Relationship between oscillatory volume and oscillatory pressure in neonatal high-frequency oscillatory ventilators: an in vitro study.

OBJECTIVE: We analysed the relationship between oscillatory volume (VOSC) and pressure amplitude (ΔP) in six neonatal high-frequency oscillatory (HFO) ventilators and related it to (1) the accuracy of VOSC and ΔP measurements and (2) the maximal delivered ΔP. DESIGN: In vitro study. SETTING: Neonatal intensive care unit. INTERVENTIONS: Ventilators tested were VN800 (Dräger), Servo-n (Maquet Getinge), SensorMedics 3100A (Vyaire Medical), Fabian HFOi (Vyaire Medical), SLE6000 (SLE UK) and Humming Vue (Metran). We changed various settings and mechanical characteristics of the test lung to mimic preterm and term conditions. MAIN OUTCOME MEASURES: For each condition, we measured VOSC and ΔP. We assessed the accuracy of the VOSC and ΔP measurements versus a reference measurement system using linear regression and Bland-Altman analysis. We evaluated the maximum delivered ΔP at different oscillatory frequencies. RESULTS: We observed large variability between machines in the ΔP displayed at any target VOSC. Most ventilators over-read ΔP with errors up to 30 cmH2O or 60%. The error in the measurement of VOSC was up to ±2 mL or ±30%. We observed high variability in the accuracy of ΔP and VOSC measurements; the SLE6000 committed the lowest errors in ΔP measurements and the Fabian HFOi in VOSC. The maximum delivered ΔP varied depending on the ventilator, being maximal for the Humming Vue, followed by the SLE6000 and SensorMedics 3100A. CONCLUSIONS: The variability in the relationship between VOSC and ΔP among HFO ventilators is largely explained by the variable accuracy in ΔP and VOSC measurement. Different ventilators also exhibit important differences in the maximal generated ΔP.

Performance characteristics of high-frequency percussive ventilation under hyperbaric conditions.

Introduction: Safe administration of critical care hyperbaric medicine requires specialized equipment and advanced training. Equipment must be tested in order to evaluate function in the hyperbaric environment. High-frequency percussive ventilation (HFPV) has been used in intensive care settings effectively, but it has never been tested in a hyperbaric chamber. Methods: Following a modified U.S. Navy testing protocol used to evaluate hyperbaric ventilators, we evaluated an HFPV transport ventilator in a multiplace hyperbaric chamber at 1.0, 1.9, and 2.8 atmospheres absolute (ATA). We used a test lung with analytical software for data collection. The ventilator uses simultaneous cyclic pressure-controlled ventilation at a pulsatile flow rate (PFR)/oscillatory continuous positive airway pressure (oCPAP) ratio of 30/10 with a high-frequency oscillation percussive rate of 500 beats per minute. Inspiratory and expiratory times were maintained at two seconds throughout each breathing cycle. Results: During manned studies, the PFR/oCPAP ratios were 26/6, 22/7, and 22.5/8 at an airway resistance of 20cm H2O/L/second and 18/9, 15.2/8.5, and 13.6/7 at an airway resistance of 50 cm/H2O/L/second at 1, 1.9, and 2.8 ATA. The resulting release volumes were 800, 547, and 513 mL at airway resistance of 20 cm H2O/L/sec and 400, 253, and 180 mL at airway resistance of 50 cm/H2O/L/sec at 1, 1.9, and 2.8 ATA. Unmanned testing showed similar changes. The mean airway pressure (MAP) remained stable throughout all test conditions; theoretically, supporting adequate lung recruitment and gas exchange. A case where HFPV was used to treat a patient for CO poisoning was presented to illustrate that HFPV worked well under HBO2 conditions and no complications occurred during HBO2 treatment. Conclusion: The HFPV transport ventilator performed adequately under hyperbaric conditions and should be considered a viable option for hyperbaric critical care. This ventilator has atypical terminology and produces unique pulmonary physiology, thus requiring specialized training prior to use.

Use of high frequency oscillatory ventilator in neonates with respiratory failure: the clinical practice in Taiwan and early multimodal outcome prediction.

High-frequency oscillatory ventilation (HFOV) can be a rescue for neonates with refractory respiratory failure or an early elective therapy for preterm infants with severe respiratory distress syndrome (RDS). However, little is known about the current evolution and therapeutic limitations of HFOV. We therefore aimed to describe its use in clinical practice and predict the risk of mortality for neonates receiving HFOV. A retrospective observational study of all neonates treated with HFOV in a quaternary referral NICU between January 2007 and December 2016 was conducted. We classified these patients into five subgroups based on primary respiratory diagnoses. We performed the logistic regression and decision tree regression analyses to identify independent factors of 30-day mortality following HFOV. A total of 1125 patients who were ever supported on HFOV were enrolled, of whom 64.1% received HFOV as a rescue therapy, 27.2% received it as an elective therapy, and 8.7% received it for air leak. An average oxygenation index (OI) greater than 25 in the first 24 hours after the initiation of HFOV and patients with secondary pulmonary hypertension were found to have the greatest risk of in-hospital mortality (p < 0.0001). The overall in-hospital mortality rate was 25.8% (290/1125). Decision tree regression analysis revealed that neonates with refractory respiratory failure who had a pre-HFOV OI value higher than 20.5 and OI values higher than 21.5, 23.5 and 34 at 2 hours, 6 hours, and 12 hours after the use of HFOV, respectively, had a significantly increased risk of 30-day mortality. We identified the predictors and cutoff points of OI before and after the initiation of HFOV in neonates with respiratory failure, which can be clinically used as a reference for 30-day mortality. Further efforts are still needed to optimize the outcomes.

Comparison of Endotracheal Reintubation between Nasal High-Frequency Oscillation and Continuous Positive Airway Pressure in Neonates.

OBJECTIVE: This study aimed to compare the endotracheal reintubation between nasal high-frequency oscillation (nHFO) and nasal continuous positive airway pressure (nCPAP) with face mask groups who were followed up for up to 7 days. STUDY DESIGN: We performed a retrospective cohort study of extubated neonates admitted between 2013 and 2017. We used a Cox's proportional hazards model to adjust for significant between-group differences in baseline characteristics. RESULTS: One hundred and ninety-nine neonates were on either nHFO or nCPAP after extubation. The median (interquartile range) gestational age and birth weight were 31 (29, 33) weeks and 1,450 (1,065, 1,908) grams, respectively. From the univariate analysis, gestational age, ventilator modes, mean airway pressure, fraction of inspired oxygen, oxygen index, caffeine therapy, and initial continuous positive airway pressure level were significantly different between the nHFO and nCPAP groups. There was no significant difference in the 7-day reintubation rate of neonates on nHFO compared with nCPAP (hazard ratio: 2.39; 95% confidence interval: 0.97-5.84; p = 0.05). By multivariate analysis, there was no statistically significant difference of reintubation rate between nHFO and nCPAP by Cox's proportional hazards model. CONCLUSION: The nHFO mode with face mask is the choice for noninvasive ventilation to prevent reintubation during the week following extubation.

Current views of complications associated with neonatal ventilation.

Infants born prematurely require external respiratory support device like ventilation for the purpose of life saving. However, these ventilation machines have complications that sometimes unfortunately result in morbidity. New ventilation techniques have been developed to prevent morbidity, but have yet to be fully evaluated. The present review article would discuss current aspects of this life saving gear especially for pediatric patients in clinical setting. Besides basic ventilation apparatus, advancements in the filed like proportional assist ventilation, volume targeted ventilation would be discussed.

Aerosol Delivery During Continuous High Frequency Oscillation for Simulated Adults During Quiet and Distressed Spontaneous Breathing.

BACKGROUND: Continuous high-frequency oscillation (CHFO) is a therapeutic mode for the mobilization of secretions. The Metaneb CHFO device also incorporates aerosol administration using an integrated jet nebulizer. However, the effectiveness of aerosol delivery and influential factors remain largely unreported. METHODS: A collecting filter was placed between an adult manikin with a representative upper airway and a breath simulator, set to simulate quiet and distressed patterns of spontaneous adult breathing. The Metaneb CHFO device was attached to the manikin via a mask. Two jet nebulizers were tested in 2 different positions: placement in the manifold and placement between manifold and mask. A vibrating mesh nebulizer was placed between the manifold and mask with and without extension tubing. Aerosol administration was compared during CHFO and during nebulization mode alone. Albuterol (2.5 mg in 3 mL) was nebulized for each condition. The drug was eluted from the filter and assayed with ultraviolet spectrophotometry (276 nm). RESULTS: During CHFO, inhaled doses with jet nebulizers were low (∼ 2%), regardless of nebulizer placement. Inhaled dose was improved with the vibrating mesh nebulizer placed between the manifold and mask (12.48 ± 2.24% vs 2.58 ± 0.48%, P = .004). Inhaled doses with the jet nebulizer in the manifold with nebulization mode alone was lower than with the jet nebulizer with an aerosol mask (4.03 ± 1.82% vs 10.39 ± 2.79%, P = .004). Inhaled dose was greater with distressed breathing than quiet breathing. The use of a vibrating mesh nebulizer (P < .001) and distressed breathing (P = .001) were identified as predictors of increased inhaled dose. CONCLUSIONS: Inhaled dose with a jet nebulizer via the Metaneb CHFO device was lower than with a jet nebulizer alone. Placement of a vibrating mesh nebulizer at the airway and distressed breathing increased inhaled dose.

Mechanics of nasal mask-delivered HFOV in neonates: A physiologic study.

OBJECTIVES: To clarify if nasal mask influences noninvasive high-frequency oscillatory ventilation (NHFOV) mechanics to optimize the clinical use of nasal mask-delivered NHFOV. WORKING HYPOTHESIS: Nasal mask may affect the mechanical efficacy of NHFOV. METHODOLOGY: We designed a physiologic study composed of an in vitro phase aiming to investigate pressure transmission and volume delivery in a bench model of nasal mask-delivered NHFOV. In a second phase, we measured the leaks in vivo in a series of neonates receiving nasal mask-delivered NHFOV or other forms of noninvasive respiratory support with same nasal masks. RESULTS: In vitro pressure transmission is lower with nasal mask (pressure at the lung [Plung]: 2 [0.8]), than with the endotracheal tube (Plung 9.5 [1.5] cmH2 O; P = 0.007). Same applies for volume delivery (Vol: 0.6 [0.2] vs 1.8 [0.5] mL; P = 0.0001). Increasing ventilatory boundaries slowly affects pressure and volume delivery. Ventilating the model with maximal parameters (∆P = 55 cmH2 O; frequency = 8 Hz) we obtained a Vol 1.5 (0.2) mL. The nasal mask provides lower volume delivery and ventilation, compared with nasal prongs studied in previously published studies. Changing frequency allows a better performance than changing ∆P. In vivo leaks are approximately 30% and are similar during NHFOV or other forms of nasal mask-delivered noninvasive ventilation. CONCLUSIONS: Nasal mask-delivered NHFOV is feasible, but it may require more aggressive ventilatory parameters to increase volume delivery and ventilation. The use of the nasal mask is associated with some leaks, but this is independent from the type of noninvasive respiratory support applied.

The Use of Noninvasive Ventilation with High Frequency in Newborns-A Single-Center Experience.

OBJECTIVE: The aim of the study is to evaluate the efficacy of noninvasive high-frequency ventilation (nHFV) in respiratory-deficient infants. STUDY DESIGN: Retrospective analysis of 32 cases of nHFV in 30 term (n = 4) and preterm (n = 26) newborns using a noninvasive ventilation (NIV) device. nHFV avoided intubation of children performed with NIV and reintubation after long-term mechanical ventilation (MV). Patients were divided into three groups: Group 1: NIV from birth (n = 18, mean birth weight [BW]: 1,987 g, gestational age [GA]: 33.1 weeks); Group 2: MV, also used temporarily, and NIV (n = 10, BW: 1,074 g, GA: 28.2 weeks); and Group 3: two cases with nHFV avoided reintubation after long-term MV (BW: 725 g, GA: 24.5 weeks). RESULTS: From 32 episodes of nHFV application, positive effect was achieved 26 times (81%) (24 of 30 children). All newborns had a significant increase in pH (7.23-7.27) and reduction in partial pressure of CO2 (66.7-58.9 mm Hg, over 1-2 hours). Failures in application of nHFV reported only in Group 1 (6/18, 33%) (failures primarily due to increasing demand for oxygen). There were two reports of pneumothorax in preterm infants with congenital pneumonia. No other nHFV-related complications were noted. CONCLUSION: nHFV is a promising NIV mode which can be also used with NIV devices.

Ambient Noise Production by High-Frequency Neonatal Ventilators.

OBJECTIVE: To assess sound levels of 4 high-frequency neonatal ventilators to determine whether there is a safety benefit in using modern high-frequency ventilators compared with older models. STUDY DESIGN: We performed a bench study comparing noise production of the Sensormedics 3100A Oscillator, Bunnell Life Pulse Jet Ventilators Model 203 and Model 204, and Dräger VN500 in high-frequency mode. A wide range of ventilation settings was examined. All measurements were performed in triplicate using a high-fidelity sound meter, with data analyzed using ANOVA and regression analyses. RESULTS: The Dräger ventilator was quietest overall, with average sound levels of 49.8 ± 0.49 dB across all settings. The average noise from the Sensormedics was 53.6 ± 2.01 dB, for Bunnell Model 203 was 54.1 ± 1.09 dB, and for Bunnell Model 204 was 53.7 ± 1.45 dB. Adjustments made to frequency/rate and mean airway pressure/positive end-expiratory pressure had minimal effect on noise, and increasing amplitude/peak inspiratory pressure resulted in significantly more noise by all ventilators. At all settings, the Sensormedics and Bunnell ventilators were louder than the Dräger, and the difference became greater as amplitude/peak inspiratory pressure was increased. CONCLUSIONS: The Dräger VN500 in high-frequency mode produces significantly less noise that both the Sensormedics and Bunnell ventilators. These data suggest that using the Dräger VN500 as a high-frequency ventilator may reduce the potential for adverse outcomes created by ventilator noise.

Imposed Work of Breathing During High-Frequency Oscillatory Ventilation in Spontaneously Breathing Neonatal and Pediatric Models.

BACKGROUND: High-frequency oscillatory ventilation (HFOV) is used in cases of neonatal and pediatric acute respiratory failure, sometimes even as the primary ventilatory mode. Allowing patients (at least neonates) on HFOV to breathe spontaneously soon after intubation has been shown to be feasible, and this is becoming a more generally used approach for infants and small children. However, such an approach may increase the imposed work of breathing (WOB), raising the question of whether the imposed WOB varies with the use of newer-generation HFOV devices, which operate according to different functional principles. METHODS: A bench test was designed to compare the pressure-time product (PTP), a surrogate marker of the imposed WOB, produced with the use of 7 HFOV devices. Scenarios corresponding to various age groups (preterm newborn [1 kg], term newborn [3.5 kg], infant [10 kg], and child [25 kg]) and 2 respiratory system conditions (physiologic and pathologic) were tested. RESULTS: The PTP varied between devices and increased with the oscillation frequency for all devices, independent of the respiratory system condition. Furthermore, the PTP increased with age and was higher for physiologic than for pathologic respiratory system conditions. We considered a change of ≥ 20% as being of clinically relevant; the effect of oscillation frequency was the most important parameter influencing imposed WOB during spontaneous breathing. CONCLUSIONS: Variations in imposed WOB, as expressed by PTP values, during spontaneous breathing depend mainly on the oscillator frequency, respiratory system condition, and, though to a lesser extent, on the device itself.

The Use of High-Frequency Percussive Ventilation for Whole-Lung Lavage: A Case Report.

Whole-lung lavage (WLL) remains the gold standard in the treatment of pulmonary alveolar proteinosis. However, anesthetic management during WLL can be challenging because of the risk of intraoperative hypoxemia and various cardiorespiratory complications of 1-lung ventilation. Here, we describe a novel strategy involving the application of high-frequency percussive ventilation using a volumetric diffusive respirator (VDR-4) during WLL in a 47-year-old woman with pulmonary alveolar proteinosis. Our observations suggest that high-frequency percussive ventilation is a potentially effective ventilation strategy during WLL that may reduce the risk of hypoxemia and facilitate lavage.

High-Frequency Airway Oscillating Device for Respiratory Muscle Training in Subjects With COPD.

BACKGROUND: COPD is characterized by expiratory flow limitation, which results in symptomatic dyspnea and reduced exercise capacity. Changes in breathing mechanics mean the respiratory muscles are unable to respond to the ventilatory demands, increasing the sensation of dyspnea. A high-frequency oscillating device has been developed to improve dyspnea in patients with COPD. We conducted a feasibility trial to gain insight into the potential for recruitment, retention, and study design for a future randomized controlled trial. METHODS: Symptomatic subjects with COPD were included on the basis of a Medical Research Council (MRC) score ≥ 3 and FEV1/FVC < 0.70). Patients were excluded if they received pulmonary rehabilitation within the last 6 months. The intervention employed the device for 8 weeks, 3 times daily. Clinical outcomes included the MRC score, maximal expiratory and inspiratory pressures (PEmax/PImax), the incremental shuttle walk test (ISWT), and the endurance shuttle walk test (ESWT). RESULTS: We successfully recruited 23 subjects with established COPD (65.2% male, mean age 65 ± 5.03 y, mean % predicted FEV1 43.9 ± 16, mean FEV1/FVC ratio 0.46 ± 0.13, and median [interquartile range] MRC 4 [3-5]). There was a significant change in MRC from 4 to 3 pre to post intervention (P = .003). There was a statistically significant difference in PEmaxP < .008 and PImaxP = .044. There were no significant differences observed in the ISWT or ESWT. CONCLUSIONS: This study design appeared feasible to proceed to a clinical effectiveness trial. The use of the device for 8 weeks showed a significant improvement in PEmax, PImax, and reduced symptomatic dyspnea on the MRC dyspnea score. The results of this study should encourage a randomized controlled trial.

The value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure.

OBJECTIVE: To investigate the value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure. METHODS: A single-center, prospective, randomized, controlled pilot trial was conducted between January 2013 and December 2014. Sixty enrolled patients were randomized immediately after extubation into either a high-flow nasal cannula group (n=30) or an air entrainment mask group (n=30) at a fixed inspired oxygen fraction (40%). The success rate of oxygen therapy, respiratory and hemodynamic parameters and subjective discomfort (using a visual analogue scale) were assessed at 24h after extubation. RESULTS: The two groups were comparable at extubation. A total of 46 patients were successfully treated including 27 patients in the high-flow nasal cannula group and 19 patients in the air entrainment mask group. Compared to the air entrainment mask group, the success rate of oxygen therapy and the partial pressure of arterial oxygen were significantly higher and the respiratory rate was lower in the high-flow nasal cannula group. In addition, less discomfort related to interface displacement and airway dryness was observed in the high-flow nasal cannula group than in the air entrainment mask group. CONCLUSIONS: At a fixed inspired oxygen fraction, the application of a high-flow nasal cannula after extubation achieves a higher success rate of oxygen therapy and less discomfort at 24h than an air entrainment mask in patients with acute respiratory failure.

The value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure

OBJECTIVE: To investigate the value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure. METHODS: A single-center, prospective, randomized, controlled pilot trial was conducted between January 2013 and December 2014. Sixty enrolled patients were randomized immediately after extubation into either a high-flow nasal cannula group (n=30) or an air entrainment mask group (n=30) at a fixed inspired oxygen fraction (40%). The success rate of oxygen therapy, respiratory and hemodynamic parameters and subjective discomfort (using a visual analogue scale) were assessed at 24h after extubation. RESULTS: The two groups were comparable at extubation. A total of 46 patients were successfully treated including 27 patients in the high-flow nasal cannula group and 19 patients in the air entrainment mask group. Compared to the air entrainment mask group, the success rate of oxygen therapy and the partial pressure of arterial oxygen were significantly higher and the respiratory rate was lower in the high-flow nasal cannula group. In addition, less discomfort related to interface displacement and airway dryness was observed in the high-flow nasal cannula group than in the air entrainment mask group. CONCLUSIONS: At a fixed inspired oxygen fraction, the application of a high-flow nasal cannula after extubation achieves a higher success rate of oxygen therapy and less discomfort at 24h than an air entrainment mask in patients with acute respiratory failure.

Volume and Pressure Delivery During Pediatric High-Frequency Oscillatory Ventilation.

OBJECTIVE: Identify variables independently associated with delivered tidal volume (VT) and measured mean airway pressure during high-frequency oscillatory ventilation across the range of pediatric endotracheal tube sizes. DESIGN: In vitro study. SETTING: Research laboratory. INTERVENTIONS: An in vitro bench model of the intubated pediatric respiratory system during high-frequency oscillatory ventilation was used to obtain delivered VT and mean airway pressure (in the distal lung) for various endotracheal tube sizes. Measurements were taken at different combinations of ventilator set mean airway pressure (Paw), amplitude (ΔP), frequency, and test lung compliance. Multiple regression analysis was used to construct multivariable models predicting delivered VT and mean airway pressure. MEASUREMENTS AND MAIN RESULTS: Variables independently associated with higher delivered VT for all endotracheal tube sizes include higher ΔP (p < 0.001), lower frequency (p < 0.001), and higher test lung compliance (p < 0.001). A multiplicative interaction between frequency and ΔP magnifies the delivered VT when ΔP is high and frequency is low (p < 0.001). Delivered mean airway pressure becomes lower than set Paw as ΔP increases (p < 0.001) and frequency increases (p < 0.05). Ventilator set Paw is the largest determinant of delivered mean airway pressure; however, increasing ΔP resulted in a lower delivered mean airway pressure. For example, in a 4.0 mm ID endotracheal tube, increasing ΔP by 10 cm H2O resulted in an average decrease of delivered mean airway pressure by 4.5%. CONCLUSIONS: This is the first study to quantify the interaction between ΔP and frequency in delivered VT and the effect of ΔP and frequency on delivered mean airway pressure. These results demonstrate the need to measure or estimate VT and delivered pressures during high-frequency oscillatory ventilation and may be useful in determining optimal strategies for lung protective ventilation during high-frequency oscillatory ventilation.

Optimizing care of ventilated infants by improving weighing accuracy on incubator scales.

OBJECTIVES: To determine the accuracy of weighing ventilated infants on incubator scales and whether the accuracy can be improved by the addition of a ventilator tube compensator (VTC) device to counterbalance the force exerted by the ventilator tubing. STUDY DESIGN: Body weights on integral incubator scales were compared in ventilated infants (with and without a VTC), with body weights on standalone electronic scales (true weight). Individual and series of trend weights were obtained on the infants. The method of Bland and Altman was used to assess the introduced bias. RESULTS: The study included 60 ventilated infants; 66% of them weighed <1000 g. A total of 102 paired-weight datasets for 30 infants undergoing conventional ventilation and 30 undergoing high frequency oscillator ventilation (HFOV) supported by a SensorMedics oscillator, (with and without a VTC) were obtained. The mean differences and (95% CI for the bias) between the integral and true scale weighing methods was 60.8 g (49.1 g to 72.5 g) without and -2.8 g (-8.9 g to 3.3 g) with a VTC in HFOV infants; 41.0 g (32.1 g to 50.0 g) without and -5.1 g (-9.3 g to -0.8 g) with a VTC for conventionally ventilated infants. Differences of greater than 2% were considered clinically relevant and occurred in 93.8% without and 20.8% with a VTC in HFOV infants and 81.5% without and 27.8% with VTC in conventionally ventilated infants. CONCLUSIONS: The use of the VTC device represents a substantial improvement on the current practice for weighing ventilated infants, particularly in the extreme preterm infants where an over- or underestimated weight can have important clinical implications for treatment. A large-scale clinical trial to validate these findings is needed.

Active cycle of breathing technique for cystic fibrosis.

BACKGROUND: People with cystic fibrosis experience chronic airway infections as a result of mucus build up within the lungs. Repeated infections often cause lung damage and disease. Airway clearance therapies aim to improve mucus clearance, increase sputum production, and improve airway function. The active cycle of breathing technique (also known as ACBT) is an airway clearance method that uses a cycle of techniques to loosen airway secretions including breathing control, thoracic expansion exercises, and the forced expiration technique. This is an update of a previously published review. OBJECTIVES: To compare the clinical effectiveness of the active cycle of breathing technique with other airway clearance therapies in cystic fibrosis. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews.Date of last search: 25 April 2016. SELECTION CRITERIA: Randomised or quasi-randomised controlled clinical studies, including cross-over studies, comparing the active cycle of breathing technique with other airway clearance therapies in cystic fibrosis. DATA COLLECTION AND ANALYSIS: Two review authors independently screened each article, abstracted data and assessed the risk of bias of each study. MAIN RESULTS: Our search identified 62 studies, of which 19 (440 participants) met the inclusion criteria. Five randomised controlled studies (192 participants) were included in the meta-analysis; three were of cross-over design. The 14 remaining studies were cross-over studies with inadequate reports for complete assessment. The study size ranged from seven to 65 participants. The age of the participants ranged from six to 63 years (mean age 22.33 years). In 13 studies, follow up lasted a single day. However, there were two long-term randomised controlled studies with follow up of one to three years. Most of the studies did not report on key quality items, and therefore, have an unclear risk of bias in terms of random sequence generation, allocation concealment, and outcome assessor blinding. Due to the nature of the intervention, none of the studies blinded participants or the personnel applying the interventions. However, most of the studies reported on all planned outcomes, had adequate follow up, assessed compliance, and used an intention-to-treat analysis.Included studies compared the active cycle of breathing technique with autogenic drainage, airway oscillating devices, high frequency chest compression devices, conventional chest physiotherapy, and positive expiratory pressure. Preference of technique varied: more participants preferred autogenic drainage over the active cycle of breathing technique; more preferred the active cycle of breathing technique over airway oscillating devices; and more were comfortable with the active cycle of breathing technique versus high frequency chest compression. No significant difference was seen in quality of life, sputum weight, exercise tolerance, lung function, or oxygen saturation between the active cycle of breathing technique and autogenic drainage or between the active cycle of breathing technique and airway oscillating devices. There was no significant difference in lung function and the number of pulmonary exacerbations between the active cycle of breathing technique alone or in conjunction with conventional chest physiotherapy. All other outcomes were either not measured or had insufficient data for analysis. AUTHORS' CONCLUSIONS: There is insufficient evidence to support or reject the use of the active cycle of breathing technique over any other airway clearance therapy. Five studies, with data from eight different comparators, found that the active cycle of breathing technique was comparable with other therapies in outcomes such as participant preference, quality of life, exercise tolerance, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of the active cycle of breathing technique on outcomes important for people with cystic fibrosis such as quality of life and preference.

Effect of High-Frequency Oscillations on Cough Peak Flows Generated by Mechanical In-Exsufflation in Medically Stable Subjects With Amyotrophic Lateral Sclerosis.

BACKGROUND: Mechanically assisted coughing with mechanical in-exsufflation (MI-E) is recommended for noninvasive management of respiratory secretions in amyotrophic lateral sclerosis (ALS). To improve the effectiveness of the technique, a new device combining MI-E with high-frequency oscillations (HFO) has been developed. This work aimed to assess the effect of HFO on the cough peak flow generated by MI-E in medically stable subjects with ALS. METHODS: This was a prospective study that included subjects with ALS in a medically stable condition. Cough peak flow generated by MI-E was measured in 4 situations: without HFO, with HFO during insufflation, with HFO during exsufflation, and with HFO in both cycles. The parameters used were: insufflation pressure of +40 cm H2O, exsufflation pressure of -40 cm H2O, insufflation time 2 s, exsufflation time 3 s, amplitude of oscillations 10 cm H2O, and frequency of oscillations 15 Hz. RESULTS: Forty-seven subjects with ALS were included: 66% males, 68.2 ± 9.2 y, 40% with bulbar onset, FVC = 1.7 ± 1.1 L, percent-of-predicted FVC = 54.4 ± 26.6%, cough peak flow = 3.8 ± 2.2 L/s, PImax = -39.4 ± 26.4 cm H2O, revised ALS scale = 28.5 ± 9.3, Norris bulbar subscore = 26.1 ± 10.4. No statistical differences were found in cough peak flow generated by MI-E in the 4 situations (without HFO = 4.0 ± 1.2 L/s, with insufflation HFO = 3.9 ± 1.2 L/s, with exsufflation HFO = 4.1 ± 1.2 L/s, with in-exsufflation HFO = 3.9 ± 1.1 L/s). CONCLUSIONS: The addition of HFO to mechanically assisted coughing with MI-E does not have an effect on the cough peak flow of medically stable subjects with ALS.

A noninvasive high frequency oscillation ventilator: Achieved by utilizing a blower and a valve.

After the High Frequency Oscillatory Ventilation (HFOV) has been applied in the invasive ventilator, the new technique of noninvasive High Frequency Oscillatory Ventilation (nHFOV) which does not require opening the patient's airway has attracted much attention from the field. This paper proposes the design of an experimental positive pressure-controlled nHFOV ventilator which utilizes a blower and a special valve and has three ventilation modes: spontaneous controlled ventilation combining HFOV, time-cycled ventilation combining HFOV (T-HFOV), and continuous positive airway pressure ventilation combining HFOV. Experiments on respiratory model are conducted and demonstrated the feasibility of using nHFOV through the control of fan and valve. The experimental ventilator is able to produce an air flow with small tidal volume (VT) and a large minute ventilation volume (MV) using regular breath tubes and nasal mask (e.g., under T-HFOV mode, with a maximum tidal volume of 100 ml, the minute ventilation volume reached 14,400 ml). In the process of transmission, there is only a minor loss of oscillation pressure. (Under experimental condition and with an oscillation frequency of 2-10 Hz, peak pressure loss was around 0%-50% when it reaches the mask.).