Phase two: in-vivo study
This prospective observational study took place between January 2021 and
January 2022 in the neonatal intensive care unit (NICU) of the Centre
Hospitalier Intercommunal de Creteil. We included ELBW born ≤ 28 weeks
of gestational age with a body weight of less than 1500 g at the time of
the study and requiring mechanical ventilation. Patients were included
in the analysis when a recording of humidity was possible in both IPPV
and HFOV during their ventilatory support course. The choice of
ventilatory mode and ventilatory settings were left to the clinician’s
expertise and were not modified due to the study. Parents were informed
of the study and stated that they did not object. The institutional
ethics committee approved the study on December 1, 2020. The number of
subjects to include could not be predicted because the difference of
inspired airway humidity between the two ventilatory modes has never
been described. Thus, the study duration was set at one year.
The standard Y-piece was replaced by a sterilized Y-piece equipped with
a hygrometer during nursing care to record the humidity and temperature.
This recording lasted for two hours for each patient and each
ventilatory mode. The Y-piece with the hygrometer was removed the next
time a nurse attended the baby. Ventilator settings, heater-humidifier
device information (chamber inlet and outlet temperature and flow rate),
ambient temperature, and barometric pressure were all collected during
the 2-hour recording. After a stabilization period, any intervention
(such as opening the incubator or changing ventilatory settings) during
the 2-hour recording period was recorded. Only MR-B was used as a heater
humidifier to adhere to the airway humidification protocol in the NICU.