The impact of high frequency oscillatory ventilation on mortality in paediatric acute respiratory distress syndrome.

BACKGROUND: High-frequency oscillatory ventilation (HFOV) use was associated with greater mortality in adult acute respiratory distress syndrome (ARDS). Nevertheless, HFOV is still frequently used as rescue therapy in paediatric acute respiratory distress syndrome (PARDS). In view of the limited evidence for HFOV in PARDS and evidence demonstrating harm in adult patients with ARDS, we hypothesized that HFOV use compared to other modes of mechanical ventilation is associated with increased mortality in PARDS. METHODS: Patients with PARDS from 10 paediatric intensive care units across Asia from 2009 to 2015 were identified. Data on epidemiology and clinical outcomes were collected. Patients on HFOV were compared to patients on other modes of ventilation. The primary outcome was 28-day mortality and secondary outcomes were 28-day ventilator- (VFD) and intensive care unit- (IFD) free days. Genetic matching (GM) method was used to analyse the association between HFOV treatment with the primary outcome. Additionally, we performed a sensitivity analysis, including propensity score (PS) matching, inverse probability of treatment weighting (IPTW) and marginal structural modelling (MSM) to estimate the treatment effect. RESULTS: A total of 328 patients were included. In the first 7 days of PARDS, 122/328 (37.2%) patients were supported with HFOV. There were significant differences in baseline oxygenation index (OI) between the HFOV and non-HFOV groups (18.8 [12.0, 30.2] vs. 7.7 [5.1, 13.1] respectively; p < 0.001). A total of 118 pairs were matched in the GM method which found a significant association between HFOV with 28-day mortality in PARDS [odds ratio 2.3, 95% confidence interval (CI) 1.3, 4.4, p value 0.01]. VFD was indifferent between the HFOV and non-HFOV group [mean difference - 1.3 (95%CI - 3.4, 0.9); p = 0.29] but IFD was significantly lower in the HFOV group [- 2.5 (95%CI - 4.9, - 0.5); p = 0.03]. From the sensitivity analysis, PS matching, IPTW and MSM all showed consistent direction of HFOV treatment effect in PARDS. CONCLUSION: The use of HFOV was associated with increased 28-day mortality in PARDS. This study suggests caution but does not eliminate equivocality and a randomized controlled trial is justified to examine the true association.

High-frequency oscillatory ventilation guided by transpulmonary pressure in acute respiratory syndrome: an experimental study in pigs.

BACKGROUND: Recent clinical studies have not shown an overall benefit of high-frequency oscillatory ventilation (HFOV), possibly due to injurious or non-individualized HFOV settings. We compared conventional HFOV (HFOVcon) settings with HFOV settings based on mean transpulmonary pressures (PLmean) in an animal model of experimental acute respiratory distress syndrome (ARDS). METHODS: ARDS was induced in eight pigs by intrabronchial installation of hydrochloric acid (0.1 N, pH 1.1; 2.5 ml/kg body weight). The animals were initially ventilated in volume-controlled mode with low tidal volumes (6 ml kg- 1) at three positive end-expiratory pressure (PEEP) levels (5, 10, 20 cmH2O) followed by HFOVcon and then HFOV PLmean each at PEEP 10 and 20. The continuous distending pressure (CDP) during HFOVcon was set at mean airway pressure plus 5 cmH2O. For HFOV PLmean it was set at mean PL plus 5 cmH2O. Baseline measurements were obtained before and after induction of ARDS under volume controlled ventilation with PEEP 5. The same measurements and computer tomography of the thorax were then performed under all ventilatory regimens at PEEP 10 and 20. RESULTS: Cardiac output, stroke volume, mean arterial pressure and intrathoracic blood volume index were significantly higher during HFOV PLmean than during HFOVcon at PEEP 20. Lung density, total lung volume, and normally and poorly aerated lung areas were significantly greater during HFOVcon, while there was less over-aerated lung tissue in HFOV PLmean. The groups did not differ in oxygenation or extravascular lung water index. CONCLUSION: HFOV PLmean is associated with less hemodynamic compromise and less pulmonary overdistension than HFOVcon. Despite the increase in non-ventilated lung areas, oxygenation improved with both regimens. An individualized approach with HFOV settings based on transpulmonary pressure could be a useful ventilatory strategy in patients with ARDS. Providing alveolar stabilization with HFOV while avoiding harmful distending pressures and pulmonary overdistension might be a key in the context of ventilator-induced lung injury.

High frequency percussive ventilation increases alveolar recruitment in early acute respiratory distress syndrome: an experimental, physiological and CT scan study.

BACKGROUND: High frequency percussive ventilation (HFPV) combines diffusive (high frequency mini-bursts) and convective ventilation patterns. Benefits include enhanced oxygenation and hemodynamics, and alveolar recruitment, while providing hypothetic lung-protective ventilation. No study has investigated HFPV-induced changes in lung aeration in patients with early acute respiratory distress syndrome (ARDS). METHODS: Eight patients with early non-focal ARDS were enrolled and five swine with early non-focal ARDS were studied in prospective computed tomography (CT) scan and animal studies, in a university-hospital tertiary ICU and an animal laboratory. Patients were optimized under conventional "open-lung" ventilation. Lung CT was performed using an end-expiratory hold (Conv) to assess lung morphology. HFPV was applied for 1 hour to all patients before new CT scans were performed with end-expiratory (HFPV EE) and end-inspiratory (HFPV EI) holds. Lung volumes were determined after software analysis. At specified time points, blood gases and hemodynamic data were collected. Recruitment was defined as a change in non-aerated lung volumes between Conv, HFPV EE and HFPV EI. The main objective was to verify whether HFPV increases alveolar recruitment without lung hyperinflation. Correlation between pleural, upper airways and HFPV-derived pressures was assessed in an ARDS swine-based model. RESULTS: One-hour HFPV significantly improved oxygenation and hemodynamics. Lung recruitment significantly rose by 12.0% (8.5-18.0%), P = 0.05 (Conv-HFPV EE) and 12.5% (9.3-16.8%), P = 0.003 (Conv-HFPV EI). Hyperinflation tended to increase by 2.0% (0.5-2.5%), P = 0.89 (Conv-HFPV EE) and 3.0% (2.5-4.0%), P = 0.27 (Conv-HFPV EI). HFPV hyperinflation correlated with hyperinflated and normally-aerated lung volumes at baseline: r = 0.79, P = 0.05 and r = 0.79, P = 0.05, respectively (Conv-HFPV EE); and only hyperinflated lung volumes at baseline: r = 0.88, P = 0.01 (Conv-HFPV EI). HFPV CT-determined tidal volumes reached 5.7 (1.1-8.1) mL.kg-1 of ideal body weight (IBW). Correlations between pleural and HFPV-monitored pressures were acceptable and end-inspiratory pleural pressures remained below 25cmH20. CONCLUSIONS: HFPV improves alveolar recruitment, gas exchanges and hemodynamics of patients with early non-focal ARDS without relevant hyperinflation. HFPV-derived pressures correlate with corresponding pleural or upper airways pressures. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02510105 . Registered on 1 June 2015. The trial was retrospectively registered.

Non-invasive high-frequency oscillatory ventilation in preterm infants: a randomised controlled cross-over trial.

OBJECTIVE: Non-invasive high-frequency oscillatory ventilation (nHFOV) has recently been described as a novel mode of respiratory support for premature infants. This study was designed to determine whether nHFOV decreases CO2 partial pressure (pCO2) in premature infants more effectively than non-invasive continuous positive airway pressure (nCPAP). DESIGN: Non-blinded prospective randomised controlled cross-over study. SETTING: University Medical Center tertiary neonatal intensive care unit. PATIENTS: 26 premature infants of 27±2 weeks of gestational age after extubation or non-invasive surfactant treatment. INTERVENTIONS: Infants were treated with 4 hours of nHFOV and 4 hours of nCPAP in a cross-over design. The sequence of the ventilation mode was randomly allocated. MAIN OUTCOME MEASURES: The primary outcome measure was pCO2 of arterial or arterialised blood 4 hours after commencing the respective mode of respiratory support. Secondary outcome criteria included events of apnoea and bradycardia, respiratory rate, heart rate, pain and/or discomfort, mean airway pressure, fraction of inspired oxygen and failure of non-invasive respiratory support. RESULTS: pCO2 after 4 hours of nHFOV was similar compared with 4 hours of nCPAP (p=0.33). pCO2 was 54.8 (14.6) vs 52.7 (9.3) mm Hg mean (SD) for the nHFOV-nCPAP period (n=13) and 49.0 (8.1) vs 47.7 (9.5) mm Hg for the nCPAP-nHFOV period (n=13). There was no difference in any of the secondary outcome measures. nHFOV was terminated prematurely in five cases for predefined failure criteria (p=0.051). CONCLUSIONS: We could not demonstrate an increased carbon dioxide clearance applying nHFOV compared with nCPAP in this cohort of preterm infants. TRIAL REGISTRATION NUMBER: DRKS00007171, results.

Pediatric ARDS.

The Pediatric Acute Lung Injury Consensus Conference (PALICC) has provided the critical care community with the first pediatric-focused definition for ARDS. The PALICC recommendations provide guidance on conventional ventilator management, gas exchange goals, use of high-frequency ventilation, adjunct management approaches, and the application of extracorporeal membrane oxygenation for pediatric ARDS (PARDS). Although outcomes for PARDS have improved over the past decade, mortality and morbidity remain significant. Pediatric-specific criteria may provide the ability to more promptly recognize and diagnose PARDS in clinical practice. Improvements in prognostication and stratification of disease severity may help to guide therapeutic interventions. Improved comparisons between patients and studies may help to promote future clinical investigations. Hopefully, the recommendations provided by PALICC, in terms of defining and managing ARDS, will stimulate additional research to better guide therapy and further improve outcomes for critically ill infants and children with ARDS.

Are All Oscillators Created Equal? In vitro Performance Characteristics of Eight High-Frequency Oscillatory Ventilators.

BACKGROUND: The mode of waveform generation and circuit characteristics differ between high-frequency oscillators. It is unknown if this influences performance. OBJECTIVES: To describe the relationships between set and delivered pressure amplitude (x0394;P), and the interaction with frequency and endotracheal tube (ETT) diameter, in eight high-frequency oscillators. METHODS: Oscillators were evaluated using a 70-ml test lung at 1.0 and 2.0 ml/cm H2O compliance, with mean airway pressures (PAW) of 10 and 20 cm H2O, frequencies of 5, 10 and 15 Hz, and an ETT diameter of 2.5 and 3.5 mm. At each permutation of PAW, frequency and ETT, the set x0394;P was sequentially increased from 15 to 50 cm H2O, or from 20 to 100% maximum amplitude (10% increments) depending on the oscillator design. The x0394;P at the ventilator (x0394;PVENT), airway opening (x0394;PAO) and within the test lung (x0394;PTRACH), and tidal volume (V(T)) at the airway opening were determined at each set x0394;P. RESULTS: In two oscillators the relationships between set and delivered x0394;P were non-linear, with a plateau in x0394;P thresholds noted at all frequencies (Dräger Babylog 8000) or ≥10 Hz (Dräger VN500). In all other devices there was a linear relationship between x0394;PVENT, x0394;PAO and x0394;PTRACH (all r2 >0.93), with differing attenuation of the pressure wave. Delivered V(T) at the different settings tested varied between devices, with some unable to deliver V(T) >3 ml at 15 Hz, and others generating V(T)>20 ml at 5 Hz and a 1:1 inspiratory-to-expiratory time ratio. CONCLUSIONS: Clinicians should be aware that modern high-frequency oscillators exhibit important differences in the delivered x0394;P and V(T).

Science and evidence: separating fact from fiction.

Evidence-based medicine (EBM) is the integration of individual clinical expertise with the best available research evidence from systematic research and the patient's values and expectations. A hierarchy of evidence can be used to assess the strength upon which clinical decisions are made. The efficient approach to finding the best evidence is to identify systematic reviews or evidence-based clinical practice guidelines. Respiratory therapies that evidence supports include noninvasive ventilation for appropriately selected patients, lung-protective ventilation, and ventilator discontinuation protocols. Evidence does not support use of weaning parameters, albuterol for ARDS, and high frequency oscillatory ventilation for adults. Therapy with equivocal evidence includes airway clearance, selection of an aerosol delivery device, and PEEP for ARDS. Although all tenets of EBM are not universally accepted, the principles of EBM nonetheless provide a valuable approach to respiratory care practice.

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.

Ventilação oscilatória de alta frequência em crianças: uma experiência de 10 anos / High-frequency oscillatory ventilation in children: a 10-year experience

OBJETIVOS: O objetivo do estudo foi descrever a experiência com ventilação oscilatória de frequência (VOAF) em uma unidade portuguesa de Cuidados Intensivos Neonatais e Pediátricos e avaliar se a VOAF permitiu uma melhoria na oxigenação e na ventilação. MÉTODOS: Estudo de coorte retrospectivo observacional em crianças submetidas À ventilação com VOAF entre janeiro de 2002 e dezembro de 2011. Os seguintes parâmetros foram registrados: dados demográficos e clínicos; gases sanguíneos; e parâmetros ventilatórios durante as primeiras 48 horas de VOAF. RESULTADOS: O estudo incluiu 80crianças com uma idade média de 1,5 mês (mínima: uma semana; máxima: 36 meses). Pneumonia (n = 50; 62,5%) e bronquiolite (n = 18; 22,5%) foram os principais diagnósticos. Cerca de 40% (n = 32) dos pacientes desenvolveram a síndrome da angústia respiratória aguda (SARA). A ventilação mecânica convencional foi utilizada em 68 (85%) pacientes antes da VOAF. Todos os pacientes que começaram a VOAF tiveram hipoxemia, e 56 (70%) também apresentaram hipercapnia persistente. Duas horas após o início da VOAF, foi observada uma melhoria significativa na proporção SatO2/FiO2 (128 ± 0,63 em comparação a 163 ± 0,72; p < 0,001), que foi mantida durante as 24 horas de VOAF, e uma redução da FiO2. Desde o início da VOAF, a PCO2 média teve uma queda significativa (87 ± 33 em comparação a 66 ± 25; p < 0,001) e o pH aumentou significativamente (7,21 ± 0,17 em comparação a 7,32 ± 0,15; p < 0,001). A sobrevida geral foi de 83,8%. CONCLUSÕES: A VOAF permitiu uma melhoria na hipercapnia e na oxigenação. Trata-se de uma opção segura no tratamento da SARA e de doenças graves das pequenas vias aéreas.

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.

High-frequency ventilation with the Dräger Babylog 8000plus: measuring the delivered frequency.

BACKGROUND: Ventilator frequency is one of the determinants of tidal volume delivery during high-frequency ventilation. Clinicians increasingly use data on ventilator displays to inform their decisions. AIM: To measure the frequencies delivered by the Dräger Babylog 8000plus ventilator when used in high-frequency mode. METHODS: Ventilator waveforms using a test lung were recorded at the full range of settings 5-20 Hz using Spectra software at 1000 Hz. The changes in frequency produced by a 1-Hz change in set frequency were calculated. Actual and displayed frequencies were compared. RESULTS: For settings up to 12 Hz, median (range) difference between set and delivered frequencies was 0 (-0.4 to +0.1) Hz. Above 12 Hz, delivered frequency varied by -0.3 (-1.9 to +0.3) Hz. For 1-Hz changes in frequency settings, in the range 5-12 Hz, 1-Hz changes produced a change in delivered frequency of 1.0 (0.6-1.4) Hz. Above 12 Hz, the corresponding changes were 0.7 (0-2.9) Hz. The ventilator displays the set frequency during operation rather than the delivered frequency. CONCLUSION: At 12 Hz and below, the differences between set and delivered frequencies were relatively small compared with those at 13 Hz and higher. Above 13 Hz, the difference between set and delivered frequencies was up to 2.9 Hz. Some frequency setting changes did not result in a change in delivered frequency.

Comparable effect of conventional ventilation versus early high-frequency oscillation on serum CC16 and IL-6 levels in preterm neonates.

OBJECTIVE: Clara cell 16 kD protein (CC16) and interleukin (IL)-6 have been used as peripheral blood biomarkers of alveolar leakage and inflammation, respectively. Thus, their measurement in the bloodstream could be used to assess ventilator-induced lung injury. The objective of this study was to evaluate the effect of optimized synchronized intermittent mandatory ventilation (SIMV) and high-frequency oscillatory ventilation (HFOV) on circulating CC16 and IL-6 levels when used as the initial ventilation modes in preterm neonates. STUDY DESIGN: Single center, prospective, randomized clinical study in preterm neonates (gestational age 30 weeks) requiring mechanical ventilation within the first 2 h of life. Serum CC16 and IL-6 were measured on establishment of the assigned ventilation mode after admission, at days 3 and 14 of life as well as at 36 weeks postmenstrual age. Demographic-perinatal data and clinical parameters were also recorded. RESULT: Of the 30 neonates studied, 24 (gestational age 27.1±1.7 weeks, birth weight 942±214 g) were finally analyzed, equally assigned into the SIMV and HFOV groups. Both groups had comparable demographic-perinatal characteristics and clinical parameters. Serum CC16 and IL-6 altered significantly over time (repeated-measures analysis of variance, both P<0.001). However, changes were not affected by the ventilation mode. Post hoc analysis showed a significant decrease in CC16 and IL-6 from birth up to 36 weeks postmenstrual age in both groups. CONCLUSION: In preterm neonates, SIMV and HFOV are associated with comparable circulating CC16 and IL-6 levels. These findings suggest a similar alveolar leakage and systemic inflammation with any of the ventilation modes evaluated when their usage is optimized.

Evaluation of performance of two high-frequency oscillatory ventilators using a model lung with a position sensor.

PURPOSE: High-frequency oscillatory ventilation (HFOV) is thought to protect the lungs of acute respiratory distress syndrome (ARDS) patients. The performance and mechanical characteristics of high-frequency oscillatory ventilators, especially with regard to delivering appropriate tidal volume (V(T)) to compromised lungs, might affect the outcome of patients. We evaluated the performance of two such ventilators using a model lung with a position sensor. METHODS: We tested the Metran R100 and SensorMedics 3100B. V(T) was measured using the model lung with the compliance set at 20 or 50 ml/cmH2O and the resistance at 0 or 20 cmH2O/l/s. Oscillator frequency was set at 5, 7, and 9 Hz, and amplitude was set at 25%, 50%, 75%, and 100% (100% being maximum amplitude available at each setting configuration). RESULTS: At each model lung setting, R100 delivered greater V(T) at 5 Hz. V(T) differences between the ventilators decreased as frequency increased and were negligible at 9 Hz. At each model lung setting and frequency, as amplitude increased from 25% to 100%, V(T) increased proportionally more with R100. With an I:E ratio of 1:1, 3100B delivered greater V(T) than with 1:2. CONCLUSION: Because it is able to deliver comparably greater V(T), R100 may be a better choice for HFOV in critical ARDS patients. Better proportionality may be a result of more effective amplitude titration for adjusting PaCO2 during oscillation.

Protocolized approach to the management of congenital diaphragmatic hernia: benefits of reducing variability in care.

PURPOSE: Variable approaches to the care of infants with congenital diaphragmatic hernia (CDH) by multiple providers may contribute to inconsistent care. Our institution developed a comprehensive evidence-based protocol to standardize the management of CDH infants. This report reviews patient outcomes before and after the implementation of the protocol. METHODS: Retrospective chart review of CDH infants managed with individualized care (preprotocol group, January 1997-December 2001, n = 22) or on the protocol (Protocol group, January 2002-July 2009, n = 47). Survival and other categorical variables were compared by chi(2) analysis, and continuous variables were compared using 1-sided analysis of variance analysis, with significance defined as P < .05. RESULTS: Survival to discharge was significantly greater in the Protocol group (40/47; 85%) than the preprotocol group (12/22; 52%; P = .006), although mean gestational age, mean birth weight, and expected survival were not statistically different between the 2 groups. The use of supportive therapies, including high-frequency jet ventilation, inhaled nitric oxide, and extracorporeal life support, was similar between groups as well. CONCLUSIONS: Since the implementation of a management protocol for infants with CDH, survival has improved significantly compared with expected survival and preprotocol controls. Reduction in the variability of care through use of an evidence-based protocol may improve the survival of CDH infants.

Assessment of neonatal ventilation during high-frequency oscillatory ventilation.

OBJECTIVE: To determine alterations in high-frequency oscillatory ventilation (HFOV) performance during clinical ventilator management. DESIGN: Clinical investigation. SETTING: Two level III intensive care nurseries in Wilmington, Delaware, and Philadelphia, Pennsylvania. PATIENTS: Thirty infants 1.49 +/- 1.01 kg with respiratory distress receiving HFOV. INTERVENTIONS: Due to the demonstrated benchtop load sensitivity of the HFOV (SensorMedics 3100), we hypothesized that measured tidal volume (Vt/kg) and high-frequency minute ventilation (HFMV) would vary inversely with respiratory rate adjustments and that ventilator performance will be affected with endotracheal tube (ETT) suctioning. Both Vt/kg and HFMV were recorded using a novel hot-wire anemometry technique at the time of ETT suctioning or changes in ventilator settings. MEASUREMENTS AND MAIN RESULTS: During HFOV it was found that Vt/kg = 2.52 +/- 0.68 mL/kg and HFMV = 69 +/- 45 ([mL/kg]2 x Hz); effective ventilation was observed in the range of HFMV = 29-113 ([mL/kg]2 x Hz). HFMV decreased with an increase in breathing frequency. Although there was a significant increase in the mean Vt/kg after suctioning events, there was no difference in Vt/kg or HFMV after disconnection of the ETT alone. There were significant alterations in HFOV performance as a result of clinical adjustments in respiratory rate and suctioning. In addition, we found that measured Vt during clinically effective HFOV is at least equivalent to expected deadspace. CONCLUSIONS: Measurement of tidal volume and HFMV may be clinically important in optimizing HFOV performance both during ETT suctioning and adjustments to breathing frequency.

[High-frequency ventilation in children and adolescents with acute respiratory distress syndrome (impact on the use of ECMO)]. / Ventilação de alta freqüência em crianças e adolescentes com síndrome do desconforto respiratório agudo (impacto sobre o uso de ECMO).

OBJECTIVE: To assess the effect of high-frequency ventilation (HFV) in children and adolescents with acute respiratory distress syndrome (ARDS) through estimates of survival rate and time of ventilation. To verify whether HFV can reduce the indication for extracorporeal membrane oxygenation (ECMO) in children and adolescents with ARDS. METHODS: a systematic review of medical literature on the use of HFV and ECMO in children and adolescents with ARDS was carried out. Medline, Lilacs and Embase databases were searched for the following terms: adult respiratory distress syndrome, ARDS, acute respiratory distress syndrome, respiratory distress syndrome, extracorporeal membrane oxygenation, ECMO, high-frequency ventilation, high-frequency jet ventilation and high-frequency oscillatory ventilation. Search was conducted for controlled and randomized clinical trials, cohort studies and a series of cases which compared HFV with conventional mechanic ventilation (CMV), ECMO with CMV, or HFV preceding the use of ECMO. RESULTS: Two hundred eighty nine publications related to HFV, ARDS and ECMO were found. Of these, only nine matched pre-established selection criteria which refer to use of HFV and/or ECMO in children and adolescents with ARDS. CONCLUSION: It was not possible to determine if use of HFV improves the survival rate of children and adolescent with ARDS. Regarding ventilation time, there is no study that confirms, with statistical significance, its increase or decrease. Whether HFV reduces indication of ECMO for children and adolescents with ARDS or not was also determined.