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.

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.

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.

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.

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.

Corrective measures for compromised oxygen delivery during endotracheal tube cuff deflation with high-frequency percussive ventilation.

OBJECTIVE: To determine the effect of endotracheal-tube cuff deflation on airflow and F(IO2) during high-frequency percussive ventilation (HFPV), and explore methods of correcting the cuff-deflation-associated decrease in mean airway pressure and F(IO2) at the carina. METHODS: Using a mechanical lung model in our respiratory research laboratory, we measured circuit pressure near the connection to the endotracheal tube (P(vent)), mean airway pressure (P(aw)), pulsatile tidal volume (V(T)), and F(IO2) at the artificial carina. During cuff deflation we manipulated the pulsatile frequency, pulsatile flow, and the HFPV integral nebulizer. We then assessed 4 methods of correcting the decreased F(IO2) and airway pressure during cuff deflation: (1) oxygen delivery at the inspiratory fail-safe valve, (2) oxygen delivery at the T-piece between the HFPV and the endotracheal tube, (3) continuous activation of the HFPV's integral nebulizer, and (4) oxygen insufflation into the suction channel of the endotracheal tube. RESULTS: Cuff deflation reduced P(vent), P(aw), pulsatile V(T), and F(IO2). Increasing the pulsatile flow and decreasing the pulsatile frequency further reduced F(IO2) during cuff deflation. Injecting supplemental oxygen at the inspiratory fail-safe valve provided the best F(IO2) increase. Injecting oxygen at the T-piece provided the second best F(IO2) increase. Continuous activation of the integral nebulizer provided the third best F(IO2) increase. Oxygen insufflation to the suction channel was least effective in correcting the F(IO2) decrease caused by cuff deflation. CONCLUSION: Cuff-deflation-associated F(IO2), P(aw), and pulsatile V(T) compromise can be partially corrected by any of the 4 methods we studied. Injecting supplemental oxygen at the inspiratory fail-safe valve is the most effective method.

[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.

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).

High frequency ventilation--the relationship between ventilator design and clinical strategy in the treatment of hyaline membrane disease and its complications: a brief review.

Progress in the application of techniques of HFV to clinical settings has been hampered by a lack of comparative data. Ventilator design and/or strategy place clear limitations on the effective and safe use of these devices. There is a definite need to develop clear therapeutic goals for HFV, to define the operating characteristics and limitations of each device, and to develop effective and safe strategies for their use in various clinical settings. Only then can adequate controlled clinical trials be performed and the role of these techniques be firmly established.

Accuracy of the volume and pressure displays of high frequency oscillators.

OBJECTIVE: To determine the effect of frequency on the accuracy of volume and pressure displays of high frequency oscillators. METHODS: The effect of frequency on the displayed volume of the Stephanie, Dräger Babylog 8000 Plus, and SLE 5000 oscillators was assessed. A sine wave pump delivered a constant tidal volume at frequencies of 5-15 Hz to the patient manifold of the oscillators. The displayed volumes at each frequency were compared with the delivered volume. The effect of frequency on displayed pressure was assessed by connecting the oscillator's patient manifold to a lung model; three types of oscillator were studied (SensorMedics 3100A, SLE 5000, and Stephanie). Airway pressure was measured from the manifold using a pressure transducer and non-compliant tubing; the pressure measuring system had a flat frequency response to 30 Hz. RESULTS: The SLE 5000 volume display overread the delivered volume (by about 5%), but was not affected by frequency. At 5 Hz, the Dräger Babylog 8000 Plus and the Stephanie underread the delivered volume (by about 20%). Increasing frequency resulted in a greater discrepancy between the delivered and displayed volume with the Stephanie, but a smaller discrepancy with the Dräger Babylog 8000 Plus. Altering frequency had a small effect (maximum difference 6%) on the relation between the displayed and delivered pressure for all three oscillators. CONCLUSION: Frequency affects the accuracy of displayed volumes and, to a lesser extent, displayed pressures of high frequency oscillators. The results emphasise that data displayed by new devices should not be uncritically accepted.

Alternative modes of ventilation in the prevention and treatment of bronchopulmonary dysplasia.

Recent technologic innovations and refinements have increased and enhanced the armamentarium that potentially can prevent or ameliorate bronchopulmonary dysplasia. Short of altering the most important factor in the development of BPD--premature delivery--these new tools should allow individualization of ventilator treatment plans with a degree of sophistication not previously possible. By so doing, these techniques may shorten the often prolonged and uncertain course of recovery from BPD, and by so doing, limit the ongoing injury associated with BPD. The results of studies designed to test the utility of this new technology in the management of BPD are eagerly awaited.

High-frequency ventilation: issues of strategy.

Although each high-frequency ventilator has functional characteristics that are design related, it now appears that when used with similar treatment strategies and within their functional limitations, similar clinical outcomes can be realized. Optimized treatment protocols must vary depending on the pulmonary disease to be treated, with strategies during treatment for pulmonary injury different from those used in pulmonary injury prevention. It is still unclear whether any one particular high-frequency ventilator will have specific disadvantages that cannot be overcome by device modification and that are inherent in a particular HFV methodology. Experimental and clinical data suggest that HFV will contribute significantly in reducing neonatal pulmonary morbidity and aid in the prevention of chronic pulmonary disease.

Comparison of high-frequency flow interruption ventilation and hyperventilation in persistent pulmonary hypertension of the newborn.

INTRODUCTION: Because of the high mortality, potential limitations, and inherent adverse effects associated with conventional therapies, as well as extracorporeal membrane oxygenation, for persistent pulmonary hypertension of the newborn (PPHN), alternative modes of ventilatory support have been researched. There is anecdotal evidence that high-frequency flow interruption ventilation (HFFI) benefits neonates with severe air leak and lung diseases unresponsive to conventional ventilation, so we conducted a study to compare the hospital course, survival rate, and incidence of chronic lung disease of neonates with PPHN treated with hyperventilation (HV) and HFFI. METHODS: Enrolled in the study were 36 neonates who (1) were treated with HV and a fraction of inspired oxygen of 1.0 for PPHN, (2) had arterial partial pressure of oxygen (P(aO2)) values or= 120 mm Hg; (3) shorter mean time to P(aO2) >or= 120 mm Hg (13.5 vs 50.2 h, p = 0.001); (4) shorter mean time to reduced fraction of inspired oxygen (16 vs 84 h, p < 0.001); (5) shorter mean time to fraction of inspired oxygen 0.70 (53 vs 187 h, p < 0.001); (6) shorter mean time to extubation (8.1 vs 18.7 d, p = 0.033); (7) shorter length of hospitalization (22.7 vs 50.6 d, p = 0.025); and (8) fewer neonates with chronic lung disease (1 vs 5, p = 0.018). CONCLUSIONS: HFFI with the ventilation strategy we describe accomplishes sustained hyperoxygenation without hypocarbia and alkalosis, and response to HFFI can predict outcomes. HFFI does not significantly reduce mortality, but it does reduce the length of mechanical ventilation, the length of hospitalization, and the incidence of chronic lung disease in neonates with PPHN. The nonrandomized design of our study precludes firm conclusions about the potential benefits of HFFI. The results may be biased by practice variations. Additional randomized controlled trials are warranted to determine the efficacy of HFFI in neonates with PPHN.

New methods advance treatment for respiratory distress syndrome.

The past 20 years of hard labor in neonatal respiratory distress have resulted in several important advances arising from our understanding of lung chemistry and physiology. Our knowledge of surfactant chemistry has enabled us to identify infants at high risk for developing neonatal distress due to surfactant deficiency, reducing this risk with antenatal corticosteroid treatment, and improving the neonatal outcome by means of administration of effective surfactant replacement. Recognition of the roles of oxygen toxicity and barotrauma in promoting lung injury has premitted the development of more effective means of assisted ventilation less likely to injure the lungs of severely ill infants with pulmonary failure. Nitric oxide has proven to be an effective pulmonary vasodilator and permits the successful treatment of patients with pulmonary hypertension who might previously have required an invasive surgical treatment to achieve a desirable clinical outcome.

AANA Journal course: new technologies in anesthesia: update for nurse anesthetists--high frequency ventilation.

The introduction of high frequency ventilation (HFV) to the clinical arena has offered patients with severe respiratory disease a method for adequate ventilation and oxygenation with improved hemodynamics and diminished lung barotrauma. The scientific community has been investigating for a number of years the mechanism of gas transport in the airways using high frequencies with tidal volumes approaching or less than anatomical dead space. Clinicians have been attempting to identify the clinical circumstances for which this new technology can be applied. This course will discuss some of these theoretical mechanisms responsible for gas transport during three types of HFV, and also present the high frequency ventilators which have been recently approved by the U.S. Food and Drug Administration and the clinical indications for use for each of them.