Page 158 - Physiological based CPAP for preterm infants at birth Tessa Martherus

Summary
Introduction
Most preterm infants require respiratory support at birth, which is currently most commonly applied non-invasively along with a focus on stimulating and supporting spontaneous breathing (1). Recent studies demonstrated that breathing effort can be improved by repetitive tactile stimulation, caffeine administration and adequate oxygenation (2-4). There is, however, little data on the optimal continuous positive airway pressure (CPAP) approach to assist preterm infants in establishing and maintaining lung aeration at birth (5). Lung aeration is driven by the transpulmonary pressure gradient that is generated during inspiration and this gradient can be increased by applying CPAP. Currently, 5-8 cmH2O is used for CPAP in the delivery room (DR), however this pressure range is extrapolated from CPAP support in the neonatal intensive care unit. As the physiology of a newborn infant at birth is considerably different than it is later on in the unit, it is likely that a different CPAP strategy may also be needed to establish lung aeration at birth.
The underlying principle of physiological based (PB)-CPAP is to tailor the CPAP level to take into account the physiological changes that occur in the infant during the transition at birth. Immediately at birth, the main role of CPAP is assist the infants attempts to move liquid out of the airways into the interstitial tissue and hence promote lung aeration. During this process, the high airway resistance requires (6-8) higher pressure gradients and, therefore, high initial CPAP levels (9, 10). After lung aeration has been established, airway resistance decreases and the role of CPAP converts to maintaining lung aeration. Lower CPAP levels match the lower airway resistance and are likely to be sufficient to prevent alveolar collapse and liquid re-entry in the post aeration period (6-14). When the CPAP titration is guided by real time parameters, PB-CPAP can be individualized and CPAP levels will suit the different phases of lung aeration.
The aim of this thesis was to develop a PB-CPAP strategy and to investigate the effect on cardiopulmonary stabilization of preterm infants at birth. We hypothesized that infants at birth benefit from PB-CPAP, mostly by promoting lung aeration. The potential benefits and harms of PB-CPAP were evaluated in preclinical studies and the feasibility was investigated in a small clinical trial.
Which CPAP levels to use for PB-CPAP?
In Chapter 1 we evaluated the available literature to determine which CPAP levels to use for our PB-CPAP approach. As the existing literature was limited, the search strategy included articles on CPAP during spontaneous breathing and positive end-expiratory pressures (PEEP) levels during positive pressure ventilation at birth. Studies found that higher CPAP levels could be beneficial, as animal studies showed that 8-20 cmH2O CPAP/PEEP improves aeration and oxygenation (10, 15-19) and clinical studies found that 6-15 cmH2O of PEEP reduced intubation and ventilation rates in the DR when compared to 4-5 cmH2O (20-22). However,
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