Page 19 - Physiological based CPAP for preterm infants at birth Tessa Martherus
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pattern, the larynx will be predominantly closed immediately after birth, only allowing air to enter the lungs during a spontaneous breath. The larynx will switch to a predominantly open state only after a stable breathing pattern is achieved. This means that when given via a facemask, iPPV delivered to infants who are apnoeic or breathe insufficiently, is often ineffective in ventilating the lungs (17). While iPPV fails to aerate the lungs, hypoxia will worsen and when severe, it is possible that the the larynx will relax, allowing iPPV to ventilate the lungs. However, this far from ideal as hypoxia should be avoided wherever possible as this is associated with higher mortality and morbidities (51).
It is clear that spontaneous breathing is essential for effective non-invasive respiratory support and to reduce the need for iPPV. During regular spontaneous breathing, the larynx will open allowing respiratory support to reach the lungs. Although most very preterm infants do breathe at birth (42, 43), their respiratory effort is weak and this should be stimulated and supported in an optimal manner. Enhancing spontaneous breathing will likely reduce the need for iPPV and improve gas exchange, which increases oxygenation and provides a further positive stimulus for breathing. Reaching an increased oxygenation level sooner increases the likelihood of achieving a sustainable and stable regular breathing pattern in the newborn, thereby creating a patent airway that enables any additional respiratory support to be applied (52).
The era of stimulating and supporting spontaneous breathing
In recent years, research has been focusing on stimulating spontaneous breathing using tactile stimulation, caffeine and supplemental oxygen. The most basic intervention to enhance breathing is tactile stimulation, and although it is widely recommended by guidelines (53, 54), the methods of tactile stimulation in the delivery room vary widely (55-59). To date, only one clinical trial (60) has been performed, which showed favourable effects of repetitive tactile stimulation on respiratory effort leading to a significant increase in oxygen saturation.
Caffeine, an adenosine antagonist, is another intervention that was introduced to enhance breathing effort in the delivery room. While caffeine is routinely used in the neonatal unit to promote breathing and reduce the incidence of apnoea, it is not commonly used to improve breathing effort at birth. In a recent trial, caffeine was shown to increase respiratory effort in preterm infants, as indicated by a significant increase in minute volume, tidal volume and the number of recruitment breaths (61).
The use of supplemental oxygen in the delivery room has also been investigated extensively and various clinical trials have been performed to find the optimal initial oxygen concentration (62-64). While there is no convincing evidence, guidelines recommend using low inspired oxygen concentrations initially (0.21-0.3) and to titrate the inspired oxygen content, guided by the infant’s preductal oxygen saturation (53, 65). Balancing the use of supplemental oxygen is crucial as hypoxia suppresses spontaneous breathing at birth (66, 67) and increases the risk of death and intraventricular haemorrhages (51). However, hyperoxia
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General introduction
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