33 investigations were performed in 22 ventilated neonates.
• Respiratory dead space was determined using the single-breath CO2 test (SBT-CO2) and transcutaneous partial pressure of carbon dioxide (PCO2) measurements, analyzed via automated software, interactive analysis, and manual calculation using Bohr/Enghoff equations.

Main Results:

• Automated and interactive VD measurement methods were unsuccessful in 67% of investigations, particularly in preterm neonates, due to signal disturbances.
• Manual calculation using Bohr/Enghoff equations enabled VD measurement in all cases.
• VDana/kg and VDana/tidal volume were lower than in spontaneously breathing infants, while VDphys/kg and VDphys/VT were comparable to literature values.
• Transcutaneous PCO2 increased slightly after sensor insertion, with a greater rise in lower birthweight infants.

Conclusions:

• Respiratory dead space measurement in ventilated neonates using SBT-CO2 is feasible in all cases via manual Bohr/Enghoff equations, but not reliably with automated methods.
• Improvements in software could enhance the efficiency of VD analysis.