Page 53 - Physiological based CPAP for preterm infants at birth Tessa Martherus

Comparison of two respiratory support strategies for stabilization of very preterm infants at birth
The delivery room management is essentially as described by Mehler et al. (31), however lower pressures and higher FiO2 values were used at that time.
Study Outcomes
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The primary study outcome was SpO2 in the first 7 min after birth. The 7 min timeframe was chosen to minimize the effect of other medical interventions. An overview of the data showed that FiO2 in the lower CPAP group was increased above 0.40 in median (IQR) 2.55 (2.48-3.22) min. To compare the effect of different pressure support strategies only, we analyzed the data in Phase I and II, represented before and after FiO2 increase.
Secondary delivery room study outcomes were heart rate, FiO2, mean airway pressure and
the SpO2/FiO2 ratio. The SpO2/FiO2 ratio represents the gas exchange efficiency of the lungs 2 as the surface area and the oxygen gradient mainly drive gas exchange. Apgar score at 5 min
after birth, pneumothorax rate <72 hours, the incidence of intubation <72 hours, intraventricular hemorrhages (>grade 2) and spontaneous intestinal perforations, reflected
the short-term clinical outcome. The occurrence of spontaneous intestinal perforations could
be a potential effect of high pressures on gas entering the intestinal tract. Gestational age,
birth weight, gender, mode of delivery and Apgar score at 1 min after birth were collected
from the medical records to describe baseline characteristics.
To record SpO2 and heart rate, a Masimo SET pulse oximeter probe (Masimo Radical, Masimo Corporation, Irvine, California, USA) was placed around the right wrist of the infant. FiO2 was measured using a portable oxygen analyzer AX300-I (Teledyne Analytical Instruments, CA, USA), and the airway pressures were registered by a variable orifice flow sensor (Avea Varflex Flow Transducer, Carefusion, Yorba Linda, CA, USA) connected to the facemask, measuring the flow in and out the infant. The signals were digitized at 200 Hz using the NewLifeBox-R physiological recording system (Advanced Life Diagnostics, Weener, Germany) and all signals were recorded by the NewLifeBox Neo-RSD computer system (Advanced Life Diagnostics, Weener, Germany) supported by Polybench physiological software (Applied Biosignals, Weener, Germany). Pulmochart software (Applied Biosignals, Weener, Germany) was used to calculate the mean airway pressure averaging the airway pressure between two inspiratory onsets.
Recordings started 1 min after birth, with the exception of infants who were delivered on the resuscitation table within the amniotic sac, as previously described by Mehler et al. (31). Opening of the amniotic sac was considered time of birth. Raw data were assessed on validity by the best clinical judgment of the researcher, as the signal IQ was not collected by the respiratory function monitor. In case of doubt, a second researcher assessed the data. Each presented value is calculated based on 60 measurements within a 30 sec interval, if <10 measurements were available the mean was excluded from the analysis.
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