Event-related potentials following contraction of respiratory muscles in pre-term and full-term infants

The effect of acute respiratory events and respiratory stimulants on EEG-recorded brain activity in neonates: A systematic review

Objective

We conducted a systematic review to investigate electroencephalography (EEG) changes during periods of acute respiratory events such as apnoea and the effect of respiratory stimulants on EEG features in infants.

Methods

Studies examining respiration and EEG-recorded brain activity in human neonates between 28 and 42 weeks postmenstrual age were included. Two reviewers independently screened all records and included studies were assessed using the Joanna Briggs Institute Critical Appraisal Tool. The protocol was registered in PROSPERO (CRD42022339873).

Results

We identified 14 studies with a total of 534 infants. Nine articles assessed EEG changes in relation to apnoea, one assessed hiccups, and four investigated the effect of respiratory stimulants. The relationship between neonatal apnoea and EEG changes was inconsistent; EEG suppression and decreased amplitude and frequency were observed during some, but not all, apnoeas. Respiratory stimulants increased EEG continuity compared with before use.

Conclusions

Current studies in this area are constrained by small sample sizes. Diverse exposure definitions and outcome measures impact inference.

Significance

This review highlights the need for further work; understanding the relationship between respiration and the developing brain is key to mitigating the long-term effects of apnoea.

Intrapulmonary Volume Changes during Hiccups versus Spontaneous Breaths in a Preterm Infant

Hiccups occur at all ages but are most common during fetal development, and accordingly, they are seen regularly in preterm infants. However, the physiologic correlate of hiccups has never been established. We present the case of a preterm infant who developed a spell of hiccups and compared lung volume changes during hiccups with spontaneous breaths using electrical impedance tomography. Hiccups mostly occurred during the expiratory phase of breathing and were associated with a shorter inspiratory time and a larger tidal volume compared with spontaneous breaths. The center of ventilation was shifted toward the ventral (non-gravity-dependent) part of the lung during hiccups and volume changes were mainly restricted to the larger airways, but some gas flow also reached the lung parenchyma. Our observations shed new light on this phenomenon, which is well known but little researched, and our findings may imply a physiological impact of hiccups during fetal development.

Spontaneous and apnea arousals from sleep in preterm infants

BACKGROUND

The significance of arousal in apnea termination in preterm infants is not known.

METHODS

We investigated the appearance of arousals from sleep with polysomnography for 21 preterm infants at a median age of 36 gestational weeks.

RESULTS

The polysomnographic appearance of sleep was fragmented by frequent arousals. The number of spontaneous arousals unrelated to apneas was 18 per hour in sleep; higher in rapid eye movement (REM) sleep than in non-REM sleep (p < 0.001). Eighty-two percent of arousals were regarded as spontaneous, and 18% were related to apneas. In turn, arousal followed 5% of all apneas; 30% of mixed, 2% of central, and 20% of long apneas defined as apnea of prematurity. Apneas without an arousal led to lower oxygen saturation levels than those followed by an arousal (p < 0.001). Mixed apneas with an arousal had stronger breathing effort and a higher number of breaths compared with apneas without an arousal (p < 0.05).

CONCLUSIONS

In preterm infants, frequent spontaneous arousals or arousal-type phenomena make the polysomnographic appearance of sleep fragmented. However, even long apneas or hypoxia commonly fail to elicit arousals or any sign of sleep interruption. Our findings suggest that arousal appears not to be the main mechanism for apnea termination in preterm infants.

IMPACT

Polysomnographic appearance of sleep in preterm infants is fragmented by arousals. Contrary to older children and adults, arousal to apnea is uncommon in preterm infants. Even long mixed apneas with desaturation mostly fail to elicit an arousal response. In preterm infants, apnea termination appears not to depend on an arousal. Low arousability is suggested to be caused by a low ventilation response to hypoxia.

Long-range temporal organisation of limb movement kinematics in human neonates

OBJECTIVE

Movement provides crucial sensorimotor information to the developing brain, evoking somatotopic cortical EEG activity. Indeed, temporal-spatial organisation of these movements, including a diverse repertoire of accelerations and limb combinations (e.g. unilateral progressing to bilateral), predicts positive sensorimotor outcomes. However, in current clinical practice, movements in human neonates are qualitatively characterised only during brief periods (a few minutes) of wakefulness, meaning that the vast majority of sensorimotor experience remains unsampled. Here our objective was to quantitatively characterise the long-range temporal organisation of the full repertoire of newborn movements, over multi-hour recordings.

METHODS

We monitored motor activity across 2-4 h in 11 healthy newborn infants (median 1 day old), who wore limb sensors containing synchronised tri-axial accelerometers and gyroscopes. Movements were identified using acceleration and angular velocity, and their organisation across the recording was characterised using cluster analysis and spectral estimation.

RESULTS

Movement occurrence was periodic, with a 1-hour cycle. Peaks in movement occurrence were associated with higher acceleration, and a higher proportion of movements being bilateral.

CONCLUSIONS

Neonatal movement occurrence is cyclical, with periods consistent with sleep-wake behavioural architecture. Movement kinematics are organised by these fluctuations in movement occurrence. Recordings that exceed 1-hour are necessary to capture the long-range temporal organisation of the full repertoire of newborn limb movements.

SIGNIFICANCE

Future work should investigate the prognostic value of combining these movement recordings with synchronised EEG, in at-risk infants.