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Abstract Body

This review is on potential associations between intermittent hypoxia (IH) and impaired neurodevelopment in infants and children. In extremely preterm infants (<28 wk gestation), such an association has been established based on a secondary analysis of Cana­dian Oxygen Trial data. These showed, in 997 infants, that the odds of developing cognitive or language impairment at 18 months corrected age were 3 times higher in infants who were in the highest decile for the proportion of time spent with events where pulse oximeter saturation (SpO₂) was <80% for ≥1 min. during their first 10 postnatal weeks compared to those who had very few intermittent hypoxemia (IH) events after birth. In older term and preterm infants, the occurrence of 5 or more events with prolonged apnea and bradycardia during home monitoring was associated with 5 points less on the mental development index of the Bayley-II scales. For older children, associations between sleep-disordered breathing and impaired cognition/academic achievements have also been established, but not consistently, and it remains unclear whether this association is primarily mediated via IH or via sleep deprivation resulting from frequent apnea-induced arousals. Animal data show that IH may cause apoptosis particularly in the hippocampus. Although we need to stress that associations cannot prove causality, current evidence provides support for IH to be detected and prevented early. Future studies should focus on IH rather than on apnea/bradycardia.

Background and Aims

Apnea is a cessation of breathing that may cause bradycardia and desaturation. Monitoring devices use peripheral oxygen saturation and heart rate as proxies of apnea, rather than directly measuring the pause in breathing. The signal of the electrical activity of the diaphragm (Edi signal) represents neural respiratory drive and can be used to monitor breathing patterns. This study used the Edi signal to detect and quantify the number of central respiratory pauses.

Methods

We performed 12-hour-long registrations of vital signs including Edi signal of infants born ≤ 32 gestational weeks. Edi signal data were analyzed with dedicated software.

Results

A total of 39 infants born at a median age of 30+4 weeks and with a birth weight of 1370 g were included in the study. Their apnea registrations were performed at a median postmenstrual age of 35+4 weeks. Based on the Edi signal analysis, 1019 (median) respiratory pauses lasted for 2-5 seconds, 185 pauses lasted for 5-10 seconds, and six pauses lasted for 10-15 seconds. The number of short respiratory pauses (5-10 seconds) was strongly correlated with the number of longer respiratory pauses (>10 seconds). The number of very short respiratory pauses (2-5 seconds) showed only a weak correlation with the number of respiratory pauses longer than 10 seconds.

Conclusions

It is clinically important that the appearance of short central respiratory pauses indicates a risk for long respiratory pauses. Future studies will evaluate the relationship between short respiratory pauses and apnea with bradycardia. This might help to identify infants not ready for discharge home.

Background and Aims

Non-invasive high-frequency oscillatory ventilation (nHFOV) may be effective in treating apnea of prematurity. However, the mechanisms underpinning this benefit are unclear.

Methods

Electrical impedance tomography (EIT) data from a randomized crossover trial comparing nHFOV with nasal continuous positive airway pressure (nCPAP) were screened to identify apneas ≥10 seconds. Oscillatory volumes (V_Osc) during apneas were identified using a band-pass filter at 8 and 16 Hz (set frequency during nHFOV and second harmonic). End-expiratory lung impedance (EELI) and tidal volumes (V_T) were calculated before and after apneas. Oxygen saturation (SpO₂) and heart rate (HR) were extracted for 60 seconds after apneas.

Results

In 30 preterm infants, 213 apneas were identified. During apneas, V_Osc were detectable during nHFOV. EELI decreased significantly during apneas [∆EELI nCPAP: -8.0 (-11.9 to -4.1) AU/kg, p<0.001; ∆EELI nHFOV: -3.4 (-6.5 to -0.3), p=0.03] but recovered over the first five breaths after apneas. Compared with before apneas, V_T was increased for the first breath after apneas during nCPAP [∆V_T: 7.5 (3.1–11.2) AU/kg, p=0.001]. Falls inSpO₂ and HR after apneas were greater during nCPAP compared with nHFOV [Mean difference (95% CI): SpO₂: 3.6 (2.7 to 4.6) %, p<0.001; HR: 15.9 (13.4 to 18.5), p<0.001].

Conclusions

Apneas were characterized by a significant decrease in EELI which was regained over the first breaths after apneas, mediated by a larger V_T of the first breath. Apneas were followed by a considerable drop in SpO₂ and HR, particularly during nCPAP, leading to longer episodes of hypoxemia during nCPAP. Transmitted oscillations during nHFOV may explain these benefits.

Background and Aims

Very-low-birthweight (VLBW) premature infants experience frequent desaturation episodes during the first weeks of life. The length of tube feeding, among VLBW infants supported by non-invasive ventilation (NIV), might influence the incidence of desaturation episodes as bolus feeding might increase gastrointestinal reflux, while in continuous feeding, the inability to vent the stomach during feeding may lead to gaseous abdominal distention and hinder ventilation.

Aim:To compare oxygenation instability, as documented by the SpO₂ histograms, around bolus versus continuous feeding among VLBW premature infants, supported with NIV.

Methods

A randomized prospective study. VLBW supported with NIV were randomized to receive 3 consecutive feeds of bolus-continuous-bolus or continuous-bolus-continuous feeding in random order. Two-hour histograms were recorded, documenting oxygenation stability during the two hours in which the infant was continuously fed (continuous feeding) or fed by bolus (30-minutes of feeding, followed by 30-minutes with a closed gastric tube, followed by 1hour of gastric venting with an open gastric tube).

Results

Twenty-four infants were included in our study (14-NIPPV, 1-CPAP, 9-HHHFNC). Mean(SD) GA -27.0±1.6, BW 820±168g. Seventy-two histograms were obtained- 36-during bolus and 36-during continuous feeding. No differences in min-max FiO₂ and number of apnea events were observed. Time spent in SpO₂ 90-94%, <80%, <90% and >95% was comparable during bolus and continuous feeding. When analysing the effect of changing from bolus to continuous and continuous to bolus per infant, no differences in oxygenation stability was observed too.

Conclusions

Among VLBW infants supported with NIV, oxygenation instability, as documented by SpO₂ histograms, was comparable between bolus and continuous feeding.