Background: There are limited and partially contradictory data on the effects of airway pressure release ventilation (APRV) in COVID-19-associated acute respiratory distress syndrome (CARDS). ...Therefore, we analyzed the clinical outcome, complications, and longitudinal course of ventilation parameters and laboratory values in patients with CARDS, who were mechanically ventilated using APRV. Methods: Respective data from 4 intensive care units (ICUs) were collected and compared to a matched cohort of patients receiving conventional low tidal volume ventilation (LTV). Propensity score matching was performed based on age, sex, blood gas analysis, and APACHE II score at admission, as well as the implementation of prone positioning. Findings: Forty patients with CARDS, who were mechanically ventilated using APRV, and 40 patients receiving LTV were matched. No significant differences were detected for tidal volumes per predicted body weight, peak pressure values, and blood gas analyses on admission, 6 h post admission as well as on day 3 and day 7. Regarding ICU survival, no significant difference was identified between APRV patients (40%) and LTV patients (42%). Median duration of mechanical ventilation and duration of ICU treatment were comparable in both groups. Similar complication rates with respect to ventilator-associated pneumonia, septic shock, thromboembolic events, barotrauma, as well as the necessity for hemodialysis were detected for both groups. Clinical characteristics that were associated with increased mortality in a Cox proportional hazards regression analysis included age (hazard ratio HR 1.08, 95% confidence interval CI 1.04-1.1; P < .001), severe acute respiratory distress syndrome (HR 2.62, 95% CI 1.02-6.7; P = .046) and the occurrence of septic shock (HR 17.18, 95% CI 2.06-143.2; P = .009), but not the ventilation mode. Interpretation: Intensive care unit survival, duration of mechanical ventilation, and ICU treatment as well as ventilation-associated complication rates were equivalent using APRV compared to conventional LTV in patients with CARDS.
OBJECTIVES:To compare a time-controlled adaptive ventilation strategy, set in airway pressure release ventilation mode, versus a protective mechanical ventilation strategy in pulmonary and ...extrapulmonary acute respiratory distress syndrome with similar mechanical impairment.
DESIGN:Animal study.
SETTING:Laboratory investigation.
SUBJECTS:Forty-two Wistar rats.
INTERVENTIONS:Pulmonary acute respiratory distress syndrome and extrapulmonary acute respiratory distress syndrome were induced by instillation of Escherichia coli lipopolysaccharide intratracheally or intraperitoneally, respectively. After 24 hours, animals were randomly assigned to receive 1 hour of volume-controlled ventilation (n = 7/etiology) or time-controlled adaptive ventilation (n = 7/etiology) (tidal volume = 8 mL/kg). Time-controlled adaptive ventilation consisted of the application of continuous positive airway pressure 2 cm H2O higher than baseline respiratory system peak pressure for a time (Thigh) of 0.75–0.85 seconds. The release pressure (Plow = 0 cm H2O) was applied for a time (Tlow) of 0.11–0.18 seconds. Tlow was set to target an end-expiratory flow to peak expiratory flow ratio of 75%. Nonventilated animals (n = 7/etiology) were used for Diffuse Alveolar Damage and molecular biology markers analyses.
MEASUREMENT AND MAIN RESULTS:Time-controlled adaptive ventilation increased mean respiratory system pressure regardless of acute respiratory distress syndrome etiology. The Diffuse Alveolar Damage score was lower in time-controlled adaptive ventilation compared with volume-controlled ventilation in pulmonary acute respiratory distress syndrome and lower in time-controlled adaptive ventilation than nonventilated in extrapulmonary acute respiratory distress syndrome. In pulmonary acute respiratory distress syndrome, volume-controlled ventilation, but not time-controlled adaptive ventilation, increased the expression of amphiregulin, vascular cell adhesion molecule-1, and metalloproteinase-9. Collagen density was higher, whereas expression of decorin was lower in time-controlled adaptive ventilation than nonventilated, independent of acute respiratory distress syndrome etiology. In pulmonary acute respiratory distress syndrome, but not in extrapulmonary acute respiratory distress syndrome, time-controlled adaptive ventilation increased syndecan expression.
CONCLUSION:In pulmonary acute respiratory distress syndrome, time-controlled adaptive ventilation led to more pronounced beneficial effects on expression of biomarkers related to overdistension and extracellular matrix homeostasis.
Background: Forward head posture (FHP) is a misalignment of the head on trunk that makes the external moment longer by shifting the gravitational center in front of the load bearing axis causing ...stress on the suboccipital muscles with functional movement limitations and formation of myofascial trigger points (MTrPs). Objectives: To compare between suboccipital muscle inhibition technique (SMIT) and progressive pressure release technique (PPRT) on craniovertebral angle (CVA) and neck range of motion (ROM) in individuals with FHP and active suboccipital MTrPs. Methods: Forty-five subjects were randomly assigned in three groups. Group A was given postural correction exercise, group B received SMIT and postural correction exercise, and group C received suboccipital PPRT and postural correction exercise. Results: Statistical significance was found within and between groups in respect to ROM in all directions (P < 0.05) except for right and left side bending between groups A and B, which was P = 0.54 and P = 0.67, respectively. CVA had shown significant results for within and between groups (P < 0.05) except for group A versus group B (P = 0.41). Conclusion: Both techniques work to increase CVA and improve ROM in individuals with FHP. However, suboccipital PPRT has shown to be more effective.
Antecedentes: La postura de la cabeza hacia adelante (FHP, por sus siglas en inglés) es una desalineación de la cabeza sobre el tronco que prolonga el momento externo al desplazar el centro gravitacional frente al eje que soporta la carga, causando estrés en los músculos suboccipitales con limitaciones de movimiento funcional y formación de puntos gatillo miofasciales (PGM). Objetivos: Comparar entre la técnica de inhibición del músculo suboccipital (SMIT) y la técnica de liberación progresiva de presión (PPRT) en el ángulo craneovertebral (CVA) y el rango de movimiento del cuello (ROM) en individuos con FHP y PGM suboccipitales activos. Métodos: Cuarenta y cinco sujetos fueron asignados aleatoriamente en tres grupos. El grupo A recibió ejercicio de corrección postural, el grupo B recibió SMIT y ejercicio de corrección postural, y el grupo C recibió PPRT suboccipital y ejercicio de corrección postural. Resultados: Se encontró significación estadística dentro y entre los grupos con respecto al ROM en todas las direcciones (P <0,05) excepto para la flexión del lado derecho e izquierdo entre los grupos A y B, que fue P = 0,54 y P = 0,67, respectivamente. CVA había mostrado resultados significativos dentro y entre los grupos (P <0,05), excepto para el grupo A versus el grupo B (P = 0,41). Conclusión: Ambas técnicas funcionan para aumentar el CVA y mejorar el ROM en individuos con FHP. Sin embargo, la PPRT suboccipital ha demostrado ser más eficaz.
Microfiltration membranes retain bacteria predominantly by size-exclusion. However, some empirical data points towards the fact, that alterations in flow rate as well as changes in the quality of ...adhesive interactions between the membrane surface and the bacteria can affect their retention. For parvo virus retaining normal flow virus-filters, systematic investigations have been undertaken to characterize the impact of flow alterations as well as modulations of particle-membrane interactions on virus particle retention. For depth filters used, e.g., for the clarification of fermentation broths, it is well known that alterations in flow rate typically lead to elevated levels of turbidity. This work adopts the acquired knowledge from virus- and depth-filters and investigates their applicability for bacteria retention by microfiltration membranes. It presents particle retention data for mycoplasma and Gram-negative and Gram-positive bacteria. Single layer flat sheet PES model microfiltration membranes with maximum pore sizes varying from 0.3 to 1.5 µm and an overall low retention were used in order to easily detect and differentiate their retention properties for the different particle species. The event of particle breakthrough is elucidated depending on the adsorptive character of the membrane surface, the pore size, and changes in flow rate including the interruption of flow. Moreover, this work investigates how the chemical and physical solution properties influence bacterial retention. These properties include the temperature of the fluid, the presence of a surfactant, the salt concentration and the pH. Flow interruptions using B. diminuta were also applied to commercially available PES sterilizing-grade microfiltration membranes showing no bacterial breakthrough.
•Study elucidates the breakthrough of bacteria after flow alterations during microfiltration.•Study covers broad range of bacteria and polystyrene spheres.•Breakthrough is a combined effect of a kinetic (particle motion) and a force-driven proportion.•Breakthrough depends on membrane hydrophilicity, pore size and filtration fluid properties.•No breakthrough of bacteria using commercial sterilizing-grade microfiltration membranes.
The recently developed Gas Kinetic Method (GKM) for computing fluid flow is enhanced with advanced reconstruction (interpolation) schemes to enable direct simulations of highly compressible ...transition and turbulence fields. Variants of Weighted Essentially Non-Oscillatory (WENO) reconstruction schemes of different orders of accuracy are implemented and examined along with more elementary van Leer method. The competing schemes are evaluated for their accuracy, efficiency and numerical stability. The computed results are compared against the Rapid Distortion Theory for the case of compressible shear turbulence and ‘pressure-released’ Burgers solution. In the case of decaying isotropic turbulence, the efficacy of the reconstruction schemes is evaluated by comparison against a ‘gold standard’ high-resolution simulation. The capabilities of the reconstruction schemes to capture linear, non-linear, pressure-released and viscous flow physics as well as solenoidal and dilatational features of the flow fields are established in isolation and combination. The most suitable WENO variant for integration with GKM is identified. Another important outcome of the study is the finding that temperature-interpolation is superior to energy-interpolation in avoiding negative temperatures arising due to the Gibbs phenomenon. Overall, this work advances the applicability of kinetic theory based GKM to a wider range of high Mach number flow physics.
Adult respiratory distress syndrome is often refractory to treatment and develops after entering the health care system. This suggests an opportunity to prevent this syndrome before it develops. The ...objective of this study was to demonstrate that early application of airway pressure release ventilation in high-risk trauma patients reduces hospital mortality as compared with similarly injured patients on conventional ventilation.
Systematic review of observational data in patients who received conventional ventilation in other trauma centers were compared with patients treated with early airway pressure release ventilation in our trauma center. Relevant studies were identified in a PubMed and MEDLINE search from 1995 to 2012 and included prospective and retrospective observational and cohort studies enrolling 100 or more adult trauma patients with reported adult respiratory distress syndrome incidence and mortality data.
Early airway pressure release ventilation as compared with the other trauma centers represented lower mean adult respiratory distress syndrome incidence (14.0% vs. 1.3%) and in-hospital mortality (14.1% vs. 3.9%).
These data suggest that early airway pressure release ventilation may prevent progression of acute lung injury in high-risk trauma patients, reducing trauma-related adult respiratory distress syndrome mortality.
Systematic review, level IV.
Acute respiratory failure (ARF) strikes an estimated two million people in the United States each year, with care exceeding US$50 billion. The hallmark of ARF is a heterogeneous injury, with normal ...tissue intermingled with a large volume of low compliance and collapsed tissue. Mechanical ventilation is necessary to oxygenate and ventilate patients with ARF, but if set inappropriately, it can cause an unintended ventilator-induced lung injury (VILI). The mechanism of VILI is believed to be overdistension of the remaining normal tissue known as the 'baby' lung, causing volutrauma, repetitive collapse and reopening of lung tissue with each breath, causing atelectrauma, and inflammation secondary to this mechanical damage, causing biotrauma. To avoid VILI, extracorporeal membrane oxygenation (ECMO) can temporally replace the pulmonary function of gas exchange without requiring high tidal volumes (V
) or airway pressures. In theory, the lower V
and airway pressure will minimize all three VILI mechanisms, allowing the lung to 'rest' and heal in the collapsed state. The optimal method of mechanical ventilation for the patient on ECMO is unknown. The ARDSNetwork Acute Respiratory Management Approach (ARMA) is a Rest Lung Approach (RLA) that attempts to reduce the excessive stress and strain on the remaining normal lung tissue and buys time for the lung to heal in the collapsed state. Theoretically, excessive tissue stress and strain can also be avoided if the lung is fully open, as long as the alveolar re-collapse is prevented during expiration, an approach known as the Open Lung Approach (OLA). A third lung-protective strategy is the Stabilize Lung Approach (SLA), in which the lung is initially stabilized and gradually reopened over time. This review will analyze the physiologic efficacy and pathophysiologic potential of the above lung-protective approaches.
The aim of this study was to investigate the physiological impact of airway pressure release ventilation (APRV) on patients with early moderate-to-severe acute respiratory distress syndrome (ARDS) by ...electrical impedance tomography (EIT).
In this single-center prospective physiological study, adult patients with early moderate-to-severe ARDS mechanically ventilated with APRV were assessed by EIT shortly after APRV (T0), and 6 h (T1), 12 h (T2), and 24 h (T3) after APRV initiation. Regional ventilation and perfusion distribution, dead space (%), shunt (%), and ventilation/perfusion matching (%) based on EIT measurement at different time points were compared. Additionally, clinical variables related to respiratory and hemodynamic condition were analyzed.
Twelve patients were included in the study. After APRV, lung ventilation and perfusion were significantly redistributed to dorsal region. One indicator of ventilation distribution heterogeneity is the global inhomogeneity index, which decreased gradually 0.61 (0.55-0.62) to 0.50 (0.42-0.53), p < 0.001. The other is the center of ventilation, which gradually shifted towards the dorsal region (43.31 ± 5.07 to 46.84 ± 4.96%, p = 0.048). The dorsal ventilation/perfusion matching increased significantly from T0 to T3 (25.72 ± 9.01 to 29.80 ± 7.19%, p = 0.007). Better dorsal ventilation (%) was significantly correlated with higher PaO
/FiO
(r = 0.624, p = 0.001) and lower PaCO
(r = -0.408, p = 0.048).
APRV optimizes the distribution of ventilation and perfusion, reducing lung heterogeneity, which potentially reduces the risk of ventilator-induced lung injury.
Chronic nonspecific low back pain is a frequent clinical condition affecting the general population and influencing disability level and quality of life. We performed a single-blinded, randomized, ...and controlled study to compare the effectiveness of manual pressure release (MPR) and electrical neuromodulation (ENM) treatments in the management of chronic low back pain. There were 20 patients with chronic low back pain randomly assigned to 6 treatment sessions with either technique. Both groups were treated for 2 days a week for 3 weeks. Myofascial trigger points (MTrPs) were identified and skin conductance, pressure-pain threshold, postural changes, and the Oswestry Disability Index were assessed before and after each treatment session, along with the protocol-end data compared against the baseline data in each group. We found an outstanding and about equal deactivation of MTrPs from pre- to post-treatment in both groups, reducing disability in patients with chronic low back pain. The study highlights the ENM as a reliable tool for the evaluation of MTrPs, given a high agreement with the MPR. The effect on the neuromuscular condition of treating the "key trigger points" found in this study advances the knowledge of medical rehabilitation.
The acute respiratory distress syndrome (ARDS) is a critical illness with high mortality and a worse prognosis. Mechanical ventilation (MV) is currently considered to be one of the most effective ...methods of treating ARDS. In this meta-analysis, we discussed the efficacy of airway pressure release ventilation (APRV) in treating ARDS.
Following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA), Ovid Medline, Embase, and PubMed were systematically searched with the keywords of "ARDS" and "APRV". The studies containing the treatment of APRV in ARDS were included. According to the MV protocol used in the studies, the comparison was undertaken between the APRV group vs low tidal volume (LTV) group and synchronized intermittent mandatory ventilation (SIMV) group. The relative risk (RR) and the standard mean difference with 95% confidence intervals (CI) were used for the comparison between groups.
Fourteen studies with 2096 patients were included in the meta-analysis. The average increasing rate of PaO2/FiO2 was 75.4% in the APRV group vs 44.1% in the non-APRV group. No significant differences were found in mortality and duration of ICU stay between APRV vs LTV (P = .073 and P = .404) and APRV vs SIMV (P = .370 and P = .894).
The APRV protocol would have a higher increase in the PaO2/FiO2 ratio, which was a safe protocol with a compatible effect comparing to LTV and SIMV.
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