Monitoring interactions between spontaneous respiration and mechanical inflations in preterm neonates

Detection and quantitative analysis of patient-ventilator interactions in ventilated infants by deep learning networks

BACKGROUND

The study of patient-ventilator interactions (PVI) in mechanically ventilated neonates is limited by the lack of unified PVI definitions and tools to perform large scale analyses.

METHODS

An observational study was conducted in 23 babies randomly selected from 170 neonates who were ventilated with SIPPV-VG, SIMV-VG or PSV-VG mode for at least 12 h. 500 breaths were randomly selected and manually annotated from each recording to train convolutional neural network (CNN) models for PVI classification.

RESULTS

The average asynchrony index (AI) over all recordings was 52.5%. The most frequently occurring PVIs included expiratory work (median: 28.4%, interquartile range: 23.2-40.2%), late cycling (7.6%, 2.8-10.2%), failed triggering (4.6%, 1.2-6.2%) and late triggering (4.4%, 2.8-7.4%). Approximately 25% of breaths with a PVI had two or more PVIs occurring simultaneously. Binary CNN classifiers were developed for PVIs affecting ≥1% of all breaths (n = 7) and they achieved F1 scores of >0.9 on the test set except for early triggering where it was 0.809.

CONCLUSIONS

PVIs occur frequently in neonates undergoing conventional mechanical ventilation with a significant proportion of breaths containing multiple PVIs. We have developed computational models for seven different PVIs to facilitate automated detection and further evaluation of their clinical significance in neonates.

IMPACT

The study of patient-ventilator interactions (PVI) in mechanically ventilated neonates is limited by the lack of unified PVI definitions and tools to perform large scale analyses. By adapting a recent taxonomy of PVI definitions in adults, we have manually annotated neonatal ventilator waveforms to determine prevalence and co-occurrence of neonatal PVIs. We have also developed binary deep learning classifiers for common PVIs to facilitate their automatic detection and quantification.

Kölliker-Fuse nuclei regulate respiratory rhythm variability via a gain-control mechanism

Respiration varies from breath to breath. On the millisecond timescale of spiking, neuronal circuits exhibit variability due to the stochastic properties of ion channels and synapses. Does this fast, microscopic source of variability contribute to the slower, macroscopic variability of the respiratory period? To address this question, we modeled a stochastic oscillator with forcing; then, we tested its predictions experimentally for the respiratory rhythm generated by the in situ perfused preparation during vagal nerve stimulation (VNS). Our simulations identified a relationship among the gain of the input, entrainment strength, and rhythm variability. Specifically, at high gain, the periodic input entrained the oscillator and reduced variability, whereas at low gain, the noise interacted with the input, causing events known as "phase slips", which increased variability on a slow timescale. Experimentally, the in situ preparation behaved like the low-gain model: VNS entrained respiration but exhibited phase slips that increased rhythm variability. Next, we used bilateral muscimol microinjections in discrete respiratory compartments to identify areas involved in VNS gain control. Suppression of activity in the nucleus tractus solitarii occluded both entrainment and amplification of rhythm variability by VNS, confirming that these effects were due to the activation of the Hering-Breuer reflex. Suppressing activity of the Kölliker-Fuse nuclei (KFn) enhanced entrainment and reduced rhythm variability during VNS, consistent with the predictions of the high-gain model. Together, the model and experiments suggest that the KFn regulates respiratory rhythm variability via a gain control mechanism.

Effect of morphine on respiratory drive in trigger ventilated pre-term infants

The response to morphine (100 microgram (microg)/kg bolus, 10 microg/kg/h infusion) of 14 babies (median birth weight/gestation 1. 37 kg/30 weeks) trigger ventilated for hyaline membrane disease was compared to a group of 26 babies (median birth weight/gestation 1.1 kg/28 weeks) also trigger ventilated for hyaline membrane disease but not treated with morphine. The effect of morphine on triggered breath rate was very variable with no significant difference between the groups seen until 12 h after starting the infusion (mean [95% CI] difference=-17 [-33, -2] breaths/min). In those babies (n=11) who had plasma morphine levels measured there was no significant reduction in triggered rate over time despite significantly increasing plasma morphine levels. Babies who produced morphine-6-glucuronide at 12 h showed a significantly greater reduction in triggered breath rate than those who did not (median change -22 breaths/min compared to -4 breaths/min).

International randomised controlled trial of patient triggered ventilation in neonatal respiratory distress syndrome

AIM

To compare the effects of patient triggered ventilation (PTV) with conventional ventilation (IMV) in preterm infants ventilated for respiratory distress syndrome (RDS).

METHODS

Nine hundred and twenty four babies from 22 neonatal intensive care units were assessed. They were under 32 weeks of gestation and had been ventilated for respiratory distress syndrome (RDS) for less than 6 hours within 72 hours of birth. The infants were randomly allocated to receive either PTV or IMV. Analysis was on an "intention to treat" basis. Death before discharge home or oxygen therapy at 36 weeks of gestation; pneumothorax while ventilated; cerebral ultrasound abnormality nearest to 6 weeks; and duration of ventilation in survivors were the main outcome measures.

RESULTS

There was no significant difference in outcome between the two groups. Unadjusted rates for death or oxygen dependency at 36 weeks of gestation were 47.4% and 48.7%, for PTV and IMV, respectively; for pneumothorax these were 13.4% and 10.3%; and for cerebral ultrasound abnormality nearest to 6 weeks these were 35.4% and 36.9%. Median duration of ventilation for survivors in both groups was 6 days. Overall, 79% of babies received only their assigned ventilation. PTV babies were more likely to depart from their intended ventilation (27% vs 15%). The trend towards higher pneumothorax rates with PTV occurred only in infants below 28 weeks of gestation (18.8% vs 11.8%).

CONCLUSIONS

There was no observed benefit from the use of PTV, with a trend towards a higher rate of pneumothorax under 28 weeks of gestation. Although PTV has a similar outcome to IMV for treatment of RDS in infants of 28 weeks or more gestation, within 72 hours of birth, it was abandoned more often. It cannot be recommended for infants of less than 28 weeks' gestation with the ventilators used in this study.