Page 119 - Physiological based CPAP for preterm infants at birth Tessa Martherus

Feasibility and effect of physiological based CPAP in preterm infants at birth
Introduction
Historically, elective intubation and mechanical ventilation were standard care in the delivery room (DR), but now respiratory support is primarily given non-invasively to minimize risk of injury (1-3). The effectiveness of non-invasive support is dependent on infants having a patent airway since the larynx of newborn infants closes during apnea (4-8). As the larynx only opens during a breath, support at birth now focuses on stimulating and supporting spontaneous breathing (9). Recent studies showed that breathing effort can be stimulated by adequate oxygenation, repetitive tactile stimulation and caffeine (10-12). However, ongoing breathing activity is totally reliant on lung aeration and these interventions do not necessarily enhance lung aeration (13). Respiratory support in the DR can further be optimized by improving lung aeration.
P
Lung aeration is driven by the transpulmonary pressure, which is a pressure gradient generated during inspiration (14-16) and can be increased by applying continuous positive airway pressure (CPAP) to the mouth opening. Preterm infants are routinely supported with 5-8 cmH2O CPAP in the DR, yet this strategy has been extrapolated from care used in the neonatal intensive care unit (NICU). However, in the NICU, CPAP is used to support infants hours to days after birth when the lungs are well aerated (17, 18). There is little evidence that a CPAP of 5-8 cmH2O is the optimal pressure range to promote lung aeration when infants have a liquid-filled highly incompliant lung at birth.
Physiological based (PB)-CPAP takes the changes that are required to transition from fetus to 5 newborn infant into consideration (Figure 1). When infants are born, their airways are filled
with liquid that needs to be replaced with air. Initially, the role of CPAP is to assist liquid movement from the airways into the interstitial tissue during inspiration, by increasing the
pressure gradient across the airway wall (19, 20). High pressures are needed to overcome the high airway resistance generated by the viscosity of liquid and its movement across the epithelium (14-16). Once lung aeration is established, the role of CPAP changes to maintaining lung aeration. Lower CPAP levels are then likely sufficient to prevent liquid re-entry and alveolar collapse at end-expiration (14-16, 19-24). As real time parameters guide how caregivers decrease CPAP levels, PB-CPAP is tailored to each individual and CPAP levels will suit the different phases of the neonatal transition.
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