Dataset Information

Lung Recruitment Strategies During High Frequency Oscillatory Ventilation in Preterm Lambs.

ABSTRACT: Background: High frequency oscillatory ventilation (HFOV) is considered a lung protective ventilation mode in preterm infants only if lung volume is optimized. However, whilst a "high lung volume strategy" is advocated for HFOV in preterm infants this strategy is not precisely defined. It is not known to what extent lung recruitment should be pursued to provide lung protection. In this study we aimed to determine the relationship between the magnitude of lung volume optimization and its effect on gas exchange and lung injury in preterm lambs. Methods: 36 surfactant-deficient 124-127 d lambs commenced HFOV immediately following a sustained inflation at birth and were allocated to either (1) no recruitment (low lung volume; LLV), (2) medium- (MLV), or (3) high lung volume (HLV) recruitment strategy. Gas exchange and lung volume changes over time were measured. Lung injury was analyzed by post mortem pressure-volume curves, alveolar protein leakage, gene expression, and histological injury score. Results: More animals in the LLV developed a pneumothorax compared to both recruitment groups. Gas exchange was superior in both recruitment groups compared to LLV. Total lung capacity tended to be lower in the LLV group. Other parameters of lung injury were not different. Conclusions: Lung recruitment during HFOV optimizes gas exchange but has only modest effects on lung injury in a preterm animal model. In the HLV group aiming at a more extensive lung recruitment gas exchange was better without affecting lung injury.

SUBMITTER: Miedema M

PROVIDER: S-EPMC6349831 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Lung Recruitment Strategies During High Frequency Oscillatory Ventilation in Preterm Lambs.

Miedema Martijn M McCall Karen E KE Perkins Elizabeth J EJ Oakley Regina B RB Pereira-Fantini Prue M PM Rajapaksa Anushi E AE Waldmann Andreas D AD Tingay David G DG van Kaam Anton H AH

Frontiers in pediatrics 20190122

<b>Background:</b> High frequency oscillatory ventilation (HFOV) is considered a lung protective ventilation mode in preterm infants only if lung volume is optimized. However, whilst a "high lung volume strategy" is advocated for HFOV in preterm infants this strategy is not precisely defined. It is not known to what extent lung recruitment should be pursued to provide lung protection. In this study we aimed to determine the relationship between the magnitude of lung volume optimization and its e ...[more]

PMID: 30723711

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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:BACKGROUND:Titration 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. METHODS:Respiratory 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. RESULTS:41/54 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. CONCLUSIONS:Absence 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.

Dataset Information

Lung Recruitment Strategies During High Frequency Oscillatory Ventilation in Preterm Lambs.

Publications

Lung Recruitment Strategies During High Frequency Oscillatory Ventilation in Preterm Lambs.

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