TitelLooking for the smallest possible dead space

Flow sensors are placed directly in front of the endotracheal tube when ventilating premature infants. In this position, they increase the instrumental dead space. Higher tidal volumes are required to overcome the dead space, increasing the risk of ventilator-induced lung injury. In an experimental setup, the dead space of several flow sensors with different dead space and various adapters were tested how to keep the dead space as small as possible.

Patient/en und Methoden

The experiment was conducted with the continuous flow ventilator Sophie, connected to a pneumotachograph and a test lung, simulating a 1000 g infant. Four different flow sensors from Stephan GmbH with various adapters and Microstream CO2 sampling were tested: A, B, Double, and the new Neo pneumotachograph for preterm infants. The dead space could be determined by flooding the lung with CO2 and measuring the CO2 elimination time using a capnograph. The measurements were carried out twenty times with each combination. Mean elimination times (±SD) were compared.


Mean CO2 elimination time was 27.4 s (± 0.05 s) with and 28.4 s (± 0.05 s) without the dead space minimizer for the A Sensor, 32.4 s (± 0.06 s) and 36.5 s (± 0.13 s) for the B Sensor, 27.5 s (± 0.05 s) and 27.5 s (± 0.08 s) for the Double Sensor and 30.4 (± 0.15 s) without for the Neo Sensor because it is not compatible with it. If no dead space minimizer was installed, the standard adapter for the endotracheal tube was used as a reference. Using the Microstream CO2 sampling, mean elimination time was 29.3 s (± 0.1 s) for the A, 36.1 s (±0.05 s) for B, 28.5 s (± 0.05 s) for Double and 31.3 s (±0.07 s) for the Neo pneumotachograph.


CO2 elimination time was significantly lower with the dead space minimizer for A and B Sensor, not significant for Double, and not assessable for Neo Pneumotachograph. CO2 sampling leads to a slight increase in dead space, which is relevant for extremely preterm infants. However, the effect does not appear to be so great that a justified use can be considered.

Erstautor*in ist unter 35 Jahre alt
Autor*in 1Linda Mur Paracelsus Medical University
Autor*in 2Martin Wald, MD, PD, Assoc. Prof. Division of Neonatology, Department of Paediatrics and Adolescent Medicine, Paracelsus Medical University, University Hospital Salzburg