Transmission of Oscillatory Volumes into the Preterm Lung during Noninvasive High-Frequency Ventilation

Rescue nasopharyngeal tube for preterm infants non-responsive to initial ventilation after birth

BACKGROUND

Physiological changes during the insertion of a rescue nasopharyngeal tube (NPT) after birth are unclear.

METHODS

Observational study of very preterm infants in the delivery room. Data were extracted at predefined timepoints starting with first facemask placement after birth until 5 min after insertion of NPT. End-expiratory lung impedance (EELI), heart rate (HR) and SpO2/FiO2-ratio were analysed over time. Changes during the same time span of NIPPV via facemask and NIPPV via NPT were compared.

RESULTS

Overall, 1154 inflations in 15 infants were analysed. After NPT insertion, EELI increased significantly [0.33 AU/kg (0.19-0.57), p < 0.001]. Compared with the mask period, changes in EELI were not significantly larger during the NPT period [median difference (IQR) = 0.14 AU/kg (-0.14-0.53); p = 0.12]. Insertion of the NPT was associated with significant improvement in HR [52 (33-96); p = 0.001] and SpO2/FiO2-ratio [161 (69-169); p < 0.001] not observed during the mask period.

CONCLUSIONS

In very preterm infants non-responsive to initial facemask ventilation after birth, insertion of an NPT resulted in a considerable increase in EELI. This additional gain in lung volume was associated with an immediate improvement in clinical parameters. The use of a NPT may prevent intubation in selected non-responsive infants.

IMPACT

After birth, a nasopharyngeal tube may be considered as a rescue airway in newborn infants non-responsive to initial positive pressure ventilation via facemask. Although it is widely used among clinicians, its effect on lung volumes and physiological parameters remains unclear. Insertion of a rescue NPT resulted in a considerable increase in lung volume but this was not significantly larger than during facemask ventilation. However, insertion of a rescue NPT was associated with a significant and clinically important improvement in heart rate and oxygenation. This study highlights the importance of individual strategies in preterm resuscitation and introduces the NPT as a valid option.

Non-invasive high-frequency ventilation in newborn infants with respiratory distress

BACKGROUND

Respiratory distress occurs in up to 7% of newborns, with respiratory support (RS) provided invasively via an endotracheal (ET) tube or non-invasively via a nasal interface. Invasive ventilation increases the risk of lung injury and chronic lung disease (CLD). Using non-invasive strategies, with or without minimally invasive surfactant, may reduce the need for mechanical ventilation and the risk of lung damage in newborn infants with respiratory distress.

OBJECTIVES

To evaluate the benefits and harms of nasal high-frequency ventilation (nHFV) compared to invasive ventilation via an ET tube or other non-invasive ventilation methods on morbidity and mortality in preterm and term infants with or at risk of respiratory distress.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL and three trial registries in April 2023.

SELECTION CRITERIA

Randomised controlled trials (RCTs), cluster- or quasi-RCTs of nHFV in newborn infants with respiratory distress compared to invasive or non-invasive ventilation.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the trials for inclusion, extracted data, assessed the risk of bias, and undertook GRADE assessment.

MAIN RESULTS

We identified 33 studies, mostly in low- to middle-income settings, that investigated this therapy in 5068 preterm and 46 term infants. nHFV compared to invasive respiratory therapy for initial RS We are very uncertain whether nHFV reduces mortality before hospital discharge (RR 0.67, 95% CI 0.20 to 2.18; 1 study, 80 infants) or the incidence of CLD (RR 0.38, 95% CI 0.09 to 1.59; 2 studies, 180 infants), both very low-certainty. ET intubation, death or CLD, severe intraventricular haemorrhage (IVH) and neurodevelopmental disability (ND) were not reported. nHFV vs nasal continuous positive airway pressure (nCPAP) used for initial RS We are very uncertain whether nHFV reduces mortality before hospital discharge (RR 1.00, 95% CI 0.41 to 2.41; 4 studies, 531 infants; very low-certainty). nHFV may reduce ET intubation (RR 0.52, 95% CI 0.33 to 0.82; 5 studies, 571 infants), but there may be little or no difference in CLD (RR 1.35, 95% CI 0.80 to 2.27; 4 studies, 481 infants); death or CLD (RR 2.50, 95% CI 0.52 to 12.01; 1 study, 68 participants); or severe IVH (RR 1.17, 95% CI 0.36 to 3.78; 4 studies, 531 infants), all low-certainty evidence. ND was not reported. nHFV vs nasal intermittent positive-pressure ventilation (nIPPV) used for initial RS nHFV may result in little to no difference in mortality before hospital discharge (RR 1.86, 95% CI 0.90 to 3.83; 2 studies, 84 infants; low-certainty). nHFV may have little or no effect in reducing ET intubation (RR 1.33, 95% CI 0.76 to 2.34; 5 studies, 228 infants; low-certainty). There may be a reduction in CLD (RR 0.63, 95% CI 0.42 to 0.95; 5 studies, 307 infants; low-certainty). A single study (36 infants) reported no events for severe IVH. Death or CLD and ND were not reported. nHFV vs high-flow nasal cannula (HFNC) used for initial RS We are very uncertain whether nHFV reduces ET intubation (RR 2.94, 95% CI 0.65 to 13.27; 1 study, 37 infants) or reduces CLD (RR 1.18, 95% CI 0.46 to 2.98; 1 study, 37 participants), both very low-certainty. There were no mortality events before hospital discharge or severe IVH. Other deaths, CLD and ND, were not reported. nHFV vs nCPAP used for RS following planned extubation nHFV probably results in little or no difference in mortality before hospital discharge (RR 0.92, 95% CI 0.52 to 1.64; 6 studies, 1472 infants; moderate-certainty). nHFV may result in a reduction in ET reintubation (RR 0.42, 95% CI 0.35 to 0.51; 11 studies, 1897 infants) and CLD (RR 0.78, 95% CI 0.67 to 0.91; 10 studies, 1829 infants), both low-certainty. nHFV probably has little or no effect on death or CLD (RR 0.90, 95% CI 0.77 to 1.06; 2 studies, 966 infants) and severe IVH (RR 0.80, 95% CI 0.57 to 1.13; 3 studies, 1117 infants), both moderate-certainty. We are very uncertain whether nHFV reduces ND (RR 0.92, 95% CI 0.37 to 2.29; 1 study, 74 infants; very low-certainty). nHFV versus nIPPV used for RS following planned extubation nHFV may have little or no effect on mortality before hospital discharge (RR 1.83, 95% CI 0.70 to 4.79; 2 studies, 984 infants; low-certainty). There is probably a reduction in ET reintubation (RR 0.69, 95% CI 0.54 to 0.89; 6 studies, 1364 infants), but little or no effect on CLD (RR 0.88, 95% CI 0.75 to 1.04; 4 studies, 1236 infants); death or CLD (RR 0.92, 95% CI 0.79 to 1.08; 3 studies, 1070 infants); or severe IVH (RR 0.78, 95% CI 0.55 to 1.10; 4 studies, 1162 infants), all moderate-certainty. One study reported there might be no difference in ND (RR 0.88, 95% CI 0.35 to 2.16; 1 study, 72 infants; low-certainty). nHFV versus nIPPV following initial non-invasive RS failure nHFV may have little or no effect on mortality before hospital discharge (RR 1.44, 95% CI 0.10 to 21.33); or ET intubation (RR 1.23, 95% CI 0.51 to 2.98); or CLD (RR 1.01, 95% CI 0.70 to 1.47); or severe IVH (RR 0.47, 95% CI 0.02 to 10.87); 1 study, 39 participants, all low- or very low-certainty. Other deaths or CLD and ND were not reported.

AUTHORS' CONCLUSIONS

For initial RS, we are very uncertain if using nHFV compared to invasive respiratory therapy affects clinical outcomes. However, nHFV may reduce intubation when compared to nCPAP. For planned extubation, nHFV may reduce the risk of reintubation compared to nCPAP and nIPPV. nHFV may reduce the risk of CLD when compared to nCPAP. Following initial non-invasive respiratory support failure, nHFV when compared to nIPPV may result in little to no difference in intubation. Large trials, particularly in high-income settings, are needed to determine the role of nHFV in initial RS and following the failure of other non-invasive respiratory support. Also, the optimal settings of nHVF require further investigation.

Deciphering Mechanisms of Respiratory Fetal-to-Neonatal Transition in Very Preterm Infants

Rationale: The respiratory mechanisms of a successful transition of preterm infants after birth are largely unknown. Objectives: To describe intrapulmonary gas flows during different breathing patterns directly after birth. Methods: Analysis of electrical impedance tomography data from a previous randomized trial in preterm infants at 26-32 weeks gestational age. Electrical impedance tomography data for individual breaths were extracted, and lung volumes as well as ventilation distribution were calculated for end of inspiration, end of expiratory braking and/or holding maneuver, and end of expiration. Measurements and Main Results: Overall, 10,348 breaths from 33 infants were analyzed. We identified three distinct breath types within the first 10 minutes after birth: tidal breathing (44% of all breaths; sinusoidal breathing without expiratory disruption), braking (50%; expiratory brake with a short duration), and holding (6%; expiratory brake with a long duration). Only after holding breaths did end-expiratory lung volume increase: Median (interquartile range [IQR]) = 2.0 AU/kg (0.6 to 4.3), 0.0 (-1.0 to 1.1), and 0.0 (-1.1 to 0.4), respectively; P < 0.001]. This was mediated by intrathoracic air redistribution to the left and non-gravity-dependent parts of the lung through pendelluft gas flows during braking and/or holding maneuvers. Conclusions: Respiratory transition in preterm infants is characterized by unique breathing patterns. Holding breaths contribute to early lung aeration after birth in preterm infants. This is facilitated by air redistribution during braking/holding maneuvers through pendelluft flow, which may prevent lung liquid reflux in this highly adaptive situation. This study deciphers mechanisms for a successful fetal-to-neonatal transition and increases our pathophysiological understanding of this unique moment in life. Clinical trial registered with www.clinicaltrials.gov (NCT04315636).

Neonatal high frequency ventilation: Current trends and future directions

High frequency ventilation (HFV) in neonates has been in use for over forty years. Some early HFV ventilators are no longer available, but high frequency oscillatory ventilation (HFOV) and jet ventilators (HFJV) continue to be commonly employed. Advanced HFOV models available outside of the United States are much quieter and easier to use, and are available as options on many conventional ventilators, providing important improvements such as tidal volume measurement and targeting. HFJV excels in treating air leak and non-homogenous lung disease and is often used for other diseases as well. High frequency non-invasive ventilation (hfNIV) is a novel application of HFV that remains under investigation. Similar to bubble CPAP, hfNIV has been applied with a variety of high-frequency ventilators. Efficacy and safety of hfNIV with any device have not yet been established. This article describes the current approaches to these HFV therapies and stresses the importance of understanding how each device works and what disease processes may respond best to the technology employed.

Nasal high frequency oscillatory highflow therapy in preterm infants: A randomized crossover trial

OBJECTIVES

To assess the clinical efficacy, safety, and potential physiological mechanisms of highflow therapy with superimposed high frequency oscillations ("osciflow").

STUDY DESIGN

In this prospective, randomized, single center crossover trial, 30 preterm infants were randomized to receive osciflow or highflow therapy first, each for 180 min. During osciflow, an oscillatory amplitude of 20 mbar and a frequency of 6 Hz were set. The flow rate was 4 L/min during both interventions. Primary outcome was the paired difference in the combined number of desaturations (SpO2  < 80%) and bradycardia (heart rate <80 beats per min) between interventions. Safety outcomes included nasal trauma, pneumothorax and treatment failure, and a pain score was assessed. In 20 infants, electrical impedance tomography (EIT) recordings were performed to evaluate oscillatory (VOsc ) and tidal volumes (VT ) at the lung level.

RESULTS

Infants with a mean (SD) postnatal age of 33.1 ± 1.2 weeks were included. The median (IQR) number of episodes of desaturation and bradycardia was 19.5 (6-49) during osciflow and 26 (6-44) during highflow therapy (paired difference -2; IQR -10 to 9; p = .37). There were no differences in safety outcomes and pain scores. During osciflow, EIT recordings showed a signal at 6 Hz, which was not detectable during highflow. Corresponding mean (SD) VOsc /VT ratio was 9% (±5%).

CONCLUSIONS

In preterm infants, osciflow did not reduce the number of desaturations and bradycardia compared with highflow therapy. Although VOsc were transmitted to the lung during osciflow, their magnitude was small. Osciflow was safe and well tolerated.

Imaging of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a multifactorial disease with many associated co-morbidities, responsible for most cases of chronic lung disease in childhood. The use of imaging exams is pivotal for the clinical care of BPD and the identification of candidates for experimental therapies and a closer follow-up. Imaging is also useful to improve communication with the family and objectively evaluate the clinical evolution of the patient's disease. BPD imaging has been classically performed using only chest X-rays, but several modern techniques are currently available, such as lung ultrasound, thoracic tomography, magnetic resonance imaging and electrical impedance tomography. These techniques are more accurate and provide clinically meaningful information. We reviewed the most recent evidence published in the last five years regarding these techniques and analyzed their advantages and disadvantages.

Optimising success of neonatal extubation: Respiratory support

In this review, we examine lung physiology before, during and after neonatal extubation and propose a three-phase model for the extubation procedure. We perform meta-analyses to compare different modes of non-invasive respiratory support after neonatal extubation and based on the findings, the following clinical recommendations are made.

State of the art on neonatal noninvasive respiratory support: How physiological and technological principles explain the clinical outcomes

Noninvasive respiratory support has gained significant popularity in neonatal units because of its potential to reduce lung injury associated with invasive mechanical ventilation. To minimize lung injury, clinicians aim to apply for noninvasive respiratory support as early as possible. However, the physiological background and the technology behind such support modes are not always clear, and many open questions remain regarding the indications of use and clinical outcomes. This narrative review discusses the currently available evidence for various noninvasive respiratory support modes applied in Neonatal Medicine in terms of physiological effects and indications. Reviewed modes include nasal continuous positive airway pressure, nasal high-flow therapy, noninvasive high-frequency oscillatory ventilation, nasal intermittent positive pressure ventilation (NIPPV), synchronized NIPPV and noninvasive neurally adjusted ventilatory assist. To enhance clinicians' awareness of each support mode's strengths and limitations, we summarize technical features related to the functioning mechanisms of devices and the physical properties of the interfaces commonly used for providing noninvasive respiratory support to neonates. We finally address areas of current controversy and suggest possible areas of research for implementing noninvasive respiratory support in neonatal intensive care units.

Early prediction of pulmonary outcomes in preterm infants using electrical impedance tomography

Introduction

Electrical impedance tomography (EIT) allows assessment of ventilation and aeration homogeneity which may be associated with respiratory outcomes in preterm infants.

Methods

This was a secondary analysis to a recent randomized controlled trial in very preterm infants in the delivery room (DR). The predictive value of various EIT parameters assessed 30 min after birth on important respiratory outcomes (early intubation <24 h after birth, oxygen dependency at 28 days after birth, and moderate/severe bronchopulmonary dysplasia; BPD) was assessed.

Results

Thirty-two infants were analyzed. A lower percentage of aerated lung volume [OR (95% CI) = 0.8 (0.66-0.98), p = 0.027] as well as a higher aeration homogeneity ratio (i.e., more aeration in the non-gravity-dependent lung) predicted the need for supplemental oxygen at 28 days after birth [9.58 (5.16-17.78), p = 0.0028]. Both variables together had a similar predictive value to a model using known clinical contributors. There was no association with intubation or BPD, where numbers were small.

Discussion

In very preterm infants, EIT markers of aeration at 30 min after birth accurately predicted the need for supplemental oxygen at 28 days after birth but not BPD. EIT-guided individualized optimization of respiratory support in the DR may be possible.

Lung volume changes during apnoeas in preterm infants

OBJECTIVE

Mechanisms of non-invasive high-frequency oscillatory ventilation (nHFOV) in preterm infants are unclear. We aimed to compare lung volume changes during apnoeas in preterm infants on nHFOV and nasal continuous positive airway pressure (nCPAP).

METHODS

Analysis of electrical impedance tomography (EIT) data from a randomised crossover trial comparing nHFOV with nCPAP in preterm infants at 26-34 weeks postmenstrual age. EIT data were screened by two reviewers to identify apnoeas ≥10 s. End-expiratory lung impedance (EELI) and tidal volumes (V_T) were calculated before and after apnoeas. Oxygen saturation (SpO₂) and heart rate (HR) were extracted for 60 s after apnoeas.

RESULTS

In 30 preterm infants, 213 apnoeas were identified. During apnoeas, oscillatory volumes were detectable during nHFOV. EELI decreased significantly during apnoeas (∆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 apnoeas. Compared with before apnoeas, V_T was increased for the first breath after apnoeas during nCPAP (∆V_T: 7.5 (3.1 to 11.2) AU/kg, p=0.001). Falls in SpO₂ and HR after apnoeas were greater during nCPAP than nHFOV (mean difference (95% CI): SpO₂: 3.6% (2.7 to 4.6), p<0.001; HR: 15.9 bpm (13.4 to 18.5), p<0.001).

CONCLUSION

Apnoeas were characterised by a significant decrease in EELI which was regained over the first breaths after apnoeas, partly mediated by a larger V_T. Apnoeas 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.

TRIAL REGISTRATION NUMBER

ACTRN12616001516471.

Prophylactic surfactant nebulisation for the early aeration of the preterm lung: a randomised clinical trial

OBJECTIVE

The effect of prophylactic surfactant nebulisation (SN) is unclear. We aimed to determine whether prophylactic SN improves early lung aeration.

DESIGN

Parallel, randomised clinical trial, conducted between March 2021 and January 2022.

SETTING

Delivery room (DR) of a tertiary neonatal centre in Zurich, Switzerland.

PATIENTS

Preterm infants between 26 ^0/7 and 31 ^6/7 weeks gestation INTERVENTIONS: Infants were randomised to receive positive distending pressure alone or positive distending pressure and additional SN (200 mg/kg; poractant alfa) using a customised vibrating membrane nebuliser. SN commenced with the first application of a face mask immediately after birth.

MAIN OUTCOME MEASURES

Primary outcome was the difference in end-expiratory lung impedance from birth to 30 min after birth (∆EELI_30min). EELI correlates well with functional residual capacity. Secondary outcomes included physiological and clinical outcomes.

RESULTS

Data from 35 infants were collected, and primary outcome data were analysed from 32 infants (n=16/group). Primary outcome was not different between intervention and control group (median (IQR): 25 (7-62) vs 10 (0-26) AU/kg, p=0.21). ∆EELI was slightly higher in the intervention group at 6 and 12 hours after birth, particularly in the central areas of the lung. There were no differences in cardiorespiratory and clinical parameters. Two adverse events were noted in the intervention group.

CONCLUSIONS

Prophylactic SN in the DR did not significantly affect ∆EELI_30min and showed only minimal effects on lung physiology. Prophylactic SN in the DR was feasible. There were no differences in clinical outcomes.

TRIAL REGISTRATION NUMBER

NCT04315636.

Comparison of nasal intermittent positive pressure ventilation and bubble CPAP with an in-line high-frequency interrupter in a premature infant lung model

INTRODUCTION

Noninvasive ventilation has become a staple in the care of premature infants. However, failure rates continue to be high in this population. Modifications to noninvasive support, such as nasal intermittent positive pressure ventilation (NIPPV), are used clinically to reduce such failure. Previous in vitro studies have shown improved CO₂ clearance when superimposing high-frequency oscillations onto bubble continuous positive airway pressure (BCPAP).

OBJECTIVE

To compare the CO₂ clearance of NIPPV to BCPAP with an in-line high-frequency interrupter (HFI) in a premature infant lung model.

METHODS

A premature infant lung model was connected to either a Dräger VN500 for delivery of NIPPV or a BCPAP device with superimposed high-frequency oscillations generated by an in-line HFI. Change in end-tidal CO₂  (ETCO₂ ) and mean airway pressure at the simulated trachea were measured and compared for both noninvasive modalities.

RESULTS

Superimposing HF oscillations onto BCPAP with an in-line HFI resulted in improved CO₂ clearance relative to BCPAP alone for all tested oscillation frequencies at all CPAP levels (p < 0.001). NIPPV also resulted in improved CO₂  clearance relative to nasal CPAP (NCPAP) alone (p < 0.001). Among the tested settings, BCPAP with an in-line HFI resulted in decreased ETCO₂ relative to BCPAP ranging from -14% to -36%, while NIPPV resulted in decreased ETCO₂  relative to NCPAP ranging from -2% to -12%.

CONCLUSION

Superimposing high-frequency oscillations onto BCPAP using a novel in-line HFI was found to be more effective at clearing CO₂ than NIPPV in a premature infant lung model.

Lung volume distribution in preterm infants on non-invasive high-frequency ventilation

INTRODUCTION

Non-invasive high-frequency oscillatory ventilation (nHFOV) is an extension of nasal continuous positive airway pressure (nCPAP) support in neonates. We aimed to compare global and regional distribution of lung volumes during nHFOV versus nCPAP.

METHODS

In 30 preterm infants enrolled in a randomised crossover trial comparing nHFOV with nCPAP, electrical impedance tomography data were recorded in prone position. For each mode of respiratory support, four episodes of artefact-free tidal ventilation, each comprising 30 consecutive breaths, were extracted. Tidal volumes (V_T) in 36 horizontal slices, indicators of ventilation homogeneity and end-expiratory lung impedance (EELI) for the whole lung and for four horizontal regions of interest (non-gravity-dependent to gravity-dependent; EELI_NGD, EELI_midNGD, EELI_midGD, EELI_GD) were compared between nHFOV and nCPAP. Aeration homogeneity ratio (AHR) was determined by dividing aeration in non-gravity-dependent parts of the lung through gravity-dependent regions.

MAIN RESULTS

Overall, 228 recordings were analysed. Relative V_T was greater in all but the six most gravity-dependent lung slices during nCPAP (all p<0.05). Indicators of ventilation homogeneity were similar between nHFOV and nCPAP (all p>0.05). Aeration was increased during nHFOV (mean difference (95% CI)=0.4 (0.2 to 0.6) arbitrary units per kilogram (AU/kg), p=0.013), mainly due to an increase in non-gravity-dependent regions of the lung (∆EELI_NGD=6.9 (0.0 to 13.8) AU/kg, p=0.028; ∆EELI_midNGD=6.8 (1.2 to 12.4) AU/kg, p=0.009). Aeration was more homogeneous during nHFOV compared with nCPAP (mean difference (95% CI) in AHR=0.01 (0.00 to 0.02), p=0.0014).

CONCLUSION

Although regional ventilation was similar between nHFOV and nCPAP, end-expiratory lung volume was higher and aeration homogeneity was slightly improved during nHFOV. The aeration difference was greatest in non-gravity dependent regions, possibly due to the oscillatory pressure waveform. The clinical importance of these findings is still unclear.

Noninvasive High-Frequency Oscillatory Ventilation vs Nasal Continuous Positive Airway Pressure vs Nasal Intermittent Positive Pressure Ventilation as Postextubation Support for Preterm Neonates in China: A Randomized Clinical Trial

IMPORTANCE

Several respiratory support techniques are available to minimize the use of invasive mechanical ventilation (IMV) in preterm neonates. It is unknown whether noninvasive high-frequency oscillatory ventilation (NHFOV) is more efficacious than nasal continuous positive airway pressure (NCPAP) or nasal intermittent positive pressure ventilation (NIPPV) in preterm neonates after their first extubation.

OBJECTIVE

To test the hypothesis that NHFOV is more efficacious than NCPAP or NIPPV in reducing IMV after extubation and until neonatal intensive care unit discharge among preterm neonates.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, pathophysiology-based, assessor-blinded, 3-group, randomized clinical trial was conducted in 69 tertiary referral neonatal intensive care units in China, recruiting participants from December 1, 2017, to May 31, 2021. Preterm neonates who were between the gestational age of 25 weeks plus 0 days and 32 weeks plus 6 days and were ready to be extubated were randomized to receive NCPAP, NIPPV or NHFOV. Data were analyzed on an intention-to-treat basis.

INTERVENTIONS

The NCPAP, NIPPV, or NHFOV treatment was initiated after the first extubation and lasted until discharge.

MAIN OUTCOMES AND MEASURES

Primary outcomes were total duration of IMV, need for reintubation, and ventilator-free days. These outcomes were chosen to describe the effect of noninvasive ventilation strategy on the general need for IMV.

RESULTS

A total of 1440 neonates (mean [SD] age at birth, 29.4 [1.8] weeks; 860 boys [59.7%]) were included in the trial. Duration of IMV was longer in NIPPV (mean difference, 1.2; 95% CI, 0.01-2.3 days; P = .04) and NCPAP (mean difference, 1.5 days; 95% CI, 0.3-2.7 days; P = .01) compared with NHFOV. Neonates who were treated with NCPAP needed reintubations more often than those who were treated with NIPPV (risk difference: 8.1%; 95% CI, 2.9%-13.3%; P = .003) and NHFOV (risk difference, 12.5%; 95% CI, 7.5%-17.4%; P < .001). There were fewer ventilator-free days in neonates treated with NCPAP than in those treated with NIPPV (median [25th-75th percentile] difference, -3 [-6 to -1] days; P = .01). There were no differences between secondary efficacy or safety outcomes, except for the use of postnatal corticosteroids (lower in NHFOV than in NCPAP group; risk difference, 7.3%; 95% CI, 2.6%-12%; P = .002), weekly weight gain (higher in NHFOV than in NCPAP group; mean difference, -0.9 g/d; 95% CI, -1.8 to 0 g/d; P = .04), and duration of study intervention (shorter in NHFOV than in NIPPV group; median [25th-75th percentile] difference, -1 [-3 to 0] days; P = .01).

CONCLUSIONS AND RELEVANCE

Results of this trial indicated that NHFOV, if used after extubation and until discharge, slightly reduced the duration of IMV in preterm neonates, and both NHFOV and NIPPV resulted in a lower risk of reintubation than NCPAP. All 3 respiratory support techniques were equally safe for this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03181958.

The DELUX study: development of lung volumes during extubation of preterm infants

OBJECTIVE

To measure changes in end-expiratory lung impedance (EELI) as a marker of functional residual capacity (FRC) during the entire extubation procedure of very preterm infants.

METHODS

Prospective observational study in preterm infants born at 26-32 weeks gestation being extubated to non-invasive respiratory support. Changes in EELI and cardiorespiratory parameters (heart rate, oxygen saturation) were recorded at pre-specified events during the extubation procedure compared to baseline (before first handling of the infant).

RESULTS

Overall, 2912 breaths were analysed in 12 infants. There was a global change in EELI during the extubation procedure (p = 0.029). EELI was lowest at the time of extubation [median (IQR) difference to baseline: -0.30 AU/kg (-0.46; -0.14), corresponding to an FRC loss of 10.2 ml/kg (4.8; 15.9), p_adj = 0.004]. The biggest EELI loss occurred during adhesive tape removal [median change (IQR): -0.18 AU/kg (-0.22; -0.07), p_adj = 0.004]. EELI changes were highly correlated with changes in the SpO₂/FiO₂ ratio (r = 0.48, p < 0.001). Forty per cent of FRC was re-recruited at the tenth breath after the initiation of non-invasive ventilation (p < 0.001).

CONCLUSIONS

The extubation procedure is associated with significant changes in FRC. This study provides novel information for determining the optimal way of extubating a preterm infant.

IMPACT

This study is the first to examine the development of lung volumes during the entire extubation procedure including the impact of associated events. The extubation procedure significantly affects functional residual capacity with a loss of approximately 10 ml/kg at the time of extubation. Removal of adhesive tape is the major contributing factor to FRC loss during the extubation procedure. Functional residual capacity is regained within the first breaths after initiation of non-invasive ventilation and is further increased after turning the infant into the prone position.

Extubation generates lung volume inhomogeneity in preterm infants

OBJECTIVE

To evaluate the feasibility of electrical impedance tomography (EIT) to describe the regional tidal ventilation (V_T) and change in end-expiratory lung volume (EELV) patterns in preterm infants during the process of extubation from invasive to non-invasive respiratory support.

DESIGN

Prospective observational study.

SETTING

Single-centre tertiary neonatal intensive care unit.

PATIENTS

Preterm infants born <32 weeks' gestation who were being extubated to nasal continuous positive airway pressure as per clinician discretion.

INTERVENTIONS

EIT measurements were taken in supine infants during elective extubation from synchronised positive pressure ventilation (SIPPV) before extubation, during and then at 2 and 20 min after commencing nasal continuous positive applied pressure (nCPAP). Extubation and pressure settings were determined by clinicians.

MAIN OUTCOME MEASURES

Global and regional ΔEELV and ΔV_T, heart rate, respiratory rate and oxygen saturation were measured throughout.

RESULTS

Thirty infants of median (range) 2 (1, 21) days were extubated to a median (range) CPAP 7 (6, 8) cm H₂O. SpO₂/FiO₂ ratio was a mean (95% CI) 50 (35, 65) lower 20 min after nCPAP compared with SIPPV. EELV was lower at all points after extubation compared with SIPPV, and EELV loss was primarily in the ventral lung (p=0.04). V_T was increased immediately after extubation, especially in the central and ventral regions of the lung, but the application of nCPAP returned V_T to pre-extubation patterns.

CONCLUSIONS

EIT was able to describe the complex lung conditions occurring during extubation to nCPAP, specifically lung volume loss and greater use of the dorsal lung. EIT may have a role in guiding peri-extubation respiratory support.

Nasal high-frequency oscillatory ventilation versus nasal continuous positive airway pressure as primary respiratory support strategies for respiratory distress syndrome in preterm infants: a systematic review and meta-analysis

Nasal high-frequency oscillatory ventilation (NHFOV) is a new respiratory support strategy despite lacking of enough evidence in preterm infants with respiratory distress syndrome (RDS). The aim of the present systematic review was to explore whether NHFOV reduced the intubation rate as compared with nasal continuous positive airway pressure (NCPAP) as the primary respiratory support strategies in preterm infants with RDS. Medline, the Cochrane library, the Cochrane Controlled Trials Register, EMBASE, Chinese National Knowledge Infrastructure (CNKI), and Wanfang data Information Site were searched from inception to Jan 1, 2021(Prospero2019 CRD42019129316, date and name of registration: Apr 23,2019, The clinical effectiveness of NHFOV vs NCPAP for preterm babies with respiratory distress syndrome). Pooled data from clinically randomized controlled trials (RCTs) comparing NHFOV with NCPAP as the primary respiratory supporting strategies in preterm infants with RDS were performed using the fixed-effects models whenever no heterogeneity was shown. The primary outcome was intubation rate. Four randomized controlled trials involving 570 participants were included. Comparing with NCPAP, NHFOV resulted in less intubation (relative risk (RR) 0.44; 95% confidence interval (CI) 0.29-0.67, P = 0.0002), and heterogeneity was not found among the trials in the fixed-effects model (P = 0.78, I² = 0%). Similar result also appeared in sensitivity analysis after excluding one study with significant difference (RR 0.44; 95% CI 0.25-0.78, P = 0.005) (P = 0.58, I² = 0%).Conclusion: NHFOV decreased the intubation rate as compared with NCPAP as primary respiratory supporting strategies in preterm infants suffering from RDS. Future research should assess whether NHFOV can reduce the incidence of bronchopulmonary dysplasia (BPD) and intubation rate in preterm infants with BPD. Fund by Natural Science Foundation of Chongqing (cstc2020jcyj-msxmX0197), and "guan'ai" preterm Study Program of Renze Foundation of Beijing(K022). What is Known: • Nasal high-frequency oscillatory ventilation (NHFOV) has been described to be another advanced version of nasal continuous positive airway pressure (NCPAP). However, its beneficial effects among different studies as the primary modes in the early life of preterm infants with respiratory distress syndrome (RDS) were inconsistent. What is New: • Comparing with NCPAP, NHFOV decreases the risk of intubation as a primary respiratory supporting strategy in early life for preterm infants suffering from RDS.

Case report: Intrapulmonary tidal volumes in a preterm infant with chest wall rigidity

BACKGROUND

Chest wall rigidity is a known side effect of fentanyl use, which is why fentanyl is usually combined with a muscle relaxant such as mivacurium. Verifying endotracheal intubation is difficult in case of a rigid chest wall.

CASE PRESENTATION

We present the case of a preterm infant (29 completed weeks gestation, birth weight 1,150 g) with a prolonged chest wall rigidity after fentanyl administration for intubation despite adequate doses of mivacurium. This resulted in a pronounced desaturation without any effect on heart rate. Clinically, the infant showed no chest wall movement despite intubation and common tools to verify intubation (including end-tidal carbon dioxide measurement and auscultation) were inconclusive. However, using electrical impedance tomography (EIT), we were able to demonstrate minimal tidal volumes at lung level and thereby, EIT was able to accurately show correct placement of the endotracheal tube.

CONCLUSIONS

This case may increase vigilance for fentanyl-induced chest wall rigidity in the neonatal population even when simultaneously administering mivacurium. Higher airway pressures exceeding 30 mmHg and the use of μ-receptor antagonists such as naloxone should be considered to reverse opioid-induced chest wall rigidity. Most importantly, our data may imply a relevant clinical benefit of using EIT during neonatal intubation as it may accurately show correct endotracheal tube placement.

The Intertemporal Role of Respiratory Support in Improving Neonatal Outcomes: A Narrative Review

Defining improvements in healthcare can be challenging due to the need to assess multiple outcomes and measures. In neonates, although progress in respiratory support has been a key factor in improving survival, the same degree of improvement has not been documented in certain outcomes, such as bronchopulmonary dysplasia. By exploring the evolution of neonatal respiratory care over the last 60 years, this review highlights not only the scientific advances that occurred with the application of invasive mechanical ventilation but also the weakness of the existing knowledge. The contributing role of non-invasive ventilation and less-invasive surfactant administration methods as well as of certain pharmacological therapies is also discussed. Moreover, we analyze the cost-benefit of neonatal care-respiratory support and present future challenges and perspectives.

Comparison of Two Noninvasive Ventilation Strategies (NHFOV Versus NIPPV) as Initial Postextubation Respiratory Support in High-Risk Infants After Congenital Heart Surgery

OBJECTIVE

This study aimed to compare the effects of nasal high-frequency oscillatory ventilation (NHFOV) and noninvasive positive-pressure ventilation (NIPPV) as the initial postextubation therapies on preventing extubation failure (EF) in high-risk infants younger than three months after congenital heart surgery (CHS).

DESIGN

This was a single-center, randomized, unblinded clinical trial.

SETTING

The study was performed in a teaching hospital.

PARTICIPANTS

Between January 2020 and January 2021, a total of 150 infants underwent CHS in the authors' hospital.

INTERVENTIONS

Infants younger than three months with a high risk for extubation failure who were ready for extubation were randomized to either an NHFOV therapy group or an NIPPV therapy group, and received the corresponding noninvasive mechanical ventilation to prevent EF.

MEASUREMENTS

Primary outcomes were reintubation, long-term noninvasive ventilation (NIV) support (more than 72 hours), and the time in NIV therapy. The secondary outcomes were adverse events, including mild-moderate hypercapnia, severe hypercapnia, severe hypoxemia, treatment intolerance, signs of discomfort, unbearable dyspnea, inability to clear secretions, emesis, and aspiration.

MAIN RESULTS

Of 92 infants, 45 received NHFOV therapy, and 47 received NIPPV therapy after extubation. There were no significant differences between the NHFOV and the NIPPV therapy groups in the incidences of reintubation, long-term NIV support, and total time under NIV therapy. No significant difference was found of the severe hypercapnia between the two groups, but NHFOV treatment significantly decreased the rate of mild-moderate hypercapnia (p < 0.05). Other outcomes were similar in the two groups.

CONCLUSIONS

Among infants younger than three months after CHS who had undergone extubation, NIPPV therapy and NHFOV therapy were the equivalent NIV strategies for preventing extubation failure, and NHFOV therapy was more effective in avoiding mild-moderate hypercapnia.

Use of Electrical Impedance Tomography (EIT) to Estimate Tidal Volume in Anaesthetized Horses Undergoing Elective Surgery

Simple Summary

The aim of this study was to explore the usefulness of electrical impedance tomography (EIT), a novel monitoring tool measuring impedance change, to estimate tidal volume (volume of gas in litres moved in and out the airways and lungs with each breath) in anaesthetised horses. The results of this study, performed in clinical cases, demonstrated that there was a positive linear relationship between tidal volume measurements obtained with spirometry and impedance changes measured by EIT within each subject and this individual relationship could be used to estimate tidal volume that showed acceptable agreement with a measured tidal volume in each horse. Thus, EIT can be used to observe changes in tidal volume by the means of impedance changes. However, absolute measurement of tidal volume is only possible after establishment of the individual relationship.

Abstract

This study explores the application of electric impedance tomography (EIT) to estimate tidal volume (VT) by measuring impedance change per breath (∆Z_breath). Seventeen healthy horses were anaesthetised and mechanically ventilated for elective procedures requiring dorsal recumbency. Spirometric VT (VT_SPIRO) and ∆Z_breath were recorded periodically; up to six times throughout anaesthesia. Part 1 assessed these variables at incremental delivered VT of 10, 12 and 15 mL/kg. Part 2 estimated VT (VT_EIT) in litres from ∆Z_breath at three additional measurement points using a line of best fit obtained from Part 1. During part 2, VT was adjusted to maintain end-tidal carbon dioxide between 45–55 mmHg. Linear regression determined the correlation between VT_SPIRO and ∆Z_breath (part 1). Estimated VT_EIT was assessed for agreement with measured VT_SPIRO using Bland Altman analysis (part 2). Marked variability in slope and intercepts was observed across horses. Strong positive correlation between ∆Z_breath and VT_SPIRO was found in each horse (R² 0.9–0.99). The agreement between VT_EIT and VT_SPIRO was good with bias (LOA) of 0.26 (−0.36–0.88) L. These results suggest that, in anaesthetised horses, EIT can be used to monitor and estimate VT after establishing the individual relationship between these variables.

U-Net-based approach for automatic lung segmentation in electrical impedance tomography

OBJECTIVE

Electrical impedance tomography (EIT) is a non-invasive technique that constitutes a promising tool for real-time imaging and long-term monitoring of the ventilation distribution at bedside. However, clinical monitoring and diagnostic evaluations depend on various methods to assess ventilation-dependent parameters useful for ventilation therapy. This study develops an automatic, robust, and rapidly accessible method for lung segmentation that can be used to define appropriate regions-of-interest (ROIs) within EIT images.

APPROACH

To date, available methods for patients with defected lungs have the disadvantage of not being able to identify lung regions because of their poor ventilation responses. Furthermore, the challenges related to the identification of lung areas in EIT images are attributed to the low spatial resolution of EIT. In this study, a U-Net-based automatic lung segmentation model is used as a postprocessor to transform the original EIT image to a lung ROI image and refine the inherent conductivity distribution of the original EIT image. The trained U-Net network is capable of performing an automatic segmentation of conductivity changes in EIT images without requiring prior information.

MAIN RESULTS

The experimental design of this study was based on a finite element method (FEM) phantom used to assess the feasibility and effectiveness of the proposed method, and evaluation of the trained models on the test dataset was performed using the Dice similarity coefficient (DSC) and the mean absolute error (MAE). The FEM experimental results yielded values of 0.0065 for MAE, and values >0.99 for DSC in simulations.

SIGNIFICANCE

The use of a deep-learning-based approach attained automatic and convenient segmentation of lung ROIs into distinguishable images, which represents a direct benefit for regional lung ventilation-dependent parameter extraction and analysis. However, further investigations and validation are warranted in real human datasets with different physiology conditions with CT cross-section dataset to refine the suggested model.

Non-invasive High-Frequency Oscillatory Ventilation as Initial Respiratory Support for Preterm Infants With Respiratory Distress Syndrome

Objectives: The aim of this study was to investigate the safety and feasibility of nHFOV as initial respiratory support in preterm infants with RDS. Methods: This study retrospectively analyzed the clinical data of 244 premature infants with RDS who were treated in our hospital from January 2016 to January 2019 and divided into the nHFOV group (n = 115) and the BiPAP group (n = 129) based on the initial respiratory support method. Results: Respiratory outcomes showed that the rate of NIV failure during the first 72 hours of life in the nHFOV group was significantly lower than that in the BiPAP group. The time of NIV in the nHFOV group was significantly shorter than that in the BiPAP group. The time of supplemental oxygen in the nHFOV group was significantly shorter than that in the BiPAP group. The incidence of air leakage syndrome in the nHFOV group was significantly lower than that in the BiPAP group, and the length of hospital stay of the nHFOV group was also significantly shorter than that in the BiPAP group. Although the rate of infants diagnosed with BPD was similar between the two groups, the rate of severe BPD in the nHFOV group was significantly lower than that in the BiPAP group. Conclusion: This study showed that nHFOV as initial respiratory support for preterm infants with RDS was feasible and safe compared to BiPAP. Furthermore, nHFOV can reduce the need for IMV and reduce the incidence of severe BPD and air leak syndrome.