High-frequency Oscillatory Ventilation In Patients Research Articles

The Physiological Basis of High-Frequency Oscillatory Ventilation and Current Evidence in Adults and Children: A Narrative Review.

High-frequency oscillatory ventilation (HFOV) is a type of invasive mechanical ventilation that employs supra-physiologic respiratory rates and low tidal volumes (VT) that approximate the anatomic deadspace. During HFOV, mean airway pressure is set and gas is then displaced towards and away from the patient through a piston. Carbon dioxide (CO2) is cleared based on the power (amplitude) setting and frequency, with lower frequencies resulting in higher VT and CO2 clearance. Airway pressure amplitude is significantly attenuated throughout the respiratory system and mechanical strain and stress on the alveoli are theoretically minimized. HFOV has been purported as a form of lung protective ventilation that minimizes volutrauma, atelectrauma, and biotrauma. Following two large randomized controlled trials showing no benefit and harm, respectively, HFOV has largely been abandoned in adults with ARDS. A multi-center clinical trial in children is ongoing. This article aims to review the physiologic rationale for the use of HFOV in patients with acute respiratory failure, summarize relevant bench and animal models, and discuss the potential use of HFOV as a primary and rescue mode in adults and children with severe respiratory failure.

A randomised controlled trial and cost-effectiveness analysis of high-frequency oscillatory ventilation against conventional artificial ventilation for adults with acute respiratory distress syndrome. The OSCAR (OSCillation in ARDS) study.

Patients with the acute respiratory distress syndrome (ARDS) require artificial ventilation but this treatment may produce secondary lung damage. High-frequency oscillatory ventilation (HFOV) may reduce this damage. To determine the clinical benefit and cost-effectiveness of HFOV in patients with ARDS compared with standard mechanical ventilation. A parallel, randomised, unblinded clinical trial. UK intensive care units. Mechanically ventilated patients with a partial pressure of oxygen in arterial blood/fractional concentration of inspired oxygen (P : F) ratio of 26.7 kPa (200 mmHg) or less and an expected duration of ventilation of at least 2 days at recruitment. Treatment arm HFOV using a Novalung R100(®) ventilator (Metran Co. Ltd, Saitama, Japan) ventilator until the start of weaning. Control arm Conventional mechanical ventilation using the devices available in the participating centres. The primary clinical outcome was all-cause mortality at 30 days after randomisation. The primary health economic outcome was the cost per quality-adjusted life-year (QALY) gained. One hundred and sixty-six of 398 patients (41.7%) randomised to the HFOV group and 163 of 397 patients (41.1%) randomised to the conventional mechanical ventilation group died within 30 days of randomisation (p = 0.85), for an absolute difference of 0.6% [95% confidence interval (CI) -6.1% to 7.5%]. After adjustment for study centre, sex, Acute Physiology and Chronic Health Evaluation II score, and the initial P : F ratio, the odds ratio for survival in the conventional ventilation group was 1.03 (95% CI 0.75 to 1.40; p = 0.87 logistic regression). Survival analysis showed no difference in the probability of survival up to 12 months after randomisation. The average QALY at 1 year in the HFOV group was 0.302 compared to 0.246. This gives an incremental cost-effectiveness ratio (ICER) for the cost to society per QALY of £88,790 and an ICER for the cost to the NHS per QALY of £ 78,260. The use of HFOV had no effect on 30-day mortality in adult patients undergoing mechanical ventilation for ARDS and no economic advantage. We suggest that further research into avoiding ventilator-induced lung injury should concentrate on ventilatory strategies other than HFOV. Current Controlled Trials ISRCTN10416500.

High-frequency oscillatory ventilation in patients with acute respiratory distress syndrome: a meta-analysis

To evaluate the effects of high-frequency oscillatory ventilation (HFOV) on mortality in patients with acute respiratory distress syndrome (ARDS). Randomized controlled trials (RCTs) of HFOV as compared with conventional mechanical ventilation (CMV) in adult patients with ARDS from January 1970 to May 2013 were recruited. The data were analyzed with the methods recommended by the Cochrane Collaboration's software RevMan 5.0. Six RCTs using HFOV in adult patients with ARDS were collected for analysis. Among 1 634 eligible ARDS patients, 827 of them were enrolled into HFOV group and the reminder into CMV group. Meta-analysis revealed HFOV did not significantly decrease the hospitalization or 30-day mortality of adult ARDS patients (OR = 0.95, 95% CI 0.62-1.46, P = 0.83). Compared with CMV, HFOV dose not improve prognosis in adult patients with ARDS. Thus more high-quality RCTs with larger samples are warranted.

High-frequency oscillatory ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease

PurposeHigh-frequency oscillatory ventilation (HFOV) is usually considered not indicated for treatment of patients with chronic obstructive pulmonary disease (COPD) because of the theoretical risk of air trapping and hyperinflation. The aim of our study was to establish whether HFOV can be safely applied in patients with acute exacerbation of COPD and hypercapnic respiratory failure. MethodsTen patients (age, 63-83 years) requiring intensive care treatment who failed on noninvasive ventilation were studied. After initial conventional mechanical ventilation (CMV) of less than 72 hours, all patients were transferred to HFOV for 24 hours and then back to CMV. Arterial blood gases, spirometry, and hemodynamic parameters were repeatedly obtained in all phases of CMV and HFOV at different settings. Regional lung aeration and ventilation were assessed by electrical impedance tomography. ResultsHigh-frequency oscillatory ventilation was tolerated well; no adverse effects or severe hyperinflation and hemodynamic compromise were observed. Effective CO2 elimination and oxygenation were achieved. Ventilation was more homogeneously distributed during HFOV than during initial CMV. Higher respiratory system compliance and tidal volume were found during CMV after 24 hours of HFOV. ConclusionsOur study indicates that short-term HFOV, using lower mean airway pressures than recommended for acute respiratory distress syndrome, appears safe in patients with COPD while securing adequate pulmonary gas exchange.

Clinical use of high-frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome

High-frequency oscillatory ventilation (HFOV) is an emerging ventilatory strategy for adults that has been used successfully in the neonatal and pediatric population. This modality utilizes high mean airway pressures to maintain an open lung and low tidal volumes at a high frequency that allow for adequate ventilation while at the same time preventing alveolar overdistension. With the current understanding that excessive lung stretch and inadequate end-expiratory ventilatory volume may be injurious to the lungs, HFOV seems to be the ideal lung-protective ventilatory mode. During the past 8 yrs, there have been increasing numbers of studies describing its use in adult patients with acute respiratory distress syndrome. This article aims to review the published studies of HFOV in adults with acute respiratory distress syndrome with regard to its safety and efficacy. To assist us with our review, we did a search of MEDLINE (from 1966 to present) and EMBASE (1980 to present) databases to identify adult, clinical, English-language, research articles related to HFOV use. In addition, we reviewed relevant animal and mechanical ventilation studies. We did not perform a formal systematic review. The application of HFOV was mainly reported as a rescue ventilatory mode in adult patients with acute respiratory distress syndrome who were thought to have failed conventional ventilation. In these patients, HFOV has consistently been shown to improve oxygenation without obvious increases in complications measured. There was only one randomized, controlled trial comparing HFOV with conventional ventilation. This study showed that there was a nonsignificant trend toward a lower mortality rate in the HFOV group. In addition, HFOV was as effective and safe as conventional ventilation. Although there are limitations, multiple studies have shown that earlier initiation of HFOV in patients with severe acute respiratory distress syndrome may also be associated with a lower mortality. HFOV seems to be safe and effective for adults with severe acute respiratory distress syndrome who have failed conventional ventilation. Further research is needed to determine the ideal patients, timing, and optimal technique with which to provide HFOV. When considering HFOV as an early, lung-protective mode of ventilation, there is still a need to perform an adequately powered, randomized, controlled trial comparing it with the best available form of conventional ventilation. However, we believe that such a trial should wait until we have a better understanding of HFOV in adults.

High-frequency oscillatory ventilation for acute respiratory distress syndrome in adult patients.

High-frequency oscillatory ventilation (HFOV) using an open-lung strategy has been demonstrated to improve oxygenation in neonatal and pediatric respiratory failure, without increasing barotrauma. Animal studies using small (<4 mm) endotracheal tubes have shown reduced histopathologic evidence of lung injury and inflammatory mediator release, suggesting reduced ventilator-induced lung injury. During the last decade, case reports and observational studies of HFOV in patients failing conventional ventilation strategies have suggested improved oxygenation in adult patients with severe acute respiratory distress syndrome. These reports have also suggested that early (2 days) initiation of HFOV is more likely to result in survival than delayed initiation (>7 days). A recently published randomized, controlled trial in acute respiratory distress syndrome patients (n = 148) comparing HFOV with a pressure-control ventilation strategy (Pao(2)/Fio(2) ratio of <or=200 mm Hg on positive end-expiratory pressure of >10 cm H(2)O) demonstrated early (<16 hrs) improvement in Pao(2)/Fio(2) (p =.008) in the HFOV group but no significant difference in oxygenation index between the two groups during the initial 72 hrs of treatment. Thirty-day mortality was 37% in the HFOV group and 52% in the conventional ventilation group (p =.102). There was no significant difference between treatment groups in the prevalence of barotrauma, hemodynamic instability, or mucus plugging. This study suggests that HFOV is as effective and safe as the conventional strategy to which it was compared. For clinical use in adults, a trial of HFOV may be considered when Fio(2) requirements exceed 60% and mean airway pressure is approaching 20 cm H(2)O or higher (or, alternatively, positive end-expiratory pressure of >15 cm H(2)O). It is currently unknown whether initiating HFOV at a lower severity threshold would result in reduced ventilator-associated lung injury or mortality. Future studies should compare different algorithms of applying HFOV to determine the optimal techniques for achieving oxygenation and ventilation, while minimizing ventilator-associated lung injury. The potential role of adjunctive therapies used with HFOV (e.g., prone ventilation, inhaled nitric oxide, aerosolized vasodilators, liquid ventilation) will require further research.