High frequency percussive ventilation in pediatric acute respiratory failure

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

2021 Year in Review: Pediatric Mechanical Ventilation

Mechanical ventilation is commonly used in the pediatric intensive care unit. This paper reviews studies of pediatric mechanical ventilation published in 2021. Topics include physiology, ventilator modes, alarms, disease states, airway suctioning, ventilator liberation, prolonged ventilation, and others.

Expiratory high-frequency percussive ventilation: a novel concept for improving gas exchange

Background

Although high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about tissue overdistension caused by the oscillations and consequent lung damage. We compared a modified percussive ventilation modality created by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) with conventional mechanical ventilation (CMV) and standard HFPV.

Methods

Hypoxia and hypercapnia were induced by decreasing the frequency of CMV in New Zealand White rabbits (n = 10). Following steady-state CMV periods, percussive modalities with oscillations randomly introduced to the entire breathing cycle (HFPV) or to the expiratory phase alone (eHFPV) with varying amplitudes (2 or 4 cmH₂O) and frequencies were used (5 or 10 Hz). The arterial partial pressures of oxygen (PaO₂) and carbon dioxide (PaCO₂) were determined. Volumetric capnography was used to evaluate the ventilation dead space fraction, phase 2 slope, and minute elimination of CO₂. Respiratory mechanics were characterized by forced oscillations.

Results

The use of eHFPV with 5 Hz superimposed oscillation frequency and an amplitude of 4 cmH₂O enhanced gas exchange similar to those observed after HFPV. These improvements in PaO₂ (47.3 ± 5.5 vs. 58.6 ± 7.2 mmHg) and PaCO₂ (54.7 ± 2.3 vs. 50.1 ± 2.9 mmHg) were associated with lower ventilation dead space and capnogram phase 2 slope, as well as enhanced minute CO₂ elimination without altering respiratory mechanics.

Conclusions

These findings demonstrated improved gas exchange using eHFPV as a novel mechanical ventilation modality that combines the benefits of conventional and small-amplitude high-frequency oscillatory ventilation, owing to improved longitudinal gas transport rather than increased lung surface area available for gas exchange.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02215-2.

High-Frequency Percussive Ventilation in Viral Bronchiolitis

BACKGROUND

High-frequency percussive ventilation (HFPV) is an alternative mode of mechanical ventilation that has been shown to improve gas exchange in subjects with severe respiratory failure. We hypothesized that HFPV use would improve ventilation and oxygenation in intubated children with acute bronchiolitis.

METHODS

In this single-center prospective cohort study we included mechanically ventilated children in the pediatric ICU with bronchiolitis 1-24 months old who were transitioned to HFPV from conventional invasive mechanical ventilation from November 2018-April 2020. Patients with congenital heart disease, on extracorporeal membrane oxygenation (ECMO), and with HFPV duration < 12 h were excluded. Subject gas exchange metrics and ventilator parameters were compared before and after HFPV initiation.

RESULTS

Forty-one of 192 (21%) patients intubated with bronchiolitis underwent HFPV, and 35 met inclusion criteria. Median age of cohort was 4 months, and 60% were previously healthy. All subjects with available oxygenation saturation index (OSI) measurements pre-HFPV met pediatric ARDS criteria (31/35, 89%). Mean CO2 decreased from 65.4 in the 24 h pre-HFPV to 51 (P < .001) in the 24 h post initiation. SpO2 /FIO2 was significantly improved at 24 h post-HFPV (153.3 to 209.7, P = .001), whereas the decrease in mean OSI at 24 h did not meet statistical significance (11.9 to 10.2, P = .15). The mean peak inspiratory pressure (PIP) decreased post-HFPV from 29.7 to 25.0 at 24 h (P < .001). No subjects developed an air leak or hemodynamic instability secondary to HFPV. Two subjects required ECMO, and of these, one subject died.

CONCLUSIONS

HFPV was associated with significant improvement in ventilation and decreased exposure to high PIPs for mechanically ventilated children with bronchiolitis in our cohort and had a potential association with improved oxygenation. Our study shows that HFPV may be an effective alternative mode of ventilation in patients with bronchiolitis who have poor gas exchange on conventional invasive mechanical ventilation.

Update on ventilation management in the Pediatric Intensive Care Unit

Studies have shown that up to 63% of pediatric intensive care unit patients admitted with acute respiratory or cardiorespiratory illness require mechanical ventilation. Mechanical ventilator support can be divided into three phases: initiation, escalation, and resolution. Noninvasive ventilation is typical during the initiation phase in the management of acute pediatric respiratory failure. The major advancements in the use of noninvasive ventilation involve the emergence of high-flow nasal cannula and how widespread the use of high-flow nasal cannula has become in pediatric critical care practice. When high-flow nasal cannula fails, escalation to continuous positive airway pressure or bi-level positive airway pressure is the next step in respiratory care progression. Careful clinical assessment is necessary to avoid delayed escalation between forms of noninvasive support or escalation to intubation and invasive mechanical ventilation. Advancements in conventional mechanical ventilation are centered on optimizing ventilator settings and customizing monitoring with the overarching goal to reduce complications of mechanical ventilation, such as ventilator-induced lung injury. New mechanical ventilator strategies integrating esophageal pressure monitoring, volumetric capnography, and neurally adjusted ventilator assist help to optimize conventional ventilator support. Nonconventional modes of ventilation in the intensive care unit are high-frequency modes and airway pressure release ventilation. Extracorporeal pulmonary support via extracorporeal membrane oxygenation or paracorporeal lung assist devices provides rescue options when conventional and nonconventional methods fail. During resolution of a course of mechanical ventilator support, reliable weaning strategies and extubation readiness testing are lacking in pediatric critical care. Further, timing of tracheostomy, risk reduction in ventilator-induced lung injury, and decreased sedation requirements in pediatric patients requiring mechanical ventilation in the pediatric intensive care unit are areas of ongoing research.