High frequency oscillatory ventilation in children: an overview

Outcomes of Severe PARDS on High-Frequency Oscillatory Ventilation - A Single Centre Experience

OBJECTIVE

To describe experience with high-frequency oscillatory ventilation (HFOV) in children with acute respiratory distress syndrome (ARDS) transitioned from conventional mechanical ventilation (CMV) due to refractory hypoxemia and to assess factors associated with survival and also compare outcomes of patients who were managed with early HFOV (within 24 h of intubation) vs. late HFOV.

METHODS

This retrospective, observational study was conducted in a tertiary care hospital's pediatric intensive care unit. Thirty-four children with pediatric acute respiratory distress syndrome (PARDS) managed with HFOV were included.

RESULTS

Of 34 children with PARDS managed with HFOV after failure of conventional ventilation to improve oxygenation, 8 survived. Improvement in the Oxygenation Index (OI) at 48 h of initiation of HFOV along with percent increase in PaO₂/FiO₂ (P/F ratio) at 24 h of HFOV were predictors of survival. The response to HFOV, based on OI and P/F ratio, between 24 and 48 h of ventilation identified potential survivors. Also, lower positive end-expiratory pressure (PEEP) on CMV and shorter duration of CMV before initiation of HFOV were associated with survival.

CONCLUSIONS

Survival in pediatric ARDS patients treated with HFOV could be predicted by using trends of OI - with survivors showing a more rapid decline in OI between 24 and 48 h of initiation compared to non-survivors.

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.

Sevoflurane improves respiratory mechanics and gas exchange in a case series of infants with severe bronchiolitis-induced acute respiratory distress syndrome

This report describes the successful use of a new intervention to improve respiratory mechanics and gas exchange in a relatively homogeneous group of infants with severe bronchiolitis‐induced PARDS after failure of conventional treatment. These results may open a new interesting area of research and management for PARDS patients.

A translational cellular model to study the impact of high-frequency oscillatory ventilation on human epithelial cell function

High-frequency oscillatory ventilation (HFOV) has been proposed as gentle ventilation strategy to prevent lung injury in the preterm infant. High-frequency jet ventilation leads to dimensional and mechanical airway deformation in animal airway models, which is consistent with translational studies demonstrating the impact of oxygen and biophysical stresses on normal airway cellular function. There is an overall paucity of clinical and cellular data on the impact of HFOV on the conducting airway. We developed an innovative method to test the impact of the clinical HFO Ventilator (SensorMedics 3100A) on human epithelial cell function. In this translational model, we were able to study the differential effects of biophysical stress due to HFOV independently and in combination with hyperoxia on a direct cellular level of the conducting airway system. Additionally, we could demonstrate that hyperoxia and pressure by HFOV independently resulted in significant cell dysfunction and inflammation, while the combination of HFOV and hyperoxia had a synergistic effect, resulting in greater cell death.

NEW & NOTEWORTHY

Traditionally, large-animal models are used to analyze the impact of clinical ventilators on lung cellular function. In our dual-chamber model, we interface high-frequency oscillatory ventilation (HFOV) directly with airway cells to study the effects of HFOV independently and combined with hyperoxia. Therefore, it is possible to study the preclinical impact of interventional factors without the high cost of animal models, thus reducing staff, time, as well as animal sparing.

High-frequency oscillatory ventilation in children: a 10-year experience

OBJECTIVES

The aim of the study was to describe the experience with high-frequency oscillatory ventilation (HFOV) in a Portuguese Pediatric Critical Care Unit, and to evaluate whether HFOV allowed improvement in oxygenation and ventilation.

METHODS

This was a retrospective observational cohort study of children ventilated by HFOV between January, 2002 and December, 2011. The following parameters were recorded: demographic and clinical data, and blood gases and ventilatory parameters during the first 48 hours of HFOV.

RESULTS

80 children were included, with a median age of 1.5 months (min: one week; max: 36 months). Pneumonia (n=50; 62.5%) and bronchiolitis (n=18; 22.5%) were the main diagnoses. Approximately 40% (n=32) of the patients developed acute respiratory distress syndrome (ARDS). Conventional mechanical ventilation was used in 68 (85%) of patients prior to HFOV. All patients who started HFOV had hypoxemia, and 56 (70%) also presented persistent hypercapnia. Two hours after starting HFOV, a significant improvement in SatO2/FiO2 ratio (128±0.63 vs. 163±0.72; p<0.001) that was sustained up to 24 hours of HFOV and a decrease in FiO2 were observed. Since the beginning of HFOV, the mean PCO2 significantly decreased (87±33 vs. 66±25; p<0.001), and the pH significantly improved (7.21±0.17 vs. 7.32±0.15; p<0.001). Overall survival was 83.8%.

CONCLUSIONS

HFOV enabled an improvement in hypercapnia and oxygenation. It is a safe option for the treatment of ARDS and severe small airway diseases.