Page 62 - Physiological based CPAP for preterm infants at birth Tessa Martherus
P. 62

Chapter 2
air, airway resistance decreases and lung compliance increases (34, 35). Pressure levels should then be decreased down to reduce the risk of adverse events such as pneumothoraxes. If infants need more respiratory support, oxygen could increase the concentration gradient thereby driving oxygen transfusion over the lungs. By dynamic titration of CPAP and oxygen based on physiological parameters, each infant gets an individual approach suited for their conditions, while minimizing the risk of overexpansion and an overly high oxygen load. Until the optimal CPAP levels are examined extensively in preclinical settings, the use of high-pressure levels should carefully be considered.
The retrospective aspect of this study comes with some pitfalls. Most importantly, the protocols at the two sites had differences that we were unable to correct. The low-pressure group used the NeopuffTM T-piece Resuscitator to provide pressure support, whereas this was provided by the Benveniste valveTM in the high-pressure group. Although bench tests (36-38) imply that the Benveniste valveTM reduces the work of breathing, the clinical relevance of this finding is unknown. Infants were also positioned differently (supine vs. lateral on the right side), although no differences in oxygenation and heart rate were previously detected when comparing left-sided and supine positions (39). As the respiratory function monitor is mostly used in infants born by cesarean section at the University Hospital of Cologne, most infants in the high-pressure group were delivered by cesarean section. As these infants require more respiratory support (40, 41), we corrected for this difference in the statistics model. We were also unable to correct for other parameters that can affect cardiopulmonary function in the newborn (32, 42-44), including; time of cord clamping, cord milking, delivery within the amniotic sac and caffeine administration within 7 min of birth.
In summary, most very preterm infants need respiratory support to transition from fetal to newborn life and start pulmonary gas exchange. Theoretically, gas exchange can be improved by; (i) increasing the gas exchange surface area by using higher CPAP levels and (ii) increasing the gradient for oxygen diffusion by increasing the FiO2. In this retrospective study we did not see a difference in oxygen saturation using different pressure levels, which is possibly due to the closure of the glottis, preventing the pressure being transmitted down into the lower airways. The oxygen saturation only increased after increasing the FiO2. Until further preclinical trials examine the effect of high-pressure CPAP, we should be careful in administering high pressures to avoid pneumothoraxes.
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