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.

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.

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.

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.

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.

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.

Pressure and flow waveform characteristics of eight high-frequency oscillators.

OBJECTIVES: The differences in performance of early generation high-frequency oscillators have been attributed to their distinct pressure and flow waveforms. Recently, five new oscillators have been commercially released. The objective of this study was to characterize the pressure and flow waveforms of eight commercially available oscillators. DESIGN: In vitro benchtop study. SETTING: Tertiary pediatric teaching hospital. INTERVENTIONS: Eight oscillators were evaluated using a test lung; mean airway pressure 10 and 20 cm H2O; frequencies 5, 10, and 15 Hz; pressure amplitude 30 cm H2O (or equivalent); compliance 1.0 mL/cm H2O; and endotracheal tube 3.5 mm. Ventilators tested were Sensormedics 3100A and B (Carefusion), SLE5000 (SLE), Fabian (Acutronic), Leonie+ (Heinen+Löwenstein), Sophie (Stephan), and VN500 and Babylog 8000 (Dräger). MEASUREMENTS AND MAIN RESULTS: Pressure (airway opening, at oscillator and within the test lung) and airway opening flow waveforms were recorded. Airway opening waveforms were characterized by type (square or sine) and by determining power spectral density analysis. The Sensormedics A and B and the SLE5000 delivered square waves; all other oscillators generated sine waves. Sensormedics, the SLE5000, and the Sophie had a characteristic inspiratory slope (incisura). The pressure waveform within the test lung was a sine wave for all oscillators. Oscillators with square waves or an inspiratory incisura exhibited the highest number of nonfundamental frequency components on power spectral density analysis, suggesting more complex harmonic waveforms with potentially greater transmissive power to the lungs. At frequencies of 5 and 10 Hz, all ventilators, except Babylog 8000, generated airway pressure amplitudes greater than 28.6 cm H2O and tidal volumes greater than 6 mL at the airway opening. CONCLUSIONS: Current high-frequency oscillators deliver different waveforms. As these may result in variable clinical performance, operators should be aware that these differences exist.

Mean lung pressure during adult high-frequency oscillatory ventilation: an experimental study using a lung model.

In adult high-frequency oscillatory ventilation (HFOV), stroke volume (SV) and mean lung pressure (PLung) are important for lung protection. We measured the airway pressure at the Y-piece and the lung pressure during HFOV using a lung model and HFOV ventilators for adults (R100 and 3100B). The lung model was made of a 20-liter, airtight rigid plastic container (adiabatic compliance: 19.3 ml/cmH2O) with or without a resistor (20 cmH2O/l/sec). The ventilator settings were as follows: mean airway pressure (MAP), 30 cmH2O; frequency, 5-15 Hz (every 1 Hz); airway pressure amplitude (AMP), maximum;and % of inspiratory time (IT), 50% for R100, 33% or 50% for 3100B. The measurements were also performed with an AMP of 2/3 or 1/3 maximum at 5, 10 and 15 Hz. The PLung and the measured MAP were not consistently identical to the setting MAP in either ventilator, and decreasing IT decreased the PLung in 3100B. In conclusion, we must pay attention to the possible discrepancy between the PLung and the setting MAP during adult HFOV.

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.

Intermittent recruitment with high-frequency oscillation/tracheal gas insufflation in acute respiratory distress syndrome.

In acute respiratory distress syndrome (ARDS), recruitment sessions of high-frequency oscillation (HFO) and tracheal gas insufflation (TGI) with short-lasting recruitment manoeuvres (RMs) may improve oxygenation and enable reduction of subsequent conventional mechanical ventilation (CMV) pressures. We determined the effect of adding HFO-TGI sessions to lung-protective CMV on early/severe ARDS outcome. We conducted a prospective clinical trial, subdivided into a first single-centre period and a second two-centre period. We enrolled 125 (first period, n = 54) patients with arterial oxygen tension (P(a,O(2)))/inspiratory oxygen fraction (F(I,O(2))) of <150 mmHg for >12 consecutive hours at an end-expiratory pressure of ≥ 8 cmH(2)O. Patients were randomly assigned to an HFO-TGI group (receiving HFO-TGI sessions with RMs, interspersed with lung-protective CMV; n = 61) or CMV group (receiving lung-protective CMV and RMs; n = 64). The primary outcome was survival to hospital discharge. Pre-enrolment ventilation duration was variable. During days 1-10 post-randomisation, P(a,O(2))/F(I,O(2))), oxygenation index, plateau pressure and respiratory compliance were improved in the HFO-TGI group versus the CMV group (p < 0.001 for group × time). Within days 1-60, the HFO-TGI group had more ventilator-free days versus the CMV group (median (interquartile range) 31.0 (0.0-42.0) versus 0.0 (0.0-23.0) days; p < 0.001), and more days without respiratory, circulatory, renal, coagulation and liver failure (p ≤ 0.003). Survival to hospital discharge was higher in the HFO-TGI group versus the CMV group (38 (62.3%) out of 61 versus 23 (35.9%) out of 64 subjects; p = 0.004). Intermittent recruitment with HFO-TGI and RMs may improve survival in early/severe ARDS.

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 (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. OBJECTIVES: To compare the clinical effectiveness of ACBT 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: 02 August 2012. SELECTION CRITERIA: Randomised or quasi-randomised controlled clinical studies, including cross-over studies, comparing ACBT 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: Sixty studies were identified of which 18 (375 participants) met the inclusion criteria. Five randomised controlled studies (127 participants) were included in the meta-analysis; four were of cross-over design. The 13 remaining studies were cross-over studies with inadequate reports for complete assessment.Included studies compared ACBT to autogenic drainage, airway oscillating devices, high frequency chest compression devices, conventional chest physiotherapy, and positive expiratory pressure. Patient preference varied: more patients preferred autogenic drainage over ACBT; more preferred ACBT over airway oscillating devices; and more were comfortable with ACBT versus high frequency chest compression. No significant difference was seen in sputum weight, lung function, or oxygen saturation between ACBT and autogenic drainage or between ACBT and airway oscillating devices. There was no significant difference in lung function and the number of pulmonary exacerbations between ACBT and ACBT plus 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 ACBT over any other airway clearance therapy. Five studies, with five different comparators, found that ACBT was comparable to other therapies in outcomes such as patient preference, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of ACBT on outcomes important for patients such as quality of life and patient preference.

Intrapulmonary effects of setting parameters in portable intrapulmonary percussive ventilation devices.

BACKGROUND: Despite potential benefits of intrapulmonary percussive ventilation (IPV) in various respiratory diseases, the impact of setting parameters on the mechanical effects produced by IPV in the lungs is unknown. We hypothesized that changing the parameters on IPV would modulate these effects. This in vitro study aimed at comparing the changes in intrapulmonary effects resulting from changes in parameters in 3 portable IPV devices (IMP2, Impulsator, and Pegaso). METHODS: Parameters were set in 72 combinations of frequency (90-250 cycles/min), inspiratory to expiratory (I/E) time ratio (from 1/2 to 3/1), and pressure (10-60 cm H(2)O). Four resulting effects were recorded on a test lung via a pneumotachometer: the expiratory to inspiratory flow ratio (E/I flow ratio), the PEEP, the ventilation, and the percussion. Percussion was assessed by the end-slope of the pressure curve. Analysis of variance was used for data analysis. RESULTS: E/I flow ratio increased with increasing I/E time ratio (P < .001). The Pegaso produced the lowest E/I flow ratio. PEEP raised 6 cm H(2)O in both IMP2 and Impulsator, and 17 cm H(2)O in the Pegaso with increasing frequency (P < .01), pressure, and I/E time ratio (P < .001). In all devices, ventilation increased with increasing pressure and decreasing frequency (P < .001). Percussion increased with increasing frequency and decreasing I/E time ratio (P < .001), and with increasing pressure when I/E time ratio was 1/1 or less. The Pegaso provided the poorest percussion. CONCLUSIONS: This study suggests that changing the parameters considerably modulates the mechanical effects produced by portable IPV devices in the lungs. Increasing frequency increased PEEP and percussion, but decreased ventilation. Increasing I/E time increased PEEP and E/I flow ratio, and decreased percussion. Finally, increasing pressure increased PEEP and ventilation. The Pegaso produced the highest PEEP, least percussion, and smallest change in E/I flow ratio.

Modification of a high frequency oscillator circuit with a heated expiratory filter to prevent infectious pathogen transmission: a bench study.

BACKGROUND: High frequency oscillation is a safe and effective treatment for patients with ARDS, but poses a patient and caregiver risk when the circuit is disconnected. We modified the circuit to include a heated expiratory filter, eliminating the need for daily filter changes due to buildup of condensate. The purpose of the study was to determine if substitution of the filter resulted in a clinically important change in delivered tidal volume or amplitude. We additionally compared expiratory resistance and measured efficacy for the substituted filter. METHODS: This bench study measured tidal volume and amplitude using 5 of each filter type across 6 patient setting scenarios. Filter efficacy was tested through an independent laboratory, and expiratory resistance measurements were taken after prolonged use with humidification. RESULTS: The clinically important threshold value for tidal volume (defined as 5% difference) was excluded by the limits of agreement, confirming that use of the modified circuit does not result in alterations in tidal volume. The clinically important threshold for amplitude (defined as 10% difference) was the same as the lower confidence interval on the lower limit of agreement, indicating it is possible for amplitude values to be different between the 2 filters. Filter efficacy for the substituted filter was not affected. Expiratory resistance was unchanged in the substituted filter, but nearly doubled for the manufacturer's filter after 48 hours. CONCLUSIONS: Modifying the circuit to include a heated expiratory filter does not affect tidal volume, and the filter material remains efficacious during oscillation. Amplitude varies under some conditions. Preventing the need for daily filter changes reduces the risk of alveolar de-recruitment. This does not completely eliminate exposure to expired gases, but provides an additional layer of protection against occupational exposure and nosocomial spread of respiratory pathogens. Further testing in a clinical environment is necessary.

Humidification of base flow gas during adult high-frequency oscillatory ventilation: an experimental study using a lung model.

In adult high-frequency oscillatory ventilation (HFOV) with an R100 artificial ventilator, exhaled gas from patient's lung may warm the temperature probe and thereby disturb the humidification of base flow (BF) gas. We measured the humidity of BF gas during HFOV with frequencies of 6, 8 and 10 Hz, maximum stroke volumes (SV) of 285, 205, and 160 ml at the respective frequencies, and, BFs of 20, 30, 40 l/min using an original lung model. The R100 device was equipped with a heated humidifier, Hummax Ⅱ, consisting of a porous hollow fiber in circuit. A 50-cm length of circuit was added between temperature probe (located at 50 cm proximal from Y-piece) and the hollow fiber. The lung model was made of a plastic container and a circuit equipped with another Hummax Ⅱ. The lung model temperature was controlled at 37℃. The Hummax Ⅱ of the R100 was inactivated in study-1 and was set at 35℃ or 37℃ in study-2. The humidity was measured at the distal end of the added circuit in study-1 and at the proximal end in study-2. In study-1, humidity was detected at 6 Hz (SV 285 ml) and BF 20 l/min, indicating the direct reach of the exhaled gas from the lung model to the temperature probe. In study-2 the absolute humidity of the BF gas decreased by increasing SV and by increasing BF and it was low with setting of 35℃. In this study setting, increasing the SV induced significant reduction of humidification of the BF gas during HFOV with R100.

In vitro performance comparison of the Sensormedics 3100A and B high-frequency oscillatory ventilators.

OBJECTIVE: The Sensormedics 3100A and 3100B are widely used to provide high-frequency oscillatory ventilation in clinical practice. Infants and children <35 kg are typically oscillated with the 3100A and >35 kg with the 3100B. This study compares the effect of ventilator and patient parameters on delivered tidal volume during high-frequency oscillatory ventilation of a test lung with these devices. DESIGN: Laboratory-based study. SUBJECTS: Test lung and Sensormedics 3100A and 3100B high-frequency oscillators. INTERVENTIONS: A previously validated hot-wire flowmeter (Florian) was placed in series with either a 3100A (n = 3) or 3100B (n = 3) ventilator and a Michigan test lung. Tidal volumes were measured over a range of mean airway pressure, inspiratory:expiratory ratio, frequency, pressure amplitude, and endotracheal tube internal diameter. MEASUREMENTS AND MAIN RESULTS: The 3100A and 3100B delivered similar tidal volumes across a range of ventilator parameters for an inspiratory:expiratory ratio of 1:1, differing by <10%. However, at an inspiratory:expiratory ratio of 1:2, there was a statistically significant decrease in tidal volume for the 3100B compared with the 3100A at lower frequencies, which was partially mitigated by increasing pressure amplitude. The difference in the generated pressure and flow waveforms may account for the observed tidal volume differences between the high-frequency oscillatory ventilation models. Delivered tidal volume was highly dependent on endotracheal tube size. CONCLUSIONS: Multiple variables contribute to the delivered tidal volume during high-frequency oscillatory ventilation, including ventilator model selection and endotracheal tube size. It is possible that real-time, clinical monitoring of delivered tidal volume during high-frequency oscillatory ventilation would allow better titration and maximize performance of these ventilators in caring for critically ill patients.

Comparison of two ventilator circuits for Dräger Babylog high-frequency ventilation.

AIM: The Dräger Babylog 8000plus ventilator (Dräger Medical Systems, Lübeck, Germany) can provide both conventional and high-frequency ventilation (HFV). Dräger recommends specific circuits for each of these modes. We investigated the performance of the Babylog ventilator in HFV mode when used with the recommended circuits for both conventional and HFV. METHODS: The Fisher and Paykel RT235 (conventional; Fisher and Paykel Healthcare, Auckland, New Zealand) and Hytrel (HFV; Fisher and Paykel Healthcare) circuits were studied using a 50-mL test lung. Tidal volume, high-frequency minute volume and ventilator alarms were compared at 100 combinations of mean airway pressures (10-16 cm H2O), frequencies (6-14 Hz) and amplitudes (20-60%). RESULTS: Tidal volume with the two circuits differed by < 5% for tidal volumes ≤ 2.5 mL. Above this, tidal volumes delivered with the HFV circuit were up to 15% more than that obtained with the conventional ventilation circuit, and high-frequency minute volume differed by up to 30%. With the exception of the highest tidal/minute volumes, the tidal volume delivered using the HFV circuit could also be achieved with adjusted frequency or amplitude when using the conventional circuit. More 'pressure measurement out of range' alarms were noted with the conventional ventilation circuit, particularly at mean airway pressure ≥ 14 cm H2O and frequency ≤ 10 Hz. CONCLUSIONS: The conventional ventilation circuit may allow delivery of adequate tidal volume for some infants. Where requirements are higher, the HFV circuit allows the Babylog to deliver higher tidal volumes and higher minute volume, and reduce alarms.

CareFusion 3100B high-frequency oscillatory ventilator diaphragms require pre-use inspection.

A rubber diaphragm in the driver assembly of the CareFusion 3100B high-frequency oscillatory ventilator may fail before its scheduled replacement at 4,000 hours of use, rendering the unit incapable of ventilation. CareFusion is in the process of revising the suggested replacemen schedule and adding user guidance to the device's operator's manual to address the problem. Users should thoroughly inspect the diaphragm each time they connect a breathing circuit and should remove from service any 3100B whose diaphragm shows signs of degradation.

Active cycle of breathing technique for cystic fibrosis.

BACKGROUND: People with cystic fibrosis (CF) 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 (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. OBJECTIVES: To compare the clinical effectiveness of ACBT with other airway clearance therapies in CF. SEARCH STRATEGY: We searched the Cochrane CF 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.Last search: 05 August 2010. SELECTION CRITERIA: Randomised or quasi-randomised controlled clinical studies, including crossover studies, comparing ACBT with other airway clearance therapies in CF. DATA COLLECTION AND ANALYSIS: Two review authors independently screened each article, abstracted data and assessed the risk of bias of each study. MAIN RESULTS: Fifty-eight studies were identified of which 17 (346 participants) met the inclusion criteria. Four randomised controlled studies (98 participants) were included in the meta-analysis; three were of crossover design. The 13 remaining studies were crossover studies with inadequate reports for complete assessment.Included studies compared ACBT to autogenic drainage, airway oscillating devices, high frequency chest compression devices, and conventional chest physiotherapy. Patient preference varied: more patients preferred autogenic drainage over ACBT, more preferred ACBT over airway oscillating devices, and more were comfortable with ACBT versus high frequency chest compression. No significant difference was seen in sputum weight between ACBT and autogenic drainage or between ACBT and airway oscillating devices. There was no significant difference in lung function and the number of pulmonary exacerbations between ACBT and ACBT plus 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 ACBT over any other airway clearance therapy. Four studies, with four different comparators, found that ACBT was comparable to other therapies in outcomes such as patient preference, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of ACBT on outcomes important for patients such as quality of life and patient preference.