High-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

Oscillatory ventilation redux: alternative perspectives on ventilator-induced lung injury in the acute respiratory distress syndrome

For patients with the acute respiratory distress syndrome (ARDS), ventilation strategies that limit end-expiratory derecruitment and end-inspiratory overdistension are the only interventions to have significantly reduced the morbidity and mortality. For this reason, the use of high-frequency oscillatory ventilation (HFOV) was considered to be an ideal protective strategy, given its reliance on very low tidal volumes cycled at very high rates. However, results from clinical trials in adults with ARDS have demonstrated that HFOV does not improve clinical outcomes. Recent experimental and computational studies have shown that oscillation of a mechanically heterogeneous lung with multiple simultaneous frequencies can reduce parenchymal strain, improve gas exchange, and maintain lung recruitment at lower distending pressures compared to traditional ‘single-frequency’ HFOV. This review will discuss the theoretical rationale for the use of multiple oscillatory frequencies in ARDS, as well as the mechanisms by which it may reduce the risk for ventilator-induced lung injury.

[Topical respiratory strategies in neurocritical care]

Management of the respiratory tract and maintenance of adequate gas exchange are the basic goals of critical care. Injury to the nervous system is often accompanied by development of respiratory disorders. On the other hand, changes in the gas composition of arterial blood can cause brain damage. In addition, approaches to the patient with respiratory failure, which are used in general critical care and neurocritical care, may differ. The presented literature review is devoted to modern respiratory strategies used in neurocritical care.

A comparison of clinical efficacy between high frequency oscillatory ventilation and conventional ventilation with lung volume recruitment in pediatric acute respiratory distress syndrome: A randomized controlled trial

PURPOSE

To determine the efficacy of lung volume recruitment maneuver (LVRM) with high frequency oscillatory ventilation (HFOV) on oxygenation, hemodynamic alteration, and clinical outcomes when compared to conventional mechanical ventilation (CV) in children with severe acute respiratory distress syndrome (ARDS).

MATERIALS

We performed a randomized controlled trial and enrolled pediatric patients who were diagnosed to have severe ARDS upon pediatric intensive care unit (PICU) admission. LVRM protocol combined with HFOV or conventional mechanical ventilation was used. Baseline characteristic data, oxygenation, hemodynamic parameters, and clinical outcomes were recorded.

RESULTS

Eighteen children with severe ARDS were enrolled in our study. The primary cause of ARDS was pneumonia (91.7%). Their mean age was 47.7 ± 61.2 (m) and body weight was 25.3 ± 27.1 (kg). Their initial pediatric risk of mortality score 3 and pediatric logistic organ dysfunction were 12 ± 9.2 and 15.9 ± 12.8, respectively. The initial mean oxygen index was 24.5 ± 10.4, and mean PaO2/FiO2 was 80.6 ± 25. There was no difference in oxygen parameters at baseline the between two groups. There was a significant increase in PaO2/FiO2 (119.2 ± 41.1, 49.6 ± 30.6, P = 0.01*) response after 1 h of LVRM with HFOV compare to CV. Hemodynamic and serious complications were not significantly affected after LVRM. The overall PICU mortality of our severe ARDS at 28 days was 16.7%. Three patients in CV with LVRM group failed to wean oxygen requirement and were cross-over to HFOV group.

CONCLUSIONS

HFOV combined with LVRM in severe pediatric ARDS had superior oxygenation and tended to have better clinical effect over CV. There is no significant effect on hemodynamic parameters. Moreover, no serious complication was noted.

High-frequency oscillatory ventilation for early acute respiratory distress syndrome in adults

PURPOSE OF REVIEW

High-frequency oscillatory ventilation (HFOV) has been considered a potentially ideal mode of lung-protective ventilation. A recent meta-analysis suggested improved oxygenation and reduced mortality in adults and children with acute respiratory distress syndrome (ARDS), but the use of outdated control strategies and small numbers of patients in many of the studies rendered these findings hypothesis-generating only.

RECENT FINDINGS

During 2013, two large randomized controlled trials comparing HFOV with a conventional lung-protective ventilation were published - the Oscillation for Acute Respiratory Distress Syndrome Treated Early (OSCILLATE) and the Oscillation in ARDS (OSCAR) trials. These trials suggested no benefit or even harm with HFOV in adults with early moderate-to-severe ARDS. In this article, the major characteristics of these two studies and the possible reasons for failure to achieve the expected theoretical benefits are reviewed. Moreover, future directions with potential new technical advances and the use of new bedside monitoring techniques are addressed.

SUMMARY

The OSCILLATE and OSCAR trials showed that the early application of HFOV in moderate-to-severe adult ARDS does not reduce mortality compared with conventional ventilation strategies. Future studies on HFOV will need to identify those patients who might benefit most from HFOV and to determine the best oscillator settings. Both goals require an improved capability of monitoring recruitment and overdistension, and oscillatory volumes.