Dataset Information

Bias flow rate and ventilation efficiency during adult high-frequency oscillatory ventilation: a lung model study.

ABSTRACT: BACKGROUND:Bias flow (BF) is essential to maintain mean airway pressure (MAP) and to washout carbon dioxide (CO2) from the oscillator circuit during high-frequency oscillatory ventilation (HFOV). If the BF rate is inadequate, substantial CO2 rebreathing could occur and ventilation efficiency could worsen. With lower ventilation efficiency, the required stroke volume (SV) would increase in order to obtain the same alveolar ventilation with constant frequency. The aim of this study was to assess the effect of BF rate on ventilation efficiency during adult HFOV. METHODS:The R100 oscillator (Metran, Japan) was connected to an original lung model internally equipped with a simulated bronchial tree. The actual SV was measured with a flow sensor placed at the Y-piece. Carbon dioxide (CO2) was continuously insufflated into the lung model ([Formula: see text]CO2), and the partial pressure of CO2 (PCO2) in the lung model was monitored. Alveolar ventilation ([Formula: see text]A) was estimated as [Formula: see text]CO2 divided by the stabilized value of PCO2. [Formula: see text]A was evaluated by setting SV from 80 to 180 mL (10 mL increments, n?=?5) at a frequency of 8 Hz, a MAP of 25 cmH2O, and a BF of 10, 20, 30, and 40 L/min (study 1). Ventilation efficiency was calculated as [Formula: see text]A divided by the actual minute volume. The experiment was also performed with an actual SV of 80, 100, and 120 mL and a BF from 10 to 60 L/min (10 L/min increments: study 2). RESULTS:Study 1: With the same setting SV, the [Formula: see text]A with a BF of 20 L/min or more was significantly higher than that with a BF of 10 L/min. Study 2: With the same actual SV, the [Formula: see text]A and the ventilation efficiency with a BF of 30 L/min or more were significantly higher than those with a BF of 10 or 20 L/min. CONCLUSIONS:Increasing BF up to 30 L/min or more improved ventilation efficiency in the R100 oscillator.

SUBMITTER: Nagano O

PROVIDER: S-EPMC5908780 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Bias flow rate and ventilation efficiency during adult high-frequency oscillatory ventilation: a lung model study.

Nagano Osamu O Yumoto Tetsuya T Nishimatsu Atsunori A Kanazawa Shunsuke S Fujita Takahisa T Asaba Sunao S Yamanouchi Hideo H

Intensive care medicine experimental 20180419 1

<h4>Background</h4>Bias flow (BF) is essential to maintain mean airway pressure (MAP) and to washout carbon dioxide (CO<sub>2</sub>) from the oscillator circuit during high-frequency oscillatory ventilation (HFOV). If the BF rate is inadequate, substantial CO<sub>2</sub> rebreathing could occur and ventilation efficiency could worsen. With lower ventilation efficiency, the required stroke volume (SV) would increase in order to obtain the same alveolar ventilation with constant frequency. The aim ...[more]

PMID: 29675732

Similar Datasets

Project description:ObjectivesThe theoretical basis for minimizing tidal volume during high-frequency oscillatory ventilation may not be appropriate when lung tissue stretch occurs heterogeneously and/or rapidly. The objective of this study was to assess the extent to which increased ventilation heterogeneity may contribute to ventilator-induced lung injury during high-frequency oscillatory ventilation in adults compared with neonates on the basis of lung size, using a computational model of human lungs.DesignComputational modeling study.SettingResearch laboratory.SubjectsHigh-fidelity, 3D computational models of human lungs, scaled to various sizes representative of neonates, children, and adults, with varying injury severity. All models were generated from one thoracic CT image of a healthy adult male.InterventionsOscillatory ventilation was simulated in each lung model at frequencies ranging from 0.2 to 40 Hz. Sinusoidal flow oscillations were delivered at the airway opening of each model and distributed through the lungs according to regional parenchymal mechanics.Measurements and main resultsAcinar flow heterogeneity was assessed by the coefficient of variation in flow magnitudes across all acini in each model. High-frequency oscillatory ventilation simulations demonstrated increasing heterogeneity of regional parenchymal flow with increasing lung size, with decreasing ratio of deadspace to total acinar volume, and with increasing frequency above lung corner frequency and resonant frequency. Potential for resonant amplification was greatest in injured adult-sized lungs with higher regional quality factors indicating the presence of underdamped lung regions.ConclusionsThe potential for ventilator-induced lung injury during high-frequency oscillatory ventilation is enhanced at frequencies above lung corner frequency or resonant frequency despite reduced tidal volumes, especially in adults, due to regional amplification of heterogeneous flow. Measurements of corner frequency and resonant frequency should be considered during high-frequency oscillatory ventilation management.

Project description:INTRODUCTION: The objective was to study the effects of a lung recruitment procedure by stepwise increases of mean airway pressure upon organ blood flow and hemodynamics during high-frequency oscillatory ventilation (HFOV) versus pressure-controlled ventilation (PCV) in experimental lung injury. METHODS: Lung damage was induced by repeated lung lavages in seven anesthetized pigs (23-26 kg). In randomized order, HFOV and PCV were performed with a fixed sequence of mean airway pressure increases (20, 25, and 30 mbar every 30 minutes). The transpulmonary pressure, systemic hemodynamics, intracranial pressure, cerebral perfusion pressure, organ blood flow (fluorescent microspheres), arterial and mixed venous blood gases, and calculated pulmonary shunt were determined at each mean airway pressure setting. RESULTS: The transpulmonary pressure increased during lung recruitment (HFOV, from 15 +/- 3 mbar to 22 +/- 2 mbar, P < 0.05; PCV, from 15 +/- 3 mbar to 23 +/- 2 mbar, P < 0.05), and high airway pressures resulted in elevated left ventricular end-diastolic pressure (HFOV, from 3 +/- 1 mmHg to 6 +/- 3 mmHg, P < 0.05; PCV, from 2 +/- 1 mmHg to 7 +/- 3 mmHg, P < 0.05), pulmonary artery occlusion pressure (HFOV, from 12 +/- 2 mmHg to 16 +/- 2 mmHg, P < 0.05; PCV, from 13 +/- 2 mmHg to 15 +/- 2 mmHg, P < 0.05), and intracranial pressure (HFOV, from 14 +/- 2 mmHg to 16 +/- 2 mmHg, P < 0.05; PCV, from 15 +/- 3 mmHg to 17 +/- 2 mmHg, P < 0.05). Simultaneously, the mean arterial pressure (HFOV, from 89 +/- 7 mmHg to 79 +/- 9 mmHg, P < 0.05; PCV, from 91 +/- 8 mmHg to 81 +/- 8 mmHg, P < 0.05), cardiac output (HFOV, from 3.9 +/- 0.4 l/minute to 3.5 +/- 0.3 l/minute, P < 0.05; PCV, from 3.8 +/- 0.6 l/minute to 3.4 +/- 0.3 l/minute, P < 0.05), and stroke volume (HFOV, from 32 +/- 7 ml to 28 +/- 5 ml, P < 0.05; PCV, from 31 +/- 2 ml to 26 +/- 4 ml, P < 0.05) decreased. Blood flows to the heart, brain, kidneys and jejunum were maintained. Oxygenation improved and the pulmonary shunt fraction decreased below 10% (HFOV, P < 0.05; PCV, P < 0.05). We detected no differences between HFOV and PCV at comparable transpulmonary pressures. CONCLUSION: A typical recruitment procedure at the initiation of HFOV improved oxygenation but also decreased systemic hemodynamics at high transpulmonary pressures when no changes of vasoactive drugs and fluid management were performed. Blood flow to the organs was not affected during lung recruitment. These effects were independent of the ventilator mode applied.

Project description:BackgroundTitration of the continuous distending pressure during a staircase incremental-decremental pressure lung volume optimization maneuver in children on high-frequency oscillatory ventilation is traditionally driven by oxygenation and hemodynamic responses, although validity of these metrics has not been confirmed.MethodsRespiratory inductance plethysmography values were used construct pressure-volume loops during the lung volume optimization maneuver. The maneuver outcome was evaluated by three independent investigators and labeled positive if there was an increase in respiratory inductance plethysmography values at the end of the incremental phase. Metrics for oxygenation (SpO2, FiO2), proximal pressure amplitude, tidal volume and transcutaneous measured pCO2 (ptcCO2) obtained during the incremental phase were compared between outcome maneuvers labeled positive and negative to calculate sensitivity, specificity, and the area under the receiver operating characteristic curve. Ventilation efficacy was assessed during and after the maneuver by measuring arterial pH and PaCO2. Hemodynamic responses during and after the maneuver were quantified by analyzing heart rate, mean arterial blood pressure and arterial lactate.Results41/54 patients (75.9%) had a positive maneuver albeit that changes in respiratory inductance plethysmography values were very heterogeneous. During the incremental phase of the maneuver, metrics for oxygenation and tidal volume showed good sensitivity (> 80%) but poor sensitivity. The sensitivity of the SpO2/FiO2 ratio increased to 92.7% one hour after the maneuver. The proximal pressure amplitude showed poor sensitivity during the maneuver, whereas tidal volume showed good sensitivity but poor specificity. PaCO2 decreased and pH increased in patients with a positive and negative maneuver outcome. No new barotrauma or hemodynamic instability (increase in age-adjusted heart rate, decrease in age-adjusted mean arterial blood pressure or lactate > 2.0 mmol/L) occurred as a result of the maneuver.ConclusionsAbsence of improvements in oxygenation during a lung volume optimization maneuver did not indicate that there were no increases in lung volume quantified using respiratory inductance plethysmography. Increases in SpO2/FiO2 one hour after the maneuver may suggest ongoing lung volume recruitment. Ventilation was not impaired and there was no new barotrauma or hemodynamic instability. The heterogeneous responses in lung volume changes underscore the need for monitoring tools during high-frequency oscillatory ventilation.

Project description:IntroductionTheoretically, high-frequency oscillatory ventilation (HFOV) achieves all goals of a lung-protective ventilatory mode and seems ideal for the treatment of adult patients with acute respiratory distress syndrome (ARDS). However, its effects on mortality and adverse clinical outcomes remain uncertain given the paucity of high-quality studies in this area. This meta-analysis was performed to evaluate the efficacy and adverse events of HFOV in adults with ARDS.MethodsWe searched PubMed, EMBASE and Cochrane Central Register of Controlled Trials through February 2014 to retrieve randomized controlled trials of HFOV in adult ARDS patients. Two independent reviewers extracted data on study methods, clinical and physiological outcomes and adverse events. The primary outcome was 30-day or hospital mortality. Risk of bias was evaluated with the Cochrane Collaboration's tool. Mortality, oxygenation and adverse effects of HFOV were compared to those of conventional mechanical ventilation. A random-effects model was applied for meta-analysis.ResultsA total of five trials randomly assigning 1,580 patients met inclusion criteria. Pooled data showed that HFOV significantly improved oxygenation on day one of therapy (four studies; 24% higher; 95% confidence interval (CI) 11 to 40%; P <0.01). However, HFOV did not reduce mortality risk (five studies; risk ratio (RR) 1.04; 95% CI 0.83 to 1.31; P?=?0.71) and two early terminated studies suggested a harmful effect of HFOV in ARDS (two studies; RR 1.33; 95% CI 1.09 to 1.62; P <0.01). Safety profiles showed that HFOV was associated with a trend toward increased risk of barotrauma (five studies; RR 1.19; 95% CI 0.83 to 1.72; P?=?0.34) and unfavorable hemodynamics (five studies; RR 1.16; 95% CI 0.97 to 1.39; P?=?0.12).ConclusionsHFOV improved oxygenation in adult patients with ARDS; however, it did not confer a survival benefit and might cause harm in the era of lung-protective ventilation strategy. The evidence suggests that HFOV should not be a routine practice in ARDS and further studies specifically selecting patients for this ventilator mode should be pursued.

Dataset Information

Bias flow rate and ventilation efficiency during adult high-frequency oscillatory ventilation: a lung model study.

Publications

Bias flow rate and ventilation efficiency during adult high-frequency oscillatory ventilation: a lung model study.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets