A Physiological Point of View on Expiratory (Re)action during Mechanical Ventilation.
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ABSTRACT:
SUBMITTER: Spadaro S
PROVIDER: S-EPMC7233354 | biostudies-literature | 2020 May
REPOSITORIES: biostudies-literature
Publications
A Physiological Point of View on Expiratory (Re)action during Mechanical Ventilation.
Spadaro Savino S Volta Carlo Alberto CA
American journal of respiratory and critical care medicine 20200501 10
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Project description:To investigate the effect of mechanical ventilation and mechanical ventilationon with PEEP application on diaphragmatic dysfunction, we established a model of mechanical ventilation on New Zealand rabbit, in which rabbits in the experimental group were ventilated with/without PEEP application for 48 hours continuously
2023-04-12 | GSE228739 | GEO
Project description:IntroductionUnregulated expiratory flow may contribute to ventilator-induced lung injury. The amount of energy dissipated into the lungs with tidal mechanical ventilation may be used to quantify potentially injurious ventilation. Previously reported devices for variable expiratory flow regulation (FLEX) require, either computer-controlled feedback, or an initial expiratory flow trigger. In this bench study we present a novel passive expiratory flow regulation device.MethodsThe device was tested using a commercially available mechanical ventilator with a range of settings (tidal volume 420 ml and 630 ml, max. inspiratory flow rate 30 L/min and 50 L/min, respiratory rate 10 min-1, positive end-expiratory pressure 5 cmH2O), and a test lung with six different combinations of compliance and resistance settings. The effectiveness of the device was evaluated for reduction in peak expiratory flow, expiratory time, mean airway pressure, and the reduction of tidal dissipated energy (measured as the area within the airway pressure-volume loop).ResultsMaximal and minimal reduction in peak expiratory flow was from 97.18 ± 0.41 L/min to 25.82 ± 0.07 L/min (p < 0.001), and from 44.11 ± 0.42 L/min to 26.30 ± 0.06 L/min, respectively. Maximal prolongation in expiratory time was recorded from 1.53 ± 0.06 s to 3.64 ± 0.21 s (p < 0.001). As a result of the extended expiration, the maximal decrease in I:E ratio was from 1:1.15 ± 0.03 to 1:2.45 ± 0.01 (p < 0.001). The greatest increase in mean airway pressure was from 10.04 ± 0.03 cmH2O to 17.33 ± 0.03 cmH2O. Dissipated energy was significantly reduced with the device under all test conditions (p < 0.001). The greatest reduction in dissipated energy was from 1.74 ± 0.00 J to 0.84 ± 0.00 J per breath. The least reduction in dissipated energy was from 0.30 ± 0.00 J to 0.16 ± 0.00 J per breath. The greatest and least percentage reduction in dissipated energy was 68% and 33%, respectively.ConclusionsThe device bench tested in this study demonstrated a significant reduction in peak expiratory flow rate and dissipated energy, compared to ventilation with unregulated expiratory flow. Application of the device warrants further experimental and clinical evaluation.
| S-EPMC11484996 | biostudies-literature
Project description:During one-lung ventilation (OLV), titrating the positive end-expiratory pressure (PEEP) to target a low driving pressure (∆P) could reduce postoperative pulmonary complications. However, it is unclear how to conduct PEEP titration: by stepwise increase starting from zero PEEP (PEEPINCREMENTAL) or by stepwise decrease after a lung recruiting manoeuvre (PEEPDECREMENTAL). In this randomized trial, we compared the physiological effects of these two PEEP titration strategies on respiratory mechanics, ventilation/perfusion mismatch and gas exchange. Patients undergoing video-assisted thoracoscopic surgery in OLV were randomly assigned to a PEEPINCREMENTAL or PEEPDECREMENTAL strategy to match the lowest ∆P. In the PEEPINCREMENTAL group, PEEP was stepwise titrated from ZEEP up to 16 cm H2O, whereas in the PEEPDECREMENTAL group PEEP was decrementally titrated, starting from 16 cm H2O, immediately after a lung recruiting manoeuvre. Respiratory mechanics, ventilation/perfusion mismatch and blood gas analyses were recorded at baseline, after PEEP titration and at the end of surgery. Sixty patients were included in the study. After PEEP titration, shunt decreased similarly in both groups, from 50 [39-55]% to 35 [28-42]% in the PEEPINCREMENTAL and from 45 [37-58]% to 33 [25-45]% in the PEEPDECREMENTAL group (both p < 0.001 vs baseline). The resulting ∆P, however, was lower in the PEEPDECREMENTAL than in the PEEPINCREMENTAL group (8 [7-11] vs 10 [9-11] cm H2O; p = 0.03). In the PEEPDECREMENTAL group the PaO2/ FIO2 ratio increased significantly after intervention (from 140 [99-176] to 186 [152-243], p < 0.001). Both the PEEPINCREMENTAL and the PEEPDECREMENTAL strategies were able to decrease intraoperative shunt, but only PEEPDECREMENTAL improved oxygenation and lowered intraoperative ΔP.Clinical trial number NCT03635281; August 2018; "retrospectively registered".
| S-EPMC7439797 | biostudies-literature
Project description:OBJECTIVE:Reinstitution of mechanical ventilation (MV) for tracheostomized patients after successful weaning may occur as the care setting changes from critical care to general care. We aimed to investigate the occurrence, consequence and associated factors of MV reinstitution. METHODS:We analyzed the clinical data and physiological measurements of tracheostomized patients with prolonged MV discharged from the weaning unit to general wards after successful weaning to compare between those with and without in-hospital MV reinstitution within 60 days. RESULTS:Of 454 patients successfully weaned, 116 (25.6%) reinstituted MV at general wards within 60 days; at hospital discharge, 42 (36.2%) of them were eventually liberated from MV, 51 (44.0%) remained MV dependent, and 33 (28.4%) died. Of the 338 patients without reinstitution within 60 days, only 3 (0.9%) were later reinstituted with MV before discharge (on day 67, 89 and 136 at general wards, respectively), and 322 (95.2%) were successfully weaned again at discharge, while 13 (3.8%) died. Patients with MV reinstitution had a significantly lower level of maximal expiratory pressure (PEmax) before unassisted breathing trial compared to those without reinstitution. Multivariable Cox regression analysis showed fever at RCC discharge (hazard ratio [HR] 14.00, 95% confidence interval [CI] 3.2-61.9) chronic obstructive pulmonary disease (HR 2.37, 95% CI 1.34-4.18), renal replacement therapy at the ICU (HR 2.29, 95% CI 1.50-3.49) and extubation failure before tracheostomy (HR 1.76, 95% CI 1.18-2.63) were associated with increased risks of reinstitution, while PEmax > 30 cmH2O (HR 0.51, 95% CI 0.35-0.76) was associated with a decreased risk of reinstitution. CONCLUSIONS:The reinstitution of MV at the general ward is significant, with poor outcomes. The PEmax measured before unassisted breathing trial was significantly associated with the risk of reinstituting MV at the general wards.
| S-EPMC7064239 | biostudies-literature
Project description:BackgroundSedation management has a major impact on outcomes in mechanically ventilated patients, but sedation strategies do not generally consider the differential effects of different sedatives on respiration and respiratory pattern. A systematic review was undertaken to quantitatively summarize the known effects of different classes of drugs used for sedation on respiratory pattern during both spontaneous breathing and assisted mechanical ventilation.MethodsThis was a systematic review and meta-analysis conducted using Ovid MEDLINE, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials up to June 2020 to retrieve studies that measured respiratory parameters before and after the administration of opioids, benzodiazepines, intravenous and inhaled anaesthetic agents, and other hypnotic agents (PROSPERO #CRD42020190017). A random-effects meta-analytic model was employed to estimate the mean percentage change in each of the respiratory indices according to medication exposure with and without mechanical ventilation. Risk of bias was assessed using the Cochrane risk of bias assessment tools.FindingsFifty-one studies were included in the analysis. Risk of bias was generally deemed to be low for most studies. Respiratory rate decreased with the administration of opioids in both non-ventilated patients (18% decrease, 95% CI 12-24%) and ventilated patients (26% decrease, 95% CI 15-37%) and increased with inhaled anaesthetics in non-ventilated patients (83% increase, 95% CI 49-118%) and ventilated patients (50% increase, 28-72%). In non-ventilated patients, tidal volume decreased following administration of inhaled aesthetics (55% decrease, 95% CI 25-86%), propofol (36% decrease, 95% CI 20-52%), and benzodiazepines (28% decrease, 95% CI 17-40%); in patients receiving assisted mechanical ventilation, tidal volume was not significantly affected by sedation. Administration of other hypnotic agents was not associated with changes in respiratory rate or tidal volume.InterpretationDifferent classes of drugs used for sedation exert differential effects on respiratory pattern, and this may influence weaning and outcomes in mechanically ventilated patients.FundingThis study did not receive any funding support.
| S-EPMC10789641 | biostudies-literature
Project description:In spite of intensive investigations, the role of spontaneous breathing (SB) activity in ARDS has not been well defined yet and little has been known about the different contribution of inspiratory or expiratory muscles activities during mechanical ventilation in patients with ARDS. In present study, oleic acid-induced beagle dogs' ARDS models were employed and ventilated with the same level of mean airway pressure. Respiratory mechanics, lung volume, gas exchange and inflammatory cytokines were measured during mechanical ventilation, and lung injury was determined histologically. As a result, for the comparable ventilator setting, preserved inspiratory muscles activity groups resulted in higher end-expiratory lung volume (EELV) and oxygenation index. In addition, less lung damage scores and lower levels of system inflammatory cytokines were revealed after 8 h of ventilation. In comparison, preserved expiratory muscles activity groups resulted in lower EELV and oxygenation index. Moreover, higher lung injury scores and inflammatory cytokines levels were observed after 8 h of ventilation. Our findings suggest that the activity of inspiratory muscles has beneficial effects, whereas that of expiratory muscles exerts adverse effects during mechanical ventilation in ARDS animal model. Therefore, for mechanically ventilated patients with ARDS, the demands for deep sedation or paralysis might be replaced by the strategy of expiratory muscles paralysis through epidural anesthesia.
| S-EPMC5322359 | biostudies-literature
Project description:The timing of extracorporeal membrane oxygenation (ECMO) initiation and its outcome in the management of respiratory and cardiac failure have received considerable attention, but very little attention has been given to mechanical ventilation during ECMO. Mechanical ventilation settings in non-ECMO studies have been shown to have an effect on survival and may also have contributed to a treatment effect in ECMO trials. Protective lung ventilation strategies established for non-ECMO-supported respiratory failure patients may not be optimal for more severe forms of respiratory failure requiring ECMO support. The influence of positive end-expiratory pressure on the reduction of the left ventricular compliance may be a matter of concern for patients receiving ECMO support for cardiac failure. The objectives of this review were to describe potential mechanisms for lung injury during ECMO for respiratory or cardiac failure, to assess the possible benefits from the use of ultra-protective lung ventilation strategies and to review published guidelines and expert opinions available on mechanical ventilation-specific management of patients requiring ECMO, including mode and ventilator settings. Articles were identified through a detailed search of PubMed, Ovid, Cochrane databases and Google Scholar. Additional references were retrieved from the selected studies. Growing evidence suggests that mechanical ventilation settings are important in ECMO patients to minimize further lung damage and improve outcomes. An ultra-protective ventilation strategy may be optimal for mechanical ventilation during ECMO for respiratory failure. The effects of airway pressure on right and left ventricular afterload should be considered during venoarterial ECMO support of cardiac failure. Future studies are needed to better understand the potential impact of invasive mechanical ventilation modes and settings on outcomes.
| S-EPMC4057516 | biostudies-literature
Project description:The extent of ventilator-induced lung injury may be related to the intensity of mechanical ventilation--expressed as mechanical power. In the present study, we investigated whether there is a safe threshold, below which lung damage is absent. Three groups of six healthy pigs (29.5 ± 2.5 kg) were ventilated prone for 48 h at mechanical power of 3, 7, or 12 J/min. Strain never exceeded 1.0. PEEP was set at 4 cmH2 O. Lung volumes were measured every 12 h; respiratory, hemodynamics, and gas exchange variables every 6. End-experiment histological findings were compared with a control group of eight pigs which did not undergo mechanical ventilation. Functional residual capacity decreased by 10.4% ± 10.6% and 8.1% ± 12.1% in the 7 J and 12 J groups (p = 0.017, p < 0.001) but not in the 3 J group (+1.7% ± 17.7%, p = 0.941). In 3 J group, lung elastance, PaO2 and PaCO2 were worse compared to 7 J and 12 J groups (all p < 0.001), due to lower ventilation-perfusion ratio (0.54 ± 0.13, 1.00 ± 0.25, 1.78 ± 0.36 respectively, p < 0.001). The lung weight was lower (p < 0.001) in the controls (6.56 ± 0.90 g/kg) compared to 3, 7, and 12 J groups (12.9 ± 3.0, 16.5 ± 2.9, and 15.0 ± 4.1 g/kg, respectively). The wet-to-dry ratio was 5.38 ± 0.26 in controls, 5.73 ± 0.52 in 3 J, 5.99 ± 0.38 in 7 J, and 6.13 ± 0.59 in 12 J group (p = 0.03). Vascular congestion was more extensive in the 7 J and 12 J compared to 3 J and control groups. Mechanical ventilation (with anesthesia/paralysis) increase lung weight, and worsen lung histology, regardless of the mechanical power. Ventilating at 3 J/min led to better anatomical variables than at 7 and 12 J/min but worsened the physiological values.
| S-EPMC8957661 | biostudies-literature
Project description:High intrapulmonary pressures, large tidal volumes, and elevated respiratory rates during controlled mechanical ventilation can lead to barotrauma, volutrauma, and atelectrauma. Mechanical power-defined as the product of the pressure-volume integral and respiratory rate-consolidates these three risk factors into a single, intuitive parameter. Several studies have demonstrated that higher mechanical power correlates with an increased risk of lung injury and mortality, prompting the suggestion that mechanical power should be minimized. However, under the constraint of maintaining a fixed alveolar minute ventilation and positive end-expiratory pressure (PEEP), it remains unclear how to adjust respiratory rate and tidal volume to minimize mechanical power. This study provides an analytical solution to this optimization problem. Accordingly, only the elastic component of mechanical power should be targeted for minimization. Regardless of lung elastance or resistance, or the mode and settings of the ventilator, the elastic power is minimized at a tidal volume equal to twice the anatomic dead space, or approximately 4.4 ml/kg of body weight.
| S-EPMC11628461 | biostudies-literature
Project description:BackgroundMany studies explored the impact of ventilation during cardiopulmonary bypass (CPB) period with conflicting results. Functional residual capacity or End Expiratory Lung Volume (EELV) may be disturbed after cardiac surgery but the specific effects of CPB have not been studied. Our objective was to compare the effect of two ventilation strategies during CPB on EELV.MethodsObservational single center study in a tertiary teaching hospital. Adult patients undergoing on-pump cardiac surgery by sternotomy were included. Maintenance of ventilation during CPB was left to the discretion of the medical team, with division between "ventilated" and "non-ventilated" groups afterwards. Iterative intra and postoperative measurements of EELV were carried out by nitrogen washin-washout technique. Main endpoint was EELV at the end of surgery. Secondary endpoints were EELV one hour after ICU admission, PaO2/FiO2 ratio, driving pressure, duration of mechanical ventilation and post-operative pulmonary complications.ResultsForty consecutive patients were included, 20 in each group. EELV was not significantly different between the ventilated versus non-ventilated groups at the end of surgery (1796 ± 586 mL vs. 1844 ± 524 mL, p = 1) and one hour after ICU admission (2095 ± 562 vs. 2045 ± 476 mL, p = 1). No significant difference between the two groups was observed on PaO2/FiO2 ratio (end of surgery: 339 ± 149 vs. 304 ± 131, p = 0.8; one hour after ICU: 324 ± 115 vs. 329 ± 124, p = 1), driving pressure (end of surgery: 7 ± 1 vs. 8 ± 1 cmH2O, p = 0.3; one hour after ICU: 9 ± 3 vs. 9 ± 3 cmH2O), duration of mechanical ventilation (5.5 ± 4.8 vs 8.2 ± 10.0 h, p = 0.5), need postoperative respiratory support (2 vs. 1, p = 1), occurrence of pneumopathy (2 vs. 0, p = 0.5) and radiographic atelectasis (7 vs. 8, p = 1).ConclusionNo significant difference was observed in EELV after cardiac surgery between not ventilated and ventilated patients during CPB.
| S-EPMC9784092 | biostudies-literature