Is there still a role for high-frequency oscillatory ventilation in neonates, children and adults?

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.

Non-invasive high frequency oscillatory ventilation inhibiting respiratory motion in healthy volunteers

Precision radiotherapy needs to manage organ movements to prevent critical organ injury. The purpose of this study is to examine the feasibility of motion control of the lung by suppressing respiratory motion. The non-invasive high frequency oscillatory ventilation (NIHFOV) is a technique commonly used in the protection of lung for patients with acute lung disease. By using a very high respiratory frequency and a low tidal volume, NIHFOV allows gas exchange, maintains a constant mean airway pressure and minimizes the respiratory movements. We tested healthy volunteers NIHFOV to explore the optimal operational parameter setting and the best possible motion suppression achievable. This study was conducted with the approval of Institutional Review Boards of the Wuwei Cancer hospital (approval number: 2021-39) and carried out in accordance with Declaration of Helsinki. The study comprises two parts. Twenty three healthy volunteers participated in the first part of the study. They had 7 sessions of training with the NIHFOV. The duration of uninterrupted, continuous breathing under the NIHFOV and the optimal operational machine settings were defined. Eight healthy volunteers took part in the second part of the study and underwent 4-dimensional CT (4DCT) scanning with and without NIHFOV. Their respiratory waveform under free breathing (FB) and NIHFOV were recorded. The maximum range of motion of the diaphragm from the two scannings was compared, and the variation of bilateral lung volume was obtained to evaluate the impact of NIHFOV technique on lung volume. The following data were collected: comfort score, transcutaneous partial pressure of oxygen (PtcO₂), transcutaneous partial pressure of carbon dioxide (PtcCO₂), and pulse rate. Data with and without NIHFOV were compared to evaluate its safety, physiological impacts and effect of lung movement suppression. All the volunteers completed the training sessions eventlessly, demonstrating a good tolerability of the procedure. The median NIHFOV-on time was 32 min (22-45 min), and the maximum range of motion in the cephalic-caudal direction was significantly reduced on NIHFOV compared with FB (1.8 ± 0.8 cm vs 0.3 ± 0.1 cm, t =  - 3.650, P = 0.003); the median range of motion was only 0.3 ± 0.1 cm on NIHFOV with a good reproducibility. The variation coefficient under NIHFOV of the right lung volume was 2.4% and the left lung volume was 9.2%. The PtcO₂ and PtcCO₂ were constantly monitored during NIHFOV. The medium PtcCO₂ under NIHFOV increased lightly by 4.1 mmHg (interquartile range [IQR], 4-6 mmHg) compared with FB (t = 17.676, P < 0.001). No hypercapnia was found, PtcO₂ increased significantly in all volunteers during NIHFOV (t = 25.453, P < 0.001). There was no significant difference in pulse rate between the two data sets (t = 1.257, P = 0.233). NIHFOV is easy to master in healthy volunteers to minimize respiratory movement with good tolerability and reproducibility. It is a feasible approach for lung motion control and could potentially be applied in accurate radiotherapy including carbon-ion radiotherapy through suppression of respiratory movement.

Ventilator-associated events in children: A multicentre prospective cohort study

BACKGROUND

The Centres for Disease Control and Prevention (CDC) broadened the focus of surveillance from ventilator-associated pneumonia to ventilator-associated event (VAE) for quality purposes. No paediatric definition of VAE (PaedVAE) has been accurately validated. We aimed to analyse the incidence and impact on patient outcomes resulting from the application of the adult and two paediatric VAE (PaedVAE) criteria.

SECONDARY OBJECTIVE

to evaluate VAE/PaedVAE as factors associated with increased duration of mechanical ventilation (MV) and Paediatric Intensive Care Unit (PICU) stay.

METHODS

Multicentre observational prospective cohort study in 15 PICUs in Spain. VAEs were assessed using the 2013/2015 CDC classification. PaedVAE were assessed using the CDC definition based on mean airway pressure (MAP-PaedVAE) versus a paediatric definition based on positive end-expiratory pressure (PEEP-PaedVAE). Children who underwent MV ≥ 48 h were included.

RESULTS

A total of 3626 ventilator-days in 391 patients were analysed. The incidence of VAE, MAP-PaedVAE and PEEP-PaedVAE was 8.55, 5.24 and 20.96 per 1000 ventilator-days, respectively. The median time [IQR] for VAE, MAP-PaedVAE and PEEP-PaedVAE development from the MV onset was 4 [3-12.5], 4 [3-14], and 5 [3-7.75] days, respectively. Among survivors, all three were associated with increased MV duration (> 7 days) and PICU stay (> 10 days) at univariate analysis. Multivariate analysis showed that PEEP-PaedVAE was the only definition independently associated with MV above 7 days [OR = 4.86, 95% CI (2.41-10.11)] and PICU stay [OR = 3.49, 95% CI (1.68-7.80)] above ten days, respectively.

CONCLUSIONS

A VAE definition based on slight PEEP increases should be preferred for VAE surveillance in children.

Mechanical Ventilation and Respiratory Support in the Pediatric Intensive Care Unit

Children admitted to the pediatric intensive care unit often require respiratory support for the treatment of respiratory distress and failure. Respiratory support comprises both noninvasive modalities (ie, heated humidified high-flow nasal cannula, continuous positive airway pressure, bilevel positive airway pressure, negative pressure ventilation) and invasive mechanical ventilation. In this article, we review the various essential elements and considerations involved in the planning and application of respiratory support in the treatment of the critically ill children.

Tidal volume significantly affects oxygenation in healthy pigs during high-frequency oscillatory ventilation compared to conventional ventilation

Background

The role of high-frequency oscillatory ventilation (HFOV) has long been debated. Numerous studies documented its benefits, whereas several more recent studies did not prove superiority of HFOV over protective conventional mechanical ventilation (CV). One of the accepted explanations is that CV and HFOV act differently, including gas exchange.

Methods

To investigate a different level of coupling or decoupling between oxygenation and carbon dioxide elimination during CV and HFOV, we conducted a prospective crossover animal study in 11 healthy pigs. In each animal, we found a normocapnic tidal volume (VT) after the lung recruitment maneuver. Then, VT was repeatedly changed over a wide range while keeping constant the levels of PEEP during CV and mean airway pressure during HFOV. Arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were recorded. The same procedure was repeated for CV and HFOV in random order.

Results

Changes in PaCO2 intentionally induced by adjustment of VT affected oxygenation more significantly during HFOV than during CV. Increasing VT above its normocapnic value during HFOV caused a significant improvement in oxygenation, whereas improvement in oxygenation during CV hyperventilation was limited. Any decrease in VT during HFOV caused a rapid worsening of oxygenation compared to CV.

Conclusion

A change in PaCO2 induced by the manipulation of tidal volume inevitably brings with it a change in oxygenation, while this effect on oxygenation is significantly greater in HFOV compared to CV.

Impact of early respiratory care for extremely preterm infants

Despite advances in neonatal intensive care, more than half of surviving infants born extremely preterm (EP; < 28 weeks' gestation) develop bronchopulmonary dysplasia (BPD). Prevention of BPD is critical because of its associated mortality and morbidity, including adverse neurodevelopmental outcomes and respiratory health in later childhood and beyond. The respiratory care of EP infants begins before birth, then continues in the delivery room and throughout the primary hospitalization. This chapter will review the evidence for interventions after birth that might improve outcomes for infants born EP, including the timing of umbilical cord clamping, strategies to avoid or minimize exposure to mechanical ventilation, modes of mechanical ventilation and non-invasive respiratory support, oxygen saturation targets, postnatal corticosteroids and other adjunct therapies.

Effect of postoperative administration of inhaled nitric oxide combined with high-frequency oscillatory ventilation in infants with acute hypoxemic respiratory failure and pulmonary hypertension after congenital heart surgery: A retrospective cohort study

OBJECTIVE

To evaluate the effect of inhaled nitric oxide (iNO) combined with high-frequency oscillatory ventilation (HFOV) in the treatment of infants with acute hypoxemic respiratory failure (AHRF) and pulmonary hypertension (PH) after congenital heart surgery.

METHODS

A retrospective study was conducted on 63 infants with AHRF and PH after congenital heart surgery in our cardiac intensive care unit (CICU) from January 2020 to March 2021. A total of 24 infants in the A group were treated with HFOV combined with iNO, and 39 infants in the B group were treated with HFOV. Relevant clinical data were collected.

RESULTS

Comparing the two groups, the improvement of the oxygenation index, PaO₂ and PaO₂ /FiO₂ was more obvious for patients in the A group than for those in the B group after intervention (p < .05). Reexamination on the third day after the initiation of HFOV treatment indicated that the systolic pulmonary artery pressure in the A group was significantly lower than that in the B group (p < .05). In addition, the duration of mechanical ventilation and the length of CICU stay in the A group were shorter than those in the B group (p < .05). However, complications between the two groups were not statistically significant. No important adverse effects arose.

CONCLUSIONS

For infants with AHRF and PH after congenital heart surgery, iNO combined with HFOV is superior to HFOV alone to improve oxygenation, decrease pulmonary pressure, and shorten the duration of mechanical ventilation and the length of CICU stay, with no adverse effects.

Impact of High-Frequency Oscillatory Ventilation Combined With Volume Guarantee on Lung Inflammatory Response in Infants With Acute Respiratory Distress Syndrome After Congenital Heart Surgery: A Randomized Controlled Trial

OBJECTIVES

Congenital heart disease (CHD) after cardiopulmonary bypass can cause systemic inflammation, and its degree is closely related to the incidence of acute respiratory distress syndrome (ARDS). The purpose of this study was to determine the effectiveness of high-frequency oscillatory ventilation (HFOV) combined with volume guarantee (VG) in reducing systemic inflammation in infants with ARDS after cardiopulmonary bypass for congenital heart surgery.

DESIGN

A randomized controlled trial.

SETTING

Single-center study in a tertiary teaching hospital.

PARTICIPANTS

A total of 58 infants with ARDS after congenital heart surgery were eligible and were randomized to the HFOV (n = 29) or the HFOV-VG (n = 29) between January 2020 and January 2021.

INTERVENTIONS

Tracheal aspirate samples for the measurement of interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) were obtained on days one, two, and three of HFOV or HFOV-VG ventilation.

MEASUREMENTS AND MAIN RESULTS

The authors found a significantly increasing trend in the HFOV group mean values of IL-6, IL-8, and TNF-α (p < 0.05 on days two and three v day one), and IL-6, IL-8, and TNF-α levels were significantly higher on day three in the HFOV group versus the HFOV+VG group (p < 0.05). In addition, the incidences of hypocapnia and hypercapnia in infants supported with HFOV-VG were significantly lower (p < 0.05). Furthermore, the postoperative mechanical ventilation duration in the HFOV-VG group also was shorter than that in the HFOV group (p < 0.05).

CONCLUSION

Compared with HFOV alone, HFOV-VG reduced proinflammatory systemic reactions after congenital cardiac surgery, decreased the incidences of hypercapnia and hypocapnia, and shortened the postoperative mechanical ventilation duration.

Ventilation-induced jet suggests biotrauma in reconstructed airways of the intubated neonate

We investigate respiratory flow phenomena in a reconstructed upper airway model of an intubated neonate undergoing invasive mechanical ventilation, spanning conventional to high-frequency ventilation (HFV) modes. Using high-speed tomographic particle image velocimetry, we resolve transient, three-dimensional flow fields and observe a persistent jet flow exiting the endotracheal tube whose strength is directly modulated according to the ventilation protocol. We identify this synthetic jet as the dominating signature of convective flow under intubated ventilation. Concurrently, our in silico wall shear stress analysis reveals a hitherto overlooked source of ventilator-induced lung injury as a result of jet impingement on the tracheal carina, suggesting damage to the bronchial epithelium; this type of injury is known as biotrauma. We find HFV advantageous in mitigating the intensity of such impingement, which may contribute to its role as a lung protective method. Our findings may encourage the adoption of less invasive ventilation procedures currently used in neonatal intensive care units.

High-frequency oscillatory ventilation: A narrative review

High-frequency oscillatory ventilation (HFOV) is a lung-protective strategy that can be utilized in the full spectrum of patient populations ranging from neonatal to adults with acute lung injury. HFOV is often utilized as a rescue strategy when conventional mechanical ventilation (CV) has failed. HFOV uses low tidal volumes and constant mean airway pressures in conjunction with high respiratory rates to provide beneficial effects on oxygenation and ventilation, while eliminating the traumatic “inflate–deflate” cycle imposed by CV. Although statistical evidence supporting HFOV is particularly low, potential benefits for its application in many clinical manifestations still remain. High-frequency oscillation is a safe and effective rescue mode of ventilation for the treatment of acute respiratory distress syndrome (ARDS). All patients who have ventilator-induced lung injury (VILI) or are at risk of developing VILI or ARDS would be suitable candidates for HFOV, especially those who have failed conventional mechanical ventilation. This narrative aims to provide a review of HFOV vis-à-vis its indications, contraindications, hazards, parameters to monitoring, patient selection, clinical goals, mechanisms of action, controls for optimizing ventilation and oxygenation, clinical application in ARDS, and a comparison with other modes of mechanical ventilation.

Effect of inhaled gas density on the pendelluft-induced lung injury

Helium, sulfur hexafluoride-oxygen, and air were modeled to examine the role of the gas density on the pendelluft-induced lung injury (PILI) under high frequency oscillatory ventilation (HFOV). Large eddy simulation coupled with physiological resistance-compliance boundary conditions was applied to capture pendelluft-induced gas entrapment and mechanical stresses in an image-based human lung model. The flow characteristics were strongly dependent on the inspired gas density. The flow partitioning, globally between the left and right lung and locally between adjacent units branches, was significantly affected by the density of inhaled gas and was more balanced when inspiring lighter gas. The incomplete loops of flow-volume and volume-pressure curves were significantly influenced by the variations of the flow redistribution, resistance, and turbulence associated with the pendelluft mechanism. Inhaling light gas reduced the entrapped gas volume and mechanical stress surrounding carina ridges signifying the important role of inhaled gas properties on PILI. In general, lung ventilation by HFOV with a gas mixture of large amounts of Helium is thought to mitigate ventilator complications.