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Ventilation by high-frequency oscillation
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1980
Year
Nonlinear OscillationMechanical VentilationHigh-frequency Small-volume OscillationsVentilationPhysiologyAnesthesia PracticeInspired AirSpontaneous RespirationLarynxRespiration (Physiology)High-frequency OscillationAnesthesiaMedicineAir ConditioningAnesthesiology
The study investigated the effect of applying a high‑frequency small‑volume sinusoidal oscillation at the airway in anesthetized apneic beagle dogs. Oscillations were generated by a piston‑driven cylinder and delivered to the lungs via an uncuffed endotracheal tube with a bias flow of fresh gas, maintaining distal airway pressures between 0–2 cmH₂O and peak pressures of 4–8 cmH₂O. At 15 Hz and 1.9 ml/kg tidal volume, the oscillation achieved efficient CO₂ elimination (PaCO₂ ≈ 33 Torr) and sustained oxygenation (PaO₂ ≈ 580–594 Torr on 100 % O₂ and 106 Torr on room air) without affecting cardiac output, showing that high‑frequency small‑volume oscillations can preserve gas exchange for hours by enhancing pulmonary gas diffusivity.
The effect of applying a high-frequency small-volume sinusoidal oscillation at the airway was investigated in anesthetized apneic beagle dogs (mean wt 11 kg, mean VDphys 6.6 +/- 0.6 ml/kg). Oscillations generated by a piston in a cylinder were transmitter to the lungs through an uncuffed endotracheal tube (4.5 mm ID, 6.0 mm OD), which allowed a substantial leak back through the vocal cords. A bias flow of fresh gas presented inspired air to the midtracheal level. The minimum distal airway pressure (measured at the end of the endotracheal tube) was maintained between 0 and 2 cmH2O. Peak airway pressures were 4-8 cmH2O. The optimal frequency for CO2 elimination was 15 Hz. Using volumes of 1.9 ml/kg (range 1.7-2.3) at this frequency the mean PaCO2 was 33.1 +/- 0.5 Torr. In four dogs breathing 100% O2 the PaO2 was 594 +/- 9 Torr during spontaneous ventilation and 580 +/- 9 Torr after 5 h of uninterrupted oscillation. In four experiments using room air the PaO2 was 95 +/- 5 Torr during spontaneous respiration and 106 +/- 1 Torr after 5 h of oscillation. In an additional seven studies there was no difference in mean cardiac output between oscillation and conventional mechanical ventilation. This study demonstrates that high-frequency small-volume oscillations can maintain gas exchange for many hours presumably by markedly enhancing the diffusivity of gases in the lung.