Accuracy of delivered airway pressure and work of breathing estimation during proportional assist ventilation: a bench study

Additional file 2: Table S1. Measured and theoretical mean airway pressure during inspiration (imeas and iTh) with different triggers in different respiratory mechanics

Intrapulmonary percussive ventilation superimposed on spontaneous breathing: a physiological study in patients at risk for extubation failure

Purpose: Intrapulmonary percussive ventilation (IPV) is a high-frequency ventilation modality that can be superimposed on spontaneous breathing. IPV may diminish respiratory muscle loading and help to mobilize secretions. The aim of this prospective study was to assess the short-term effects of IPV in patients at high risk for extubation failure who were receiving preventive non-invasive ventilation (NIV) after extubation. Methods: Respiratory rate, work of breathing, and gas exchange were evaluated in 17 extubated patients during 20min of IPV and 20min of NIV delivered via a facial mask, separated by periods of spontaneous breathing. The pressure-support level during NIV was adjusted until tidal volume reached 6-8ml/kg and positive end-expiratory pressure (PEEP) 4-5cmH2O. For IPV, the pressurisation frequency was set at 250cycles/min and driving pressure at 1.2bar. The pressure-time product of the diaphragm (PTPdi/min) was measured using an oesophageal and gastric double-balloon catheter. Results: Transdiaphragmatic pressure and PTPdi/min improved significantly (p<0.01), from a median [25th-75th percentiles] of 264 [190-300] to 192 [152-221]cmH2Os/min with IPV and from 273 [212-397] to 176 [120-216]cmH2Os/min with NIV. Respiratory rate decreased significantly from 23 [19-27] to 22 [17-24] breaths/min for IPV and from 25 [19-28] to 20 [18-22] breaths/min for NIV (p<0.01). Mean PaCO2 decreased after NIV (from 46 [42-48] to 41 [36-42]mmHg, p<0.01) but not after IPV. There was no noticeable effect on oxygenation. Conclusions: IPV is an interesting alternative to NIV in patients at risk for post-extubation respiratory failure. Both NIV and IPV diminished the respiratory rate and work of breathing, but IPV was less effective in improving alveolar ventilatio

Mechanical influences on fluid leakage past the tracheal tube cuff in a benchtop model

Purpose: High-volume low-pressure (HVLP) cuffs on endotracheal tubes do not fully protect the lower airway from leakage of potentially contaminated secretions down the longitudinal folds within the cuff. Here, our purpose was to evaluate potential effects of positive end-expiratory pressure (PEEP), inspiratory effort intensity, and tube characteristics on fluid leakage past the cuff. Methods: This benchtop study at a research laboratory used a tracheal tube inserted into an artificial Plexiglas trachea connected to a ventilator and lung model. Methylene blue was deposited above the tube cuff to simulate subglottic secretions. Five PEEP levels (0, 5, 10, 15, and 20cmH2O) were tested with volume-controlled ventilation and three simulated inspiratory effort levels with pressure-support ventilation. Several cuff materials and tube sizes were tested. Results: The leakage occurrence rate ranged from 91% with zero PEEP to 8% with 15 and 20cmH2O PEEP and was indirectly proportional to the PEEP level with significant correlation (R 2=0.39, p<0.001), an effect not explained by higher peak inspiratory pressure. Low, moderate, and high inspiratory effort intensities were associated with 38%, 46%, and 75% leakage rates, respectively (p=0.024). Leakage flow was considerably less with polyurethane than with polyvinylchloride tubes (mean 0.5 versus 31.8ml/h). Leakage increased with larger tube diameters. Conclusion: This benchtop study shows that PEEP and a polyurethane cuff prevent leakage past the endotracheal tube cuff, whereas greater inspiratory effort and larger tube diameters for given tracheal size induce or worsen leakag

Bench testing of a new hyperbaric chamber ventilator at different atmospheric pressures

Purpose: Providing mechanical ventilation is challenging at supra-atmospheric pressure. The higher gas density increases resistance, reducing the flow delivered by the ventilator. A new hyperbaric ventilator (Siaretron IPER 1000) is said to compensate for these effects automatically. The aim of this bench test study was to validate the compensation, define its limits and provide details on the ventilator's output at varied atmospheric pressures. Methods: Experiments were conducted inside a multiplace hyperbaric chamber at 1, 2.2, 2.8 and 4 atmospheres absolute (ATA), with the ventilator connected to a test lung. Transducers were recalibrated at each ATA level. Various ventilator settings were tested in volume and pressure control modes. Measured tidal volumes were compared with theoretical predictions based on gas laws. Results: Results confirmed the ventilator's ability to provide compensation, but also identified its limits. The compensation range could be predicted and depended on the maximal flow attainable, decreasing linearly with increasing atmospheric pressure. With settings inside the range, tidal volumes approximated set values (mean error 10±5%). With settings outside the range, the volume was limited to the predicted maximal value calculated from maximal flow. A practical guide for clinicians is provided. Conclusion: The IPER 1000 ventilator attempted to deliver stable tidal volume by adjusting the opening of the inspiratory valve in proportion to atmospheric pressure. Adequate compensation was observed, albeit only within a predictable range, which can be reliably predicted for each setting and ATA level combination. Setting a tidal volume outside this range can result in an unwanted decrease in minute ventilatio

Evaluate of ventilators performances on bench test studies

Les ventilateurs ont connu des progrès technologiques considérables grâce à l'application de concepts physiologiques, à l'électronique, à l'informatique et la miniaturisation. Leurs conceptions et performances intrinsèques, en revanche, ont pu rester inégales sur certains points. L'objectif de ce travail a été d'évaluer sur un banc d'essai, avec un protocole, adapté aux problématiques soulevées en pratique clinique, tous les ventilateurs de réanimation, transport et de ventilation non invasive de façon rigoureuse et reproductible. Les résultats montrent que 1) l'erreur sur le volume réellement délivré est très fréquente et correspond facilement à 1ml/kg de volume supplémentaire ; le VT indiqué sur les ventilateurs est inférieur au VT réellement délivré ; 2) les performances des nouveaux ventilateurs ne présentent pas d'améliorations significatives par rapport aux meilleurs ventilateurs testés en 2000; les ventilateurs à turbine sont identiques ou proches des meilleurs ventilateurs conventionnels ; 3) les ventilateurs dédiés à la ventilation non invasive montrent de meilleures performances pour s'adapter à la présence de fuites ; 4) la ventilation par percussion intra-pulmonaire superposée à la ventilation conventionnelle peut réduire l'apport de l'humidification, influencer les volumes administrés et induire une pression expiratoire positive intrinsèque. Les tests sur banc montrent une grande hétérogénéité des performances. Une veille technologique semble indispensable pour évaluer tout nouveau ventilateurThe ventilators have markedly improved thanks to progress in respiratory physiology, in informatics and miniaturization. However, their intrinsic performances remain unequal. The aim was to evaluate ventilators performances on reproducible bench test studies adapted to clinical questions. Tests show that 1) the error of really delivered volume is approximately 1 ml/kg of additional volume; the tidal volume (VT) indicated on the ventilators was lower than the real delivered VT ; 2) Performances of new ventilators are comparable to the best ventilators tested in 2000 ; turbine ventilators are quite similar to best conventional ventilators ; 3) The ventilators dedicated to non invasive ventilation showed better performances to cope with leaks 4) The intrapulmonary percussive ventilation superimposed on conventional ventilation can reduce humidity, increase volumes and can generate intrinsic positive expiratory pressure. The bench tests showed a large heterogeneity of performances. A technological watch seems essential to evaluate all new ventilator

Évaluation des performances et des limitations des ventilateurs sur banc d'essai

Les ventilateurs ont connu des progrès technologiques considérables grâce à l'application de concepts physiologiques, à l'électronique, à l'informatique et la miniaturisation. Leurs conceptions et performances intrinsèques, en revanche, ont pu rester inégales sur certains points. L'objectif de ce travail a été d'évaluer sur un banc d'essai, avec un protocole, adapté aux problématiques soulevées en pratique clinique, tous les ventilateurs de réanimation, transport et de ventilation non invasive de façon rigoureuse et reproductible. Les résultats montrent que 1) l'erreur sur le volume réellement délivré est très fréquente et correspond facilement à 1ml/kg de volume supplémentaire ; le VT indiqué sur les ventilateurs est inférieur au VT réellement délivré ; 2) les performances des nouveaux ventilateurs ne présentent pas d'améliorations significatives par rapport aux meilleurs ventilateurs testés en 2000; les ventilateurs à turbine sont identiques ou proches des meilleurs ventilateurs conventionnels ; 3) les ventilateurs dédiés à la ventilation non invasive montrent de meilleures performances pour s'adapter à la présence de fuites ; 4) la ventilation par percussion intra-pulmonaire superposée à la ventilation conventionnelle peut réduire l'apport de l'humidification, influencer les volumes administrés et induire une pression expiratoire positive intrinsèque. Les tests sur banc montrent une grande hétérogénéité des performances. Une veille technologique semble indispensable pour évaluer tout nouveau ventilateurThe ventilators have markedly improved thanks to progress in respiratory physiology, in informatics and miniaturization. However, their intrinsic performances remain unequal. The aim was to evaluate ventilators performances on reproducible bench test studies adapted to clinical questions. Tests show that 1) the error of really delivered volume is approximately 1 ml/kg of additional volume; the tidal volume (VT) indicated on the ventilators was lower than the real delivered VT ; 2) Performances of new ventilators are comparable to the best ventilators tested in 2000 ; turbine ventilators are quite similar to best conventional ventilators ; 3) The ventilators dedicated to non invasive ventilation showed better performances to cope with leaks 4) The intrapulmonary percussive ventilation superimposed on conventional ventilation can reduce humidity, increase volumes and can generate intrinsic positive expiratory pressure. The bench tests showed a large heterogeneity of performances. A technological watch seems essential to evaluate all new ventilatorsPARIS-EST-Université (770839901) / SudocSudocFranceF

Accuracy of delivered airway pressure and work of breathing estimation during proportional assist ventilation: a bench study

Abstract Background Proportional assist ventilation+ (PAV+) delivers airway pressure (P aw) in proportion to patient effort (P mus) by using the equation of motion of the respiratory system. PAV+ calculates automatically respiratory mechanics (elastance and resistance); the work of breathing (WOB) is estimated by the ventilator. The accuracy of P mus estimation and hence accuracy of the delivered P aw and WOB calculation have not been assessed. This study aimed at assessing the accuracy of delivered P aw and calculated WOB by PAV+ and examining the factors influencing this accuracy. Methods Using an active lung model with different respiratory mechanics, we compared (1) the actual delivered P aw by the ventilator to the theoretical P aw as defined by the equation of motion and (2) the WOB value displayed by the ventilator to the WOB measured from a Campbell diagram. Results Irrespective of respiratory mechanics and gain, the ventilator provided a P aw approximately 25 % lower than expected. This underassistance was greatest at the beginning of the inspiration. Intrinsic PEEP (PEEPi), associated with an increase in trigger delay, was a major factor affecting PAV+ accuracy. The absolute value of total WOB displayed by the ventilator was underestimated, but the changes in WOB were accurately detected by the ventilator. Conclusion The assistance provided by PAV+ well follows P mus but with a constant underassistance. This is associated with an underestimation by the ventilator of the WOB. PEEPi can be a major factor contributing to PAV+ inaccuracy. Clinical recommendations should include using a high trigger sensitivity and a careful PEEP titration

A bench study of intensive-care-unit ventilators: new versus old and turbine-based versus compressed gas-based ventilators.

International audienceOBJECTIVE: To compare 13 commercially available, new-generation, intensive-care-unit (ICU) ventilators in terms of trigger function, pressurization capacity during pressure-support ventilation (PSV), accuracy of pressure measurements, and expiratory resistance. DESIGN AND SETTING: Bench study at a research laboratory in a university hospital. METHODS: Four turbine-based ventilators and nine conventional servo-valve compressed-gas ventilators were tested using a two-compartment lung model. Three levels of effort were simulated. Each ventilator was evaluated at four PSV levels (5, 10, 15, and 20 cm H2O), with and without positive end-expiratory pressure (5 cm H2O). Trigger function was assessed as the time from effort onset to detectable pressurization. Pressurization capacity was evaluated using the airway pressure-time product computed as the net area under the pressure-time curve over the first 0.3 s after inspiratory effort onset. Expiratory resistance was evaluated by measuring trapped volume in controlled ventilation. RESULTS: Significant differences were found across the ventilators, with a range of triggering delays from 42 to 88 ms for all conditions averaged (P < 0.001). Under difficult conditions, the triggering delay was longer than 100 ms and the pressurization was poor for five ventilators at PSV5 and three at PSV10, suggesting an inability to unload patient's effort. On average, turbine-based ventilators performed better than conventional ventilators, which showed no improvement compared to a bench comparison in 2000. CONCLUSION: Technical performance of trigger function, pressurization capacity, and expiratory resistance differs considerably across new-generation ICU ventilators. ICU ventilators seem to have reached a technical ceiling in recent years, and some ventilators still perform inadequately

Effects of autoclaving and disinfection on 3D surgical guides using LCD technology for dental implant

Abstract Background Surgical guides can improve the precision of implant placement and minimize procedural errors and their related complications. This study aims to determine how different disinfection and sterilization methods affect the size changes of drill guide templates and the mechanical properties of 3D-printed surgical guides made with LCD technology. Methods We produced a total of 100 samples. Forty surgical guides were fabricated to assess the implant drill guides’ surface and geometric properties. We subjected sixty samples to mechanical tests to analyze their tensile, flexural, and compressive properties. We classified the samples into four groups based on each analytical method: GC, which served as the control group; GA, which underwent autoclave sterilization at 121 °C (+ 1 bar, 20 min); GB, which underwent autoclave sterilization at 134 °C (+ 2 bar, 10 min); and GL, which underwent disinfection with 70% isopropyl alcohol for 20 min. Result The results show that sterilization at 121 °C and 134 °C affects the mechanical and geometric characteristics of the surgical guides, while disinfection with 70% isopropyl alcohol gives better results. Conclusion Our study of 3D-printed surgical guides using LCD technology found that sterilization at high temperatures affects the guides’ mechanical and geometric properties. Instead, disinfection with 70% isopropyl alcohol is recommended