![]() groups similar at baseline, both had baseline recruitment manoeuvre to improve lung homogeneity HFOV strategy had high mean airway pressures – would a lower mean airway pressure strategy make a difference? > were given more midazolam, more NMBs, more vasopressors HFOV vs low TV high PEEP controlled ventilation strategy.548 new-onset, moderate-to-severe ARDS patients.Conclusion: no mortality difference at 1 month.HFOV groups received more sedatives and muscle relaxants less hemodynamic compromise, lower airway pressures than OSCILLATE and more protocol variation, possibly due to physician judgement limiting the harm from HFOV settings > all cause mortality at 28 days was 41.7% vs 41.1% (P=0.85 chi-square test) based on only a small number of patients results of OSCAR and OSCILLATE were not included > not associated with an increase in adverse events > mortality significantly reduced at 30 days > PF ratios higher at 24 hour intervals through improving mean airway pressure reviewed HFOV vs conventional MV as initial strategy rather than as a rescue treatment for refractory hypoxaemia.HFOV should not be a routine part of the management of ARDS patients, but is still an option for refractory ARDS patients (in the absence of ECMO)Ĭochrance Systematic Review (published prior to OSCAR and OSCILLATE).patients with homogeneous, recruitable lung) while others are harmed - but we don’t know if this is true! As ARDS is a heterogeneous lung disease from differing causes, there may be some patient subgroups that might be helped (e.g.Unclear if lack of benefit is due HFOV per se or the protocols used, patient selection or need for increased sedation and paralysis.previous studies compared HFOV to outdated ventilation strategies.HFOV found to cause harm or have no benefit in the 2 best RCTs in adult ARDS patients.no evidence of benefit, and higher mortality in adult ARDS in one important RCT (OSCILLATE).higher risk of hemodynamic instability due to high mean airway pressure.requirement for heavy sedation and paralysis.dissociation between oxygenation and carbon dioxide clearance.Initial frequency based on most recent arterial blood gas:Īfter initial HFOV settings are established, perform an initial recruitment maneuver and oxygen/mPaw adjustment as per protocol (see Fessler et al, 2007).These factors can be independently adjusted amplitude of oscillations (delta P) (“power”).SpO2 > 88% or PaO2 55mmHg (decreases oxygen toxicity).utilise highest possible frequency to minimise tidal volume (only decrease for CO2 control if amplitude of oscillations maximal).alternative means of treating respiratory failure available and preferred (e.g.ARDS/ALI in primary treatment or rescue in failed oxygenation with conventional ventilation.oxygenation failure: requiring an FiO2 > 0.7 and PEEP >14 cmH20.Cardiogenic mixing = agitation of surrounding lung tissue with molecular diffusion.Coaxial flow patterns = net flow through the centre of the airway on way down, then on outside of airway on way up.Taylor dispersion = dispersion of molecules beyond the bulk flow front.Augmented diffusion = gas mixing within the alveolar units. ![]() Pendelluft mixing = mixing of gas between lung units due to impedance differences.TV is less than dead space -> normal bulk flow inadequate -> but gas delivery into the system still undergoes gas exchange by a number of proposed mechanisms (PAT the Cool Cat): aims to prevent lung injury from overdistention and loss of recruitment (atelectrauma).delivered at high frequencies (3-15 Hz) with an oscillatory pump.HFOV is essentially a vibrating CPAP machine Antony Tobin High Frequency Oscillation Ventilation (HFOV) is an unconventional form of mechanical ventilation that maintains lung recruitment, avoids overdistention, and does not rely on bulk flow for oxygenation and ventilation
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