Reflexes that impact spontaneous breathing of preterm infants at birth: a narrative review

Some neural circuits within infants are not fully developed at birth, especially in preterm infants. Therefore, it is unclear whether reflexes that affect breathing may or may not be activated during the neonatal stabilisation at birth. Both sensory reflexes (eg, tactile stimulation) and non-invasive ventilation (NIV) can promote spontaneous breathing at birth, but the application of NIV can also compromise breathing by inducing facial reflexes that inhibit spontaneous breathing. Applying an interface could provoke the trigeminocardiac reflex (TCR) by stimulating the trigeminal nerve resulting in apnoea and a reduction in heart rate. Similarly, airflow within the nasopharynx can elicit the TCR and/or laryngeal chemoreflex (LCR), resulting in glottal closure and ineffective ventilation, whereas providing pressure via inflations could stimulate multiple receptors that affect breathing. Stimulating the fast adapting pulmonary receptors may activate Head's paradoxical reflex to stimulate spontaneous breathing. In contrast, stimulating the slow adapting pulmonary receptors or laryngeal receptors could induce the Hering-Breuer inflation reflex or LCR, respectively, and thereby inhibit spontaneous breathing. As clinicians are most often unaware that starting primary care might affect the breathing they intend to support, this narrative review summarises the currently available evidence on (vagally mediated) reflexes that might promote or inhibit spontaneous breathing at birth.